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da Silveira Bueno C, Paytan A, de Souza CD, Franco TT. Global warming and coastal protected areas: A study on phytoplankton abundance and sea surface temperature in different regions of the Brazilian South Atlantic Coastal Ocean. Ecol Evol 2024; 14:e11724. [PMID: 39114175 PMCID: PMC11303980 DOI: 10.1002/ece3.11724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 06/20/2024] [Accepted: 06/26/2024] [Indexed: 08/10/2024] Open
Abstract
In this study, we examined the relationship between sea surface temperature (SST) and phytoplankton abundance in coastal regions of the Brazilian South Atlantic: São Paulo, Paraná, and Santa Catarina, and the Protection Area of Southern right whales (Eubalaena australis) in Santa Catarina (APA), a conservation zone established along 130 km of coastline. Using SST and chlorophyll-a (Chl-a) data from 2002 to 2023, we found significant differences in SST between the regions, with São Paulo having the highest SST, followed by Paraná and Santa Catarina. All locations showed a consistent increase in SST over the years, with North Santa Catarina, APA and São Paulo experiencing the lowest rate of increase. Correlation analyses between SST and Chl-a revealed a stronger inverse relationship in North Santa Catarina and APA, indicating an increased response of Chl-a to SST variations in this region. The presence of protected area appears to play an essential role in reducing the negative impacts of increasing SST. Specifically, while there is a wealth of research on the consequences of global warming on diverse coastal and oceanic areas, heterogeneity among different settings persists and the causes for this necessitating attention. Our findings have implications for both localized scientific approaches and broader climate policies, emphasizing the importance of considering coastal ecosystem resilience to climate change in future conservation and adaptation strategies.
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Affiliation(s)
- Carolina da Silveira Bueno
- Earth and Planetary Sciences, Ocean Sciences Departament, Institute of Marine SciencesUniversity of CaliforniaSanta CruzCaliforniaUnited States
- Interdisciplinary Center of Energy PlanningUniversidade Estadual de CampinasCampinasBrazil
- Department of Climate and EnvironmentFederal Institute of Education, Science and Technology of Santa CatarinaFlorianopolisBrazil
| | - Adina Paytan
- Earth and Planetary Sciences, Ocean Sciences Departament, Institute of Marine SciencesUniversity of CaliforniaSanta CruzCaliforniaUnited States
| | | | - Telma Teixeira Franco
- Earth and Planetary Sciences, Ocean Sciences Departament, Institute of Marine SciencesUniversity of CaliforniaSanta CruzCaliforniaUnited States
- Faculty of Chemical Engineering & Interdisciplinary Center of Energy PlanningUniversidade Estadual de CampinasCampinasBrazil
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2
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Zhang W, Huang R, Deng S, Wang W, Wang Y. Spatio-temporal distribution of sea surface chlorophyll-a in coral reefs of the South China Sea over the past decade based on Landsat-8 Operational Land Images. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 935:173433. [PMID: 38782288 DOI: 10.1016/j.scitotenv.2024.173433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 05/05/2024] [Accepted: 05/20/2024] [Indexed: 05/25/2024]
Abstract
The concentration of chlorophyll-a (Chl-a) in seawater reflects phytoplankton growth and water eutrophication, which are usually assessed for evaluation of primary productivity and carbon source/sink of coral reefs. However, the precise delineation of Chl-a concentration in coral reefs remains a challenge when ocean satellites with low spatial resolution are utilized. In this study, a remote sensing inversion model for Chl-a was developed in fringing reefs (R2 = 0.76, RMSE =0.41 μg/L, MRE = 14 %) and atolls (R2 = 0.79, RMSE =0.02 μg/L, MRE = 8 %), utilizing reflectance data from the sensitive band of the Landsat-8 Operational Land Imagers (OLI) with a spatial resolution of 30 m. The aforementioned model was utilized to invert high-resolution distribution maps of Chl-a concentration in six major coral reef regions of the South China Sea from 2013 to 2022 and subsequently used to analyze the variations in Chl-a concentration and its influencing factors. The results indicate a Chl-a concentration gradient among coral reefs Daya Bay, Weizhou Island, Luhuitou, Xuwen, Huangyan Island, and Xisha Island in that order. The Chl-a concentration in coral reefs exhibited an overall increasing trend, with significant seasonal fluctuations, characterized by higher concentrations during winter and spring and lower concentrations during summer and autumn. The concentration of Chl-a in coral reefs was positively correlated with the average wind speed.
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Affiliation(s)
- Wei Zhang
- Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China; Coral Reef Research Center of China, Guangxi University, Nanning 530004, China; School of Marine Sciences, Guangxi University, Nanning 530004, China
| | - Rongyong Huang
- Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China; Coral Reef Research Center of China, Guangxi University, Nanning 530004, China; School of Marine Sciences, Guangxi University, Nanning 530004, China
| | - Songwen Deng
- School of Marine Sciences, Guangxi University, Nanning 530004, China
| | - Wenhuan Wang
- Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China; Coral Reef Research Center of China, Guangxi University, Nanning 530004, China; School of Marine Sciences, Guangxi University, Nanning 530004, China
| | - Yinghui Wang
- Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China; Coral Reef Research Center of China, Guangxi University, Nanning 530004, China; School of Marine Sciences, Guangxi University, Nanning 530004, China.
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3
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Guo H, Huang JJ, Zhu X, Tian S, Wang B. Spatiotemporal variation reconstruction of total phosphorus in the Great Lakes since 2002 using remote sensing and deep neural network. WATER RESEARCH 2024; 255:121493. [PMID: 38547788 DOI: 10.1016/j.watres.2024.121493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 02/18/2024] [Accepted: 03/18/2024] [Indexed: 04/24/2024]
Abstract
Total phosphorus (TP) is non-optically active, thus TP concentration (CTP) estimation using remote sensing still exists grand challenge. This study developed a deep neural network model (DNN) for CTP estimation with synchronous in-situ measurements and MODIS-derived remote sensing reflectance (Rrs) (N = 3916). Using DNN, the annual and intra-annual CTP spatial distributions of the Great Lakes since 2002 were reconstructed. Then, the reconstructions were correlated to nine potential factors, e.g., Chlorophyll-a, snowmelt, and cropland, to explain seasonal and long-term CTP variations. The results showed that DNN reliably estimated CTP from MODIS Rrs, with R2, mean absolute error (MAE), root mean squared error (RMSE), mean absolute percentage error (MAPE), and root mean squared logarithmic error (RMSLE) of 0.83, 1.05 μg/L, 2.95 μg/L, 9.92%, and 0.13 on the test set. The near-surface CTP in the Great Lakes decreased significantly (p < 0.05) during 2002 - 2022, primarily attributed to cropland reduction, coupled with improvements in basin natural ecosystems. The sensitivity analysis verified the model robustness when confronted with input feature changes < 35%. This result along with the marginal difference between CTP derived from two sensors (R2 = 0.76, MAE = 2.12 μg/L, RMSE = 2.51 μg/L, MAPE = 11.52%, RMSLE = 0.24) suggested the model transferability from MODIS to VIIRS. This transformation facilitated optimal usage of MODIS-related archive and enhanced the continuity of CTP estimation at moderate resolution. This study presents a practical method for spatiotemporal reconstruction of CTP using remote sensing, and contributes to better understandings of driving factors behind CTP variations in the Great Lakes.
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Affiliation(s)
- Hongwei Guo
- School of Geographic Information and Tourism, Chuzhou University, Chuzhou, 239099, Anhui, China; College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environmental Safety, Nankai University, Tianjin, 300457, China
| | - Jinhui Jeanne Huang
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environmental Safety, Nankai University, Tianjin, 300457, China.
| | - Xiaotong Zhu
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environmental Safety, Nankai University, Tianjin, 300457, China
| | - Shang Tian
- Key Laboratory for Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
| | - Benlin Wang
- School of Geographic Information and Tourism, Chuzhou University, Chuzhou, 239099, Anhui, China
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Franz BA, Cetinić I, Ibrahim A, Sayer AM. Anomalous trends in global ocean carbon concentrations following the 2022 eruptions of Hunga Tonga-Hunga Ha'apai. COMMUNICATIONS EARTH & ENVIRONMENT 2024; 5:247. [PMID: 38736528 PMCID: PMC11087252 DOI: 10.1038/s43247-024-01421-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 04/23/2024] [Indexed: 05/14/2024]
Abstract
We report on observed trend anomalies in climate-relevant global ocean biogeochemical properties, as derived from satellite ocean color measurements, that show a substantial decline in phytoplankton carbon concentrations following eruptions of the submarine volcano Hunga Tonga-Hunga Ha'apai in January 2022. The anomalies are seen in remotely-sensed ocean color data sets from multiple satellite missions, but not in situ observations, thus suggesting that the observed anomalies are a result of ocean color retrieval errors rather than indicators of a major shift in phytoplankton carbon concentrations. The enhanced concentration of aerosols in the stratosphere following the eruptions results in a violation of some fundamental assumptions in the processing algorithms used to obtain marine biogeochemical properties from satellite radiometric observations, and it is demonstrated through radiative transfer simulations that this is the likely cause of the anomalous trends. We note that any future stratospheric aerosol disturbances, either natural or geoengineered, may lead to similar artifacts in satellite ocean color and other remote-sensing measurements of the marine environment, thus confounding our ability to track the impact of such events on ocean ecosystems.
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Affiliation(s)
| | - Ivona Cetinić
- NASA Goddard Space Flight Center, Greenbelt, MD USA
- Morgan State University, Baltimore, MD USA
| | - Amir Ibrahim
- NASA Goddard Space Flight Center, Greenbelt, MD USA
| | - Andrew M. Sayer
- NASA Goddard Space Flight Center, Greenbelt, MD USA
- University of Maryland Baltimore County, Baltimore, MD USA
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5
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Adhikary S, Tiwari SP, Banerjee S, Dwivedi AD, Rahman SM. Global marine phytoplankton dynamics analysis with machine learning and reanalyzed remote sensing. PeerJ 2024; 12:e17361. [PMID: 38737741 PMCID: PMC11088370 DOI: 10.7717/peerj.17361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 04/18/2024] [Indexed: 05/14/2024] Open
Abstract
Phytoplankton are the world's largest oxygen producers found in oceans, seas and large water bodies, which play crucial roles in the marine food chain. Unbalanced biogeochemical features like salinity, pH, minerals, etc., can retard their growth. With advancements in better hardware, the usage of Artificial Intelligence techniques is rapidly increasing for creating an intelligent decision-making system. Therefore, we attempt to overcome this gap by using supervised regressions on reanalysis data targeting global phytoplankton levels in global waters. The presented experiment proposes the applications of different supervised machine learning regression techniques such as random forest, extra trees, bagging and histogram-based gradient boosting regressor on reanalysis data obtained from the Copernicus Global Ocean Biogeochemistry Hindcast dataset. Results obtained from the experiment have predicted the phytoplankton levels with a coefficient of determination score (R2) of up to 0.96. After further validation with larger datasets, the model can be deployed in a production environment in an attempt to complement in-situ measurement efforts.
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Affiliation(s)
| | | | | | | | - Syed Masiur Rahman
- King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia
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6
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Zhang Y, Yu X, Lee Z, Shang S, Qiao H, Lin G, Lai W. Performance of two semi-analytical algorithms in deriving water inherent optical properties in the Southern Ocean. OPTICS EXPRESS 2024; 32:15741-15759. [PMID: 38859217 DOI: 10.1364/oe.515341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 04/02/2024] [Indexed: 06/12/2024]
Abstract
Remotely sensed inherent optical properties (IOPs) are key proxies for synoptic mapping of primary production and carbon export in the global ocean. However, the IOPs inversion algorithms are scarcely evaluated in the Southern Ocean (SO) because of limited field observations. In this study, the performance of two widely used semi-analytical algorithms (SAAs), i.e., the quasi-analytical algorithm (QAA) and the generalized IOP model (GIOP), were evaluated using a compiled in situ bio-optical dataset in SO, as well as measurements from the Visible Infrared Imaging Radiometer Suite (VIIRS). Evaluations with in situ data show that QAA and GIOP have comparable performance in retrieving the total absorption coefficient (a(λ)), absorption coefficients of phytoplankton (aph(λ)), and that of detritus and colored dissolved organic matter (adg(λ)). Overall, it was found that remotely sensed a(λ) and aph(λ) by both SAAs agreed well with field measurements, with the mean absolute percentage difference (MAPD) of derived a(λ) and aph(λ) in the blue-green bands being ∼20% and ∼40%, respectively. However, derived adg(λ) by both SAAs were higher than the measured values at the lower end (adg(443) < ∼0.01 m-1), but lower at the higher end (adg(443) > ∼0.02 m-1), with MAPD of ∼60%. Results of this effort suggest confident products of a(λ) and aph(λ) from VIIRS in SO, but more dedicated efforts on the measurements and evaluation of adg(λ) in SO would be desired.
