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Yang R, Song H, Qin Q, Chen Y, Li D, Qiu Y, Lu K, Tan Y, Chen Q, Cao X, Liu S. The shifting pattern of CO 2 source sink in a subtropical urbanizing lightly eutrophic lake. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 946:174376. [PMID: 38964398 DOI: 10.1016/j.scitotenv.2024.174376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 06/16/2024] [Accepted: 06/27/2024] [Indexed: 07/06/2024]
Abstract
Globally, numerous freshwater lakes exist, and rapid urbanization has impacted carbon biogeochemical cycling at the interface where water meets air in these bodies. However, there is still a limited understanding of CO2 absorption/emission in eutrophic urbanizing lakes. This study therefore involved biweekly in-situ monitoring to evaluate fluctuations in the partial pressure (pCO2) and flux (fCO2) of CO2 and associated parameters from January to September 2020 (7:00-17:00 CST) in an urbanizing lake in southwestern China. Our study revealed that during the daylight hours of the 11 sampling days, both pCO2 and fCO2 consistently demonstrated decreasing trends from the early morning period to the late afternoon period, with notable increases on May 7th and August 15th, respectively. Interestingly, unlike our previous findings, an nonsignificant difference (p > 0.05) in mean pCO2 and fCO2 was observed between the morning period and the afternoon period (n = 22). Furthermore, the mean pCO2 in January (~105 μatm; n = 4) and April (133-212 μatm; n = 8) was below the typical atmospheric CO2 level (C-sink), while that in the other months surpassed 410 μatm (C-source), although the average values (n = 44) of pCO2 and fCO2 were 960 ± 841 μatm and 57 ± 85 mmol m-2 h-1, respectively. Moreover, the pCO2 concentration was significantly greater in summer (May to August, locally reaching 1087 μatm) than in spring (January to April at 112 μatm), indicating a seasonal shift between the C-sink (spring) and the C-source (summer). In addition, a significant positive correlation in pCO2/fCO2 with chlorophyll-a/nitrate but a negative correlation in dissolved oxygen and total phosphorus were recorded, suggesting that photosynthesis and respiration were identified as the main drivers of CO2 absorption/emissions, while changes in nitrate and phosphorus may be attributed to urbanization. Overall, our investigations indicated that this lightly eutrophic lake demonstrated a distinct shifting pattern of CO2 source-sink variability at daily and seasonal scales.
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Affiliation(s)
- Rongjie Yang
- School of Tourism and Culture Industry, Chengdu University, Chengdu 610106, China; College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China.
| | - Huixing Song
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China.
| | - Qiao Qin
- The First Construction Engineering Co., Ltd., China Construction Third Engineering Bureau, Wuhan 430040, China
| | - Yingying Chen
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China
| | - Di Li
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China; Geophysical Exploration Brigade of Hubei Geological Bureau, Wuhan 430056, China
| | - Yuling Qiu
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China
| | - Kezhu Lu
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China
| | - Yike Tan
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China
| | - Qingqing Chen
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China
| | - Xinhao Cao
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China
| | - Shiliang Liu
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China; Sichuan Yuze Landscape Planning and Design Co., Ltd., Chengdu 610093, China.
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Tan Y, Zhao W, Li J, Li Y, Yang B, Zhu L, Tuo Y. Spatiotemporal distribution of pCO 2 and CO 2 flux and the regulatory factors: From the perspective of a subtropical canyon-shaped reservoir, southwest China. WATER RESEARCH 2024; 267:122558. [PMID: 39366324 DOI: 10.1016/j.watres.2024.122558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2024] [Revised: 09/26/2024] [Accepted: 09/29/2024] [Indexed: 10/06/2024]
Abstract
Reservoir carbon cycling is a critical component of the global carbon cycle, particularly in subtropical canyon-shaped reservoirs where unique geomorphological features and hydrological regulation under monsoon climate provide a distinct perspective for carbon cycle research. This study takes the Zipingpu Reservoir (ZPPR) in southwestern China as an example and reveals significant seasonal variations in partial pressure of carbon dioxide (pCO2) and carbon dioxide flux at the water-air interface (FCO2) through annual monitoring. The average pCO2 in ZPPR is 486 μatm, and the average FCO2 is 0.093 g C m-2d-1, with approximately 42.4 % of FCO2 measurements being negative, indicating the reservoir's role can act as a carbon sink. The study also estimated the gas transfer coefficient (K), with an average value of 1.888 md-1. Peak FCO2 during spring and summer is three times higher than in other seasons, consistent with the main influencing factors of inflow dynamics, metabolic processes, and reservoir operation strategies. Inflow and operational activities, particularly during spring and summer, drive CO2 emissions in the downstream reach and upstream tributary, while biological activity facilitates CO2 uptake in the lacustrine area and forebay tributary, with enhanced absorption occurring in the autumn. Concurrently, high-intensity FCO2 emissions from the upstream river section during summer underscore the importance of carbon emission monitoring and management during critical periods. The findings not only enhance the understanding of FCO2 assessment accuracy but also provide a framework for evaluating and optimizing carbon dynamics management strategies in canyon-shaped reservoirs, contributing valuable insights to global carbon cycle research.
