Wind-induced circulation driving the spatial distribution of dominant algae population in a plateau lake, Erhai,...

Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution. This study constructed a three-dimensional hydrodynamic model (EFDC) of the plateau lake Erhai, China using accuracy wind field observation, runoff data and monthly algae data during 2022-2023. The model successfully reproduced the circulation characteristics of Erhai under prevailing wind directions. The results showed that the lake flow velocity in Lake Erhai is higher in winter than in summer, with lower velocities near shore particularly in the northern and central parts of the lake. There is a negative correlation between algal biomass and flow velocity (FV) in different zones, with lower FV favoring the accumulation of algal biomass, particularly for Microcystis, Dolichospermum, and Peridinium. Additionally, due to buoyancy, cyanobacteria are highly affected by wind direction and tend to accumulate in downwind regions of the prevailing wind direction. This study demonstrates that wind-induced circulation is a crucial factor affecting the spatial distribution of dominant algae populations in shallow plateau lakes with weak hydrodynamic force. Further, the risk of bloom occurrence in Lake Erhai will be higher due to the background of global climate change and the lake's wind speed decline. In conclusion, we suggest implementing targeted zoning measures to control algal blooms and establishing stricter regulations for nitrogen and phosphorus control to counterbalance the promotion of algal bloom accumulation in low-velocity zones caused by reduced wind speed.