The presence of organic matter in lakes profoundly impacts drinking water supplies,yet treatment processes involving coagulants and disinfectants can yield carcinogenic disinfection by-products.Traditional assessments...The presence of organic matter in lakes profoundly impacts drinking water supplies,yet treatment processes involving coagulants and disinfectants can yield carcinogenic disinfection by-products.Traditional assessments of organic matter,such as chemical oxygen demand(COD_(Mn))and biochemical oxygen demand(BOD_(5)),are often time-consuming.Alternatively,optical measurements of dissolved organic matter(DOM)offer a rapid and reliable means of obtaining organic matter composition data.Here we employed DOM optical measurements in conjunction with parallel factor analysis to scrutinize COD_(Mn)and BOD_(5)variability.Validation was performed using an independent dataset encompassing six lakes on the Yungui Plateau from 2014 to 2016(n=256).Leveraging multiple linear regressions(MLRs)applied to DOM absorbance at 254 nm(a254)and fluorescence components C1-C5,we successfully traced COD_(Mn)and BOD_(5)variations across the entire plateau(68 lakes,n=271,R^(2)>0.8,P<0.0001).Notably,DOM optical indices yielded superior estimates(higher R^(2))of COD_(Mn)and BOD_(5)during the rainy season compared to the dry season and demonstrated increased accuracy(R^(2)>0.9)in mesotrophic lakes compared to oligotrophic and eutrophic lakes.This study underscores the utility of MLR-based DOM indices for inferring COD_(Mn)and BOD_(5)variability in plateau lakes and highlights the potential of integrating in situ and remote sensing platforms for water pollution early warning.展开更多
The authors regret that the following statements in the original article were wrong and have been corrected.The authors would like to apologise for any inconvenience caused.
The authors regret that the following statements in the original article were wrong and have been corrected.The authors would like to apologise for any inconvenience caused.
Aquatic vegetation is crucial for improving water quality,supporting fisheries and preserving biodiversity in lakes.Monitoring the spatiotemporal dynamics of aquatic vegetation is indispensable for the assessment and ...Aquatic vegetation is crucial for improving water quality,supporting fisheries and preserving biodiversity in lakes.Monitoring the spatiotemporal dynamics of aquatic vegetation is indispensable for the assessment and protection of lake ecosystems.Nevertheless,a comprehensive global assessment of lacustrine aquatic vegetation is lacking.This study introduces an automatic identification algorithm(with a total accuracy of 94.4%)for Sentinel-2 MSI,enabling the first-ever global mapping of aquatic vegetation distribution in 1.4 million lakes using 14.8 million images from 2019 to 2022.Results show that aquatic vegetation occurred in 81,116 lakes across six continents over the past four years,covering a cumulative maximum aquatic vegetation area(MVA)of 16,111.8 km^(2).The global median aquatic vegetation occurrence(VO,in%)is 3.0%,with notable higher values observed in South America(7.4%)and Africa(4.1%)compared with Asia(2.7%)and North America(2.4%).High VO is also observed in lakes near major rivers such as the Yangtze,Ob,and ParanáRivers.Integrating historical data with our calculated MVA,the aquatic vegetation changes in 170 lakes worldwide were analyzed.It shows that 72.4%(123/170)of lakes experienced a decline in aquatic vegetation from the early 1980s to 2022,encompassing both submerged and overall aquatic vegetation.The most substantial decrease is observed in Asia and Africa.Our findings suggest that,beyond lake algal blooms and temperature,the physical characteristics of the lakes and their surrounding environments could also influence aquatic vegetation distribution.Our research provides valuable information for the conservation and restoration of lacustrine aquatic vegetation.展开更多
Phosphorus is a vital nutrient for algal growth,thus,a better understanding of phosphorus availability is essential to mitigate harmful algal blooms in lakes.Wind waves are a ubiquitous characteristic of lake ecosyste...Phosphorus is a vital nutrient for algal growth,thus,a better understanding of phosphorus availability is essential to mitigate harmful algal blooms in lakes.Wind waves are a ubiquitous characteristic of lake ecosystems.However,its effects on the cycling of organic phosphorus and its usage by phytoplankton remain poorly elucidated in shallow eutrophic lakes.A mesocosm experiment was carried out to investigate the responses of alkaline phosphatase activity fractions to wind waves in large,shallow,eutrophic Lake Taihu.Results showed that wind-driven waves induced the release of alkaline phosphatase and phosphorus from the sediment,and dramatically enhanced phytoplanktonic alkaline phosphatase activity.However,compared to the calm conditions,bacterial and dissolved alkaline phosphatase activity decreased in wind-wave conditions.Consistently,the gene copies of Microcystis phoX increased but bacterial phoX decreased under wind-wave conditions.The ecological effects of these waves on phosphorus and phytoplankton likely accelerated the biogeochemical cycling of phosphorus and promoted phytoplankton production in Lake Taihu.This study provides an improved current understanding of phosphorus availability and the phosphorus strategies of plankton in shallow,eutrophic lakes.展开更多
