Characteristics of Phytoplankton Production in Wet and Dry Seasons in Hyper-Eutrophic Lake Taihu, China

Abstract

Primary productivity plays a key role in aquatic lake ecosystems. This study addresses the characteristics of primary phytoplankton productivity and its relationship with environmental factors in a large, shallow, and eutrophic lake (Lake Taihu, China). Surface water samples were collected in wet and dry seasons from eight lake areas to investigate physicochemical factors and primary productivity. The results show obvious seasonal differences in phytoplankton primary productivity and physicochemical factors in Lake Taihu. The primary productivity in the wet season is about five times larger than that in the dry season, and the spatial distribution of primary productivity is obviously inhomogeneous in the wet season, while in the dry season, there are no significant differences in different lake areas. Most of the lake areas are in the middle eutrophic state regardless of the season; the northwest region has the heaviest degree of eutrophication, while the southeast region has the lightest degree of eutrophication. Pearson correlation indicated that nutrients are the main factors affecting primary productivity in the wet season, while temperature is the most important factor affecting primary productivity in the dry season. Multiple stepwise regression suggested that chlorophyll-a (Chl-a), temperature (T), and water transparency (SD) can be used to estimate the phytoplankton primary productivity in Lake Taihu in different seasons, and the main influencing factors for primary productivity are Chl-a, nutrients, and SD/total suspended solids (TSS) in the wet season and T, Chl-a, and SD/TSS in the dry season.