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Liu Y, Zhang C, Chen X. Knowledge-guided mixture density network for chlorophyll-a retrieval and associated pixel-by-pixel uncertainty assessment in optically variable inland waters. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 919:170843. [PMID: 38340821 DOI: 10.1016/j.scitotenv.2024.170843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 02/06/2024] [Accepted: 02/07/2024] [Indexed: 02/12/2024]
Abstract
Machine learning has been increasingly used to retrieve chlorophyll-a (Chl-a) in optically variable waters. However, without the guidance of physical principles or expert knowledge, machine learning may produce biased mapping relationships, or waste considerable time searching for physically infeasible hyperparameter domains. In addition, most Chl-a retrieval models cannot evaluate retrieval uncertainty when ground observations are not available, and the retrieval uncertainty is crucial for understanding the model limitations and evaluating the reliability of retrieval results. In this study, we developed a novel knowledge-guided mixture density network to retrieve Chl-a in optically variable inland waters based on Sentinel-3 Ocean and Land Color Instrument (OLCI) imagery. The proposed method embedded prior knowledge derived from spectral shape classification into the mixture density network. Compared to another deterministic model, the knowledge-guided mixture density network outputted the conditional distribution of Chl-a given an input spectrum, enabling us to estimate the optimal retrieval and the associated uncertainty. The proposed method showed favorable correspondence with the field Chl-a, with root mean square error (RMSE) of 6.56 μg/L, and mean absolute percentage error (MAPE) of 43.64 %. Calibrated against Sentinel-3 OLCI spectrum, the proposed method also performed well when applied to field spectrum (RMSE = 4.58 μg/L, MAPE = 72.70 %), suggesting its effectiveness and good generalization. The proposed method provided the standard deviation of each estimated Chl-a, which enabled us to inspect the reliability of the estimated results and understand the model limitations. Overall, the proposed method improved the Chl-a retrieval in terms of model accuracy and uncertainty evaluation, providing a more comprehensive Chl-a observation of inland waters.
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Affiliation(s)
- Yongxin Liu
- National Engineering Research Center for Satellite Remote Sensing Applications, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China.
| | - Chenlu Zhang
- School of Earth and Space Sciences, Peking University, Beijing 100871, China; Engineering Research Center of Earth Observation and Navigation (CEON), Ministry of Education of the PRC, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, China
| | - Xiuwan Chen
- School of Earth and Space Sciences, Peking University, Beijing 100871, China; Engineering Research Center of Earth Observation and Navigation (CEON), Ministry of Education of the PRC, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, China
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8
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Zhao D, Huang J, Li Z, Yu G, Shen H. Dynamic monitoring and analysis of chlorophyll-a concentrations in global lakes using Sentinel-2 images in Google Earth Engine. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 912:169152. [PMID: 38061660 DOI: 10.1016/j.scitotenv.2023.169152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/11/2023] [Accepted: 12/04/2023] [Indexed: 01/18/2024]
Abstract
Remote estimation of Chlorophyll-a (Chl-a) has long been used to investigate the responses of aquatic ecosystems to global climate change. High-spatiotemporal-resolution Sentinel-2 satellite images make it possible to routinely monitor and trace the spatial distributions of lake Chl-a if reliable retrieval algorithms are available. In this study, Sentinel-2 images and in-situ measured data were used to develop a Chl-a retrieval algorithm based on 13 optical water types (OWTs) with a satisfying performance (R2 = 0.74, RMSE = 0.42 mg/m3, MAE = 0.33 mg/m3, and MAPE = 55.56 %). After removing the disturbance of algal blooms and other factors, the distribution of Chl-a in 3067 of the largest global lakes (≥50 km2) was mapped using the Google Earth Engine (GEE). From 2019 to 2021, the average Chl-a concentration was 16.95 ± 5.95 mg/m3 for the largest global lakes. During the COVID-19 pandemic, global lake-averaged Chl-a concentration reached its lowest value in 2020. From the perspective of spatial distribution, lakes with low Chl-a concentrations were mainly distributed in high-latitude, high-elevation, or economically underdeveloped areas. Among all the potential influencing factors, lake surface temperature had the largest contribution to Chl-a and showed a positive correlation with Chl-a in approximately 92.39 % of the lakes. Conversely, factors such as precipitation and tree cover area around the lake were negatively correlated with Chl-a concentration in nearly 61.44 % of the lakes.
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Affiliation(s)
- Desong Zhao
- College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China
| | - Jue Huang
- College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China.
| | - Zhengmao Li
- Shandong Marine Resource and Environment Research Institute, Shandong Key Laboratory of Marine Ecological Restoration, Yantai 264006, China
| | - Guangyue Yu
- College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China
| | - Huagang Shen
- Qingdao Topscomm Communication Co., Ltd, TOPSCOMM Industry Park, Qingdao 266109, China
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Baldrich ÁM, Díaz PA, Rosales SA, Rodríguez-Villegas C, Álvarez G, Pérez-Santos I, Díaz M, Schwerter C, Araya M, Reguera B. An Unprecedented Bloom of Oceanic Dinoflagellates ( Karenia spp.) Inside a Fjord within a Highly Dynamic Multifrontal Ecosystem in Chilean Patagonia. Toxins (Basel) 2024; 16:77. [PMID: 38393154 PMCID: PMC10892511 DOI: 10.3390/toxins16020077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 01/18/2024] [Accepted: 01/30/2024] [Indexed: 02/25/2024] Open
Abstract
At the end of summer 2020, a moderate (~105 cells L-1) bloom of potential fish-killing Karenia spp. was detected in samples from a 24 h study focused on Dinophysis spp. in the outer reaches of the Pitipalena-Añihue Marine Protected Area. Previous Karenia events with devastating effects on caged salmon and the wild fauna of Chilean Patagonia had been restricted to offshore waters, eventually reaching the southern coasts of Chiloé Island through the channel connecting the Chiloé Inland Sea to the Pacific Ocean. This event occurred at the onset of the COVID-19 lockdown when monitoring activities were slackened. A few salmon mortalities were related to other fish-killing species (e.g., Margalefidinium polykrikoides). As in the major Karenia event in 1999, the austral summer of 2020 was characterised by negative anomalies in rainfall and river outflow and a severe drought in March. Karenia spp. appeared to have been advected in a warm (14-15 °C) surface layer of estuarine saline water (S > 21). A lack of daily vertical migration patterns and cells dispersed through the whole water column suggested a declining population. Satellite images confirmed the decline, but gave evidence of dynamic multifrontal patterns of temperature and chl a distribution. A conceptual circulation model is proposed to explain the hypothetical retention of the Karenia bloom by a coastally generated eddy coupled with the semidiurnal tides at the mouth of Pitipalena Fjord. Thermal fronts generated by (topographically induced) upwelling around the Tic Toc Seamount are proposed as hot spots for the accumulation of swimming dinoflagellates in summer in the southern Chiloé Inland Sea. The results here provide helpful information on the environmental conditions and water column structure favouring Karenia occurrence. Thermohaline properties in the surface layer in summer can be used to develop a risk index (positive if the EFW layer is thin or absent).
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Affiliation(s)
- Ángela M. Baldrich
- Centro i~mar, Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile; (Á.M.B.); (P.A.D.); (C.R.-V.); (I.P.-S.); (C.S.)
- Centre for Biotechnology and Bioengineering (CeBiB), Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile
| | - Patricio A. Díaz
- Centro i~mar, Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile; (Á.M.B.); (P.A.D.); (C.R.-V.); (I.P.-S.); (C.S.)
- Centre for Biotechnology and Bioengineering (CeBiB), Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile
| | - Sergio A. Rosales
- Programa de Doctorado en Biología y Ecología Aplicada, Universidad Católica del Norte, Coquimbo 1780000, Chile;
| | - Camilo Rodríguez-Villegas
- Centro i~mar, Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile; (Á.M.B.); (P.A.D.); (C.R.-V.); (I.P.-S.); (C.S.)
| | - Gonzalo Álvarez
- Facultad de Ciencias del Mar, Departamento de Acuicultura, Universidad Católica del Norte, Coquimbo 1780000, Chile;
- Centro de Investigación y Desarrollo Tecnológico en Algas (CIDTA), Facultad de Ciencias del Mar, Universidad Católica del Norte, Coquimbo 1780000, Chile;
| | - Iván Pérez-Santos
- Centro i~mar, Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile; (Á.M.B.); (P.A.D.); (C.R.-V.); (I.P.-S.); (C.S.)
- Centro de Investigación Oceanográfica COPAS Sur-Austral y COPAS COASTAL, Universidad de Concepción, Concepción 4030000, Chile
| | - Manuel Díaz
- Programa de Investigación Pesquera, Universidad Austral de Chile, Puerto Montt 5480000, Chile;
| | - Camila Schwerter
- Centro i~mar, Universidad de Los Lagos, Casilla 557, Puerto Montt 5480000, Chile; (Á.M.B.); (P.A.D.); (C.R.-V.); (I.P.-S.); (C.S.)
| | - Michael Araya
- Centro de Investigación y Desarrollo Tecnológico en Algas (CIDTA), Facultad de Ciencias del Mar, Universidad Católica del Norte, Coquimbo 1780000, Chile;
| | - Beatriz Reguera
- Centro Oceanográfico de Vigo, Centro Nacional Instituto Español de Oceanografía (IEO-CSIC), Subida a Radio Faro 50, 36390 Vigo, Spain
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Lopez Barreto BN, Hestir EL, Lee CM, Beutel MW. Satellite Remote Sensing: A Tool to Support Harmful Algal Bloom Monitoring and Recreational Health Advisories in a California Reservoir. GEOHEALTH 2024; 8:e2023GH000941. [PMID: 38404693 PMCID: PMC10885757 DOI: 10.1029/2023gh000941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 12/08/2023] [Accepted: 01/31/2024] [Indexed: 02/27/2024]
Abstract
Cyanobacterial harmful algal blooms (cyanoHABs) can harm people, animals, and affect consumptive and recreational use of inland waters. Monitoring cyanoHABs is often limited. However, chlorophyll-a (chl-a) is a common water quality metric and has been shown to have a relationship with cyanobacteria. The World Health Organization (WHO) recently updated their previous 1999 cyanoHAB guidance values (GVs) to be more practical by basing the GVs on chl-a concentration rather than cyanobacterial counts. This creates an opportunity for widespread cyanoHAB monitoring based on chl-a proxies, with satellite remote sensing (SRS) being a potentially powerful tool. We used Sentinel-2 (S2) and Sentinel-3 (S3) to map chl-a and cyanobacteria, respectively, classified chl-a values according to WHO GVs, and then compared them to cyanotoxin advisories issued by the California Department of Water Resources (DWR) at San Luis Reservoir, key infrastructure in California's water system. We found reasonably high rates of total agreement between advisories by DWR and SRS, however rates of agreement varied for S2 based on algorithm. Total agreement was 83% for S3, and 52%-79% for S2. False positive and false negative rates for S3 were 12% and 23%, respectively. S2 had 12%-80% false positive rate and 0%-38% false negative rate, depending on algorithm. Using SRS-based chl-a GVs as an early indicator for possible exposure advisories and as a trigger for in situ sampling may be effective to improve public health warnings. Implementing SRS for cyanoHAB monitoring could fill temporal data gaps and provide greater spatial information not available from in situ measurements alone.
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Affiliation(s)
- Brittany N. Lopez Barreto
- Environmental Systems Graduate GroupDepartment of Civil & Environmental EngineeringUniversity of California MercedMercedCAUSA
- Center for Information Technology Research in the Interest of SocietyThe Banatao InstituteUniversity of California MercedMercedCAUSA
| | - Erin L. Hestir
- Environmental Systems Graduate GroupDepartment of Civil & Environmental EngineeringUniversity of California MercedMercedCAUSA
- Center for Information Technology Research in the Interest of SocietyThe Banatao InstituteUniversity of California MercedMercedCAUSA
| | - Christine M. Lee
- NASA Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - Marc W. Beutel
- Environmental Systems Graduate GroupDepartment of Civil & Environmental EngineeringUniversity of California MercedMercedCAUSA
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11
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Zhang M, Ibrahim A, Franz BA, Sayer AM, Werdell PJ, McKinna LI. Spectral correlation in MODIS water-leaving reflectance retrieval uncertainty. OPTICS EXPRESS 2024; 32:2490-2506. [PMID: 38297777 DOI: 10.1364/oe.502561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 12/20/2023] [Indexed: 02/02/2024]
Abstract
Spectral remote sensing reflectance, Rrs(λ) (sr-1), is the fundamental quantity used to derive a host of bio-optical and biogeochemical properties of the water column from satellite ocean color measurements. Estimation of uncertainty in those derived geophysical products is therefore dependent on knowledge of the uncertainty in satellite-retrieved Rrs. Furthermore, since the associated algorithms require Rrs at multiple spectral bands, the spectral (i.e., band-to-band) error covariance in Rrs is needed to accurately estimate the uncertainty in those derived properties. This study establishes a derivative-based approach for propagating instrument random noise, instrument systematic uncertainty, and forward model uncertainty into Rrs, as retrieved using NASA's multiple-scattering epsilon (MSEPS) atmospheric correction algorithm, to generate pixel-level error covariance in Rrs. The approach is applied to measurements from Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite and verified using Monte Carlo (MC) analysis. We also make use of this full spectral error covariance in Rrs to calculate uncertainty in phytoplankton pigment chlorophyll-a concentration (chla, mg/m3) and diffuse attenuation coefficient of downwelling irradiance at 490 nm (Kd(490), m-1). Accounting for the error covariance in Rrs generally reduces the estimated relative uncertainty in chla by ∼1-2% (absolute value) in waters with chla < 0.25 mg/m3 where the color index (CI) algorithm is used. The reduction is ∼5-10% in waters with chla > 0.35 mg/m3 where the blue-green ratio (OCX) algorithm is used. Such reduction can be higher than 30% in some regions. For Kd(490), the reduction by error covariance is generally ∼2%, but can be higher than 20% in some regions. The error covariance in Rrs is further verified through forward-calculating chla from MODIS-retrieved and in situ Rrs and comparing estimated uncertainty with observed differences. An 8-day global composite of propagated uncertainty shows that the goal of 35% uncertainty in chla can be achieved over deep ocean waters (chla ≤ 0.1 mg/m3). While the derivative-based approach generates reasonable error covariance in Rrs, some assumptions should be updated as our knowledge improves. These include the inter-band error correlation in top-of-atmosphere reflectance, and uncertainties in the calibration of MODIS 869 nm band, in ancillary data, and in the in situ data used for system vicarious calibration.