Interactions between dissolved organic matter(DOM)and bacteria are central in the biogeochemical cycles of aquatic ecosystems;however,the relative importance of biodegradable dissolved organic carbon(BDOC)compared wit...Interactions between dissolved organic matter(DOM)and bacteria are central in the biogeochemical cycles of aquatic ecosystems;however,the relative importance of biodegradable dissolved organic carbon(BDOC)compared with other environmental variables in structuring the bacterial communities needs further investigation.Here,we investigated bacterial communities,chromophoric DOM(CDOM)characteristics and physico-chemical parameters as well as examined BDOC via bioassay incubations in large eutrophic Lake Taihu,China,to explore the importance of BDOC for shaping bacterial community structures and co-occurrence patterns.We found that the proportion of BDOC(%BDOC)correlated significantly and positively with the DOC concentration and the index of the contribution of recent produced autochthonous CDOM(BIX).%BDOC,further correlated positively with the relative abundance of the tryptophan-like component and negatively with CDOM aromaticity,indicating that autochthonous production of protein-like CDOM was an important source of BDOC.The richness of the bacterial communities correlated negatively with%BDOC,indicating an enhanced number of species in the refractory DOC environments.%BDOC was identified as a significant stronger factor than DOC in shaping bacterial community composition and the co-occurrence network,suggesting that substrate biodegradability is more significant than DOC quantity determining the bacterial communities in a eutrophic lake.Environmental factors explained a larger proportion of the variation in the conditionally rare and abundant subcommunity than for the abundant and the rare bacterial subcommunities.Our findings emphasize the importance of considering bacteria with different abundance patterns and DOC biodegradability when studying the interactions between DOM and bacteria in eutrophic lakes.展开更多
The global application of nitrogen is far greater than phosphorus, and it is widely involved in the eutrophication of lakes and reservoirs. We used a bibliometric method to quantitatively and qualitatively evaluate ni...The global application of nitrogen is far greater than phosphorus, and it is widely involved in the eutrophication of lakes and reservoirs. We used a bibliometric method to quantitatively and qualitatively evaluate nitrogen research in eutrophic lakes and reservoirs to reveal research developments, current research hotspots, and emerging trends in this area. A total of 2695 articles in the past 25 years from the online database of the Scientific Citation Index Expended（SCI-Expanded） were analyzed. Articles in this area increased exponentially from 1991 to 2015.Although the USA was the most productive country over the past 25 years, China achieved the top position in terms of yearly publications after 2010. The most active keywords related to nitrogen in the past 25 years included phosphorus, nutrients, sediment, chlorophyll-a, carbon,phytoplankton, cyanobacteria, water quality, modeling, and stable isotopes, based on analysis within 5-year intervals from 1991 to 2015 as well as the entire past 25 years. In addition, researchers have drawn increasing attention to denitrification, climate change, and internal loading. Future trends in this area should focus on：（1） nutrient amounts, ratios, and major nitrogen sources leading to eutrophication;（2） nitrogen transformation and the bioavailability of different nitrogen forms;（3）nitrogen budget, mass balance model, control, and management;（4） ecosystem responses to nitrogen enrichment and reduction, as well as the relationships between these responses; and（5）interactions between nitrogen and other stressors（e.g., light intensity, carbon, phosphorus, toxic contaminants, climate change, and hydrological variations） in terms of eutrophication.展开更多
To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were...To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were conducted. The results show that there was no significant variation in the euphotic depth（Z（eu）） across the four seasons, and no significant correlations between Z（eu） and potential influencing factors in seasons other than summer, suggesting that the water itself may be a major factor regulating the Z（eu）in general. Nevertheless, significant differences in Z（eu） between the north region（NR） and the south region（SR） were observed in all seasonal tests except spring. This finding relates to a higher abundance of chromophoric dissolved organic matter（CDOM） in the NR due to runoff, especially in the rainy seasons（summer and autumn）.CDOM and its terrigenous component had an important impact on Z（eu）in summer, with the highest precipitation, and impacts from suspended solids and non-algal particles were also found in the NR in summer. The Secchi disk depth in the lake decreased clearly over the years,with significantly negative correlations with the increasing permanganate index and air temperature, implying that organic contaminants（CDOM and/or phytoplankton） are important regulators of water transparency. We estimate that the combined effects of climate warming and changes in land use and land cover are also indirect regulating factors. These findings should be considered in the protection of Lake Fuxian, owing to the importance of light penetration in aquatic ecosystems.展开更多
