Responses of zooplankton community to anthropogenic organic matters in representative lake in highly urbanized area: Taking lake Taihu as an example.

Although terrestrial organic matter is known to sustain food chains, its impact on zooplankton communities in lakes within urbanized areas remains unclear. This study analyzed a comprehensive, decade-long dataset (1998-2007) that included COD, BOD, and monthly zooplankton records from Lake Taihu to assess the effects of anthropogenic organic matter. Significant spatial variations in COD and BOD were observed across different areas of Lake Taihu (p < 0.01), with the average COD ranged from 4.1 mg/L to 7.6 mg/L and the average BOD from 1.9 mg/L to 8.6 mg/L. The abundance of zooplankton (1170-5182 individuals/L) showed marked responses to these spatial differences in organic matter, particularly in rotifers (236-1930 individuals/L) and protozoans (674-3180 individuals/L) (p < 0.01). Additionally, zooplankton abundance, along with the abundance and biomass of rotifers and protozoans, exhibited significant positive correlations with COD, BOD, and the BOD/COD ratio (p < 0.01). The ratio of rotifers to zooplankton displayed significant positive correlations with COD, BOD, and the BOD/COD ratio (p < 0.01), while the ratio of protozoans to zooplankton showed significant negative correlations with these parameters (p < 0.01). The findings indicate that organic matters predominantly supports zooplankton growth by fostering the proliferation of rotifers and protozoans. Additionally, organic matters may enhance the proportions of rotifers and protozoans, thereby shifting the whole group to smaller zooplankton community. The BOD/COD ratio also emerged as an important indicator of the influence of organic matters on zooplankton. These results suggest how zooplankton might respond to future environmental changes, including increased inputs of terrestrial organic matters and eutrophication under climate change scenarios.