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Affiliation(s)
- Yi Tan
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, Sichuan, China
| | - Wenjie Zhao
- Sichuan Province Zipingpu Development Co., Ltd., Chengdu 610091, China
| | - Jia Li
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, Sichuan, China
| | - Yong Li
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, Sichuan, China.
| | - Bing Yang
- Sichuan Province Zipingpu Development Co., Ltd., Chengdu 610091, China.
| | - Lei Zhu
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, Sichuan, China.
| | - Youcai Tuo
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, Sichuan, China.
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Wei N, Hu C, Dittmann E, Song L, Gan N. The biological functions of microcystins. WATER RESEARCH 2024; 262:122119. [PMID: 39059200 DOI: 10.1016/j.watres.2024.122119] [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: 05/21/2024] [Revised: 07/16/2024] [Accepted: 07/17/2024] [Indexed: 07/28/2024]
Abstract
Microcystins are potent hepatotoxins predominantly produced by bloom-forming freshwater cyanobacteria (e.g., Microcystis, Planktothrix, Dolichospermum). Microcystin biosynthesis involves large multienzyme complexes and tailoring enzymes encoded by the mcy gene cluster. Mutation, recombination, and deletion events have shaped the mcy gene cluster in the course of evolution, resulting in a large diversity of microcystin congeners and the natural coexistence of toxic and non-toxic strains. The biological functions of microcystins and their association with algal bloom formation have been extensively investigated over the past decades. This review synthesizes recent advances in decoding the biological role of microcystins in carbon/nitrogen metabolism, antioxidation, colony formation, and cell-to-cell communication. Microcystins appear to adopt multifunctional roles in cyanobacteria that reflect the adaptive plasticity of toxic cyanobacteria to changing environments.
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Affiliation(s)
- Nian Wei
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Chenlin Hu
- College of Pharmacy, University of Houston, Houston, TX 77204, USA
| | - Elke Dittmann
- Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam-Golm, Germany
| | - Lirong Song
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Nanqin Gan
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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He H, Liu Z, Li D, Liu X, Han Y, Sun H, Zhao M, Shao M, Shi L, Hao P, Lai C. Effects of carbon limitation and carbon fertilization on karst lake-reservoir productivity. WATER RESEARCH 2024; 261:122036. [PMID: 38981350 DOI: 10.1016/j.watres.2024.122036] [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: 04/07/2024] [Revised: 06/11/2024] [Accepted: 07/01/2024] [Indexed: 07/11/2024]
Abstract
Nitrogen and phosphorus are universally recognized as limiting elements in the eutrophication processes affecting the majority of the world's lakes, reservoirs, and coastal ecosystems. However, despite extensive research spanning several decades, critical questions in eutrophication science remain unanswered. For example, there is still much to understand about the interactions between carbon limitation and ecosystem stability, and the availability of carbon components adds significant complexity to aquatic resource management. Mounting evidence suggests that aqueous CO2 could be a limiting factor, influencing the structure and succession of aquatic plant communities, especially in karstic lake and reservoir ecosystems. Moreover, the fertilization effect of aqueous CO2 has the potential to enhance carbon sequestration and phosphorus removal. Therefore, it is important to address these uncertainties to achieve multiple positive outcomes, including improved water quality and increased carbon sinks in karst lakes and reservoirs.
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Affiliation(s)
- Haibo He
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China
| | - Zaihua Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China.
| | - Dongli Li
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Xing Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongqiang Han
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hailong Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China
| | - Min Zhao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China
| | - Mingyu Shao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China
| | - Liangxing Shi
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pengyun Hao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chaowei Lai
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang 550081, China
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Shen D, Li Y, Wang Y, Huo S, Liu Y, Jia J, Wang S, Sun K, Gao Y. Decadal shifts in Qingzang Plateau lake carbon dynamics (1970-2020): From predominant carbon sources to emerging sinks. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2024; 21:100389. [PMID: 38293646 PMCID: PMC10823105 DOI: 10.1016/j.ese.2024.100389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 01/01/2024] [Accepted: 01/02/2024] [Indexed: 02/01/2024]
Abstract
The evasion of carbon dioxide (CO2) from lakes significantly influences the global carbon equilibrium. Amidst global climatic transformations, the role of Qingzang Plateau (QZP) lakes as carbon (C) sources or sinks remains a subject of debate. Furthermore, accurately quantifying their contribution to the global carbon budget presents a formidable challenge. Here, spanning half a century (1970-2020), we utilize a synthesis of literature and empirical field data to assess the CO2 exchange flux of QZP lakes. We find markedly higher CO2 exchange flux in the southeast lakes than that in the northern and western regions from 1970 to 2000. During this time, both freshwater and saltwater lakes served primarily as carbon sources. The annual CO2 exchange flux was estimated at 2.04 ± 0.37 Tg (Tg) C yr-1, mainly influenced by temperature fluctuations. The CO2 exchange flux patterns underwent a geographical inversion between 2000 and 2020, with increased levels in the west and decreased levels in the east. Notably, CO2 emissions from freshwater lakes diminished, and certain saltwater lakes in the QTP transitioned from carbon sources to sinks. From 2000 to 2020, the annual CO2 exchange flux from QZP lakes is estimated at 1.34 ± 0.50 Tg C yr-1, with solar radiation playing a more pronounced role in carbon emissions. Cumulatively, over the past five decades, QZP lakes have generally functioned as carbon sources. Nevertheless, the total annual CO2 emissions have declined since the year 2000, indicating a potential shift trend from being a carbon source to a sink, mirroring broader patterns of global climate change. These findings not only augment our understanding of the carbon cycle in plateau aquatic systems but also provide crucial data for refining China's carbon budget.