Light climate is of key importance for the growth, community composition of submerged macrophytes in lakes and, they, in turn, are affected by lake depth and the degree of eutrophication. To test the relationships bet...Light climate is of key importance for the growth, community composition of submerged macrophytes in lakes and, they, in turn, are affected by lake depth and the degree of eutrophication. To test the relationships between submerged macrophyte presence and the ratio of Secchi disk depth(SDD) to water depth, i.e. SDD/depth, nutrients and wind, we conducted an extensive sampling campaign in a macrophyte-dominated area of the eastern region( n = 36) in 2016 in Lake Taihu, China, and combined the data gathered with results from extensive physico-chemical monitoring data from the entire lake. We confirmed that SDD/Depth is the primary factor controlling the community composition of macrophytes and showed that plant abundance increased with increasing SDD/Depth ratio( p < 0.01), but that only SDD/Depth > 0.4 ensured growth of submerged macrophytes. Total phosphorus and total nitrogen also influenced the growth and community composition of macrophytes( p < 0.01), while Chl a was an indirectly affecting factor by reducing underwater light penetration. Wave height significantly influenced plant abundance( p < 0.01), whereas it had little effect on the biomass( p > 0.05). The key to restore the macrophyte beds in the lake is to reduce the nutrient loading. A decrease of the water level may contribute as well in the shallow bays but will not bring plants back in the main part of the lake. As the tolerance of shade and nutrients varied among the species studied, this should be taken into account in the restoration of lakes by addition of plants.展开更多
Long-term decreases in the incident total radiation and water clarity might substantially affect the underwater light environment in aquatic ecosystems.However,the underlying mechanism and relative contributions of ra...Long-term decreases in the incident total radiation and water clarity might substantially affect the underwater light environment in aquatic ecosystems.However,the underlying mechanism and relative contributions of radiation dimming and decreasing water clarity to the underwater light environment on a national or global scale remains largely unknown.Here,we present a comprehensive dataset of unprecedented scale in China’s lakes to address the combined effects of radiation dimming and decreasing water clarity on underwater darkening.Long-term total radiation and sunshine duration showed 5.8%and 7.9%decreases,respectively,after 2000 compared to 1961–1970,resulting in net radiation dimming.An in situ Secchi disk depth(SDD)dataset in 170 lakes showed that the mean SDD significantly decreased from 1.80±2.19 m before 1995 to 1.28±1.82 m after 2005.SDD remote sensing estimations for 641 lakes with areas≥10 km^2 showed that SDD markedly decreased from 1.26±0.62 m during 1985–1990 to 1.14±0.66 m during 2005–2010.Radiation dimming and decreasing water clarity jointly caused an approximately 10%decrease in the average available photosynthetically active radiation(PAR)in the euphotic layer.Our results revealed a more important role of decreasing water clarity in underwater darkening than radiation dimming.A meta-analysis of long-term SDD observation data from 61 various waters further elucidated a global extensive underwater darkening.Underwater darkening implies a decrease in water quality for potable water supplies,recession in macrophytes and benthic algae,and decreases in benthic primary production,fishery production,and biodiversity.展开更多
Timely monitoring, detection and quantification of cyanobacterial blooms are especially important for controlling public health risks and understanding aquatic ecosystem dynamics. Due to the advantages of simultaneous...Timely monitoring, detection and quantification of cyanobacterial blooms are especially important for controlling public health risks and understanding aquatic ecosystem dynamics. Due to the advantages of simultaneous data acquisition over large geographical areas and high temporal coverage, remote sensing strongly facilitates cyanobacterial bloom monitoring in inland waters. We provide a comprehensive review regarding cyanobacterial bloom remote sensing in inland waters including cyanobacterial optical characteristics, operational remote sensing algorithms of chlorophyll, phycocyanin and cyanobacterial bloom areas, and satellite imaging applications. We conclude that there have many significant progresses in the remote sensing algorithm of cyanobacterial pigments over the past 30 years. The