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Kim J, La HS, Kim JH, Jo N, Lee J, Kim BK, Son W, Kim K, Jang HK, Park S, Yoo H, Kim J, Park J, Ahn SH, Lee SH. Spatio-temporal variations in organic carbon composition driven by two different major phytoplankton communities in the Ross Sea, Antarctica. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 891:164666. [PMID: 37286011 DOI: 10.1016/j.scitotenv.2023.164666] [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: 02/06/2023] [Revised: 05/30/2023] [Accepted: 06/02/2023] [Indexed: 06/09/2023]
Abstract
The compositions of organic carbon could be important in determining biological carbon pump efficiency. However, little information on them in relation to each algal assemblage is currently available in the Ross Sea. Here, we investigated the seasonal variations in organic carbon composition and the relative abundance of each organic carbon, including particulate organic carbon (POC), dissolved organic carbon (DOC), and transparent exopolymer particles (TEPs), characterized by different algal groups in the Ross Sea. The average POC and DOC contributions to the total organic carbon (TOC = POC + DOC) were 13.8 ± 3.7 % and 86.2 ± 3.7 % in mid-January 2019 and 20.9 ± 4.1 % and 79.1 ± 4.1 % in February-March 2018, respectively. The carbon content of TEP (TEP-C) contributed 19.6 ± 11.7 % and 4.6 ± 7.0 % of POC and TOC in mid-January and 36.2 ± 14.8 % and 9.0 ± 6.7 % in February-March, respectively. We found that the organic carbon compositions were affected by seasonal variations in the phytoplankton bloom phase, physical characteristics, and phytoplankton community structure. DOC concentrations and contributions to the TOC increased as phytoplankton cells became senescent in mid-January and decreased in February-March when phytoplankton were relatively active. From February-March, the deepened mixed layer depth encouraged TEP formation, subsequently increasing the TEP contributions. Regardless of the sampling season, all organic carbon concentrations per unit Chl-a were significantly higher in P. antarctica-abundant groups. The DOC contributions to the TOC were correspondingly higher at the P. antarctica-abundant stations in mid-January, which indicates that P. antarctica could be also important in the DOC contributions in the Ross Sea. The rapid alteration in environmental characteristics and phytoplankton community structures in the Ross Sea due to climate change could affect the organic carbon pool at the euphotic layer which consequently could determine the efficiency of the biological pump.
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Affiliation(s)
- Jaehong Kim
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Hyoung Sul La
- Division of Ocean Sciences, Korea Polar Research Institute, Incheon, South Korea
| | - Jeong-Hoon Kim
- Division of Life Sciences, Korea Polar Research Institute, Incheon, South Korea
| | - Naeun Jo
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Junbeom Lee
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Bo Kyung Kim
- Division of Ocean Sciences, Korea Polar Research Institute, Incheon, South Korea
| | - Wuju Son
- Division of Ocean Sciences, Korea Polar Research Institute, Incheon, South Korea; Department of Polar Science, University of Science and Technology, Daejeon, South Korea
| | - Kwanwoo Kim
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Hyo-Keun Jang
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Sanghoon Park
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Hyeju Yoo
- Division of Ocean Sciences, Korea Polar Research Institute, Incheon, South Korea
| | - Jaesoon Kim
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Jisoo Park
- Division of Ocean Sciences, Korea Polar Research Institute, Incheon, South Korea
| | - So Hyun Ahn
- Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, USA
| | - Sang Heon Lee
- Department of Oceanography, Pusan National University, Busan, South Korea.