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Affiliation(s)
- Di Shen
- College of Earth and Environment Science, Lanzhou University, Lanzhou, 730000, PR China
- State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, PR China
| | - Yu Li
- College of Earth and Environment Science, Lanzhou University, Lanzhou, 730000, PR China
| | - Yafeng Wang
- State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, PR China
| | - Shouliang Huo
- Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China
| | - Yong Liu
- College of Environmental Sciences and Engineering, Peking University, Beijing, 1008714, PR China
| | - Junjie Jia
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, PR China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Shuoyue Wang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, PR China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Kun Sun
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, PR China
| | - Yang Gao
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, PR China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, PR China
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Lai C, Liu Z, Yu Q, Sun H, Xia F, He X, Ma Z, Han Y, Liu X, Hao P, Bao Q, Shao M, He H. Control of carbon dioxide exchange fluxes by rainfall and biological carbon pump in karst river-lake systems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 937:173486. [PMID: 38796009 DOI: 10.1016/j.scitotenv.2024.173486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 05/19/2024] [Accepted: 05/22/2024] [Indexed: 05/28/2024]
Abstract
As an important component of inland water, the primary factors affecting the carbon cycle in karst river-lake systems require further investigation. In particular, the impacts of climatic factors and the biological carbon pump (BCP) on carbon dioxide (CO2) exchange fluxes in karst rivers and lakes deserve considerable attention. Using quarterly sampling, field monitoring, and meteorological data collection, the spatiotemporal characteristics of CO2 exchange fluxes in Erhai Lake (a typical karst lake in Yunnan, SW China) and its inflow rivers were investigated and the primary influencing factors were analyzed. The average river CO2 exchange flux reached 346.80 mg m-2 h-1, compared to -6.93 mg m-2 h-1 for the lake. The carbon cycle in rivers was strongly influenced by land use within the basin; cultivated and construction land were the main contributors to organic carbon (OC) in the river (r = 0.66, p < 0.01) and the mineralization of OC was a major factor in CO2 oversaturation in most rivers (r = 0.76, p < 0.01). In addition, the BCP effect of aquatic plants and the high pH in karst river-lake systems enhance the ability of water body to absorb CO2, resulting in undersaturated CO2 levels in the lake. Notably, under rainfall regulation, riverine OC and dissolved inorganic carbon (DIC) flux inputs controlled the level of CO2 exchange fluxes in the lake (rOC = 0.78, p < 0.05; rDIC = 0.97, p < 0.01). We speculate that under future climate and human activity scenarios, the DIC and OC input from rivers may alleviate the CO2 limitation of BCP effects in karst eutrophication lakes, possibly enabling aquatic plants to convert more CO2 into OC for burial. The results of this research can help advance our understanding of CO2 emissions and absorption mechanisms in karst river-lake systems.
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Affiliation(s)
- Chaowei Lai
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
| | - Zaihua Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China.