band ratio algorithms in the red and near-infrared(NIR) spectral regions have great potential for the remote estimation of chlorophyll a in eutrophic and hypereutrophic inland waters, and the floating algae index(FAI) is the most widely used spectral index for detecting dense cyanobacterial blooms. Landsat, MODIS(Moderate Resolution Imaging Spectroradiometer) and MERIS(MEdium Resolution Imaging Spectrometer) are the most widely used products for monitoring the spatial and temporal dynamics of cyanobacteria in inland waters due to the appropriate temporal, spatial and spectral resolutions. Future work should primarily focus on the development of universal algorithms, remote retrievals of cyanobacterial blooms in oligotrophic waters, and the algorithm applicability to mapping phycocyanin at a large spatial-temporal scale. The applications of satellite images will greatly improve our understanding of the driving mechanism of cyanobacterial blooms by combining numerical and ecosystem dynamics models.展开更多
基金the support of the Science and Technology Project of Yunnan Province(No.202103AC100001)the National Natural Science Foundation of China(Nos.42322104 and 42071131)+3 种基金the National Key Research and Development Programof China(No.2017YFA0605202)the Youth Innovation Promotion Association CAS(No.2021312)the Provincial Natural Science Foundation of Jiangsu(No.BK20220162)the TÜBITAK program BIDEB2232(project 118C250).
文摘The presence of organic matter in lakes profoundly impacts drinking water supplies,yet treatment processes involving coagulants and disinfectants can yield carcinogenic disinfection by-products.Traditional assessments of organic matter,such as chemical oxygen demand(COD_(Mn))and biochemical oxygen demand(BOD_(5)),are often time-consuming.Alternatively,optical measurements of dissolved organic matter(DOM)offer a rapid and reliable means of obtaining organic matter composition data.Here we employed DOM optical measurements in conjunction with parallel factor analysis to scrutinize COD_(Mn)and BOD_(5)variability.Validation was performed using an independent dataset encompassing six lakes on the Yungui Plateau from 2014 to 2016(n=256).Leveraging multiple linear regressions(MLRs)applied to DOM absorbance at 254 nm(a254)and fluorescence components C1-C5,we successfully traced COD_(Mn)and BOD_(5)variations across the entire plateau(68 lakes,n=271,R^(2)>0.8,P<0.0001).Notably,DOM optical indices yielded superior estimates(higher R^(2))of COD_(Mn)and BOD_(5)during the rainy season compared to the dry season and demonstrated increased accuracy(R^(2)>0.9)in mesotrophic lakes compared to oligotrophic and eutrophic lakes.This study underscores the utility of MLR-based DOM indices for inferring COD_(Mn)and BOD_(5)variability in plateau lakes and highlights the potential of integrating in situ and remote sensing platforms for water pollution early warning.
文摘The authors regret that the following statements in the original article were wrong and have been corrected.The authors would like to apologise for any inconvenience caused.
文摘The authors regret that the following statements in the original article were wrong and have been corrected.The authors would like to apologise for any inconvenience caused.
基金supported by the Open Research Program of the International Research Center of Big Data for Sustainable Development Goals(CBAS2022ORP04)the National Natural Science Foundation of China(42301392)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(23qnpy08)。
文摘Aquatic vegetation is crucial for improving water quality,supporting fisheries and preserving biodiversity in lakes.Monitoring the spatiotemporal dynamics of aquatic vegetation is indispensable for the assessment and protection of lake ecosystems.Nevertheless,a comprehensive global assessment of lacustrine aquatic vegetation is lacking.This study introduces an automatic identification algorithm(with a total accuracy of 94.4%)for Sentinel-2 MSI,enabling the first-ever global mapping of aquatic vegetation distribution in 1.4 million lakes using 14.8 million images from 2019 to 2022.Results show that aquatic vegetation occurred in 81,116 lakes across six continents over the past four years,covering a cumulative maximum aquatic vegetation area(MVA)of 16,111.8 km^(2).The global median aquatic vegetation occurrence(VO,in%)is 3.0%,with notable higher values observed in South America(7.4%)and Africa(4.1%)compared with Asia(2.7%)and North America(2.4%).High VO is also observed in lakes near major rivers such as the Yangtze,Ob,and ParanáRivers.Integrating historical data with our calculated MVA,the aquatic vegetation changes in 170 lakes worldwide were analyzed.It shows that 72.4%(123/170)of lakes experienced a decline in aquatic vegetation from the early 1980s to 2022,encompassing both submerged and overall aquatic vegetation.The most substantial decrease is observed in Asia and Africa.Our findings suggest that,beyond lake algal blooms and temperature,the physical characteristics of the lakes and their surrounding environments could also influence aquatic vegetation distribution.Our research provides valuable information for the conservation and restoration of lacustrine aquatic vegetation.
