Multidimensional ecosystem assessment of Poyang Lake under anthropogenic influences

Watershed anthropogenic activities, including pollutant discharge, sand mining, and upstream reservoir operation, have increased nutrient loads and decreased water levels and sediment concentrations in Poyang Lake, and thus affected the aqueous ecosystem. In this study, we developed an ecological model from the framework of AQUATOX to simulate the physical, chemical, and biological evolution of Poyang Lake under watershed anthropogenic influences, and used model output for a multidimensional ecosystem assessment of ecosystem structure, function, service, material flow, temporal dynamics, and collapse probability. The potential impacts of a proposed Poyang Lake water conservancy project (PYWCP) to build a sluice near the outlet of Poyang Lake to regulate lake level were explored. Results show that the watershed anthropogenic activities have worsened the Poyang Lake ecosystem. Specifically, the phytoplankton biomass increased, while benthos and fish decreased; the exergy, capacity of nutrient change, and the total biomass-gross primary production ratio decreased; as the lake's volume decreased, fishes’ trophic levels and food web robustness decreased, the food web shrank, single species dependence increased, and ecosystem stability decreased. The PYWCP could mitigate most of these effects, however, it would not recover Poyang Lake to historical conditions, and close monitoring with attention to sluice operational scheduling are required.