| | - Qingchun Yu
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
| | - Hailong Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China
| | - Fan Xia
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuejun He
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen Ma
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China
| | - Yongqiang Han
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xing Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pengyun Hao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
| | - Qian Bao
- Key Laboratory of Land Resources Evaluation and Monitoring in Southwest, Ministry of Education, Sichuan Normal University, Chengdu 610066, China
| | - Mingyu Shao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China
| | - Haibo He
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China
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Kramer BJ, Turk-Kubo K, Zehr JP, Gobler CJ. Intensification of harmful cyanobacterial blooms in a eutrophic, temperate lake caused by nitrogen, temperature, and CO 2. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 915:169885. [PMID: 38190910 DOI: 10.1016/j.scitotenv.2024.169885] [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: 07/11/2023] [Revised: 01/01/2024] [Accepted: 01/01/2024] [Indexed: 01/10/2024]
Abstract
Warmer temperatures can significantly increase the intensity of cyanobacterial harmful algal blooms (CHABs) in eutrophic freshwater ecosystems. However, few studies have examined the effects of CO2 enrichment in tandem with elevated temperature and/or nutrients on cyanobacterial taxa in freshwater ecosystems. Here, we observed changes in the biomass of cyanobacteria, nutrients, pH, and carbonate chemistry over a two-year period in a shallow, eutrophic freshwater lake and performed experiments to examine the effects and co-effects of CO2, temperature, and nutrient enrichment on cyanobacterial and N2-fixing (diazotrophic) communities assessed via high throughput sequencing of the 16S rRNA and nifH genes, respectively. During both years, there were significant CHABs (50-500 μg cyanobacterial chlorophyll-a L-1) and lake CO2 levels were undersaturated (≤300 μatm pCO2). NH4+ significantly increased the net growth rates of cyanobacteria as well as the biomass of the diazotrophic cyanobacterial order Nostocales under elevated and ambient CO2 conditions. In a fall experiment, the N2 fixation rates of Nostocales were significantly higher when populations were enriched with CO2 and P, relative to CO2-enriched populations that were not amended with P. During a summer experiment, N2 fixation rates increased significantly under N and CO2 - enriched conditions relative to N-enriched and ambient CO2 conditions. Nostocales dominated the diazotrophic communities of both experiments, achieving the highest relative abundance under CO2-enriched conditions when N was added in the first experiment and when CO2 and temperature were elevated in the second experiment, when N2 fixation rates also increased significantly. Collectively, this study indicates that N promotes cyanobacterial blooms including those formed by Dolichospermum and that the biomass and N2 fixation rates of diazotrophic cyanobacterial taxa may benefit from enhanced CO2 levels in eutrophic lakes.
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Affiliation(s)
- Benjamin J Kramer
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States
| | - Kendra Turk-Kubo
- Oceans Sciences Department, University of California at Santa Cruz, CA, United States
| | - Jonathan P Zehr
- Oceans Sciences Department, University of California at Santa Cruz, CA, United States
| | - Christopher J Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States.
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Zhang L, Xu YJ, Li S. Changes in CO 2 concentration and degassing of eutrophic urban lakes associated with algal growth and decline. ENVIRONMENTAL RESEARCH 2023; 237:117031. [PMID: 37660875 DOI: 10.1016/j.envres.2023.117031] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 07/28/2023] [Accepted: 08/30/2023] [Indexed: 09/05/2023]
Abstract
Urban lakes are numerous in the world, but their role in carbon storage and emission is not well understood. This study aimed to answer the critical questions: How does algal growing season influence carbon dioxide concentration (cCO2) and exchange flux (FCO2) in eutrophic urban lakes? We investigated trophic state, seasonality of algal productivity, and their association with CO2 dynamics in four urban lakes in Central China. We found that these lightly-to moderately-eutrophic urban lakes showed a shifting pattern of CO2 source-sink dynamics. In the non-algal bloom phase, the moderately-eutrophic lakes outgassed on average of 12.18 ± 24.37 mmol m-2 d-1 CO2; but, during the algal bloom phase, the lakes sequestered an average 1.07 ± 6.22 mmol m-2 d-1 CO2. The lightly-eutrophic lakes exhibited lower CO2 emission in the algal bloom (0.60 ± 10.24 mmol m-2 d-1) compared to the non-algal bloom (3.84 ± 12.38 mmol m-2 d-1). Biological factors such as Chl-a (chlorophyll a) and AOU (apparent oxygen utilization), were found to be important factors to potentially affect the shifting pattern of lake CO2 source-sink dynamics in moderately-eutrophic lakes, explaining 48% and 34% of the CO2 variation in the non-algal and algal bloom phases, respectively. Moreover, CO2 showed positive correlations with AOU, and negative correlations with Chl-a in both phases. In the lightly-eutrophic lakes, biological factors explained a higher proportion of CO2 variations (29%) in the non-algal bloom phase, with AOU accounting for 19%. Our results indicate that algal growth and decline phases largely affect dissolved CO2 level and exchange flux by regulating in-lake respiration and photosynthesis. Based on the findings, we conclude that shallow urban lakes can act as both sources and sinks of CO2, with algal growth seasonality and trophic state playing pivotal roles in controlling their carbon dynamics.
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Affiliation(s)
- Liuqing Zhang
- School of Environmental Ecology and Biological Engineering, Institute of Changjiang Water Environment and Ecological Security, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan, 430205, China; Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Y Jun Xu
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA; Coastal Studies Institute, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Siyue Li
- School of Environmental Ecology and Biological Engineering, Institute of Changjiang Water Environment and Ecological Security, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan, 430205, China.