基金the National Natural Science Foundation of China(Nos.41701098,41621002,and 41830757)the Major Science and Technology Program for Water Pollution Control and Treatment(No.2018ZX07701001-24)“One-Three-Five”Strategic Planning of Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences(Nos.NIGLAS2017GH03,NIGLAS2017GH04,and NIGLAS2017GH05)。
文摘Phosphorus is a vital nutrient for algal growth,thus,a better understanding of phosphorus availability is essential to mitigate harmful algal blooms in lakes.Wind waves are a ubiquitous characteristic of lake ecosystems.However,its effects on the cycling of organic phosphorus and its usage by phytoplankton remain poorly elucidated in shallow eutrophic lakes.A mesocosm experiment was carried out to investigate the responses of alkaline phosphatase activity fractions to wind waves in large,shallow,eutrophic Lake Taihu.Results showed that wind-driven waves induced the release of alkaline phosphatase and phosphorus from the sediment,and dramatically enhanced phytoplanktonic alkaline phosphatase activity.However,compared to the calm conditions,bacterial and dissolved alkaline phosphatase activity decreased in wind-wave conditions.Consistently,the gene copies of Microcystis phoX increased but bacterial phoX decreased under wind-wave conditions.The ecological effects of these waves on phosphorus and phytoplankton likely accelerated the biogeochemical cycling of phosphorus and promoted phytoplankton production in Lake Taihu.This study provides an improved current understanding of phosphorus availability and the phosphorus strategies of plankton in shallow,eutrophic lakes.
基金supported by the National Natural Science Foundation of China (Nos.41930760, 41807362, and 41977322)the Provincial Natural Science Foundation of Jiangsu in China (No.BK20181104)+2 种基金the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (No.QYZDB-SSWDQC016)supported by WATEC (Centre for Water Technology, AU)the TüBITAK outstanding scientists program 2232 (project 118C250)。
文摘Interactions between dissolved organic matter(DOM)and bacteria are central in the biogeochemical cycles of aquatic ecosystems;however,the relative importance of biodegradable dissolved organic carbon(BDOC)compared with other environmental variables in structuring the bacterial communities needs further investigation.Here,we investigated bacterial communities,chromophoric DOM(CDOM)characteristics and physico-chemical parameters as well as examined BDOC via bioassay incubations in large eutrophic Lake Taihu,China,to explore the importance of BDOC for shaping bacterial community structures and co-occurrence patterns.We found that the proportion of BDOC(%BDOC)correlated significantly and positively with the DOC concentration and the index of the contribution of recent produced autochthonous CDOM(BIX).%BDOC,further correlated positively with the relative abundance of the tryptophan-like component and negatively with CDOM aromaticity,indicating that autochthonous production of protein-like CDOM was an important source of BDOC.The richness of the bacterial communities correlated negatively with%BDOC,indicating an enhanced number of species in the refractory DOC environments.%BDOC was identified as a significant stronger factor than DOC in shaping bacterial community composition and the co-occurrence network,suggesting that substrate biodegradability is more significant than DOC quantity determining the bacterial communities in a eutrophic lake.Environmental factors explained a larger proportion of the variation in the conditionally rare and abundant subcommunity than for the abundant and the rare bacterial subcommunities.Our findings emphasize the importance of considering bacteria with different abundance patterns and DOC biodegradability when studying the interactions between DOM and bacteria in eutrophic lakes.
