Microbial and Planktonic Community Characteristics of <i>Eriocheir sinensis</i> Culture Ponds Experiencing Harmful Algal Blooms

The Chinese mitten crab, <i>Eriocheir sinensis</i> (H. Milne Edwards, 1853), is an economically important aquaculture species in China. It is a significantly desirable species by Chinese consumers that causes a high demand for environmentally friendly culture farming. In aiming to break through bottlenecks, i.e., “pond moss” and cyanobacteria, we investigated the microbial community and plankton composition of ponds with filamentous algae and cyanobacterial blooms. As results, we found Actinobacteria, Proteobacteria, and Bacteroidetes were dominant bacterial phyla, while Chlorophyta and Bacillariophyta were dominant phytoplankton phyla in <i>E. sinensis</i> ponds. <i>Nitrospira</i> sp., <i>Flectobacillus</i> sp. BAB-3569, <i>Staphylococcus warneri</i>, <i>Fusarium oxysporum</i>, <i>Gromochytrium mamkaevae</i>, and <i>Rhizophydium</i> sp. JEL317 were screened as bioindicators for harmful algal blooms. We found a close relationship between water quality parameters and the species composition of bacteria and zooplankton in the present study. Specifically, total nitrogen and total ammonia nitrogen significantly affected the bacterial community composition, while total phosphorus contributed to the phytoplankton community composition. We further indicated the potential competitive inhibition of Chlamydomonadales on the direct regulation of the control of harmful algal blooms. Finally, we suggested a combination of probiotics and microalgae, e.g., <i>C. vulgaris</i>, to prevent and control potential risks in the culture of <i>E. sinensis</i>. In conclusion, the present study deepened our understanding of harmful algal blooms in aquaculture ponds and suggested the baseline indications for the prevention and control of algal blooms.