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9
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Lai C, Ma Z, Liu Z, Sun H, Yu Q, Xia F, He X, Bao Q, Han Y, Liu X, He H. Alleviating eutrophication by reducing the abundance of Cyanophyta due to dissolved inorganic carbon fertilization: Insights from Erhai Lake, China. J Environ Sci (China) 2023; 131:68-83. [PMID: 37225382 DOI: 10.1016/j.jes.2022.10.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 10/19/2022] [Accepted: 10/19/2022] [Indexed: 05/26/2023]
Abstract
The eutrophication of lakes is a global environmental problem. Regulating nitrogen (N) and phosphorus (P) on phytoplankton is considered to be the most important basis of lake eutrophication management. Therefore, the effects of dissolved inorganic carbon (DIC) on phytoplankton and its role in mitigating lake eutrophication have often been overlooked. In this study, the relationships between phytoplankton and DIC concentrations, carbon isotopic composition, nutrients (N and P), and hydrochemistry in the Erhai Lake (a karst lake) were investigated. The results showed that when the dissolved carbon dioxide (CO2(aq)) concentrations in the water were higher than 15 µmol/L, the productivity of phytoplankton was controlled by the concentrations of TP and TN, especially by that of TP. When the N and P were sufficient and the CO2(aq) concentrations were lower than 15 µmol/L, the phytoplankton productivity was controlled by the concentrations of TP and DIC, especially by that of DIC. Additionally, DIC significantly affected the composition of the phytoplankton community in the lake (p<0.05). When the CO2(aq) concentrations were higher than 15 µmol/L, the relative abundance of Bacillariophyta and Chlorophyta was much higher than those of harmful Cyanophyta. Thus, high concentrations of CO2(aq) can inhibit harmful Cyanophyta blooms. During lake eutrophication, when controlling N and P, an appropriate increase in CO2(aq) concentrations by land-use changes or pumping of industrial CO2 into water may reduce the proportion of harmful Cyanophyta and promote the growth of Chlorophyta and Bacillariophyta, which may provide effectively assist in mitigating water quality deterioration in surface waters.
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Affiliation(s)
- Chaowei Lai
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
| | - Zhen Ma
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; Hefei University, Hefei 230601, China
| | - Zaihua Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China.
| | - Hailong Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China
| | - Qingchun Yu
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
| | - Fan Xia
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuejun He
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qian Bao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; Sichuan Normal University Key Laboratory of Land Resources Evaluation and Monitoring in Southwest China of Ministry of Education, Chengdu 610066, China
| | - Yongqiang Han
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xing Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Haibo He
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, China
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10
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Kramer BJ, Hem R, Gobler CJ. Elevated CO 2 significantly increases N 2 fixation, growth rates, and alters microcystin, anatoxin, and saxitoxin cell quotas in strains of the bloom-forming cyanobacteria, Dolichospermum. HARMFUL ALGAE 2022; 120:102354. [PMID: 36470609 DOI: 10.1016/j.hal.2022.102354] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 11/02/2022] [Accepted: 11/11/2022] [Indexed: 06/17/2023]
Abstract
The effect of rising CO2 levels on cyanobacterial harmful algal blooms (CHABs) is an emerging concern, particularly within eutrophic ecosystems. While elevated pCO2 has been associated with enhanced growth rates of some cyanobacteria, few studies have explored the effect of CO2 and nitrogen availability on diazotrophic (N2-fixing) cyanobacteria that produce cyanotoxins. Here, the effects of elevated CO2 and fixed nitrogen (NO3-) availability on the growth rates, toxin production, and N2 fixation of microcystin, saxitoxin, and anatoxin-a - producing strains of the genus Dolichospermum were quantified. Growth rates of all Dolichospermum spp. were significantly increased by CO2 or both CO2 and NO3- with rates being highest in treatments with the highest levels of CO2 and NO3-for all strains. While NO3- suppressed N2 fixation, diazotrophy significantly increased when NO3--enriched Dolichospermum spp. were supplied with higher CO2 compared to cultures grown under lower CO2 levels. This suggests that diazotrophy will play an increasingly important role in N cycling in CO2-enriched, eutrophic lentic systems. NO3- significantly increased quotas of the N-rich cyanotoxins, microcystin and saxitoxin, at ambient and enriched CO2 levels, respectively. In contrast, elevated CO2 significantly decreased cell quotas of microcystin and saxitoxin, but significantly increased cell quotas of the N-poor cyanotoxin, anatoxin. N2 fixation was significantly negatively and positively correlated with quotas of N-rich and N-poor cyanotoxins, respectively. Findings suggest cellular quotas of N-rich toxins (microcystin and saxitoxin) may be significantly reduced, or cellular quotas of N-poor toxins (anatoxin) may be significantly enhanced, under elevated CO2 conditions during diazotrophic cyanobacterial blooms. Finally, in the future, ecosystems that experience combinations of excessive N loading and CO2 enrichment may become more prone to toxic blooms of Dolichospermum.
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Affiliation(s)
- Benjamin J Kramer
- School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Highway, Southampton, NY, United States, 11968
| | - Ronojoy Hem
- School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Highway, Southampton, NY, United States, 11968
| | - Christopher J Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Highway, Southampton, NY, United States, 11968.
