Effects of episodic sediment resuspension on phytoplankton in Lake Taihu: focusing on photosynthesis, biomass and community composition

Sediment resuspension is an important characteristic of large shallow lakes. To further understand the influence of sediment resuspension on the nutrients release, the algal photosynthetic activity, algal biomass and algal community composition, a 2 × 5 factorial (2 water types and 5 turbulence intensities) bioassay experiment was carried out for 2 weeks. 2 water types: one type water was filtered through GF/F filter to remove all indigenous algae (Filtered group) and the other type was source water without filtering through GF/F filter (Non-filtered group). 5 turbulence intensities in the experiment simulated the different intensity of the field wind-induced turbulence in Lake Taihu, with different turbidities (0, 30, 70, 150, 250 NTUs). Results showed that sediment resuspension had significant effects on the nutrients release that could be absorbed to support algae growing. Different turbulence intensities had no significant effects on the photosynthetic activities. The time variation of photosynthetic parameters in the Filtered and Non-filtered groups indicated that algae could moderate themselves to adapt to different intensities turbulence environment to be more in favor of photosynthesis. In addition, sediment resuspension also brought sediment-associated algae back into the water body increasing the algal biomass. The community composition in the Filtered group and Non-filtered group showed that the new phytoplankton community formed from the resuspended algae was similar to the original community. So, the research highlights the importance of sediment resuspension in long-term management goals and restoration efforts for these types of ecosystems.