The response of chlorophyll a to nutrient and hydro-meteorological factors in Lake Taihu

Abstract

Chlorophyll a (Chla) concentration is a key indicator of the biomass of phytoplankton such as algae in freshwater ecosystems. Understanding its response to nutrient and hydro-meteorological factors is vital for managing eutrophication in Lake Taihu, one of China’s largest freshwater lakes. This study investigates Chla dynamics in relation to nutrient levels (nitrogen, phosphorus, etc.), hydro-meteorological parameters (temperature, wind, precipitation, etc.), and previous season factors (the values of the factors mentioned above in the previous season) in Lake Taihu. By using various statistical analyzing methods (such as partial least squares regression) and introducing two new indices (similarity and influence), this research witnessed an upward trend in Chla concentration over the past three decades. And the similarity index between predicted and observed results is 0.8425, if all factors are considered, while the similarity index decreases by 6.94% and 33.27% when considering only current or previous factors, respectively. This demonstrates that antecedent seasonal parameters exert some influence on the developmental trend of Chla concentrations in Lake Taihu. When temporal seasonality is abstracted from consideration, air temperature emerges as the predominant forcing factor governing Chla dynamics. Seasonal correlations indicate that, in spring and summer, to control eutrophication and algae bloom in Lake Taihu, a comprehensive approach considering multiple factors is necessary, but the most important action should be controlling biomass of phytoplankton, while in autumn, reducing phosphorus input is crucial. This study provides not only quantitative analyses of the seasonal trends in Chla concentration but also detailed and actionable insights for sustainable freshwater ecosystem management in Lake Taihu.