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11
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Zepernick BN, Niknejad DJ, Stark GF, Truchon AR, Martin RM, Rossignol KL, Paerl HW, Wilhelm SW. Morphological, physiological, and transcriptional responses of the freshwater diatom Fragilaria crotonensis to elevated pH conditions. Front Microbiol 2022; 13:1044464. [PMID: 36504786 PMCID: PMC9732472 DOI: 10.3389/fmicb.2022.1044464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 11/07/2022] [Indexed: 11/27/2022] Open
Abstract
Harmful algal blooms (HABs) caused by the toxin-producing cyanobacteria Microcystis spp., can increase water column pH. While the effect(s) of these basified conditions on the bloom formers are a high research priority, how these pH shifts affect other biota remains understudied. Recently, it was shown these high pH levels decrease growth and Si deposition rates in the freshwater diatom Fragilaria crotonensis and natural Lake Erie (Canada-US) diatom populations. However, the physiological mechanisms and transcriptional responses of diatoms associated with these observations remain to be documented. Here, we examined F. crotonensis with a set of morphological, physiological, and transcriptomic tools to identify cellular responses to high pH. We suggest 2 potential mechanisms that may contribute to morphological and physiological pH effects observed in F. crotonensis. Moreover, we identified a significant upregulation of mobile genetic elements in the F. crotonensis genome which appear to be an extreme transcriptional response to this abiotic stress to enhance cellular evolution rates-a process we have termed "genomic roulette." We discuss the ecological and biogeochemical effects high pH conditions impose on fresh waters and suggest a means by which freshwater diatoms such as F. crotonensis may evade high pH stress to survive in a "basified" future.
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Affiliation(s)
| | - David J. Niknejad
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States
| | - Gwendolyn F. Stark
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States
| | - Alexander R. Truchon
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States
| | - Robbie M. Martin
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States
| | - Karen L. Rossignol
- Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC, United States
| | - Hans W. Paerl
- Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC, United States
| | - Steven W. Wilhelm
- Department of Microbiology, University of Tennessee, Knoxville, TN, United States
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12
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Zhang L, He K, Wang T, Liu C, An Y, Zhong J. Frequent algal blooms dramatically increase methane while decrease carbon dioxide in a shallow lake bay. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 312:120061. [PMID: 36041568 DOI: 10.1016/j.envpol.2022.120061] [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: 05/09/2022] [Revised: 08/22/2022] [Accepted: 08/24/2022] [Indexed: 06/15/2023]
Abstract
Freshwater ecosystems play a key role in global greenhouse gas estimations and carbon budgets, and algal blooms are widespread owing to intensified anthropological activities. However, little is known about greenhouse gas dynamics in freshwater experiencing frequent algal blooms. Therefore, to explore the spatial and temporal variations in methane (CH4) and carbon dioxide (CO2), seasonal field investigations were performed in the Northwest Bay of Lake Chaohu (China), where there are frequent algal blooms. From the highest site in the nearshore to the pelagic zones, the CH4 concentration in water decreased by at least 80%, and this dynamic was most obvious in warm seasons when algal blooms occurred. CH4 was 2-3 orders of magnitude higher than the saturated concentration, with the highest in spring, which makes this bay a constant source of CH4. However, unlike CH4, CO2 did not change substantially, and river mouths acted as hotspots for CO2 in most situations. The highest CO2 concentration appeared in winter and was saturated, whereas at other times, CO2 was unsaturated and acted as a sink. The intensive photosynthesis of rich algae decreased the CO2 in the water and increased dissolved oxygen and pH. The increase in CH4 in the bay was attributed to the mineralization of autochthonous organic carbon. These findings suggest that frequent algal blooms will greatly absorb more CO2 from atmosphere and increasingly release CH4, therefore, the contribution of the bay to the lake's CH4 emissions and carbon budget will be major even though it is small. The results of this study will be the same to other shallow lakes with frequent algal bloom, making lakes a more important part of the carbon budget and greenhouse gases emission.
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Affiliation(s)
- Lei Zhang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China.
| | - Kai He
- School of Resources and Environmental Engineering, Anhui University, Hefei, 230601, PR China
| | - Tong Wang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Cheng Liu
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China
| | - Yanfei An
- School of Resources and Environmental Engineering, Anhui University, Hefei, 230601, PR China
| | - Jicheng Zhong
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China
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13
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Wang S, Gao Y, Jia J, Lu Y, Wang J, Ha X, Li Z, Sun K. Determining whether hydrological processes drive carbon source and sink conversion shifts in a large floodplain-lake system in China. WATER RESEARCH 2022; 224:119105. [PMID: 36122449 DOI: 10.1016/j.watres.2022.119105] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 08/15/2022] [Accepted: 09/10/2022] [Indexed: 06/15/2023]
Abstract
Lake carbon (C) cycling is a key component of the global C cycle and associated C source and sink processes. The partial pressure of carbon dioxide (pCO2) and carbon dioxide (CO2) exchange flux at the lake-air interface (Fc) are controlled by complex physical, chemical, and biological mechanisms. It would be instructively significant to determine whether hydrological processes drive conversion shifts between C sources and sinks in floodplain-lake systems. Findings from this study show that exogenous input and in situ metabolism related to photosynthesis, respiration, and organic matter degradation were the main driving mechanisms of CO2 absorption and release in a large floodplain-lake system (i.e., Lake Poyang). Moreover, the intense and frequent water-level fluctuations inherent to floodplain-lakes may also have a direct or indirect impact on C cycling processes and CO2 exchange rates in floodplain-lake systems via their effect on physical processes, inorganic C transport, in-situ metabolic processes. We confirmed the potential of C source and sink conversion in floodplain-lakes under hydrological fluctuations, and strengthen the understanding of driving mechanisms of C source and sink conversion in floodplain systems.