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Kwon YS, La HS, Kang HW, Park J. A regional-scale approach for modeling primary production and biogenic silica export in the Southern Ocean. ENVIRONMENTAL RESEARCH 2023; 217:114811. [PMID: 36414105 DOI: 10.1016/j.envres.2022.114811] [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: 08/13/2022] [Revised: 11/09/2022] [Accepted: 11/12/2022] [Indexed: 06/16/2023]
Abstract
Persistent uncertainties in the representations of net primary production (NPP) and silicate in the Southern Ocean have been noted in recent assessments ofthe ocean biogeochemical components of Earth system models (ESMs). Consequently, more mechanistic studies at the regional scale are required. To reduce these uncertainties, we applied a one-dimensional (1D) marine ecosystem model to different bioregions in the Southern Ocean: the Polar Frontal Zone in the Pacific sector, the seasonal sea ice zone in the northwestern Ross Sea, and the inner shelf of Terra Nova Bay. To make the existing ecosystem model applicable to the Southern Ocean, we modified the phytoplankton physiology (stoichiometry depending on species) and the silicate cycle (dissolution rate of biogenic silica (BSi) depending on latitude) in the model. We quantified and compared seasonal variations in several limitation factors of NPP, namely, iron, irradiance, silicate and temperature, in the three regions. The simulation results showed that dissolved iron plays the most significant role in determining the magnitude of NPP and the phytoplankton community structure during summer. Additionally, the modified model successfully reproduced the vertical flux of BSi and particulate organic carbon (POC). The POC export efficiency was high in the inner shelf zone, which had high levels of iron concentration, NPP, and Phaeocystis biomass. In contrast, BSi export occurred most efficiently in the Polar Frontal Zone, where diatoms are dominant, the BSi dissolution rate is low, and NPP is extremely low. Our results from the integrated mechanistic framework at the regional scale demonstrate which specific processes should be urgently included in ESMs for better representation of the biogeochemical dynamics in the Southern Ocean.
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Affiliation(s)
- Young Shin Kwon
- Korea Institute of Ocean Science and Technology, Busan, Republic of Korea; Korea Polar Research Institute, Incheon, Republic of Korea
| | - Hyoung Sul La
- Korea Polar Research Institute, Incheon, Republic of Korea; University of Science and Technology, Daejeon, Republic of Korea.
| | - Hyoun-Woo Kang
- Korea Institute of Ocean Science and Technology, Busan, Republic of Korea
| | - Jisoo Park
- Korea Polar Research Institute, Incheon, Republic of Korea
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Sedwick PN, Sohst BM, O’Hara C, Stammerjohn SE, Loose B, Dinniman MS, Buck NJ, Resing JA, Ackley SF. Seasonal Dynamics of Dissolved Iron on the Antarctic Continental Shelf: Late-Fall Observations From the Terra Nova Bay and Ross Ice Shelf Polynyas. JOURNAL OF GEOPHYSICAL RESEARCH. OCEANS 2022; 127:e2022JC018999. [PMID: 36590600 PMCID: PMC9788290 DOI: 10.1029/2022jc018999] [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: 06/21/2022] [Revised: 09/19/2022] [Accepted: 09/23/2022] [Indexed: 06/17/2023]
Abstract
Over the Ross Sea shelf, annual primary production is limited by dissolved iron (DFe) supply. Here, a major source of DFe to surface waters is thought to be vertical resupply from the benthos, which is assumed most prevalent during winter months when katabatic winds drive sea ice formation and convective overturn in coastal polynyas, although the impact of these processes on water-column DFe distributions has not been previously documented. We collected hydrographic data and water-column samples for trace metals analysis in the Terra Nova Bay and Ross Ice Shelf polynyas during April-May 2017 (late austral fall). In the Terra Nova Bay polynya, we observed intense katabatic wind events, and surface mixed layer depths varied from ∼250 to ∼600 m over lateral distances <10 km; there vertical mixing was just starting to excavate the dense, iron-rich Shelf Waters, and there was also evidence of DFe inputs at shallower depths in the water column. In the Ross Ice Shelf polynya, wind speeds were lower, mixed layers were <300 m deep, and DFe distributions were similar to previous, late-summer observations, with concentrations elevated near the seafloor. Corresponding measurements of dissolved manganese and zinc, and particulate iron, manganese, and aluminum, suggest that deep DFe maxima and some mid-depth DFe maxima primarily reflect sedimentary inputs, rather than remineralization. Our data and model simulations imply that vertical resupply of DFe in the Ross Sea occurs mainly during mid-late winter, and may be particularly sensitive to changes in the timing and extent of sea ice production.
