Changes in Zooplankton Community Structure and Dominant Species in Rizhao Coastal Waters During the Summers of 2020–2023

This study analyzed data from zooplankton surveys conducted in the coastal waters of Rizhao during the summers of 2020–2023 to deterine trends in the number of taxa, dominant taxa, biomass, abundance, and biodiversity over the 4 years. The results indicated the presence of 41 zooplankton species belonging to Hydromedusa, Ctenophora, Copepoda, Cladocera, Amphipoda, Decapoda, Tunicata, Chaetognatha, Chordata, along with 19 types of planktonic larvae. The total number of taxa showed little change over the 4 years. A total of 10 dominant species and 8 dominant larval types were identified in the surveyed waters, and the dominant species vary from year to year. In terms of community structure, planktonic larvae, hydromedusae, and copepods were the dominant taxa. The proportion of planktonic larvae showed an upward trend, while that of hydromedusae exhibited a downward trend. The zooplankton collected by the shallow water type I (SWI) net and shallow water type II (SWII) net in the survey area could each be divided into 2 communities. Correlation analysis revealed that the abundance of zooplankton collected by the (SWI) net was significantly negatively correlated with water temperature (P<0.05), while the Shannon-Wiener index (H') was significantly positively correlated with water temperature (P<0.05). However, the total number of taxa, abundance, and biomass were significantly higher in the (SWII) net compared to (SWI) net. The average abundance of zooplankton collected in the SWI net gradually decreased over the years(P<0.05). There was no obvious difference in the community diversity indices of zooplankton collected by the two types of nets, and the community structure of zooplankton communities was consistent.