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12
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Wang J, Chen X. A new approach to quantify chlorophyll-a over inland water targets based on multi-source remote sensing data. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167631. [PMID: 37806589 DOI: 10.1016/j.scitotenv.2023.167631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/16/2023] [Accepted: 10/05/2023] [Indexed: 10/10/2023]
Abstract
Chlorophyll-a (Chl-a) concentration is a reliable indicator of phytoplankton biomass and eutrophication, especially in inland waters. Remote sensing provides a means for large-scale Chl-a estimation by linking the spectral water-leaving signal from the water surface with in situ measured Chl-a concentrations. Single-sensor images cannot meet the practical needs for long-term monitoring of Chl-a concentrations due to cloud cover and satellite operational lifetimes. However, quantifying long-term inland water Chl-a concentrations using multi-source remote sensing data remains a problem, as improper input of satellite reflectance products will affect the accuracy of Chl-a over inland waters, as well as existing models cannot meet the need for multi-source remote sensing data to retrieve high precision Chl-a. To explore these problems towards a solution, four reflectance data derived from Ocean and Land Colour Instrument (OLCI), MultiSpectral Instrument (MSI), and Operational Land Imager (OLI) were evaluated against in situ measurements of Erhai Lake. Reflectance data from these sensors were assessed to determine their consistency. Results indicate that R_rhos products (i.e., surface reflectance, a semi-atmospheric correction reflectance) that controlled for the atmospheric diffuse transmittance were highly correlated with the measured reflectance values. The in situ reflectance also confirmed the higher fidelity of satellite reflectance in the green-red band. Subsequently, a new extreme gradient boosting (XGB) model applied to multi-source remote sensing data is proposed to estimate long-term inland water Chl-a concentrations. Comparative experiments showed the XGB model with R_rhos products outperformed other solutions, providing accurate estimates for daily, monthly, and long-term trends in Erhai Lake. The XGB model was finally processed 3954 R_rhos reflectance data derived from OLCI, ENVISAT Medium Resolution Imaging Spectrometer (MERIS), MSI, and OLI sensors, mapping Chl-a concentrations in Erhai Lake over a 20-year period. This study could serve as a reference for the long-term Chl-a monitoring using multi-source remote sensing data to support inland lake management and future water quality evaluation.
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Affiliation(s)
- Jialin Wang
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China.
| | - Xiaoling Chen
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China.
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13
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Kwon DY, Kim J, Park S, Hong S. Advancements of remote data acquisition and processing in unmanned vehicle technologies for water quality monitoring: An extensive review. CHEMOSPHERE 2023; 343:140198. [PMID: 37717916 DOI: 10.1016/j.chemosphere.2023.140198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 08/28/2023] [Accepted: 09/14/2023] [Indexed: 09/19/2023]
Abstract
Regular water quality monitoring is becoming desirable due to the increase in water pollution caused by both climate change and the generation of industrial chemicals. Unmanned vehicles have emerged as key technologies for remote data acquisition, providing fast and accurate methods for water quality monitoring. However, current research on unmanned vehicles has not systematically examined their features and limitations, which are crucial for identifying future research directions and applications of unmanned vehicle technologies. Therefore, this study extensively reviews the advancements in remote data acquisition and processing using unmanned vehicle technologies for water quality monitoring to provide valuable insights for future research. First, the types of unmanned vehicles and their application ranges for water quality monitoring are summarized. Among the unmanned vehicle technologies, unmanned aerial vehicles are considered primary platforms for water quality monitoring due to their wide data acquisition range and their ability to accommodate diverse sensors and samplers. Also, the types of samplers and sensors mounted on the unmanned vehicles are analyzed based on their characteristics. It is concluded that spectral sensors offer the most cost-effective approach for acquiring real-time water quality data. Furthermore, algorithms that convert image data into water quality data are examined, focusing on data preprocessing, analysis, and validation. The findings reveal a close relationship between the analysis of spectral characteristics of each water quality parameter and the wavelength ranges of red and red-edge. Lastly, future research directions for unmanned vehicle technologies are further suggested based on the summarized technological limitations.
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Affiliation(s)
- Da Yun Kwon
- School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Jungbin Kim
- School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea; Department of Environmental Science, College of Science, Mathematics and Technology, Wenzhou-Kean University, 88 Daxue Road, Ouhai, Wenzhou, 325060, Zhejiang Province, China
| | - Seongyeol Park
- School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Seungkwan Hong
- School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea.
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14
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Chen J, Li J, He X, Tang J, Pan D. Neural network spectral relationship to improve an inherent optical properties data processing system for residual error correction. OPTICS EXPRESS 2023; 31:39583-39605. [PMID: 38041276 DOI: 10.1364/oe.498601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 10/21/2023] [Indexed: 12/03/2023]
Abstract
The residual error was a critical indicator to measure the data quality of ocean color products, which allows a user to decide the valuable envisioned application of these data. To effectively remove the residual errors from satellite remote sensing reflectance (Rrs) using the inherent optical data processing system (IDAS), we expressed the residual error spectrum as an exponential plus linear function, and then we developed neural network models to derive the corresponding spectral slope coefficients from satellite Rrs data. Coupled with the neural network models-based spectral relationship, the IDAS algorithm (IDASnn) was more effective than an invariant spectral relationship-based IDAS algorithm (IDAScw) in reducing the effects of residual errors in Rrs on IOPs retrieval for our synthetic, field, and Chinese Ocean Color and Temperature Scanner (COCTS) data. Particularly, due to the improved spectral relationship of the residual errors, the IDASnn algorithm provided more accurate and smoother spatiotemporal ocean color product than the IDAScw algorithm for the open ocean. Furthermore, we could monitor the data quality with the IDASnn algorithm, suggesting that the residual error was exceptionally large for COCTS images with low effective coverage. The product effective coverage should be rigorously controlled, or the residual error should be accurately corrected before temporal and spatial analysis of the COCTS data. Our results suggest that an accurate spectral relationship of residual errors is critical to determine how well the IDAS algorithm corrects for residual error.
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15
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Lapucci C, Antonini A, Böhm E, Organelli E, Massi L, Ortolani A, Brandini C, Maselli F. Use of Sentinel-3 OLCI Images and Machine Learning to Assess the Ecological Quality of Italian Coastal Waters. SENSORS (BASEL, SWITZERLAND) 2023; 23:9258. [PMID: 38005644 PMCID: PMC10675379 DOI: 10.3390/s23229258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 11/13/2023] [Accepted: 11/16/2023] [Indexed: 11/26/2023]
Abstract
Understanding and monitoring the ecological quality of coastal waters is crucial for preserving marine ecosystems. Eutrophication is one of the major problems affecting the ecological state of coastal marine waters. For this reason, the control of the trophic conditions of aquatic ecosystems is needed for the evaluation of their ecological quality. This study leverages space-based Sentinel-3 Ocean and Land Color Instrument imagery (OLCI) to assess the ecological quality of Mediterranean coastal waters using the Trophic Index (TRIX) key indicator. In particular, we explore the feasibility of coupling remote sensing and machine learning techniques to estimate the TRIX levels in the Ligurian, Tyrrhenian, and Ionian coastal regions of Italy. Our research reveals distinct geographical patterns in TRIX values across the study area, with some regions exhibiting eutrophic conditions near estuaries and others showing oligotrophic characteristics. We employ the Random Forest Regression algorithm, optimizing calibration parameters to predict TRIX levels. Feature importance analysis highlights the significance of latitude, longitude, and specific spectral bands in TRIX prediction. A final statistical assessment validates our model's performance, demonstrating a moderate level of error (MAE of 0.51) and explanatory power (R2 of 0.37). These results highlight the potential of Sentinel-3 OLCI imagery in assessing ecological quality, contributing to our understanding of coastal water ecology. They also underscore the importance of merging remote sensing and machine learning in environmental monitoring and management. Future research should refine methodologies and expand datasets to enhance TRIX monitoring capabilities from space.
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Affiliation(s)
- Chiara Lapucci
- National Research Council (CNR), Institute of Marine Science (ISMAR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (E.B.); (C.B.)
- LaMMA Consortium, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (A.A.); (A.O.)
| | - Andrea Antonini
- LaMMA Consortium, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (A.A.); (A.O.)
| | - Emanuele Böhm
- National Research Council (CNR), Institute of Marine Science (ISMAR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (E.B.); (C.B.)
| | - Emanuele Organelli
- National Research Council (CNR), Institute of Marine Science (ISMAR), Via Fosso del Cavaliere 100, 00133 Rome, Italy;
| | - Luca Massi
- Dipartimento di Biologia, Università Degli Studi di Firenze, Via Micheli 1, 50121 Florence, Italy;
| | - Alberto Ortolani
- LaMMA Consortium, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (A.A.); (A.O.)
- National Research Council (CNR), Institute for BioEconomy (IBE), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy
| | - Carlo Brandini
- National Research Council (CNR), Institute of Marine Science (ISMAR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (E.B.); (C.B.)
- LaMMA Consortium, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy; (A.A.); (A.O.)
| | - Fabio Maselli
- National Research Council (CNR), Institute for BioEconomy (IBE), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy
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16
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Liu D, Bai Y, Wei X, Jiang X, Wu H, Yu S. Sewage treatment decreased organic carbon resources in Hong Kong waters during 1986-2020. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 335:122219. [PMID: 37479168 DOI: 10.1016/j.envpol.2023.122219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 07/08/2023] [Accepted: 07/16/2023] [Indexed: 07/23/2023]
Abstract
Riverine organic carbon (OC) transport plays a role in regulating terrestrial and marine carbon pools and deteriorating coastal water quality. However, long-term OC transport in Asian rivers and its diffusion in marginal seas have remained unreported. This study reported the spatiotemporal variations in OC resources for Hong Kong waters, China, based on monthly monitoring data collected at 82 river stations and 94 ocean sites during 1986-2020. The station-based riverine OC varied spatially and was generally high, with a mean value of 1.4-52.0 mg/L. Moreover, along with improving water quality, OC at 97.6% of the river stations decreased during 1986-2020; overall, sewage treatment accounted for 83.4% of the exponential decrease in riverine OC (R2 = 0.68, p < 0.01). However, the reduction in riverine OC accounted for only 10.4% of the reduction in the marine five-day biochemical oxygen demand (BOD5), which occurred at 70.2% of the ocean sites, especially those closest to the shore. The linear reduction in the marine BOD5 (R2 = 0.24, p < 0.01) was mainly attributed to reduced OC input from the adjacent Pearl River (61.9%) and decreases in phytoplankton growth (19.0%). These results indicated that sewage treatment improved water quality and decreased OC resources in Hong Kong waters, which can serve as a sustainable development model for other coastal cities. This study has important implications for mitigating organic pollution in the context of human efforts to manage the water environment.
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Affiliation(s)
- Dong Liu
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China; State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China; Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Yan Bai
- State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China
| | - Xiaodao Wei
- YANGTZE Eco-Environment Engineering Research Center, China Three Gorges Corporation, Beijing, 100038, China
| | - Xintong Jiang
- College of Urban and Environmental Sciences, Northwest University, Xi'an, 710127, China
| | - Huawu Wu
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Shujie Yu
- State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China.
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17
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Rajkumar SVPB, Sivakumar R. Analysis of bio-optical active constituents for lentic ecosystem through spectral-spatial and in-vitro observation. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:99605-99619. [PMID: 37620697 DOI: 10.1007/s11356-023-29239-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 08/04/2023] [Indexed: 08/26/2023]
Abstract
The neural network algorithm approach was adopted in Kolavai Lake to retrieve the inherent optical properties (IOP) of active constituents. The retrieval of IOP by absorption and the scattering of optically active constituents (OAC) through employing Sentinel-2 MSI reflectance and field measured the salinity and temperature. The result illustrates the relationship between the IOP and measured OAC's concentrations and its sensitivity towards spectral wavelength. It shows that the phytoplankton absorption ap is highly related with chlorophyll-a concentration and has an R2 value of 0.808. Furthermore, at the total absorption of water has high correlation with chl-a which indicates the significant dominance in the lentic water. Also, the pigment constituents are showing an R2 value of 0.754. The total backscattering of water (btot) is strongly related to the total suspended matter with R value > 0.73. The spatial distribution of OAC in Kolavai Lake helps monitor the lake water quality. This approach is well-performed in estimating the inherent optical properties of optically active constituents that gives insight for assessing the relationship between IOP and water quality. The research has proved to be a good potential for monitoring lentic water quality through Sentinel-2 MSI.
