The effect of spatial pattern on the nutrient reduction is investigated based on the spatial simulation model developed for the study area of the Liaohe Delta, China. Four scenarios are designed to test the effect of ...The effect of spatial pattern on the nutrient reduction is investigated based on the spatial simulation model developed for the study area of the Liaohe Delta, China. Four scenarios are designed to test the effect of different landscape components on the nutrient reduction in the reed marsh: Canal density, reed area size, reed area shrinking pattern, and pumping station position. Based on a spatial model designed for the study area, the nutrient reduction in each case of these scenarios is simulated. The results indicate that each factor brings less than 10% change in the total nutrient reduction rate. More canals will not help much to improve nutrient reduction. Smaller areas are more efficient than larger ones. The shrinkage pattern is better than others in keeping a higher nutrient reduction rate. It is also more efficient to keep the pumping station near the border of the area to be irrigated. These conclusions provide theoretical supports to strategy makers for local land use planning, and contribute to the understanding of the relationship between landscape patterns and functions.展开更多
Large and shallow lakes are widely influenced by multiple anthropogenic stressors,including eutrophication.Normally,diverse strategies of eutrophication management are needed to restore the lake ecosystems.Dianchi Lak...Large and shallow lakes are widely influenced by multiple anthropogenic stressors,including eutrophication.Normally,diverse strategies of eutrophication management are needed to restore the lake ecosystems.Dianchi Lake,a subtropical plateau lake in Yunnan Province,SW China,has long experienced the effects of eutrophication and cyanobacterial blooms.To mitigate the eutrophication of Dianchi Lake,various efforts have been implemented since 2000,including reducing nutrient inputs,reestablishing aquatic macrophytes in lakeside zones,manipulating fishes and so on.However,little is known about the changes in its ecosystem structure and function after long-term efforts of eutrophication management in the lake.Therefore,this study on such changes was conducted by comparing the field data-based Ecopath models between 2009 and 2019,a decade marked by a rapid implementation of eutrophication management policies.Results show that both top-down and bottom-up processes have influenced the ecosystem structure and function.First,over this decade,nutrient reduction significantly reduced phytoplankton biomass by 49.4%.Nutrient recycling and path length in food web began to decrease,as indicated by the decrease of Finn's cycling index and Finn's mean path length.Secondly,fishing management strategy has greatly changed the composition of fish assemblage,which was dominated by the small zooplantivorous fishes with ecological niche overlapping with shrimps.In general,the stability of the ecosystem has been decreasing,due to the dramatic decrease in zooplankton biomass(83.67%)and hence a collapse of the microbial loop in the food web.Therefore,we strongly advocate the persistent efforts to mitigate the risk of recurrent cyanobacteria blooms in Dianchi Lake,necessitating stricter regulation of nutrient levels and implementing effective fish population management techniques.展开更多
Lake Erhai,a lake in the early stage of eutrophication,has been threatened by algal blooms(particularly the overproliferation of blue-green algae),which can have an impact on drinking water safety and the lake's e...Lake Erhai,a lake in the early stage of eutrophication,has been threatened by algal blooms(particularly the overproliferation of blue-green algae),which can have an impact on drinking water safety and the lake's ecosystem.Understanding the governing factors of cyanobacterial blooms is critical for taking timely and effective action during this key eutrophication-transition period.However,long-term records of cyanobacterial bloom and its key dominating factors remain unclear.It is,therefore,essential to understand the bloom dynamics and the driving forces before any control strategies can be determined.We investigated the cyanobacterial phycocyanin concentration variability based on satellite observations from 2003 to 2019,by using the empirical orthogonal function analysis.We observed a decrease in the coverage of the dominant mode of variability in phycocyanin magnitudes compared to the period 2003 to 2011,with variations primarily occurring in the northern bays.The largest variability was identified to be predominant in July,and an apparent timing shift in variability was observed in December 2016 and 2017.The 95%quantile regression model indicated a distinct upper boundary response in cyanobacteria proliferation to the joint Total Nitrogen(TN)and Total Phosphorus(TP)concentrations,which occurred in summer from 2003 to 2011.An apparent response of cyanobacterial bloom to TP was observed during the winters from 2016 to 2019.Additionally,water level and TN:TP ratio played a central role in summer from 2003 to 2011,while from 2016 to 2019,TN:TP ratio was found to dominate in the summer months.In winter,air temperature turned out to be a significant modulating factor compared to water level.Our results suggest that implementing a phosphorus reduction strategy,while controlling TN:TP ratio and suitable water level manipulation,should be considered to ensure the sustainability of Lake Erhai,especially under a consistent global warming scenario.展开更多