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Affiliation(s)
- Shuoyue Wang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Yang Gao
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China.
| | - Junjie Jia
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Yao Lu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Jing Wang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Xianrui Ha
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Zhaoxi Li
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Kun Sun
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China
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14
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Luo J, Hu Z, Chen X, Li X, Liu L, Yang M, Miao H, Chu Y, Xu P, Wang F. Chlorophyll maxima layer in a large subtropical reservoir (Xinanjiang Reservoir): Spatial development process and limitation by CO 2 and phosphorus. WATER RESEARCH 2022; 222:118912. [PMID: 35932705 DOI: 10.1016/j.watres.2022.118912] [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: 02/23/2022] [Revised: 06/16/2022] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
In marine investigations, the maximum chlorophyll-a (Chla) concentration is often reported to occur at a specific depth below the ocean surface, a phenomenon known as subsurface Chla maxima (SCM). However, SCM has long been overlooked in artificial reservoirs, which may lead to a serious underestimation of the primary productivity level and trophic status of reservoirs. To better understand the temporal and spatial variability of SCM and the mechanisms leading to SCM development, this study conducted a detailed survey in a large subtropical reservoir (Xinanjiang Reservoir, XAJR) from September 2020 to August 2021. The seasonal thermal stratification, in situ variables (WT, pH, DO and Chla), nutrient concentrations (DSi, NO3-, DIP and DCO2), Chla maxima depth and magnitude of the riverine region (S1), transition region (S2) and the central part of the XAJR (S3 and S4) were all thoroughly investigated. Thermal stratification and SCM in XAJR exhibited significant seasonal and spatial heterogeneity. Phytoplankton biomass in the epilimnion was limited by dissolved CO2 from June to October in the warm seasons, while it was primarily limited by phosphorus in the other seasons, according to the nutrient limitation analysis. Along the water column, dissolved CO2 limitation occurred mainly above the SCM layer, and the water column below the SCM layer gradually transitioned from dissolved CO2 limitation to phosphorus limitation. Furthermore, as the thermal stratification developed, the upstream water mass moves along the middle of the water column as density flow toward the reservoir, providing nutrients for the development of the SCM. This research contributes to a better understanding of the temporal and spatial variation of SCM and nutrient supply in deep and large stratified reservoirs.
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Affiliation(s)
- Jiajie Luo
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China.
| | - Zhehui Hu
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China.
| | - Xueping Chen
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Xiaoying Li
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Liu Liu
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Meilin Yang
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Haocheng Miao
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Yongsheng Chu
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Peifan Xu
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China
| | - Fushun Wang
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai 201800, China.
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15
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Increases in Picocyanobacteria Abundance in Agriculturally Eutrophic Pampean Lakes Inferred from Historical Records of Secchi Depth and Chlorophyll-a. WATER 2022. [DOI: 10.3390/w14020159] [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
Phytoplankton size structure has profound consequences on food-web organization and energy transfer. Presently, picocyanobacteria (size < 2 µm) represent a major fraction of the autotrophic plankton of Pampean lakes. Glyphosate is known to stimulate the development of picocyanobacteria capable of degrading the herbicide. Due to the worldwide adoption of glyphosate-resistant crops, herbicide usage has increased sharply since the mid-1990s. Unfortunately, there are very few studies (none for the Pampa region) reporting picocyanobacteria abundance before 2000. The proliferation of µm sized particles should decrease Secchi disc depth (ZSD). Therefore ZSD, conditional to chlorophyll-a, may serve as an indicator of picocyanobacteria abundance. We use generalized additive models (GAMs) to analyze a “validation” dataset consisting of 82 records of ZSD, chlorophyll-a, and picocyanobacteria abundance from two Pampean lakes surveys (2009 and 2015). In support of the hypothesis, ZSD was negatively related to picocyanobacteria after accounting for the effect of chlorophyll-a. We then fitted a “historical” dataset using hierarchical GAMs to compare ZSD conditional to chlorophyll-a, before and after 2000. We estimated that ZSD levels during 2000–2021 were, on average, only about half as deep as those during 1980–1999. We conclude that the adoption of glyphosate-resistant crops has stimulated outbreaks of picocyanobacteria populations, resulting in lower water transparency.