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Affiliation(s)
- Sri Vishnu Prasanth Balachandran Rajkumar
- Department of Civil Engineering, College of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur, Chengalpattu, Tamil Nadu, 603203, India
| | - Ramamoorthy Sivakumar
- Department of Civil Engineering, College of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur, Chengalpattu, Tamil Nadu, 603203, India.
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18
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Erickson ZK, McKinna L, Werdell PJ, Cetinić I. Bayesian approach to a generalized inherent optical property model. OPTICS EXPRESS 2023; 31:22790-22801. [PMID: 37475382 DOI: 10.1364/oe.486581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 05/01/2023] [Indexed: 07/22/2023]
Abstract
Relationships between the absorption and backscattering coefficients of marine optical constituents and ocean color, or remote sensing reflectances Rrs(λ), can be used to predict the concentrations of these constituents in the upper water column. Standard inverse modeling techniques that minimize error between the modeled and observed Rrs(λ) break down when the number of products retrieved becomes similar to, or greater than, the number of different ocean color wavelengths measured. Furthermore, most conventional ocean reflectance inversion approaches, such as the default configuration of NASA's Generalized Inherent Optical Properties algorithm framework (GIOP-DC), require a priori definitions of absorption and backscattering spectral shapes. A Bayesian approach to GIOP is implemented here to address these limitations, where the retrieval algorithm minimizes both the error in retrieved ocean color and the deviation from prior knowledge, calculated using output from a mixture of empirically-derived and best-fit values. The Bayesian approach offers potential to produce an expanded range of parameters related to the spectral shape of absorption and backscattering spectra.
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19
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Niu J, Feng Z, He M, Xie M, Lv Y, Zhang J, Sun L, Liu Q, Hu BX. Incorporating marine particulate carbon into machine learning for accurate estimation of coastal chlorophyll-a. MARINE POLLUTION BULLETIN 2023; 192:115089. [PMID: 37267869 DOI: 10.1016/j.marpolbul.2023.115089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 06/04/2023]
Abstract
Accurate predictions of coastal ocean chlorophyll-a (Chl-a) concentrations are necessary for dynamic water quality monitoring, with eutrophication as a critical factor. Prior studies that used the driven-data method have typically overlooked the relationship between Chl-a and marine particulate carbon. To address this gap, marine particulate carbon was incorporated into machine learning (ML) and deep learning (DL) models to estimate Chl-a concentrations in the Yang Jiang coastal ocean of China. Incorporating particulate organic carbon (POC) and particulate inorganic carbon (PIC) as predictors can lead to successful Chl-a estimation. The Gaussian process regression (GPR) model significantly outperforming the DL model in terms of stability and robustness. A lower POC/Chl-a ratio was observed in coastal areas, in contrast to the higher ratios detected in the southern regions of the study area. This study highlights the efficacy of the GPR model for estimating Chl-a and the importance of considering POC in modeling Chl-a concentrations.
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Affiliation(s)
- Jie Niu
- College of Resources and Environmental Engineering, Guizhou University, Guiyang 550025, China
| | - Ziyang Feng
- Research Center of Red Tides and Marine Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Mingxia He
- School of Water Resources and Environment, China University of Geosciences, Beijing 10083, China.
| | - Mengyu Xie
- School of Environment, Jinan University, Guangzhou 510632, China
| | - Yanqun Lv
- School of Environment, Jinan University, Guangzhou 510632, China
| | - Juan Zhang
- College of Geographic and Environmental Science, Tianjin Normal University, Tianjin 300387, China
| | - Liwei Sun
- Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Qi Liu
- Research Center of Red Tides and Marine Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Bill X Hu
- School of Water Conservancy and Environment, University of Jinan, Jinan 250022, China
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20
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Dias AB, Kurian S, Vijayan NT, Gauns M, Khichi R, Pratihary AK, Borker SG, Shenoy DM. Recurrence of Gonyaulax polygramma bloom in the southeastern Arabian Sea. ENVIRONMENTAL MONITORING AND ASSESSMENT 2023; 195:635. [PMID: 37133635 DOI: 10.1007/s10661-023-11278-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 04/19/2023] [Indexed: 05/04/2023]
Abstract
Gonyaulax polygramma, a bloom-forming dinoflagellate, has been repeatedly observed along the southeastern Arabian Sea in recent years. During our study in October 2021, a patch of reddish-brown water was observed in the nearshore waters off Kannur (southwest coast of India) and later identified as Gonyaulax polygramma using scanning electron microscopy (SEM) and HPLC-based phytoplankton marker pigments. Gonyaulax polygramma accounted for 99.4% of the phytoplankton abundance at the bloom location, with high concentrations of peridinin and chlorophyll-a at the study site. High concentration of SiO42- was observed at the bloom site, while other nutrients were lower than the previously reported values. The bloom of Gonyaulax polygramma also resulted in high concentrations of dimethylsulfide, an anti-greenhouse gas, at the bloom site. In addition to onsite observation, Sentinel-3 satellite data was also used in the detection and validation of the observed bloom using the NDCI index. From the satellite image, it was evident that the bloom persisted at the mouth of the rivers during the study period. Since the red tide of Gonyaulax polygramma has been observed recurrently in the southeastern Arabian Sea, it is proposed to use satellites to detect and monitor the bloom on a routine basis.
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Affiliation(s)
- Albertina B Dias
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
| | - Neethu T Vijayan
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Rahul Khichi
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Anil K Pratihary
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Sidhesh G Borker
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Damodar M Shenoy
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
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21
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Hannadige NK, Zhai PW, Werdell PJ, Gao M, Franz BA, Knobelspiesse K, Ibrahim A. Optimizing retrieval spaces of bio-optical models for remote sensing of ocean color. APPLIED OPTICS 2023; 62:3299-3309. [PMID: 37132830 DOI: 10.1364/ao.484082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We investigated the optimal number of independent parameters required to accurately represent spectral remote sensing reflectances (R rs) by performing principal component analysis on quality controlled in situ and synthetic R rs data. We found that retrieval algorithms should be able to retrieve no more than four free parameters from R rs spectra for most ocean waters. In addition, we evaluated the performance of five different bio-optical models with different numbers of free parameters for the direct inversion of in-water inherent optical properties (IOPs) from in situ and synthetic R rs data. The multi-parameter models showed similar performances regardless of the number of parameters. Considering the computational cost associated with larger parameter spaces, we recommend bio-optical models with three free parameters for the use of IOP or joint retrieval algorithms.
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22
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Williams GN, Nocera AC. Bio-optical trends of waters around Valdés Biosphere Reserve: An assessment of the temporal variability based on 20 years of ocean color satellite data. MARINE ENVIRONMENTAL RESEARCH 2023; 186:105923. [PMID: 36854223 DOI: 10.1016/j.marenvres.2023.105923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/23/2023] [Accepted: 02/16/2023] [Indexed: 06/18/2023]
Abstract
Satellite Image Time Series are becoming increasingly available and will continue to do so in the coming years thanks to the launch of space missions which aim to provide a high spatial resolution coverage of the Earth every few days. Bio-optical characteristics and their variation over time have been poorly studied in the Patagonian shelf. In this paper, we present the trends of time series analysis from satellite images that allows us to interpret the variations of bio-optical properties throughout time and their implications for planktonic organisms. The annual and seasonal trends of six variables were analyzed for two different gulfs, Nuevo and San José, in northern Patagonia from January 2003-December 2021. We present the dynamic temporal changes of chlorophyll a (Chla-sat), phytoplankton absorption (Ab_phy), detritus absorption as well as environmental features changes for the sea surface temperature (SST), depth of the euphotic zone (Z_eu) and photosynthetically active radiation (PAR). We found positive trends for SST, Ab_phy at 443 nm and PAR, but negative for Z_eu in Nuevo and San José gulfs. The positive trendlines for SST and negative for Z_eu suggest less availability of nutrients and light. These trends could change the bloom phenology and modify the phytoplankton community structure with implications for the entire food web and the ecosystem services in the VBR.
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Affiliation(s)
- Gabriela N Williams
- Centro para el Estudio de Sistemas Marinos (CESIMAR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Boulevard Brown 2915, Puerto Madryn, Chubut, Argentina.
| | - Ariadna C Nocera
- Centro para el Estudio de Sistemas Marinos (CESIMAR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Boulevard Brown 2915, Puerto Madryn, Chubut, Argentina; Universidad Nacional de la Patagonia San Juan Bosco, Puerto Madryn, Chubut, Argentina
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23
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Siegel DA, DeVries T, Cetinić I, Bisson KM. Quantifying the Ocean's Biological Pump and Its Carbon Cycle Impacts on Global Scales. ANNUAL REVIEW OF MARINE SCIENCE 2023; 15:329-356. [PMID: 36070554 DOI: 10.1146/annurev-marine-040722-115226] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The biological pump transports organic matter, created by phytoplankton productivity in the well-lit surface ocean, to the ocean's dark interior, where it is consumed by animals and heterotrophic microbes and remineralized back to inorganic forms. This downward transport of organic matter sequesters carbon dioxide from exchange with the atmosphere on timescales of months to millennia, depending on where in the water column the respiration occurs. There are three primary export pathways that link the upper ocean to the interior: the gravitational, migrant, and mixing pumps. These pathways are regulated by vastly different mechanisms, making it challenging to quantify the impacts of the biological pump on the global carbon cycle. In this review, we assess progress toward creating a global accounting of carbon export and sequestration via the biological pump and suggest a path toward achieving this goal.
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Affiliation(s)
- David A Siegel
- Earth Research Institute and Department of Geography, University of California, Santa Barbara, California, USA;
| | - Timothy DeVries
- Earth Research Institute and Department of Geography, University of California, Santa Barbara, California, USA;
| | - Ivona Cetinić
- Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, Maryland, USA
- Goddard Earth Sciences Technology and Research (GESTAR) II, Morgan State University, Baltimore, Maryland, USA
| | - Kelsey M Bisson
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
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Zhu X, Guo H, Huang JJ, Tian S, Xu W, Mai Y. An ensemble machine learning model for water quality estimation in coastal area based on remote sensing imagery. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2022; 323:116187. [PMID: 36261960 DOI: 10.1016/j.jenvman.2022.116187] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 09/01/2022] [Accepted: 09/02/2022] [Indexed: 06/16/2023]
Abstract
The accurate estimation of coastal water quality parameters (WQPs) is crucial for decision-makers to manage water resources. Although various machine learning (ML) models have been developed for coastal water quality estimation using remote sensing data, the performance of these models has significant uncertainties when applied to regional scales. To address this issue, an ensemble ML-based model was developed in this study. The ensemble ML model was applied to estimate chlorophyll-a (Chla), turbidity, and dissolved oxygen (DO) based on Sentinel-2 satellite images in Shenzhen Bay, China. The optimal input features for each WQP were selected from eight spectral bands and seven spectral indices. A local explanation strategy termed Shapley Additive Explanations (SHAP) was employed to quantify contributions of each feature to model outputs. In addition, the impacts of three climate factors on the variation of each WQP were analyzed. The results suggested that the ensemble ML models have satisfied performance for Chla (errors = 1.7%), turbidity (errors = 1.5%) and DO estimation (errors = 0.02%). Band 3 (B3) has the highest positive contribution to Chla estimation, while Band Ration Index2 (BR2) has the highest negative contribution to turbidity estimation, and Band 7 (B7) has the highest positive contribution to DO estimation. The spatial patterns of the three WQPs revealed that the water quality deterioration in Shenzhen Bay was mainly influenced by input of terrestrial pollutants from the estuary. Correlation analysis demonstrated that air temperature (Temp) and average air pressure (AAP) exhibited the closest relationship with Chla. DO showed the strongest negative correlation with Temp, while turbidity was not sensitive to Temp, average wind speed (AWS), and AAP. Overall, the ensemble ML model proposed in this study provides an accurate and practical method for long-term Chla, turbidity, and DO estimation in coastal waters.