Spatial and temporal characteristics of Zostera marina (eelgrass) in the Barnegat Bay-Little Egg Harbor Estuary are compared before (2004-2011) and after (2012-2013) major fertilizer legislation (Fertilizer Law A2290)...Spatial and temporal characteristics of Zostera marina (eelgrass) in the Barnegat Bay-Little Egg Harbor Estuary are compared before (2004-2011) and after (2012-2013) major fertilizer legislation (Fertilizer Law A2290) was enacted in New Jersey (USA) to reduce nutrient inputs from fertilizers to water bodies in the state. A significant decrease of Z. marina biomass and areal cover occurred in this eutrophic estuary between 2004 and 2011 concomitantly with increasing nitrogen and phosphorus loading from the watershed. The rate of decline in aboveground and belowground biomass was significantly sharper during 2004-2006 than during 2008-2010. In 2010, Z. marina biomass dropped to a very low level (mean aboveground biomass = 7.7 g dry wt m<sup>DŽ</sup>;mean belowground biomass = 27.0 g dry wt m<sup>DŽ</sup>), persisting through the last sampling period (October-November) in 2013. Biomass and areal cover of Z. marina decreased even further after Fertilizer Law A2290 was enacted in January 2012, with the lowest values recorded from August to November each year. These low values are the result of ongoing eutrophication of the system. More seagrass monitoring and research are necessary in future years to determine if the fertilizer law will have a positive effect on Z. marina condition in the estuary over the long term.展开更多
基金National Natural Science Foundation of China, NSFC 49631040, 40001002 Wageningen Agricultural University, the Netherlands Co-s
文摘The effect of spatial pattern on the nutrient reduction is investigated based on the spatial simulation model developed for the study area of the Liaohe Delta, China. Four scenarios are designed to test the effect of different landscape components on the nutrient reduction in the reed marsh: Canal density, reed area size, reed area shrinking pattern, and pumping station position. Based on a spatial model designed for the study area, the nutrient reduction in each case of these scenarios is simulated. The results indicate that each factor brings less than 10% change in the total nutrient reduction rate. More canals will not help much to improve nutrient reduction. Smaller areas are more efficient than larger ones. The shrinkage pattern is better than others in keeping a higher nutrient reduction rate. It is also more efficient to keep the pumping station near the border of the area to be irrigated. These conclusions provide theoretical supports to strategy makers for local land use planning, and contribute to the understanding of the relationship between landscape patterns and functions.
基金Supported by the Yunnan-Kunming Major Science and Technology Project(No.202202AH210006)the Dianchi Lake Ecosystem Observation and Research Station of Yunnan Province Project(No.202305AM340008)+2 种基金the Yunnan-Kunming Liu Yongding Academician Workstation Funds(No.YSZJGZZ-2020018)the Yunnan Science and Technology Commission(Nos.202401AS070119,202103AC100001)the National Natural Science Foundation of China(No.52379081)。
文摘Large and shallow lakes are widely influenced by multiple anthropogenic stressors,including eutrophication.Normally,diverse strategies of eutrophication management are needed to restore the lake ecosystems.Dianchi Lake,a subtropical plateau lake in Yunnan Province,SW China,has long experienced the effects of eutrophication and cyanobacterial blooms.To mitigate the eutrophication of Dianchi Lake,various efforts have been implemented since 2000,including reducing nutrient inputs,reestablishing aquatic macrophytes in lakeside zones,manipulating fishes and so on.However,little is known about the changes in its ecosystem structure and function after long-term efforts of eutrophication management in the lake.Therefore,this study on such changes was conducted by comparing the field data-based Ecopath models between 2009 and 2019,a decade marked by a rapid implementation of eutrophication management policies.Results show that both top-down and bottom-up processes have influenced the ecosystem structure and function.First,over this decade,nutrient reduction significantly reduced phytoplankton biomass by 49.4%.Nutrient recycling and path length in food web began to decrease,as indicated by the decrease of Finn's cycling index and Finn's mean path length.Secondly,fishing management strategy has greatly changed the composition of fish assemblage,which was dominated by the small zooplantivorous fishes with ecological niche overlapping with shrimps.In general,the stability of the ecosystem has been decreasing,due to the dramatic decrease in zooplankton biomass(83.67%)and hence a collapse of the microbial loop in the food web.Therefore,we strongly advocate the persistent efforts to mitigate the risk of recurrent cyanobacteria blooms in Dianchi Lake,necessitating stricter regulation of nutrient levels and implementing effective fish population management techniques.