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16
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Closed microbial communities self-organize to persistently cycle carbon. Proc Natl Acad Sci U S A 2021; 118:2013564118. [PMID: 34740965 PMCID: PMC8609437 DOI: 10.1073/pnas.2013564118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2021] [Indexed: 12/16/2022] Open
Abstract
Life on Earth depends on ecologically driven nutrient cycles to regenerate resources. Understanding how nutrient cycles emerge from a complex web of ecological processes is a central challenge in ecology. However, we lack model ecosystems that can be replicated, manipulated, and quantified in the laboratory, making it challenging to determine how changes in composition and the environment impact cycling. Enabled by a new high-precision method to quantify carbon cycling, we show that materially closed microbial ecosystems (CES) provided with only light self-organize to robustly cycle carbon. Studying replicate CES that support a carbon cycle reveals variable community composition but a conserved set of metabolic capabilities. Our study helps establish CES as model biospheres for studying how ecosystems persistently cycle nutrients. Cycles of nutrients (N, P, etc.) and resources (C) are a defining emergent feature of ecosystems. Cycling plays a critical role in determining ecosystem structure at all scales, from microbial communities to the entire biosphere. Stable cycles are essential for ecosystem persistence because they allow resources and nutrients to be regenerated. Therefore, a central problem in ecology is understanding how ecosystems are organized to sustain robust cycles. Addressing this problem quantitatively has proved challenging because of the difficulties associated with manipulating ecosystem structure while measuring cycling. We address this problem using closed microbial ecosystems (CES), hermetically sealed microbial consortia provided with only light. We develop a technique for quantifying carbon cycling in hermetically sealed microbial communities and show that CES composed of an alga and diverse bacterial consortia self-organize to robustly cycle carbon for months. Comparing replicates of diverse CES, we find that carbon cycling does not depend strongly on the taxonomy of the bacteria present. Moreover, despite strong taxonomic differences, self-organized CES exhibit a conserved set of metabolic capabilities. Therefore, an emergent carbon cycle enforces metabolic but not taxonomic constraints on ecosystem organization. Our study helps establish closed microbial communities as model ecosystems to study emergent function and persistence in replicate systems while controlling community composition and the environment.
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17
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Sun H, Lu X, Yu R, Yang J, Liu X, Cao Z, Zhang Z, Li M, Geng Y. Eutrophication decreased CO 2 but increased CH 4 emissions from lake: A case study of a shallow Lake Ulansuhai. WATER RESEARCH 2021; 201:117363. [PMID: 34174729 DOI: 10.1016/j.watres.2021.117363] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 06/03/2021] [Accepted: 06/08/2021] [Indexed: 06/13/2023]
Abstract
Eutrophic lakes, especially shallow eutrophic lakes, disproportionately contribute to greenhouse gas (GHG) emissions. To investigate the effects of eutrophication on GHG dynamics, we conducted field measurements every three months from January 2019 to October 2019 in Lake Ulansuhai, a shallow eutrophic lake (mean depth of 0.7 m) located in a semi-arid region in Northern China. We found that Lake Ulansuhai was a predominantly source of atmospheric carbon dioxide (CO2); however, it converted to a CO2 sink in July due to eutrophication. It was also a strong source of methane (CH4) with a mean CO2 emission of 35.7 ± 12.1 mmol m-2 d-1 and CH4 emission of 5.9 ± 2.9 mmol m-2 d-1. The CO2 concentrations in most sites and CH4 concentrations in all sites were supersaturated, with the average partial pressure of CO2 (pCO2) being 654±34 μatm and the partial pressure of CH4 (pCH4) being 157±37 μatm. The partial pressures and emissions of the greenhouse gases exhibited substantial seasonal and spatial variations. The correlation analysis between the trophic level index and the partial pressure of the greenhouse gases indicated that eutrophication could significantly decrease the CO2 emissions but increase the CH4 emissions from the lake, resulting in a CH4 and CO2 emission ratio of approximately 2 in terms of global warming potential. Eutrophication decreased the pCO2 in the lake and subsequently increased the pCH4 due to nutrient input, thereby enhancing primary production. The results indicated that shallow eutrophic lakes in arid regions are strong sources of CH4 and that eutrophication could alter the greenhouse gas emission patterns.
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Affiliation(s)
- Heyang Sun
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Xixi Lu
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China; Department of Geography, National University of Singapore 117570, Singapore
| | - Ruihong Yu
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China; Key Laboratory of Mongolian Plateau Ecology and Resource Utilization, Ministry of Education, Hohhot 010021, China.
| | - Jie Yang
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China; Buereau of Ecology and Environment of Inner Mongolia Autonomous Region, Hohhot 010021, China.
| | - Xinyu Liu
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Zhengxu Cao
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Zhuangzhuang Zhang
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Meixia Li
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Yue Geng
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
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