Phytoplankton community structure of Tang-Pu Reservoir: status and ecological assessment in relation to physicochemical variability

Seasonal variation in phytoplankton community structure within Tang-Pu Reservoir (Shaoxing city, Zhejiang province, China) was investigated in relation to variation in physicochemical and hydrological characteristics. Over the three-study seasons (autumn, winter, and spring), phytoplankton abundance and biomass showed a gradual increase with the peak in spring season. During this study period, phytoplankton community comprised of 7 phyla, 80 genera, and 210 species. The dominating phyla were Chlorophyta 80 species, Bacillariophyta 46, and Cyanophyta 44 as well as other phyla of freshwater ecosystems except Xanthophyta. The phytoplankton density and biomass varied in the six sampling sites between a minimum of 257.42 x 10(4) cells/L to 1054.15 x 10(4) cells/L and 1.60 mg/L to 4.56 mg/L respectively. Spring season had higher biomass and density values than autumn and winter. Furthermore, the results indicated that the Shannon-Wiener (H') and Pielou evenness (J') indices of phytoplankton community were stable although with slightly higher values in spring. Based on the calculated indices, Tang-Pu reservoir could be considered mesosaprobic in all the three seasons. Redundancy analysis (RDA) revealed that pH, total nitrogen (TN), total phosphorus (TP), transparency, chlorophyll a (Chl a), dissolve oxygen (DO), and water temperature (WT) were responsible for most phytoplankton community shift from Bacillariophyta and Cryptophyta to Cyanophyta and Chlorophyta in spring. These environmental parameters play an essential role in the community structure variation of phytoplankton in the downstream and upstream of Tang-Pu Reservoir. A decreasing phytoplankton abundance trend from the river area (inlet) to the lake (outlet) was also observed.

Automated summary

This study investigated the seasonal variation in phytoplankton community structure within Tang-Pu Reservoir in relation to physicochemical and hydrological characteristics. The results showed that the abundance and biomass of phytoplankton gradually increased over the three study seasons, with the peak in spring. The phytoplankton community comprised of 7 phyla, 80 genera, and 210 species, with dominant phyla being Chlorophyta, Bacillariophyta, and Cyanophyta. The density and biomass of phytoplankton varied among sampling sites and seasons, with higher values observed in spring. pH, total nitrogen, total phosphorus, transparency, chlorophyll a, dissolve oxygen, and water temperature were identified as important factors influencing the community structure of phytoplankton. Additionally, a decreasing trend in phytoplankton abundance from the river area (inlet) to the lake (outlet) was observed.