The effects of flood pulse on multiple aquatic organisms in a seasonal shallow lake

Different aquatic organisms have different reactions to environmental variations due to their different ways of reaction traits. Understanding the effect of hydrological disturbance on lake from the perspective of multiple aquatic organisms is important for lake management. Poyang Lake (PYL) experiences severe hydrological disturbance under the effects of flood pulse during the rainy season. In this study, we analyzed the responses of phytoplankton, zooplankton, and macroinvertebrates to hydrological disturbance during the rainy season in PYL. Flood pulse determined the spatial variation in turbidity (Turb), transparency (Trans), dissolved oxygen (DO), total phosphorus (TP), and soluble reactive phosphorus. Physical factors (Turb, Trans, conductivity) explained phytoplankton (9.6%) and zooplankton (15%) community variation, and the combination of physical and nutrient factors explained macroinvertebrate (3.8%) community variation. Cyclotella sp., Attheya zachariasi, and Melosira ambigua were the keystone taxa of phytoplankton, and these taxa were driven by Turb and Trans. Brachionus angularia, Polyarthra vulgaris , Filinia longiseta , and Diffugia globulosa were the keystone taxa of zooplankton and entire aquatic organisms, which contributed a lot to maintain the biological community stability possibly through the food web. These keystone taxa were stimulated by high Trans, DO, dissolved organic carbon (DOC) and nitrate (NO 3 − ). We found habitat conditions (Turb, Trans and DO) were the prominent factors influencing the aquatic organism structure in strong hydrological disturbance environment. For the keystone taxa, both habitat conditions (i.e., DO) and exogenous nutrient inputs (i.e., DOC and NO 3 − ) caused significant effect. This study provides new insights into the holistic response of multiple aquatic communities to flood pulse as well as the role of keystone species in maintaining community stability, which could guide the conservation and management of seasonal lake ecosystems.