基金supported by the National Natural Science Foundation of China[grant number 41971402]the Central Fund Supporting Nonprofit Scientific Institutes for Basic Research and Development[grant number PM-zx703-202104-051]+2 种基金the Science and Technology Project of Department of Natural Resources of Hubei Province[grant number ZRZY2023KJ41]the Science and Technology Program of Guangzhou,China[grant number 202102080268]the ESA-MOST Dragon Program,and the LIESMARS Special Research Funding.
文摘Lake Erhai,a lake in the early stage of eutrophication,has been threatened by algal blooms(particularly the overproliferation of blue-green algae),which can have an impact on drinking water safety and the lake's ecosystem.Understanding the governing factors of cyanobacterial blooms is critical for taking timely and effective action during this key eutrophication-transition period.However,long-term records of cyanobacterial bloom and its key dominating factors remain unclear.It is,therefore,essential to understand the bloom dynamics and the driving forces before any control strategies can be determined.We investigated the cyanobacterial phycocyanin concentration variability based on satellite observations from 2003 to 2019,by using the empirical orthogonal function analysis.We observed a decrease in the coverage of the dominant mode of variability in phycocyanin magnitudes compared to the period 2003 to 2011,with variations primarily occurring in the northern bays.The largest variability was identified to be predominant in July,and an apparent timing shift in variability was observed in December 2016 and 2017.The 95%quantile regression model indicated a distinct upper boundary response in cyanobacteria proliferation to the joint Total Nitrogen(TN)and Total Phosphorus(TP)concentrations,which occurred in summer from 2003 to 2011.An apparent response of cyanobacterial bloom to TP was observed during the winters from 2016 to 2019.Additionally,water level and TN:TP ratio played a central role in summer from 2003 to 2011,while from 2016 to 2019,TN:TP ratio was found to dominate in the summer months.In winter,air temperature turned out to be a significant modulating factor compared to water level.Our results suggest that implementing a phosphorus reduction strategy,while controlling TN:TP ratio and suitable water level manipulation,should be considered to ensure the sustainability of Lake Erhai,especially under a consistent global warming scenario.
文摘Spatial and temporal characteristics of Zostera marina (eelgrass) in the Barnegat Bay-Little Egg Harbor Estuary are compared before (2004-2011) and after (2012-2013) major fertilizer legislation (Fertilizer Law A2290) was enacted in New Jersey (USA) to reduce nutrient inputs from fertilizers to water bodies in the state. A significant decrease of Z. marina biomass and areal cover occurred in this eutrophic estuary between 2004 and 2011 concomitantly with increasing nitrogen and phosphorus loading from the watershed. The rate of decline in aboveground and belowground biomass was significantly sharper during 2004-2006 than during 2008-2010. In 2010, Z. marina biomass dropped to a very low level (mean aboveground biomass = 7.7 g dry wt m<sup>DŽ</sup>;mean belowground biomass = 27.0 g dry wt m<sup>DŽ</sup>), persisting through the last sampling period (October-November) in 2013. Biomass and areal cover of Z. marina decreased even further after Fertilizer Law A2290 was enacted in January 2012, with the lowest values recorded from August to November each year. These low values are the result of ongoing eutrophication of the system. More seagrass monitoring and research are necessary in future years to determine if the fertilizer law will have a positive effect on Z. marina condition in the estuary over the long term.