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Affiliation(s)
- P. N. Sedwick
- Department of Ocean and Earth SciencesOld Dominion UniversityNorfolkVAUSA
| | - B. M. Sohst
- Department of Ocean and Earth SciencesOld Dominion UniversityNorfolkVAUSA
| | - C. O’Hara
- Department of Ocean and Earth SciencesOld Dominion UniversityNorfolkVAUSA
| | - S. E. Stammerjohn
- Institute of Arctic and Alpine ResearchUniversity of ColoradoBoulderCOUSA
| | - B. Loose
- Graduate School of OceanographyUniversity of Rhode IslandNarragansettRIUSA
| | - M. S. Dinniman
- Center for Coastal Physical OceanographyOld Dominion UniversityNorfolkVAUSA
| | - N. J. Buck
- Cooperative Institute for Climate, Oceans, and Ecosystem StudiesUniversity of WashingtonSeattleWAUSA
- NOAA Pacific Marine Environmental LaboratorySeattleWAUSA
| | - J. A. Resing
- Cooperative Institute for Climate, Oceans, and Ecosystem StudiesUniversity of WashingtonSeattleWAUSA
- NOAA Pacific Marine Environmental LaboratorySeattleWAUSA
| | - S. F. Ackley
- Center for Advanced Measurements in Extreme EnvironmentsUniversity of Texas at San AntonioSan AntonioTXUSA
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Comment on “Lagged response of Adélie penguin (Pygoscelis adeliae) abundance to environmental variability in the Ross Sea, Antarctica”. Polar Biol 2022. [DOI: 10.1007/s00300-022-03005-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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5
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Robinson CM, Huot Y, Schuback N, Ryan-Keogh TJ, Thomalla SJ, Antoine D. High latitude Southern Ocean phytoplankton have distinctive bio-optical properties. OPTICS EXPRESS 2021; 29:21084-21112. [PMID: 34265904 DOI: 10.1364/oe.426737] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 05/28/2021] [Indexed: 06/13/2023]
Abstract
Studying the biogeochemistry of the Southern Ocean using remote sensing relies on accurate interpretation of ocean colour through bio-optical and biogeochemical relationships between quantities and properties of interest. During the Antarctic Circumnavigation Expedition of the 2016/2017 Austral Summer, we collected a spatially comprehensive dataset of phytoplankton pigment concentrations, particulate absorption and particle size distribution and compared simple bio-optical and particle property relationships as a function of chlorophyll a. Similar to previous studies we find that the chlorophyll-specific phytoplankton absorption coefficient is significantly lower than in other oceans at comparable chlorophyll concentrations. This appears to be driven in part by lower concentrations of accessory pigments per unit chlorophyll a as well as increased pigment packaging due to relatively larger sized phytoplankton at low chlorophyll a than is typically observed in other oceans. We find that the contribution of microphytoplankton (>20 µm size) to chlorophyll a estimates of phytoplankton biomass is significantly higher than expected for the given chlorophyll a concentration, especially in higher latitudes south of the Southern Antarctic Circumpolar Current Front. Phytoplankton pigments are more packaged in larger cells, which resulted in a flattening of phytoplankton spectra as measured in these samples when compared to other ocean regions with similar chlorophyll a concentration. Additionally, we find that at high latitude locations in the Southern Ocean, pheopigment concentrations can exceed mono-vinyl chlorophyll a concentrations. Finally, we observed very different relationships between particle volume and chlorophyll a concentrations in high and low latitude Southern Ocean waters, driven by differences in phytoplankton community composition and acclimation to environmental conditions and varying contribution of non-algal particles to the particulate matter. Our data confirm that, as previously suggested, the relationships between bio-optical properties and chlorophyll a in the Southern Ocean are different to other oceans. In addition, distinct bio-optical properties were evident between high and low latitude regions of the Southern Ocean basin. Here we provide a region-specific set of power law functions describing the phytoplankton absorption spectrum as a function of chlorophyll a.
