Floodplain lake response to climate-nutrient-hydrological pressure revealed through phytoplankton community succession over the past century

Abstract

In aquatic ecosystems, phytoplankton is a key primary producer that is highly sensitive to environmental change. Understanding ecological succession in lake phytoplankton community structure is important when tracking associated long-term environmental response. Such information can be used to develop a comprehensive management strategy under changing environment. This study reconstructs long-term (100 year scale) phytoplankton community succession from sediment pigments in a typical floodplain lake (Poyang Lake), revealing potential lacustrine ecosystem response mechanisms to climate-nutrition-hydrology factors. Results show that Poyang Lake’s algal community has undergone rapid growth, with diatoms increasing by 9.3%, cryptophytes increasing by 8.7%, and green algae decreasing by 26.3%. In Poyang Lake, the point of change in algal community succession occurred after 1965, representing a 5–15-year delayed response compared to lakes around the world, largely due to the coupled effects of the unique hydrological fluctuations and anthropogenic disturbances. Additionally, sediment pigments were also used to accurately track four atypical algal outbreaks in Poyang Lake (i.e., 1955, 1960–1975, 1984, and 2003). Our results emphasize the importance of hydrological conditions during ecological succession processes in floodplain lakes. Here, coupling effects between water levels and other relevant factors explained 20%–32% of algal community variation. Furthermore, results showed that Poyang Lake had previously evolved under environmental stresses of nutrients and climate conditions while currently evolving under multi-source coupling pressure (climate-nutrient-hydrology).