TY - JOUR
T1 - The Role of Top-Down and Bottom-Up Control for Phytoplankton in a Subtropical Shallow Eutrophic Lake
T2 - Evidence Based on Long-Term Monitoring and Modeling
AU - Mao, Zhigang
AU - Gu, Xiaohong
AU - Cao, Yong
AU - Zhang, Min
AU - Zeng, Qingfei
AU - Chen, Huihui
AU - Shen, Ruijie
AU - Jeppesen, Erik
N1 - We thank Taihu Laboratory for Lake Ecosystem Research (CERN TLLER) for providing the necessary data. This work was supported by Major Science and Technology Program of Nei Mongol (ZDZX2018054), Major Science and Technology Program of China for Water Pollution Control and Treatment (2017ZX07204005), National Natural Science Foundation of China (31870449), and NIGLAS Independent Deployment Program (NIGLAS2018GH04). Erik Jeppesen was supported by Centre for Water Technology, Aarhus University (WATEC). We thank Anne Mette Poulsen for valuable English editions. We have no conflict of interest to declare.
PY - 2020/11
Y1 - 2020/11
N2 - Lake ecosystems are exposed to a range of anthropogenic pressures, particularly eutrophication, and in some cases also stocking and/or overfishing of top-predator fish species, all factors that have implications for the food web structure and which could lead to dominance of nuisance cyanobacteria. Restoration of degraded lakes demands insight into the relative role of top-down for bottom-up regulating forces. While knowledge about these forces in temperate lakes is extensive, comparatively little is known of their role in subtropical lakes where the importance of herbivorous and benthic feeding fish is higher. Here, we analyzed a long-term monitoring data set on subtropical, shallow Lake Taihu, China, and applied random forests regression to examine how phytoplankton was related to environmental variables and biotic assemblages. Our results indicate that the biomass and density of phytoplankton increased with increasing biomass of benthivorous and zooplanktivorous fish and decreased with increases in ammonium concentrations, the nitrogen to phosphorus ratio, and zooplankton biomass, while the response to climate fluctuations and changes in the biomass of piscivores was weak. Effects of higher trophic levels explained as much of the variance in phytoplankton biomass as did nutrients and climatic factors. Moreover, the remarkably reduced ratio of zooplankton to phytoplankton biomass and the decline in cladoceran individual biomass emphasized the increasing importance of top-down control in regulating the phytoplankton following extensive stocking. Our findings offer insight into how fish management may be combined with catchment-level restoration measures to conserve and enhance water quality.
AB - Lake ecosystems are exposed to a range of anthropogenic pressures, particularly eutrophication, and in some cases also stocking and/or overfishing of top-predator fish species, all factors that have implications for the food web structure and which could lead to dominance of nuisance cyanobacteria. Restoration of degraded lakes demands insight into the relative role of top-down for bottom-up regulating forces. While knowledge about these forces in temperate lakes is extensive, comparatively little is known of their role in subtropical lakes where the importance of herbivorous and benthic feeding fish is higher. Here, we analyzed a long-term monitoring data set on subtropical, shallow Lake Taihu, China, and applied random forests regression to examine how phytoplankton was related to environmental variables and biotic assemblages. Our results indicate that the biomass and density of phytoplankton increased with increasing biomass of benthivorous and zooplanktivorous fish and decreased with increases in ammonium concentrations, the nitrogen to phosphorus ratio, and zooplankton biomass, while the response to climate fluctuations and changes in the biomass of piscivores was weak. Effects of higher trophic levels explained as much of the variance in phytoplankton biomass as did nutrients and climatic factors. Moreover, the remarkably reduced ratio of zooplankton to phytoplankton biomass and the decline in cladoceran individual biomass emphasized the increasing importance of top-down control in regulating the phytoplankton following extensive stocking. Our findings offer insight into how fish management may be combined with catchment-level restoration measures to conserve and enhance water quality.
KW - Biomanipulation
KW - Bottom-up
KW - Eutrophic lakes
KW - Limnetic food webs
KW - Random forests regression
KW - Top-down
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U2 - 10.1007/s10021-020-00480-0
DO - 10.1007/s10021-020-00480-0
M3 - Article
AN - SCOPUS:85078990119
SN - 1432-9840
VL - 23
SP - 1449
EP - 1463
JO - Ecosystems
JF - Ecosystems
IS - 7
ER -