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Kim K, Park J, Jo N, Park S, Yoo H, Kim J, Lee SH. Monthly Variation in the Macromolecular Composition of Phytoplankton Communities at Jang Bogo Station, Terra Nova Bay, Ross Sea. Front Microbiol 2021; 12:618999. [PMID: 33643247 PMCID: PMC7905043 DOI: 10.3389/fmicb.2021.618999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 01/21/2021] [Indexed: 11/17/2022] Open
Abstract
Organic carbon fixed by photosynthesis of phytoplankton during the polar growing period could be important for their survival and consumers during the long polar night. Differences in biochemical traits of phytoplankton between ice-free and polar night periods were investigated in biweekly water samples obtained at the Korean “Jang Bogo Station” located in Terra Nova Bay, Antarctica. The average concentration of total Chl-a from phytoplankton dominated by micro-sized species from the entire sampling period was 0.32 μg L–1 (SD = ± 0.88 μg L–1), with the highest concentration of 4.29 μg L–1 in February and the lowest concentration of 0.01 μg L–1 during the ice-covered polar night (April–October) in 2015. The highest protein concentration coincided with the peak Chl-a concentration in February and decreased rapidly relative to the carbohydrate and lipid concentrations in the early part of polar night. Among the different biochemical components, carbohydrates were the predominant constituent, accounting for 69% (SD = ± 14%) of the total particulate organic matter (POM) during the entire study period. The carbohydrate contributions to the total POM markedly increased from 39 ± 8% during the ice-free period to 73 ± 9% during the polar night period. In comparison, while we found a significant negative correlation (r2 = 0.92, p < 0.01) between protein contributions and carbohydrate contributions, lipid contributions did not show any particular trend with relatively small temporal variations during the entire observation period. The substantial decrease in the average weight ratio of proteins to carbohydrates from the ice-free period (mean ± SD = 1.0 ± 0.3) to the ice-covered period (mean ± SD = 0.1 ± 0.1) indicates a preferential loss of nitrogen-based proteins compared to carbohydrates during the polar night period. Overall, the average food material (FM) concentration and calorific contents of FM in this study were within the range reported previously from the Southern Ocean. The results from this study may serve as important background data for long-term monitoring of the regional and interannual variations in the physiological state and biochemical compositions of phytoplankton resulting from future climate change in Antarctica.
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Affiliation(s)
- Kwanwoo Kim
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Jisoo Park
- Division of Ocean Sciences, Korea Polar Research Institute, Incheon, South Korea
| | - Naeun Jo
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Sanghoon Park
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Hyeju Yoo
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Jaehong Kim
- Department of Oceanography, Pusan National University, Busan, South Korea
| | - Sang Heon Lee
- Department of Oceanography, Pusan National University, Busan, South Korea
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7
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Reconstruction of Ocean Color Data Using Machine Learning Techniques in Polar Regions: Focusing on Off Cape Hallett, Ross Sea. REMOTE SENSING 2019. [DOI: 10.3390/rs11111366] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The most problematic issue in the ocean color application is the presence of heavy clouds, especially in polar regions. For that reason, the demand for the ocean color application in polar regions is increased. As a way to overcome such issues, we conducted the reconstruction of the chlorophyll-a concentration (CHL) data using the machine learning-based models to raise the usability of CHL data. This analysis was first conducted on a regional scale and focused on the biologically-valued Cape Hallett, Ross Sea, Antarctica. Environmental factors and geographical information associated with phytoplankton dynamics were considered as predictors for the CHL reconstruction, which were obtained from cloud-free microwave and reanalysis data. As the machine learning models used in the present study, the ensemble-based models such as Random forest (RF) and Extremely randomized tree (ET) were selected with 10-fold cross-validation. As a result, both CHL reconstructions from the two models showed significant agreement with the standard satellite-derived CHL data. In addition, the reconstructed CHLs were close to the actual CHL value even where it was not observed by the satellites. However, there is a slight difference between the CHL reconstruction results from the RF and the ET, which is likely caused by the difference in the contribution of each predictor. In addition, we examined the variable importance for the CHL reconstruction quantitatively. As such, the sea surface and atmospheric temperature, and the photosynthetically available radiation have high contributions to the model developments. Mostly, geographic information appears to have a lower contribution relative to environmental predictors. Lastly, we estimated the partial dependences for the predictors for further study on the variable contribution and investigated the contributions to the CHL reconstruction with changes in the predictors.
