Phytoplankton community structure and succession in the Chinese mitten crab (Eriocheir sinensis) pond

In order to fully and accurately evaluate the characteristics of phytoplankton community structure and its relationship with environmental factors in the middle and late period of Chinese mitten crab culture, water quality indexes and phytoplankton community of cultured crab ponds were monitored from June to October 2022, during which the phytoplankton community was identified by artificial microscopy and high-throughput sequencing. The changes of phytoplankton species composition, density, biomass and diversity index in different months were analyzed, and the relationship between dominant phytoplankton species and environmental factors was discussed. The results showed that: (1) There were 65 species in 4 phyla identified by artificial microscopy, and 1488 species in 4 phyla identified by metagenomic data analysis, and the latter was 22.89 times of the former. (2) The dominant species identified by artificial microscopy were Microcystis flos-aquae, Aphanocapsa elachista, and Aphanocapsa elachista. The dominant species identified by metagenomic data analysis were Aphanizomenon flos-aquae and Microcystis aeruginosa. (3) The diversity index calculated by manual microscopy was generally lower than that of metagenomic results. (4) Ammonia nitrogen and water temperature were the key environmental factors affecting phytoplankton community structure.It is suggested to use artificial microscopy and high-throughput sequencing methods simutaneously to analyze phytoplankton community structure in aquacultural water, so as to evaluate water quality more comprehensively and accurately and timely regulate the aquaculture process.