基金supported by the International Science & Technology Cooperation Program of China (No. 2014DFG91780)the National Natural Science Foundation of China (Nos. 41325001, 41230744 and 41621002)
文摘The global application of nitrogen is far greater than phosphorus, and it is widely involved in the eutrophication of lakes and reservoirs. We used a bibliometric method to quantitatively and qualitatively evaluate nitrogen research in eutrophic lakes and reservoirs to reveal research developments, current research hotspots, and emerging trends in this area. A total of 2695 articles in the past 25 years from the online database of the Scientific Citation Index Expended（SCI-Expanded） were analyzed. Articles in this area increased exponentially from 1991 to 2015.Although the USA was the most productive country over the past 25 years, China achieved the top position in terms of yearly publications after 2010. The most active keywords related to nitrogen in the past 25 years included phosphorus, nutrients, sediment, chlorophyll-a, carbon,phytoplankton, cyanobacteria, water quality, modeling, and stable isotopes, based on analysis within 5-year intervals from 1991 to 2015 as well as the entire past 25 years. In addition, researchers have drawn increasing attention to denitrification, climate change, and internal loading. Future trends in this area should focus on：（1） nutrient amounts, ratios, and major nitrogen sources leading to eutrophication;（2） nitrogen transformation and the bioavailability of different nitrogen forms;（3）nitrogen budget, mass balance model, control, and management;（4） ecosystem responses to nitrogen enrichment and reduction, as well as the relationships between these responses; and（5）interactions between nitrogen and other stressors（e.g., light intensity, carbon, phosphorus, toxic contaminants, climate change, and hydrological variations） in terms of eutrophication.
基金supported by the National Natural Science Foundation of China(Nos.41601208,41325001)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDB-SSW-DQC016)+1 种基金the State Key Laboratory of Lake Science and Environment(No.2016SKL007)the Yunnan Science and Technology Project(Nos.2016RA081,2017FD029)
文摘To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were conducted. The results show that there was no significant variation in the euphotic depth（Z（eu）） across the four seasons, and no significant correlations between Z（eu） and potential influencing factors in seasons other than summer, suggesting that the water itself may be a major factor regulating the Z（eu）in general. Nevertheless, significant differences in Z（eu） between the north region（NR） and the south region（SR） were observed in all seasonal tests except spring. This finding relates to a higher abundance of chromophoric dissolved organic matter（CDOM） in the NR due to runoff, especially in the rainy seasons（summer and autumn）.CDOM and its terrigenous component had an important impact on Z（eu）in summer, with the highest precipitation, and impacts from suspended solids and non-algal particles were also found in the NR in summer. The Secchi disk depth in the lake decreased clearly over the years,with significantly negative correlations with the increasing permanganate index and air temperature, implying that organic contaminants（CDOM and/or phytoplankton） are important regulators of water transparency. We estimate that the combined effects of climate warming and changes in land use and land cover are also indirect regulating factors. These findings should be considered in the protection of Lake Fuxian, owing to the importance of light penetration in aquatic ecosystems.
基金jointly funded by the National Key R&D Program of China(No.2017YFC0405205)the Major Projects on Control and Rectification of Water Body Pollution(No.2017ZX07203–004)+1 种基金the National Natural Science Foundation of China(Nos.42071118 and 41621002)supported by the TüBITAK,BIDEB program 2232.
文摘Light climate is of key importance for the growth, community composition of submerged macrophytes in lakes and, they, in turn, are affected by lake depth and the degree of eutrophication. To test the relationships between submerged macrophyte presence and the ratio of Secchi disk depth(SDD) to water depth, i.e. SDD/depth, nutrients and wind, we conducted an extensive sampling campaign in a macrophyte-dominated area of the eastern region( n = 36) in 2016 in Lake Taihu, China, and combined the data gathered with results from extensive physico-chemical monitoring data from the entire lake. We confirmed that SDD/Depth is the primary factor controlling the community composition of macrophytes and showed that plant abundance increased with increasing SDD/Depth ratio( p < 0.01), but that only SDD/Depth > 0.4 ensured growth of submerged macrophytes. Total phosphorus and total nitrogen also influenced the growth and community composition of macrophytes( p < 0.01), while Chl a was an indirectly affecting factor by reducing underwater light penetration. Wave height significantly influenced plant abundance( p < 0.01), whereas it had little effect on the biomass( p > 0.05). The key to restore the macrophyte beds in the lake is to reduce the nutrient loading. A decrease of the water level may contribute as well in the shallow bays but will not bring plants back in the main part of the lake. As the tolerance of shade and nutrients varied among the species studied, this should be taken into account in the restoration of lakes by addition of plants.