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Mangoni O, Saggiomo V, Bolinesi F, Margiotta F, Budillon G, Cotroneo Y, Misic C, Rivaro P, Saggiomo M. Phytoplankton blooms during austral summer in the Ross Sea, Antarctica: Driving factors and trophic implications. PLoS One 2017; 12:e0176033. [PMID: 28430813 PMCID: PMC5400245 DOI: 10.1371/journal.pone.0176033] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 04/04/2017] [Indexed: 11/19/2022] Open
Abstract
During the austral summer of 2014, an oceanographic cruise was conducted in the Ross Sea in the framework of the RoME (Ross Sea Mesoscale Experiment) Project. Forty-three hydrological stations were sampled within three different areas: the northern Ross Sea (RoME 1), Terra Nova Bay (RoME 2), and the southern Ross Sea (RoME 3). The ecological and photophysiological characteristics of the phytoplankton were investigated (i.e., size structure, functional groups, PSII maximum quantum efficiency, photoprotective pigments), as related to hydrographic and chemical features. The aim was to identify the mechanisms that modulate phytoplankton blooms, and consequently, the fate of organic materials produced by the blooms. The observed biomass standing stocks were very high (e.g., integrated chlorophyll-a up to 371 mg m-2 in the top 100 m). Large differences in phytoplankton community composition, relative contribution of functional groups and photosynthetic parameters were observed among the three subsystems. The diatoms (in different physiological status) were the dominant taxa in RoME 1 and RoME 3; in RoME 1, a post-bloom phase was identified, whereas in RoME 3, an active phytoplankton bloom occurred. In RoME 2, diatoms co-occurred with Phaeocystis antarctica, but were vertically segregated by the upper mixed layer, with senescent diatoms dominating in the upper layer, and P. antarctica blooming in the deeper layer. The dominance of the phytoplankton micro-fraction over the whole area and the high Chl-a suggested the prevalence of non-grazed large cells, independent of the distribution of the two functional groups. These data emphasise the occurrence of significant temporal changes in the phytoplankton biomass in the Ross Sea during austral summer. The mechanisms that drive such changes and the fate of the carbon production are probably related to the variations in the limiting factors induced by the concurrent hydrological modifications to the Ross Sea, and they remain to be fully clarified. The comparison of conditions observed during summer 2014 and those reported for previous years reveal considerably different ecological assets that might be the result of current climate change. This suggests that further changes can be expected in the future, even at larger oceanic scales.
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Affiliation(s)
- Olga Mangoni
- Dipartimento di Biologia, Università degli Studi di Napoli Federico II, Naples, Italy
| | | | - Francesco Bolinesi
- Dipartimento di Biologia, Università degli Studi di Napoli Federico II, Naples, Italy
| | | | - Giorgio Budillon
- Dipartimento di Scienze e Tecnologie, Università degli Studi di Napoli Parthenope, Naples, Italy
| | - Yuri Cotroneo
- Dipartimento di Scienze e Tecnologie, Università degli Studi di Napoli Parthenope, Naples, Italy
| | - Cristina Misic
- Dipartimento di Scienze della Terra, dell’Ambiente e della Vita, Università degli Studi di Genova, Genoa, Italy
| | - Paola Rivaro
- Dipartimento di Chimica e Chimica Industriale Università degli Studi di Genova, Genoa, Italy
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9
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Structural equation modeling of the influence of environmental factors on summer phytoplankton growth in the Ross Sea. Polar Biol 2016. [DOI: 10.1007/s00300-016-1953-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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10
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Abstract
Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes.