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Affiliation(s)
- Xiaotong Zhu
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environment Safety,Nankai University, Tianjin, 300071, PR China
| | - Hongwei Guo
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environment Safety,Nankai University, Tianjin, 300071, PR China
| | - Jinhui Jeanne Huang
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environment Safety,Nankai University, Tianjin, 300071, PR China.
| | - Shang Tian
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre for Water and Environment Safety,Nankai University, Tianjin, 300071, PR China
| | - Wang Xu
- Shenzhen Environmental Monitoring Center, Shenzhen, Guangdong, 518049, PR China
| | - Youquan Mai
- Shenzhen Environmental Monitoring Center, Shenzhen, Guangdong, 518049, PR China
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Hu W, Zheng X, Li Y, Du J, Lv Y, Su S, Xiao B, Ye X, Jiang Q, Tan H, Liao B, Chen B. High vulnerability and a big conservation gap: Mapping the vulnerability of coastal scleractinian corals in South China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 847:157363. [PMID: 35843331 DOI: 10.1016/j.scitotenv.2022.157363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 06/29/2022] [Accepted: 07/10/2022] [Indexed: 06/15/2023]
Abstract
Scleractinian corals build the most complex and diverse ecosystems in the ocean with various ecosystem services, yet continue to be degraded by natural and anthropogenic stressors. Despite the rapid decline in scleractinian coral habitats in South China, they are among the least concerning in global coral vulnerability maps. This study developed a rapid assessment approach that combines vulnerability components and species distribution models to map coral vulnerability within a large region based on limited data. The approach contained three aspects including, exposure, habitat suitability, and coral-conservation-based adaptive capacity. The exposure assessment was based on seven indicators, and the habitat suitability was mapped using Maximum Entropy and Random Forest models. Vulnerability of scleractinian corals in South China was spatially evaluated using the approach developed here. The results showed that the average exposure of the study region was 0.62, indicating relatively high pressure. The highest exposure occurred from the east coast of the Leizhou Peninsula to the Pearl River Estuary. Aquaculture and shipping were the most common causes of exposure. Highly suitable habitats for scleractinian corals are concentrated between 18°N-22°N. Only 21.6 % of the potential coral habitats are included in marine protected areas, indicating that there may still be large conservation gaps for scleractinian corals in China. In total, 37.7 % of the potential coral habitats were highly vulnerable, with the highest vulnerability appearing in the Guangdong Province. This study presents the first attempt to map the vulnerability of scleractinian corals along the coast of South China. The proposed approach and findings provide an essential tool and information supporting the sustainable management and conservation of coral reef ecosystems, addressing an important gap on the world's coral reef vulnerability map.
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Affiliation(s)
- Wenjia Hu
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; Observation and Research Station of Island and Coastal Ecosystems in the Western Taiwan Strait, Ministry of Natural Resources, Xiamen 361005, China; Fujian Provincial Station for Field Observation and Research of Island and Coastal Zone, Zhangzhou 363216, China
| | - Xinqing Zheng
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; Observation and Research Station of Island and Coastal Ecosystems in the Western Taiwan Strait, Ministry of Natural Resources, Xiamen 361005, China; Fujian Provincial Station for Field Observation and Research of Island and Coastal Zone, Zhangzhou 363216, China; Observation and Research Station of wetland Ecosystem in the Beibu Gulf, Ministry of Natural Resources, Xiamen 361005, China.
| | - Yuanchao Li
- Hainan Academy of Ocean and Fisheries Sciences, Haikou 571199, China
| | - Jianguo Du
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; Observation and Research Station of Island and Coastal Ecosystems in the Western Taiwan Strait, Ministry of Natural Resources, Xiamen 361005, China; Fujian Provincial Station for Field Observation and Research of Island and Coastal Zone, Zhangzhou 363216, China
| | - Yihua Lv
- South China Sea Environmental Monitoring Center, State Oceanic Administration, Guangzhou 528248, China
| | - Shangke Su
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
| | - Baohua Xiao
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China
| | - Xiaomin Ye
- Key Laboratory of Space Ocean Remote Sensing and Application, National Satellite Ocean Application Service, Ministry of Natural Resources, Beijing 100081, China
| | - Qutu Jiang
- Department of Geography, The University of Hong Kong, Hong Kong 999077, China
| | - Hongjian Tan
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
| | - Baolin Liao
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China
| | - Bin Chen
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; Observation and Research Station of Island and Coastal Ecosystems in the Western Taiwan Strait, Ministry of Natural Resources, Xiamen 361005, China; Fujian Provincial Station for Field Observation and Research of Island and Coastal Zone, Zhangzhou 363216, China; Observation and Research Station of wetland Ecosystem in the Beibu Gulf, Ministry of Natural Resources, Xiamen 361005, China.
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Turner KJ, Tzortziou M, Grunert BK, Goes J, Sherman J. Optical classification of an urbanized estuary using hyperspectral remote sensing reflectance. OPTICS EXPRESS 2022; 30:41590-41612. [PMID: 36366633 DOI: 10.1364/oe.472765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Optical water classification based on remote sensing reflectance (Rrs(λ)) data can provide insight into water components driving optical variability and inform the development and application of bio-optical algorithms in complex aquatic systems. In this study, we use an in situ dataset consisting of hyperspectral Rrs(λ) and other biogeochemical and optical parameters collected over nearly five years across a heavily urbanized estuary, the Long Island Sound (LIS), east of New York City, USA, to optically classify LIS waters based on Rrs(λ) spectral shape. We investigate the similarities and differences of discrete groupings (k-means clustering) and continuous spectral indexing using the Apparent Visible Wavelength (AVW) in relation to system biogeochemistry and water properties. Our Rrs(λ) dataset in LIS was best described by three spectral clusters, the first two accounting for the majority (89%) of Rrs(λ) observations and primarily driven by phytoplankton dynamics, with the third confined to measurements in river and river plume waters. We found AVW effective at tracking subtle changes in Rrs(λ) spectral shape and fine-scale water quality features along river-to-ocean gradients. The recently developed Quality Water Index Polynomial (QWIP) was applied to evaluate three different atmospheric correction approaches for satellite-derived Rrs(λ) from the Sentinel-3 Ocean and Land Colour Instrument (OLCI) sensor in LIS, finding Polymer to be the preferred approach. Our results suggest that integrative, continuous indices such as AVW can be effective indicators to assess nearshore biogeochemical variability and evaluate the quality of both in situ and satellite bio-optical datasets, as needed for improved ecosystem and water resource management in LIS and similar regions.
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Kolluru S, Tiwari SP. Modeling ocean surface chlorophyll-a concentration from ocean color remote sensing reflectance in global waters using machine learning. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 844:157191. [PMID: 35810889 DOI: 10.1016/j.scitotenv.2022.157191] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 07/01/2022] [Accepted: 07/02/2022] [Indexed: 06/15/2023]
Abstract
The spatial and temporal variations of Chlorophyll-a (Chl-a) in clear and coastal waters are critical for assessing the health of the marine environment. Machine learning models have been proven to model complex relationships and provide better accuracy estimates of the derived parameters compared to traditional empirical models. The present study proposes a novel approach to derive Chl-a by using multi-layer perceptron Neural Network (MLPNN) with Resilient backpropagation method based on the four ocean color bands existent in most of the ocean color sensors. The NNs are trained on NASA's bio-optical Marine Algorithm Dataset (NOMAD) and tested on three different datasets (i) SeaWiFS and, (ii) MODIS Aqua matchup dataset, and (iii) simulated dataset for the Red Sea. These three datasets cover significant variations range in Chl-a levels under both oligotrophic and eutrophic conditions. The influence of different variations in inputs used in NN training is assessed and hyperparameter tuning of the NN is performed to obtain best NN configuration to derive Chl-a. Accuracy assessment of the present study with other global algorithms are performed by comparing the modeled and observed values of the Chl-a. The performance matrices computed from the developed model were promising. Therefore, this study provides a potential approach for the retrieval of improved Chl-a estimates in the global clear and coastal waters as compared to the traditional blue-green band ratio algorithms. Furthermore, the developed algorithm and existing algorithms are applied to SeaWiFS, MODIS, VIIRS, and Hawkeye satellite ocean color data to demonstrate how it may be utilized to accurately depict the spatial distribution of ocean color features in global waters, phytoplankton blooms and some of the physical processes in the Arabian Sea and the Red Sea. The findings of this work have potential to advance the ocean color remote sensing and biogeochemical cycles and processes in coastal and open ocean waters.
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Affiliation(s)
- Srinivas Kolluru
- Harbor Branch Oceanographic Institute, Florida Atlantic University, FL 34946, USA; Centre of Studies in Resources Engineering, Indian Institute of Technology Bombay, Bombay 400076, India
| | - Surya Prakash Tiwari
- Applied Research Center for Environment and Marine Studies, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
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28
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Zhang H, Li J, Liu Q, Lin S, Huete A, Liu L, Croft H, Clevers JGPW, Zeng Y, Wang X, Gu C, Zhang Z, Zhao J, Dong Y, Mumtaz F, Yu W. A novel red‐edge spectral index for retrieving the leaf chlorophyll content. Methods Ecol Evol 2022. [DOI: 10.1111/2041-210x.13994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Hu Zhang
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
- University of Chinese Academy of Sciences Beijing China
| | - Jing Li
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
- University of Chinese Academy of Sciences Beijing China
| | - Qinhuo Liu
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
- University of Chinese Academy of Sciences Beijing China
| | - Shangrong Lin
- School of Atmospheric Sciences, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Sun Yat‐sen University Zhuhai China
| | - Alfredo Huete
- School of Life Sciences University of Technology Sydney Broadway New South Wales Australia
| | - Liangyun Liu
- Key Laboratory of Digital Earth, Aerospace Information Research Institute Chinese Academy of Sciences Beijing China
| | - Holly Croft
- Department of Animal and Plant Sciences University of Sheffield Sheffield UK
| | - Jan G. P. W. Clevers
- Laboratory of Geo‐Information Science and Remote Sensing Wageningen University & Research Wageningen The Netherlands
| | - Yelu Zeng
- College of Land Science and Technology China Agricultural University Beijing China
| | - Xiaohan Wang
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
- University of Chinese Academy of Sciences Beijing China
| | - Chenpeng Gu
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
- University of Chinese Academy of Sciences Beijing China
| | - Zhaoxing Zhang
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
| | - Jing Zhao
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
| | - Yadong Dong
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
| | - Faisal Mumtaz
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
- University of Chinese Academy of Sciences Beijing China
| | - Wentao Yu
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences Beijing Normal University Beijing China
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29
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Neeley AR, Lomas MW, Mannino A, Thomas C, Vandermeulen R. Impact of Growth Phase, Pigment Adaptation, and Climate Change Conditions on the Cellular Pigment and Carbon Content of Fifty-One Phytoplankton Isolates. JOURNAL OF PHYCOLOGY 2022; 58:669-690. [PMID: 35844156 DOI: 10.1111/jpy.13279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
Owing to their importance in aquatic ecosystems, the demand for models that estimate phytoplankton biomass and community composition in the global ocean has increased over the last decade. Moreover, the impacts of climate change, including elevated carbon dioxide (CO2 ), increased stratification, and warmer sea surface temperatures, will likely shape phytoplankton community composition in the global ocean. Chemotaxonomic methods are useful for modeling phytoplankton community composition from marker pigments normalized to chlorophyll a (Chl a). However, photosynthetic pigments, particularly Chl a, are sensitive to nutrient and light conditions. Cellular carbon is less sensitive, so using carbon biomass instead may provide an alternative approach. To this end, cellular pigment and carbon concentrations were measured in 51 strains of globally relevant, cultured phytoplankton. Pigment-to-Chl a and pigment-to-carbon ratios were computed for each strain. For 25 strains, measurements were taken during two growth phases. While some differences between growth phases were observed, they did not exceed within-class differences. Multiple strains of Amphidinium carterae, Ditylum brightwellii and Heterosigma akashiwo were measured to determine whether time in culture influenced pigment and carbon composition. No appreciable trends in cellular pigment or carbon content were observed. Lastly, the potential impact of climate change conditions on the pigment ratios was assessed using a multistressor experiment that included increased mean light, temperature, and elevated pCO2 on three species: Thalassiosira oceanica, Ostreococcus lucimarinus, and Synechococcus. The largest differences were observed in the pigment-to-carbon ratios, while the marker pigments largely covaried with Chl a. The implications of these observations to chemotaxonomic applications are discussed.
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Affiliation(s)
- Aimee R Neeley
- NASA Goddard Space Flight Center/Science Systems and Applications Inc., Greenbelt, Maryland, 20771, USA
| | - Michael W Lomas
- Bigelow Laboratory for Ocean Sciences, Bigelow Institute of Ocean Sciences, East Boothbay, Maine, 04544, USA
| | - Antonio Mannino
- NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA
| | - Crystal Thomas
- NASA Goddard Space Flight Center/Science Systems and Applications Inc., Greenbelt, Maryland, 20771, USA
| | - Ryan Vandermeulen
- NASA Goddard Space Flight Center/Science Systems and Applications Inc., Greenbelt, Maryland, 20771, USA
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Mohseni F, Saba F, Mirmazloumi SM, Amani M, Mokhtarzade M, Jamali S, Mahdavi S. Ocean water quality monitoring using remote sensing techniques: A review. MARINE ENVIRONMENTAL RESEARCH 2022; 180:105701. [PMID: 35939895 DOI: 10.1016/j.marenvres.2022.105701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 07/09/2022] [Accepted: 07/10/2022] [Indexed: 06/15/2023]
Abstract
Ocean Water Quality (OWQ) monitoring provides insights into the quality of water in marine and near-shore environments. OWQ measurements can contain the physical, chemical, and biological characteristics of oceanic waters, where low OWQ values indicate an unhealthy ecosystem. Many parameters of water can be estimated from Remote Sensing (RS) data. Thus, RS offers significant opportunities for monitoring water quality in estuaries, coastal waterways, and the ocean. This paper reviews various RS systems and techniques for OWQ monitoring. It first introduces the common OWQ parameters, followed by the definition of the parameters and techniques of OWQ monitoring with RS techniques. In this study, the following OWQ parameters were reviewed: chlorophyll-a, colored dissolved organic matter, turbidity or total suspended matter/solid, dissolved organic carbon, Secchi disk depth, suspended sediment concentration, and sea surface temperature. This study presents a systematic analysis of the capabilities and types of spaceborne systems (e.g., optical and thermal sensors, passive microwave radiometers, active microwave scatterometers, and altimeters) which are commonly applied to OWQ assessment. The paper also provides a summary of the opportunities and limitations of RS data for spatial and temporal estimation of OWQ. Overall, it was observed that chlorophyll-a and colored dissolved organic matter are the dominant parameters applied to OWQ monitoring. It was also concluded that the data from optical and passive microwave sensors could effectively be applied to estimate OWQ parameters. From a methodological perspective, semi-empirical algorithms generally outperform the other empirical, analytical, and semi-analytical methods for OWQ monitoring.