基金supported by the National Natural Science Foundation of China(41621002,41790423,41930760)the Key Program of the Chinese Academy of Sciences(ZDRW-ZS2017-3-4)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(QYZDB-SSW-DQC016)。
文摘Long-term decreases in the incident total radiation and water clarity might substantially affect the underwater light environment in aquatic ecosystems.However,the underlying mechanism and relative contributions of radiation dimming and decreasing water clarity to the underwater light environment on a national or global scale remains largely unknown.Here,we present a comprehensive dataset of unprecedented scale in China’s lakes to address the combined effects of radiation dimming and decreasing water clarity on underwater darkening.Long-term total radiation and sunshine duration showed 5.8%and 7.9%decreases,respectively,after 2000 compared to 1961–1970,resulting in net radiation dimming.An in situ Secchi disk depth(SDD)dataset in 170 lakes showed that the mean SDD significantly decreased from 1.80±2.19 m before 1995 to 1.28±1.82 m after 2005.SDD remote sensing estimations for 641 lakes with areas≥10 km^2 showed that SDD markedly decreased from 1.26±0.62 m during 1985–1990 to 1.14±0.66 m during 2005–2010.Radiation dimming and decreasing water clarity jointly caused an approximately 10%decrease in the average available photosynthetically active radiation(PAR)in the euphotic layer.Our results revealed a more important role of decreasing water clarity in underwater darkening than radiation dimming.A meta-analysis of long-term SDD observation data from 61 various waters further elucidated a global extensive underwater darkening.Underwater darkening implies a decrease in water quality for potable water supplies,recession in macrophytes and benthic algae,and decreases in benthic primary production,fishery production,and biodiversity.
基金supported by the National Natural Science Foundation of China(U22A20561 and 41922005)the Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0202)+3 种基金the National Key Research and Development Program of China(2022YFC3204100)the Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences Foundation(E1SL002)supported by the Tübitak Program BIDEB2232(Project 118C250)supported by a UK Research and Innovation(UKRI)Natural Environment Research Council(NERC)Independent Research Fellowship(NE/T011246/1)。
基金supported by the National Natural Science Foundation of China (U22A20561 and 41922005)the Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0202)+4 种基金the Foundation of Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences (E1SL002)the Water Resource Science and Technology Project in Jiangsu Province (2020057)the Key Research and Development Program of Jiangsu Province (Social Development) (BE2022857)the TüBITAK BIDEB2232 Program (118C250)the UKRI Natural Environment Research Council (NERC) Independent Research Fellowship (NE/T011246/1)。
基金supported by the National Science and Technology Major Project of China(2017ZX07203001)the National Natural Science Foundation of China(41771472 and 41621002)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(2017365)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDB-SSW-DQC016)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA19070301)
文摘Timely monitoring, detection and quantification of cyanobacterial blooms are especially important for controlling public health risks and understanding aquatic ecosystem dynamics. Due to the advantages of simultaneous data acquisition over large geographical areas and high temporal coverage, remote sensing strongly facilitates cyanobacterial bloom monitoring in inland waters. We provide a comprehensive review regarding cyanobacterial bloom remote sensing in inland waters including cyanobacterial optical characteristics, operational remote sensing algorithms of chlorophyll, phycocyanin and cyanobacterial bloom areas, and satellite imaging applications. We conclude that there have many significant progresses in the remote sensing algorithm of cyanobacterial pigments over the past 30 years. The band ratio algorithms in the red and near-infrared(NIR) spectral regions have great potential for the remote estimation of chlorophyll a in eutrophic and hypereutrophic inland waters, and the floating algae index(FAI) is the most widely used spectral index for detecting dense cyanobacterial blooms. Landsat, MODIS(Moderate Resolution Imaging Spectroradiometer) and MERIS(MEdium Resolution Imaging Spectrometer) are the most widely used products for monitoring the spatial and temporal dynamics of cyanobacteria in inland waters due to the appropriate temporal, spatial and spectral resolutions. Future work should primarily focus on the development of universal algorithms, remote retrievals of cyanobacterial blooms in oligotrophic waters, and the algorithm applicability to mapping phycocyanin at a large spatial-temporal scale. The applications of satellite images will greatly improve our understanding of the driving mechanism of cyanobacterial blooms by combining numerical and ecosystem dynamics models.