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Affiliation(s)
- Letizia Tedesco
- Marine Research Centre, Finnish Environment Institute, Helsinki, Finland
- * E-mail:
| | - Marcello Vichi
- Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy
- Centro Euro-Mediterraneo sui Cambiamenti Climatici, Bologna, Italy
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11
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Alderkamp AC, Kulk G, Buma AGJ, Visser RJW, Van Dijken GL, Mills MM, Arrigo KR. THE EFFECT OF IRON LIMITATION ON THE PHOTOPHYSIOLOGY OF PHAEOCYSTIS ANTARCTICA (PRYMNESIOPHYCEAE) AND FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE) UNDER DYNAMIC IRRADIANCE(1). JOURNAL OF PHYCOLOGY 2012; 48:45-59. [PMID: 27009649 DOI: 10.1111/j.1529-8817.2011.01098.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The effects of iron limitation on photoacclimation to dynamic irradiance were studied in Phaeocystis antarctica G. Karst. and Fragilariopsis cylindrus (Grunow) W. Krieg. in terms of growth rate, photosynthetic parameters, pigment composition, and fluorescence characteristics. Under dynamic light conditions mimicking vertical mixing below the euphotic zone, P. antarctica displayed higher growth rates than F. cylindrus both under iron (Fe)-replete and Fe-limiting conditions. Both species showed xanthophyll de-epoxidation that was accompanied by low levels of nonphotochemical quenching (NPQ) during the irradiance maximum of the light cycle. The potential for NPQ at light levels corresponding to full sunlight was substantial in both species and increased under Fe limitation in F. cylindrus. Although the decline in Fv /Fm under Fe limitation was similar in both species, the accompanying decrease in the maximum rate of photosynthesis and growth rate was much stronger in F. cylindrus. Analysis of the electron transport rates through PSII and on to carbon (C) fixation revealed a large potential for photoprotective cyclic electron transport (CET) in F. cylindrus, particularly under Fe limitation. Probably, CET aided the photoprotection in F. cylindrus, but it also reduced photosynthetic efficiency at higher light intensities. P. antarctica, on the other hand, was able to efficiently use electrons flowing through PSII for C fixation at all light levels, particularly under Fe limitation. Thus, Fe limitation enhanced the photophysiological differences between P. antarctica and diatoms, supporting field observations where P. antarctica is found to dominate deeply mixed water columns, whereas diatoms dominate shallower mixed layers.
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Affiliation(s)
- Anne-Carlijn Alderkamp
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Gemma Kulk
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Anita G J Buma
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Ronald J W Visser
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Gert L Van Dijken
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Matthew M Mills
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Kevin R Arrigo
- Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
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Sedwick PN, Marsay CM, Sohst BM, Aguilar-Islas AM, Lohan MC, Long MC, Arrigo KR, Dunbar RB, Saito MA, Smith WO, DiTullio GR. Early season depletion of dissolved iron in the Ross Sea polynya: Implications for iron dynamics on the Antarctic continental shelf. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jc006553] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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13
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Long MC, Dunbar RB, Tortell PD, Smith WO, Mucciarone DA, DiTullio GR. Vertical structure, seasonal drawdown, and net community production in the Ross Sea, Antarctica. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2009jc005954] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Wang S, Moore JK. IncorporatingPhaeocystisinto a Southern Ocean ecosystem model. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2009jc005817] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Zhang J, Spitz YH, Steele M, Ashjian C, Campbell R, Berline L, Matrai P. Modeling the impact of declining sea ice on the Arctic marine planktonic ecosystem. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009jc005387] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | | | | | - Carin Ashjian
- Woods Hole Oceanographic Institution Woods Hole Massachusetts USA
| | | | - Léo Berline
- Laboratoire d'Océanographie de Villefranche Villefranche‐sur‐Mer France
| | - Patricia Matrai
- Bigelow Laboratory for Ocean Sciences West Boothbay Harbor Maine USA
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Abstract
Research on computational models of scientific discovery investigates both the induction of descriptive laws and the construction of explanatory models. Although the work in law discovery centers on knowledge-lean approaches to searching a problem space, research on deeper modeling tasks emphasizes the pivotal role of domain knowledge. As an example, our own research on inductive process modeling uses information about candidate processes to explain why variables change over time. However, our experience with IPM, an artificial intelligence system that implements this approach, suggests that process knowledge is insufficient to avoid consideration of implausible models. To this end, the discovery system needs additional knowledge that constrains the model structures. We report on an extended system, SC-IPM, that uses such information to reduce its search through the space of candidates and to produce models that human scientists find more plausible. We also argue that although people carry out less extensive search than SC-IPM, they rely on the same forms of knowledge--processes and constraints--when constructing explanatory models.