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Affiliation(s)
- Farzane Mohseni
- Faculty of Geodesy and Geomatics Engineering, K. N. Toosi University of Technology, Tehran, Iran; Department of Technology and Society, Faculty of Engineering, Lund University, P.O. Box 118, 221 00, Lund, Sweden.
| | - Fatemeh Saba
- Faculty of Geodesy and Geomatics Engineering, K. N. Toosi University of Technology, Tehran, Iran.
| | - S Mohammad Mirmazloumi
- Centre Tecnològic de Telecommunications de Catalunya (CTTC/CERCA), Geomatics Research Unit, Av. Gauss 7, E-08860, Castelldefels, Barcelona, Spain.
| | - Meisam Amani
- Wood Environment and Infrastructure Solutions, Ottawa, ON, K2E 7L5, Canada.
| | - Mehdi Mokhtarzade
- Faculty of Geodesy and Geomatics Engineering, K. N. Toosi University of Technology, Tehran, Iran.
| | - Sadegh Jamali
- Department of Technology and Society, Faculty of Engineering, Lund University, P.O. Box 118, 221 00, Lund, Sweden.
| | - Sahel Mahdavi
- Wood Environment and Infrastructure Solutions, Ottawa, ON, K2E 7L5, Canada.
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Application of a PLS-Augmented ANN Model for Retrieving Chlorophyll-a from Hyperspectral Data in Case 2 Waters of the Western Basin of Lake Erie. REMOTE SENSING 2022. [DOI: 10.3390/rs14153729] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We present results that demonstrate the utility of machine learning techniques that are based on partial least squares (PLS) and artificial neural networks (ANNs) for estimating low-moderate chlorophyll-a (chl-a) concentrations in the western basin of Lake Erie (WBLE). Previous ocean color studies have resulted in a large number of algorithms that are based on spectral indices to estimate water quality parameters (WQPs) such as chl-a concentration from remote sensing reflectance. However, these spectral index algorithms are based on reflectance features at specific wavelengths and do not take advantage of the wealth of spectral information that is contained in hyperspectral data, and are often not easily adaptable to waters with conditions that are different from those in the datasets that were used to originally calibrate the indices. Recently, there have been efforts to use machine learning techniques that are based on ANNs and PLS regression to exploit the spectral richness contained in hyperspectral data and retrieve WQPs. In this study, we have combined an ANN model with output from PLS regression to retrieve chl-a concentration from hyperspectral data in the WBLE. We compared the results from the PLS-ANN method to those that were obtained from a band-ratio algorithm that is based on reflectances in the blue and green spectral regions, a band ratio algorithm that is based on reflectances in the red and near-infrared (NIR) spectral regions, and a PLS-only approach. For a dataset that was collected in 2012, with chl-a concentrations ranging from 0.48 to 21.2 µg/L, the PLS-ANN method yielded a root mean square error (RMSE) of 1.22 µg/L, whereas the blue-green ratio algorithm yielded an RMSE of 1.75 µg/L, the NIR-red ratio algorithm yielded an RMSE of 1.95 µg/L, and the PLS-only approach yielded an RMSE of 1.95 µg/L. The PLS-ANN method takes advantage of the PLS regression to identify specific wavelengths that contain most information about the variation in chl-a concentration, minimize spectral collinearity and redundancy in the data, and simplify the neural network’s input structure. The better performance of the PLS-ANN method can also be attributed to the neural network’s ability to account for nonlinearity in the relationship between chl-a concentration and spectral reflectance. The results indicate that the PLS-ANN method can be reliably used to estimate and monitor low-moderate chl-a concentrations in optically complex waters.
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Zhang J, Fu P, Meng F, Yang X, Xu J, Cui Y. Estimation algorithm for chlorophyll-a concentrations in water from hyperspectral images based on feature derivation and ensemble learning. ECOL INFORM 2022. [DOI: 10.1016/j.ecoinf.2022.101783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Improvement and Assessment of Ocean Color Algorithms in the Northwest Pacific Fishing Ground Using Himawari-8, MODIS-Aqua, and VIIRS-SNPP. REMOTE SENSING 2022. [DOI: 10.3390/rs14153610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chlorophyll-a (Chl-a) is an important marine indicator, and the improvement in Chl-a concentration retrieval for ocean color remote sensing is always a major challenge. This study focuses on the northwest Pacific fishing ground (NPFG) to evaluate and improve the Chl-a products of three mainstream remote sensing satellites, Himawari-8, MODIS-Aqua, and VIIRS-SNPP. We analyzed in situ data and found that an in situ Chl-a concentration of 0.3 mg m−3 could be used as a threshold to distinguish the systematic deviation of remote sensing Chl-a data in the NPFG. Based on this threshold, we optimized the Chl-a algorithms of the three satellites by data grouping, and integrated multisource satellite Chl-a data by weighted averaging to acquire high-coverage merged data. The merged data were thoroughly verified by Argo Chl-a data. The Chl-a front of merged Chl-a data could be represented accurately and completely and had a good correlation with the distribution of the NPFG. The most important marine factors for Chl-a are nutrients and temperature, which are affected by mesoscale eddies and variations in the Kuroshio extension. The variation trend of merged Chl-a data is consistent with mesoscale eddies and Kuroshio extension and has more sensitive responses to the marine climatic conditions of ENSO.
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An Artificial Neural Network Algorithm to Retrieve Chlorophyll a for Northwest European Shelf Seas from Top of Atmosphere Ocean Colour Reflectance. REMOTE SENSING 2022. [DOI: 10.3390/rs14143353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Chlorophyll-a (Chl) retrieval from ocean colour remote sensing is problematic for relatively turbid coastal waters due to the impact of non-algal materials on atmospheric correction and standard Chl algorithm performance. Artificial neural networks (NNs) provide an alternative approach for retrieval of Chl from space and results for northwest European shelf seas over the 2002–2020 period are shown. The NNs operate on 15 MODIS-Aqua visible and infrared bands and are tested using bottom of atmosphere (BOA), top of atmosphere (TOA) and Rayleigh corrected TOA reflectances (RC). In each case, a NN architecture consisting of 3 layers of 15 neurons improved performance and data availability compared to current state-of-the-art algorithms used in the region. The NN operating on TOA reflectance outperformed BOA and RC versions. By operating on TOA reflectance data, the NN approach overcomes the common but difficult problem of atmospheric correction in coastal waters. Moreover, the NN provides data for regions which other algorithms often mask out for turbid water or low zenith angle flags. A distinguishing feature of the NN approach is generation of associated product uncertainties based on multiple resampling of the training data set to produce a distribution of values for each pixel, and an example is shown for a coastal time series in the North Sea. The final output of the NN approach consists of a best-estimate image based on medians for each pixel, and a second image representing uncertainty based on standard deviation for each pixel, providing pixel-specific estimates of uncertainty in the final product.
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35
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Satellite Observation of the Long-Term Dynamics of Particulate Organic Carbon in the East China Sea Based on a Hybrid Algorithm. REMOTE SENSING 2022. [DOI: 10.3390/rs14133220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
The distribution pattern and flux variation of POC in the continental shelf seas are essential for understanding the carbon cycle in marginal seas. The hydrodynamic environment and complicated estuarine processes in the East China Sea result in challenging estimates and substantial spatio-temporal variability in terms of POC concentrations. A hybrid retrieval model based on the mutual combination of the color index algorithm (CIPOC) and the empirical band ratio algorithm was applied in this study to effectively and dynamically monitor the surface POC concentration in the East China Sea in a long-term series for the first time using MODIS/Aqua remote sensing satellite data from 2003 to 2020. A hybrid retrieval model based on the mutual combination of the color index algorithm (CIPOC) and the empirical band ratio algorithm was applied in this study. The MODIS/Aqua remote sensing satellite data from 2003 to 2020 were employed for the first time to dynamically monitor the surface POC concentrations in the East China Sea for a long time series. The results demonstrated that the performance (R2 = 0.84, RMSE = 156.14 mg/m3, MAPE = 43.30%, bias = −64.79 mg/m3) exhibited by this hybrid retrieval algorithm confirms the usability of inversion studies of surface POC in the East China Sea. Different drivers such as river discharge, phytoplankton, wind, and the sea surface current field jointly influence the spatial and temporal distribution of POC concentrations in the East China Sea. This paper also verifies that the hybrid algorithm can be applied to retrieval tasks for POC in different seas with similar optical properties to the waters of the East China Sea. In conclusion, the long-term series East China Sea POC data record, which was established based on MODIS/Aqua, provides supplementary information for in-situ sampling, which will aid the long-term monitoring of POC fluxes in shelf seas. At the same time, it has also improved our understanding of the transport and spatio-temporal variability of POC in the East China Sea, enhancing our comprehension of the impact of POC on environmental changes and carbon cycling in marginal seas.
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Use of the Sentinel-2 and Landsat-8 Satellites for Water Quality Monitoring: An Early Warning Tool in the Mar Menor Coastal Lagoon. REMOTE SENSING 2022. [DOI: 10.3390/rs14122744] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
During recent years, several eutrophication processes and subsequent environmental crises have occurred in Mar Menor, the largest hypersaline coastal lagoon in the Western Mediterranean Sea. In this study, the Landsat-8 and Sentinel-2 satellites are jointly used to examine the evolution of the main water quality descriptors during the latest ecological crisis in 2021, resulting in an important loss of benthic vegetation and unusual mortality events affecting different aquatic species. Several field campaigns were carried out in March, July, August, and November 2021 to measure water quality variables over 10 control points. The validation of satellite biogeochemical variables against on-site measurements indicates precise results of the water quality algorithms with median errors of 0.41 mg/m3 and 2.04 FNU for chlorophyll-a and turbidity, respectively. The satellite preprocessing scheme shows consistent performance for both satellites; therefore, using them in tandem can improve mapping strategies. The findings demonstrate the suitability of the methodology to capture the spatiotemporal distribution of turbidity and chlorophyll-a concentration at 10–30 m spatial resolution on a systematic basis and in a cost-effective way. The multitemporal products allow the identification of the main critical areas close to the mouth of the Albujon watercourse and the beginning of the eutrophication process with chlorophyll-a concentration above 3 mg/m3. These innovative tools can support decision makers in improving current monitoring strategies as early warning systems for timely assistance during these ecological disasters, thus preventing detrimental conditions in the lagoon.
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OC4-SO: A New Chlorophyll-a Algorithm for the Western Antarctic Peninsula Using Multi-Sensor Satellite Data. REMOTE SENSING 2022. [DOI: 10.3390/rs14051052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chlorophyll-a (Chl-a) underestimation by global satellite algorithms in the Southern Ocean has long been reported, reducing their accuracy, and limiting the potential for evaluating phytoplankton biomass. As a result, several regional Chl-a algorithms have been proposed. The present work aims at assessing the performance of both global and regional satellite algorithms that are currently available for the Western Antarctic Peninsula (WAP) and investigate which factors are contributing to the underestimation of Chl-a. Our study indicates that a global algorithm, on average, underestimates in-situ Chl-a by ~59%, although underestimation was only observed for waters with Chl-a > 0.5 mg m−3. In high Chl-a waters (>1 mg m−3), Chl-a underestimation rose to nearly 80%. Contrary to previous studies, no clear link was found between Chl-a underestimation and the pigment packaging effect, nor with the phytoplankton community composition and sea ice contamination. Based on multi-sensor satellite data and the most comprehensive in-situ dataset ever collected from the WAP, a new, more accurate satellite Chl-a algorithm is proposed: the OC4-SO. The OC4-SO has great potential to become an important tool not only for the ocean colour community, but also for an effective monitoring of the phytoplankton communities in a climatically sensitive region where in-situ data are scarce.
