Bing LI, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, China
Guishan YANG, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, China
Understanding the key drivers of eutrophication in freshwater bodies has long been a challenge, which is particularly true for floodplain lakes characterized by highly varying hydrological connectivity due to seasonal flood pulses. In this study, the Chlorophyll a (Chl-a) variations and associated relationships to environmental stressors along the temporal hydrological connectivity gradient were investigated using a 10-year dataset in a large floodplain lake (Poyang Lake). Linear mixed effect (LME) models were developed through the inclusion of the site as a random effect to identify the limiting factors of Chl-a variations for different hydrological connectivity phases. The results showed that hydrological connectivity changes exerted great influence on environmental variables in Poyang Lake, with a decrease of nutrient concentrations as the hydrological connectivity enhanced. The Chl-a exhibited contrast variations with nutrient variables along the hydrological connectivity gradient and are generally depended on hydro-climatic related variables, such as WT and SD. Nevertheless, the relative roles of nutrient and non-nutrient variables differed from different degrees of hydrological connectivity as confirmed by the LME models, thus suggesting that hydrological connectivity strongly influences the nutrient and non-nutrient limitation in floodplain lakes. In addition, the Chl-a-stressors relationship during the high hydrological connectivity (HHC) phase yielded better model performance, and the inclusion of the site as a random effect significantly improved the model performance, indicating high spatial heterogeneity of the Chl-a-stressors relationship during this period. The present study provides some insights on phytoplankton fluctuations and on the driving mechanisms underlying phytoplankton growth along the temporal hydrological connectivity gradient in floodplain lakes.
Mots clés : eutrophication|environmental stressors|hydroloical connectivity|linear mixed model|floodplain
A103107BL