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Affiliation(s)
- Will Bridewell
- Computational Learning Laboratory, Center for the Study of Language and Information, Stanford University
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Arrigo KR, Van Dijken GL. Interannual variation in air-sea CO2flux in the Ross Sea, Antarctica: A model analysis. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jc003492] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Borrett SR, Bridewell W, Langley P, Arrigo KR. A method for representing and developing process models. ECOLOGICAL COMPLEXITY 2007. [DOI: 10.1016/j.ecocom.2007.02.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Hill SL, Murphy EJ, Reid K, Trathan PN, Constable AJ. Modelling Southern Ocean ecosystems: krill, the food-web, and the impacts of harvesting. Biol Rev Camb Philos Soc 2007. [DOI: 10.1111/j.1469-185x.2006.tb00219.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Tremblay JE, Smith W. Chapter 8 Primary Production and Nutrient Dynamics in Polynyas. POLYNYAS: WINDOWS TO THE WORLD 2007. [DOI: 10.1016/s0422-9894(06)74008-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Abstract
An apparent trophic cascade that appears during summer in the western Ross Sea, Antarctica, explains why the Antarctic silverfish (Pleuragramma antarcticum) there becomes cannibalistic; its principal prey, crystal krill (Euphausia crystallorophias) becomes scarce; and the diatom community is minimally grazed compared to adjacent areas. The krill is the major grazer of diatoms. On the basis of fieldwork at Ross Island, we suggest that the cascade results from foraging by unusually numerous Adélie Penguins (Pygoscelis adeliae), minke whales (Balaenoptera bonaerensis), and fish-eating killer whales (Orcinus orca). These species and other top predators apparently deplete the krill and silverfish. In drawing our conclusions, we were aided by two "natural experiments." In one "experiment," large, grounded icebergs altered the seasonal pattern of change in regional sea-ice cover, but not the seasonal change in penguin diet and foraging behavior that was also detected during the pre-iceberg era. In the other "experiment," a short-term polynya (opening in the ice) brought penguins and whales together in a confined area, this time altering both penguin diet and foraging behavior. We conclude that the foraging of penguins and whales, and not a formerly hypothesized seasonal decrease in sea-ice cover, explains (1) the annual switch in the penguins' prey from krill to silverfish, (2) the subsequent lengthening of penguin foraging trips, and (3) a marked decline of cetaceans in the area later in the season. Reduction in the middle-trophic-level prey is expressed in the relaxed grazing pressure on phytoplankton.
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Affiliation(s)
- David G Ainley
- H. T. Harvey and Associates, 3150 Almaden Expressway, Suite 145, San Jose, California 95118, USA.
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Uitz J, Claustre H, Morel A, Hooker SB. Vertical distribution of phytoplankton communities in open ocean: An assessment based on surface chlorophyll. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005jc003207] [Citation(s) in RCA: 531] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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25
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Tagliabue A, Arrigo KR. Processes governing the supply of iron to phytoplankton in stratified seas. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005jc003363] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Reddy TE, Arrigo KR. Constraints on the extent of the Ross Sea phytoplankton bloom. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005jc003339] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Arrigo KR, Tagliabue A. Iron in the Ross Sea: 2. Impact of discrete iron addition strategies. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jc002568] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Kevin R. Arrigo
- Department of Geophysics; Stanford University; Stanford California USA
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Tagliabue A, Arrigo KR. Iron in the Ross Sea: 1. Impact on CO2
fluxes via variation in phytoplankton functional group and non-Redfield stoichiometry. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jc002531] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Kevin R. Arrigo
- Department of Geophysics; Stanford University; Stanford California USA
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Walsh JJ. Decadal shifts in biophysical forcing of Arctic marine food webs: Numerical consequences. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jc001945] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Evaluating photosynthetic carbon fixation during Phaeocystis Antarctica blooms. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/078ars05] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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