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Dev PJ, Sukenik A, Mishra DR, Ostrovsky I. Cyanobacterial pigment concentrations in inland waters: Novel semi-analytical algorithms for multi- and hyperspectral remote sensing data. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 805:150423. [PMID: 34818810 DOI: 10.1016/j.scitotenv.2021.150423] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 08/18/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
Cyanobacteria are notorious for producing harmful algal blooms that present an ever-increasing serious threat to aquatic ecosystems worldwide, impacting the quality of drinking water and disrupting the recreational use of many water bodies. Remote sensing techniques for the detection and quantification of cyanobacterial blooms are required to monitor their initiation and spatiotemporal variability. In this study, we developed a novel semi-analytical approach to estimate the concentration of cyanobacteria-specific pigment phycocyanin (PC) and common phytoplankton pigment chlorophyll a (Chl a) from hyperspectral remote sensing data. The PC algorithm was derived from absorbance-concentration relationship, and the Chl a algorithm was devised based on a conceptual three-band structure model. The developed algorithms were applied to satellite imageries obtained by the Hyperspectral Imager for the Coastal Ocean (HICO™) sensor and tested in Lake Kinneret (Israel) during strong cyanobacterium Microcystis sp. bloom and out-of-bloom times. The sensitivity of the algorithms to errors was evaluated. The Chl a and PC concentrations were estimated with a mean absolute percentage difference (MAPD) of 16% and 28%, respectively. Sensitivity analysis shows that the influences of backscattering and other water constituents do not affect the estimation accuracy of PC (~2% MAPD). The reliable PC/Chl a ratios can be obtained at PC concentrations above 10 mg m-3. The computed PC/Chl a ratio depicts the contribution of cyanobacteria to the total phytoplankton biomass and permits investigating the role of ambient factors in the formation of a complex planktonic community. The novel algorithms have extensive practical applicability and should be suitable for the quantification of PC and Chl a in aquatic ecosystems using hyperspectral remote sensing data as well as data from future multispectral remote sensing satellites, if the respective bands are featured in the sensor.
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Affiliation(s)
- Pravin Jeba Dev
- Israel Oceanographic and Limnological Research, The Yigal Allon Kinneret Limnological Laboratory, Migdal 14950, Israel
| | - Assaf Sukenik
- Israel Oceanographic and Limnological Research, The Yigal Allon Kinneret Limnological Laboratory, Migdal 14950, Israel
| | - Deepak R Mishra
- Department of Geography, University of Georgia, Athens 30602, GA, USA
| | - Ilia Ostrovsky
- Israel Oceanographic and Limnological Research, The Yigal Allon Kinneret Limnological Laboratory, Migdal 14950, Israel.
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Mapping Chlorophyll-a Concentrations in the Kaštela Bay and Brač Channel Using Ridge Regression and Sentinel-2 Satellite Images. ELECTRONICS 2021. [DOI: 10.3390/electronics10233004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In this paper, we describe a method for the prediction of concentration of chlorophyll-a (Chl-a) from satellite data in the coastal waters of Kaštela Bay and the Brač Channel (our case study areas) in the Republic of Croatia. Chl-a is one of the parameters that indicates water quality and that can be measured by in situ measurements or approximated as an optical parameter with remote sensing. Remote sensing products for monitoring Chl-a are mostly based on the ocean and open sea monitoring and are not accurate for coastal waters. In this paper, we propose a method for remote sensing monitoring that is locally tailored to suit the focused area. This method is based on a data set constructed by merging Sentinel 2 Level-2A satellite data with in situ Chl-a measurements. We augmented the data set horizontally by transforming the original feature set, and vertically by adding synthesized zero measurements for locations without Chl-a. By transforming features, we were able to achieve a sophisticated model that predicts Chl-a from combinations of features representing transformed bands. Multiple Linear Regression equation was derived to calculate Chl-a concentration and evaluated quantitatively and qualitatively. Quantitative evaluation resulted in R2 scores 0.685 and 0.659 for train and test part of data set, respectively. A map of Chl-a of the case study area was generated with our model for the dates of the known incidents of algae blooms. The results that we obtained are discussed in this paper.
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Seegers BN, Werdell PJ, Vandermeulen RA, Salls W, Stumpf RP, Schaeffer BA, Owens TJ, Bailey SW, Scott JP, Loftin KA. Satellites for long-term monitoring of inland U.S. lakes: The MERIS time series and application for chlorophyll-a. REMOTE SENSING OF ENVIRONMENT 2021; 266:1-14. [PMID: 36424983 PMCID: PMC9680834 DOI: 10.1016/j.rse.2021.112685] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Lakes and other surface fresh waterbodies provide drinking water, recreational and economic opportunities, food, and other critical support for humans, aquatic life, and ecosystem health. Lakes are also productive ecosystems that provide habitats and influence global cycles. Chlorophyll concentration provides a common metric of water quality, and is frequently used as a proxy for lake trophic state. Here, we document the generation and distribution of the complete MEdium Resolution Imaging Spectrometer (MERIS; Appendix A provides a complete list of abbreviations) radiometric time series for over 2300 satellite resolvable inland bodies of water across the contiguous United States (CONUS) and more than 5,000 in Alaska. This contribution greatly increases the ease of use of satellite remote sensing data for inland water quality monitoring, as well as highlights new horizons in inland water remote sensing algorithm development. We evaluate the performance of satellite remote sensing Cyanobacteria Index (CI)-based chlorophyll algorithms, the retrievals for which provide surrogate estimates of phytoplankton concentrations in cyanobacteria dominated lakes. Our analysis quantifies the algorithms' abilities to assess lake trophic state across the CONUS. As a case study, we apply a bootstrapping approach to derive a new CI-to-chlorophyll relationship, ChlBS, which performs relatively well with a multiplicative bias of 1.11 (11%) and mean absolute error of 1.60 (60%). While the primary contribution of this work is the distribution of the MERIS radiometric timeseries, we provide this case study as a roadmap for future stakeholders' algorithm development activities, as well as a tool to assess the strengths and weaknesses of applying a single algorithm across CONUS.
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Affiliation(s)
- Bridget N. Seegers
- NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, MD 20771, USA
- Universities Space Research Association (USRA), Columbia, MD 21046, USA
| | - P. Jeremy Werdell
- NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, MD 20771, USA
| | - Ryan A. Vandermeulen
- NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, MD 20771, USA
- Science Systems and Applications Inc., Lanham, MD 20706, USA
| | - Wilson Salls
- U.S. Environmental Protection Agency, Office of Research and Development, Durham, NC 27711, USA
| | | | - Blake A. Schaeffer
- U.S. Environmental Protection Agency, Office of Research and Development, Durham, NC 27711, USA
| | - Tommy J. Owens
- NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, MD 20771, USA
- Science Application International Corp., Reston, VA 20190, USA
| | - Sean W. Bailey
- NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, MD 20771, USA
| | - Joel P. Scott
- NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, MD 20771, USA
- Science Application International Corp., Reston, VA 20190, USA
| | - Keith A. Loftin
- U.S. Geological Survey, Kansas Water Science Center, Lawrence, KS 66049, USA
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Consistent Multi-Mission Measures of Inland Water Algal Bloom Spatial Extent Using MERIS, MODIS and OLCI. REMOTE SENSING 2021. [DOI: 10.3390/rs13173349] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Envisat’s MERIS and its successor Sentinel OLCI have proven invaluable for documenting algal bloom conditions in coastal and inland waters. Observations over turbid eutrophic waters, in particular, have benefited from the band at 708 nm, which captures the reflectance peak associated with intense algal blooms and is key to line-height algorithms such as the Maximum Chlorophyll Index (MCI). With the MERIS mission ending in early 2012 and OLCI launched in 2016, however, time-series studies relying on these two sensors have to contend with an observation gap spanning four years. Alternate sensors, such as MODIS Aqua, offering neither the same spectral band configuration nor consistent spatial resolution, present challenges in ensuring continuity in derived bloom products. This study explores a neural network (NN) solution to fill the observation gap between MERIS and OLCI with MODIS Aqua data, delivering consistent algal bloom spatial extent products from 2002 to 2020 using these three sensors. With 14 bands of MODIS level 2 partially atmospherically corrected spectral reflectance as the NN input, the missing MERIS/OLCI band at 708 nm required for the MCI is simulated. The resulting NN-derived MODIS MCI (NNMCI) is shown to be in good agreement with MERIS and OLCI MCI in 2011 and 2017 respectively over the western basin of Lake Erie (R2 = 0.84, RMSE = 0.0032). To overcome the impact of MODIS sensor saturation over bright water targets, which otherwise renders pixels unusable for bloom detection using R-NIR wavebands, a variant NN model is employed which uses the 9 MODIS bands with the lowest probability of saturation to simulate the MCI. This variant NN predicts MCI with only a small increase in uncertainty (R2 = 0.73, RMSE = 0.005) allowing reliable estimates of bloom conditions in those previously unreported pixels. The NNMCI is shown to be robust when applied beyond the initial training dataset on Lake Erie, and when re-trained on different geographic areas (Lake Winnipeg and Lake of the Woods). Despite differences in spatial, temporal, and spectral resolution, MODIS algal bloom presence/absence was correctly classified in >92% of cases and bloom spatial extent derived within 25% uncertainty, allowing the application to the 2012–2015 time period to form a continuous and consistent multi-mission monitoring dataset from 2002 to 2020.
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Wei J, Wang M, Jiang L, Yu X, Mikelsons K, Shen F. Global Estimation of Suspended Particulate Matter From Satellite Ocean Color Imagery. JOURNAL OF GEOPHYSICAL RESEARCH. OCEANS 2021; 126:e2021JC017303. [PMID: 35844263 PMCID: PMC9285372 DOI: 10.1029/2021jc017303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 06/15/2023]
Abstract
The suspended particulate matter (SPM) concentration (unit: mg l-1) in surface waters is an essential measure of water quality and clarity. Satellite remote sensing provides a powerful tool to derive the SPM with synoptic and repeat coverage. In this study, we developed a new global SPM algorithm utilizing the remote sensing reflectance (R rs (λ)) at near-infrared (NIR), red, green, and blue bands (NIR-RGB) as input. The evaluations showed that the NIR-RGB algorithm could predict SPM with the median absolute percentage difference of ∼35%-39% over a wide range from ∼0.01 to >2,000 mg l-1. The uncertainty is smaller (29%-37%) for turbid waters where R rs (671) ≥ 0.0012 sr-1 and slightly higher (41%-44%) for clear waters where R rs (671) < 0.0012 mg l-1. The algorithm was implemented with the global R rs (λ) data from the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. We provided a brief characterization of the spatial distribution and temporal trends of the SPM products in global waters based on the monthly SPM composites. Case studies of the SPM time series in coastal and inland waters suggest that the satellite SPM estimations registered spatial and seasonal variation and episodic events in regional scales as well. The VIIRS-generated global SPM maps provide a valuable addition to the existing ocean color products for environmental and climate applications.
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Affiliation(s)
- Jianwei Wei
- NOAA Center for Satellite Applications and ResearchCollege ParkMDUSA
- Global Science & Technology Inc.GreenbeltMDUSA
| | - Menghua Wang
- NOAA Center for Satellite Applications and ResearchCollege ParkMDUSA
| | - Lide Jiang
- NOAA Center for Satellite Applications and ResearchCollege ParkMDUSA
- Cooperative Institute for Research in the AtmosphereColorado State UniversityFort CollinsCOUSA
| | - Xiaolong Yu
- State Key Laboratory of Marine Environmental ScienceCollege of Ocean and Earth SciencesXiamen UniversityXiamenChina
| | - Karlis Mikelsons
- NOAA Center for Satellite Applications and ResearchCollege ParkMDUSA
- Global Science & Technology Inc.GreenbeltMDUSA
| | - Fang Shen
- State Key Laboratory of Estuarine and Coastal ResearchEast China Normal UniversityShanghaiChina
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Li S, Song K, Wang S, Liu G, Wen Z, Shang Y, Lyu L, Chen F, Xu S, Tao H, Du Y, Fang C, Mu G. Quantification of chlorophyll-a in typical lakes across China using Sentinel-2 MSI imagery with machine learning algorithm. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 778:146271. [PMID: 33721636 DOI: 10.1016/j.scitotenv.2021.146271] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 02/07/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
Lake eutrophication has attracted the attention of the government and general public. Chlorophyll-a (Chl-a) is a key indicator of algal biomass and eutrophication. Many efforts have been devoted to establishing accurate algorithms for estimating Chl-a concentrations. In this study, a total of 273 samples were collected from 45 typical lakes across China during 2017-2019. Here, we proposed applicable machine learning algorithms (i.e., linear regression model (LR), support vector machine model (SVM) and Catboost model (CB)), which integrate a broad scale dataset of lake biogeochemical characteristics using Multispectral Imager (MSI) product to seamlessly retrieve the Chl-a concentration. A K-means clustering approach was used to cluster the 273 normalized water leaving reflectance spectra [Rrs (λ)] extracted from MSI imagery with Case 2 Regional Coast Colour (CR2CC) processor into three groups. The pH, electrical conductivity (EC), total suspended matter (TSM) and dissolved organic carbon (DOC) from three clustering groups had significant differences (p < 0.05**), indicating that water quality parameters have an integrated impact on Rrs(λ)-spectra. The results of machine learning algorithms integrating demonstrated that SVM obtained a better degree of measured- and derived- fitting (calibration: slope = 0.81, R2 = 0.91; validation: slope = 1.21, R2 = 0.88). On the contrary, the documented nine Chl-a algorithms gave poor results (fitting 1:1 linear slope < 0.4 and R2 < 0.70) with synchronous train and test datasets. It demonstrated that machine learning provides a robust model for quantifying Chl-a concentration. Further, considering three Rrs(λ) clustering groups by k-means, Chl-a SVM model indicated that cluster 1 group gave a better retrieving performance (slope = 0.71, R2 = 0.78), followed by cluster 3 group (slope = 0.77, R2 = 0.64) and cluster 2 group (slope = 0.67, R2 = 0.50). These are related to the low TSM and high DOC levels for cluster-1 and cluster-3 Rrs(λ) spectra, which reduce the influence of particle in red bands for Rrs(λ) signal. Our results highlighted the quantification of lake Chl-a concentrations using MSI imagery and SVM, which can realize the large-scale monitoring and more appropriate for medium/low Chl-a level. The remote estimation of Chl-a based on artificial intelligence can provide an effective and robust way to monitor the lake eutrophication on a macro-scale; and offer a better approach to elucidate the response of lake ecosystems to global change.
