Ecological Indicators (Dec 2021)
Temporal distribution patterns of phytoplankton and their drivers in Lake Poyang (China) – A monthly study from 2011 to 2019
Abstract
The hydrological conditions in Lake Poyang are relatively complicated (e.g., large variations in water level) due to its connection with the Yangtze River, and the drivers of phytoplankton distribution differ greatly from those in other lakes. Based on the monthly monitoring data of Lake Poyang in 2011–2019 from 6 sampling sites, we analyzed the distribution pattern of phytoplankton density and the succession of dominant genera as well as the potential drivers, including water temperature (WT), Secchi depth (SD), nutrients, and water flow velocity (V). The phytoplankton density showed an increasing trend at the interannual scale, with a mean value of 1.97 × 106 ind/L in 2011 and 6.75 × 106 ind/L in 2019. The frequency of Microcystis as the dominant genus decreased (from 31.7% in 2011 to 13.8% in 2019), while the frequency of Pseudanabaena, Cyclotella and Synedra increased overall. According to all data analyzed by the generalized additive model, the crucial factors affecting phytoplankton density were WT, V and SD, which together explained 29.1% of the variance. At the interannual scale, the increase in phytoplankton density was probably due to the significant increase in SD. The interannual value of V remained stable overall and showed a negative correlation with phytoplankton density. Nutrients and V may greatly determine the variability in dominant genera in Lake Poyang. The nutrient (total nitrogen and total phosphorus) concentrations have generally declined in recent years, especially after 2017. When Aulacoseira was dominant, V differed greatly from that when Microcystis was the dominant genus, with values of 0.40 m/s and 0.28 m/s, respectively. In particular, V generally increased yearly (P < 0.05) between June and November. The factors mentioned above may decrease the competitive advantage of Microcystis. Based on relatively long-term monitoring in Lake Poyang, our study established the distribution pattern of phytoplankton and highlighted the effect of V, which will be beneficial for local managers and departments.