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Affiliation(s)
- Sijia Li
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China
| | - Kaishan Song
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China.
| | - Shuai Wang
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China
| | - Ge Liu
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China
| | - Zhidan Wen
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China
| | - Yingxin Shang
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China
| | - Lili Lyu
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Fangfang Chen
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China; Key Laboratory of Vegetation Ecology, Ministry of Education, Institute of Grassland Science, Northeast Normal University, Changchun 130024, PR China
| | - Shiqi Xu
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China; Key Laboratory of Vegetation Ecology, Ministry of Education, Institute of Grassland Science, Northeast Normal University, Changchun 130024, PR China
| | - Hui Tao
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Yunxia Du
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Chong Fang
- Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, PR China
| | - Guangyi Mu
- Jilin Provincial Key Laboratory of Municipal Wastewater Treatment, Changchun Institute of Technology, Changchun 130012, PR China
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Inter-Comparison of Methods for Chlorophyll-a Retrieval: Sentinel-2 Time-Series Analysis in Italian Lakes. REMOTE SENSING 2021. [DOI: 10.3390/rs13122381] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Different methods are available for retrieving chlorophyll-a (Chl-a) in inland waters from optical imagery, but there is still a need for an inter-comparison among the products. Such analysis can provide insights into the method selection, integration of products, and algorithm development. This work aims at inter-comparison and consistency analyses among the Chl-a products derived from publicly available methods consisting of Case-2 Regional/Coast Colour (C2RCC), Water Color Simulator (WASI), and OC3 (3-band Ocean Color algorithm). C2RCC and WASI are physics-based processors enabling the retrieval of not only Chl-a but also total suspended matter (TSM) and colored dissolved organic matter (CDOM), whereas OC3 is a broadly used semi-empirical approach for Chl-a estimation. To pursue the inter-comparison analysis, we demonstrate the application of Sentinel-2 imagery in the context of multitemporal retrieval of constituents in some Italian lakes. The analysis is performed for different bio-optical conditions including subalpine lakes in Northern Italy (Garda, Idro, and Ledro) and a turbid lake in Central Italy (Lake Trasimeno). The Chl-a retrievals are assessed versus in situ matchups that indicate the better performance of WASI. Moreover, relative consistency analyses are performed among the products (Chl-a, TSM, and CDOM) derived from different methods. In the subalpine lakes, the results indicate a high consistency between C2RCC and WASI when aCDOM(440) < 0.5 m−1, whereas the retrieval of constituents, particularly Chl-a, is problematic based on C2RCC for high-CDOM cases. In the turbid Lake Trasimeno, the extreme neural network of C2RCC provided more consistent products with WASI than the normal network. OC3 overestimates the Chl-a concentration. The flexibility of WASI in the parametrization of inversion allows for the adaptation of the method for different optical conditions. The implementation of WASI requires more experience, and processing is time demanding for large lakes. This study elaborates on the pros and cons of each method, providing guidelines and criteria on their use.
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Remote Sensing of Dispersed Oil Pollution in the Ocean-The Role of Chlorophyll Concentration. SENSORS 2021; 21:s21103387. [PMID: 34067967 PMCID: PMC8152263 DOI: 10.3390/s21103387] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/08/2021] [Accepted: 05/10/2021] [Indexed: 11/17/2022]
Abstract
In the contrary to surface oil slicks, dispersed oil pollution is not yet detected or monitored on regular basis. The possible range of changes of the local optical properties of seawater caused by the occurrence of dispersed oil, as well as the dependencies of changes on various physical and environmental factors, can be estimated using simulation techniques. Two models were combined to examine the influence of oceanic water type on the visibility of dispersed oil: the Monte Carlo radiative transfer model and the Lorenz-Mie model for spherical oil droplets suspended in seawater. Remote sensing reflectance, Rrs, was compared for natural ocean water models representing oligotrophic, mesotrophic and eutrophic environments (characterized by chlorophyll-a concentrations of 0.1, 1 and 10 mg/m3, respectively) and polluted by three different kinds of oils: biodiesel, lubricant oil and crude oil. We found out that dispersed oil usually increases Rrs values for all types of seawater, with the highest effect for the oligotrophic ocean. In the clearest studied waters, the absolute values of Rrs increased 2-6 times after simulated dispersed oil pollution, while Rrs band ratios routinely applied in bio-optical models decreased up to 80%. The color index, CI, was nearly double reduced by dispersed biodiesel BD and lubricant oil CL, but more than doubled by crude oil FL.
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McKinna LIW, Cetinić I, Werdell PJ. Development and Validation of an Empirical Ocean Color Algorithm with Uncertainties: A Case Study with the Particulate Backscattering Coefficient. JOURNAL OF GEOPHYSICAL RESEARCH. OCEANS 2021; 126:e2021JC017231. [PMID: 34221787 PMCID: PMC8244078 DOI: 10.1029/2021jc017231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/01/2021] [Accepted: 04/10/2021] [Indexed: 06/13/2023]
Abstract
We explored how algorithm (model) and in situ measurement (observation) uncertainties can effectively be incorporated into empirical ocean color model development and assessment. In this study we focused on methods for deriving the particulate backscattering coefficient at 555 nm, b bp (555) (m-1). We developed a simple empirical algorithm for deriving b bp (555) as a function of a remote sensing reflectance line height (LH) metric. Model training was performed using a high-quality bio-optical dataset that contains coincident in situ measurements of the spectral remote sensing reflectances, R rs (λ) (sr-1), and the spectral particulate backscattering coefficients, b bp (λ). The LH metric used is defined as the magnitude of R rs (555) relative to a linear baseline drawn between R rs (490) and R rs (670). Using an independent validation dataset, we compared the skill of the LH-based model with two other models. We used contemporary validation metrics, including bias and mean absolute error (MAE), that were corrected for model and observation uncertainties. The results demonstrated that measurement uncertainties do indeed impact contemporary validation metrics such as mean bias and MAE. Zeta-scores and z-tests for overlapping confidence intervals were also explored as potential methods for assessing model skill.
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Affiliation(s)
| | - Ivona Cetinić
- GESTAR/USRAColumbiaMDUSA
- NASA Goddard Flight CenterGreenbeltMDUSA
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Abstract
Arctic and boreal regions are undergoing dramatic warming and also possess the world’s highest concentration of lakes. However, ecological changes in lakes are poorly understood. We present a continental-scale trend analysis of satellite lake color in the green wavelengths, which shows declining greenness from 1984 to 2019 in Arctic-boreal lakes across western North America. Annual 30-m Landsat composites indicate lake greenness has decreased by 15%. Our findings show a relationship between lake color, rising air temperatures, and increasing precipitation, supporting the theory that warming may be increasing connectivity between lakes and surrounding landscapes. Overall, our results bring a powerful set of observations in support of the hypothesis that lakes are sentinels for global change in rapidly warming Arctic-boreal ecosystems. The highest concentration of the world’s lakes are found in Arctic-boreal regions [C. Verpoorter, T. Kutser, D. A. Seekell, L. J. Tranvik, Geophys. Res. Lett. 41, 6396–6402 (2014)], and consequently are undergoing the most rapid warming [J. E. Overland et al., Arctic Report Card (2018)]. However, the ecological response of Arctic-boreal lakes to warming remains highly uncertain. Historical trends in lake color from remote sensing observations can provide insights into changing lake ecology, yet have not been examined at the pan-Arctic scale. Here, we analyze time series of 30-m Landsat growing season composites to quantify trends in lake greenness for >4 × 105 waterbodies in boreal and Arctic western North America. We find lake greenness declined overall by 15% from the first to the last decade of analysis within the 6.3 × 106-km2 study region but with significant spatial variability. Greening declines were more likely to be found in areas also undergoing increases in air temperature and precipitation. These findings support the hypothesis that warming has increased connectivity between lakes and the land surface [A. Bring et al., J. Geophys. Res. Biogeosciences 121, 621–649 (2016)], with implications for lake carbon cycling and energy budgets. Our study provides spatially explicit information linking climate to pan-Arctic lake color changes, a finding that will help target future ecological monitoring in remote yet rapidly changing regions.
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Deriving Water Quality Parameters Using Sentinel-2 Imagery: A Case Study in the Sado Estuary, Portugal. REMOTE SENSING 2021. [DOI: 10.3390/rs13051043] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Monitoring water quality parameters and their ecological effects in transitional waters is usually performed through in situ sampling programs. These are expensive and time-consuming, and often do not represent the total area of interest. Remote sensing techniques offer enormous advantages by providing cost-effective systematic observations of a large water system. This study evaluates the potential of water quality monitoring using Sentinel-2 observations for the period 2018–2020 for the Sado estuary (Portugal), through an algorithm intercomparison exercise and time-series analysis of different water quality parameters (i.e., colored dissolved organic matter (CDOM), chlorophyll-a (Chl-a), suspended particulate matter (SPM), and turbidity). Results suggest that Sentinel-2 is useful for monitoring these parameters in a highly dynamic system, however, with challenges in retrieving accurate data for some of the variables, such as Chl-a. Spatio-temporal variability results were consistent with historical data, presenting the highest values of CDOM, Chl-a, SPM and turbidity during Spring and Summer. This work is the first study providing annual and seasonal coverage with high spatial resolution (10 m) for the Sado estuary, being a key contribution for the definition of effective monitoring programs. Moreover, the potential of remote sensing methodologies for continuous water quality monitoring in transitional systems under the scope of the European Water Framework Directive is briefly discussed.
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Validation of Water Quality Monitoring Algorithms for Sentinel-2 and Sentinel-3 in Mediterranean Inland Waters with In Situ Reflectance Data. WATER 2021. [DOI: 10.3390/w13050686] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Freshwater quality maintenance is essential for human use and ecological functions. To ensure this objective, governments establish programs for a continuous monitoring of the inland waters state. This could be possible with Sentinel-2 (S2) and Sentinel-3 (S3), two remote sensing satellites of the European Space Agency, equipped with spectral optical sensors. To determine optimal water quality algorithms applicable to their spectral bands, 36 algorithms were tested for different key variables (chlorophyll a (Chl_a), colored dissolved organic matter (CDOM), colored dissolved organic matter (TSS), phycocyanin (PC) and Secchi disk depth (SDD)). A database of 296 water-leaving reflectance spectra were used, as well as concomitant water quality measurements of Mediterranean reservoirs and lakes of Spain. Two equal data sets were used for calibration and validation. The best algorithms were recalculated using all database and used the following band relations: SDD, R560/R700; CDOM, R665/R490; PC, R705/R665 for S2 and R620, R665, R709 and R779 for S3, using a semi-analytical algorithm; R700 for TSS < 20 mg/L and R783/R492 (S2) or R779/R510 (S3) for TSS > 20 mg/L; and for Chl_a, the maximum (R443; R492)/R560 for Chl_a < 5 mg/m3 and R700/R665 for Chl_a > 5 mg/m3. A preliminary test with a satellite image in a well-known reservoir showed results consistent with the expected ranges and spatial patterns of the variables.
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Estimating Coastal Chlorophyll-A Concentration from Time-Series OLCI Data Based on Machine Learning. REMOTE SENSING 2021. [DOI: 10.3390/rs13040576] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Chlorophyll-a (chl-a) is an important parameter of water quality and its concentration can be directly retrieved from satellite observations. The Ocean and Land Color Instrument (OLCI), a new-generation water-color sensor onboard Sentinel-3A and Sentinel-3B, is an excellent tool for marine environmental monitoring. In this study, we introduce a new machine learning model, Light Gradient Boosting Machine (LightGBM), for estimating time-series chl-a concentration in Fujian’s coastal waters using multitemporal OLCI data and in situ data. We applied the Case 2 Regional CoastColour (C2RCC) processor to obtain OLCI band reflectance and constructed four spectral indices based on OLCI feature bands as supplementary input features. We also used root-mean-square error (RMSE), mean absolute error (MAE), median absolute percentage error (MAPE), and R2 as performance indicators. The results indicate that the addition of spectral indices can easily improve the prediction accuracy of the model, and normalized fluorescence height index (NFHI) has the best performance, with an RMSE of 0.38 µg/L, MAE of 0.22 µg/L, MAPE of 28.33%, and R2 of 0.785. Moreover, we used the well-known band ratio and three-band methods for chl-a estimation validation, and another two OLCI chl-a products were adopted for comparison (OC4Me chl-a and Inverse Modelling Technique (IMT) Neural Net chl-a). The results confirmed that the LightGBM model outperforms the traditional methods and OLCI chl-a products. This study provides an effective remote sensing technique for coastal chl-a concentration estimation and promotes the advantage of OLCI data in ocean color remote sensing.
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