Study on the changes in the community structure of marine zooplankton in Dalian bay from 2013 to 2022 and its relationship with environmental factors

Analyzes the changes in zooplankton community structure and its relationship with environmental factors based on survey data of zooplankton in the spring and autumn of Dalian Bay from 2013 to 2022. A total of 64 species of zooplankton were identified, with copepods, jellyfish, and planktonic larvae being the main groups, accounting for 34%, 25%, and 20% of the species composition; The main dominant species were Centropages mcmurrichi, Acartia Omorii, Calanus sinicus and Oithona similis in spring and Evadne tergestina, Oikopleura dioica, Paracalanus parvus and Sagitta crassa in autumn. The average density of zooplankton collected by the shallow water Type Ⅰ plankton net (hereinafter referred to as Type Ⅰ net) was 652 ind/m³ in spring and 1040 ind/m³ in autumn. The average density of zooplankton collected by the shallow water Type Ⅱ plankton (hereinafter referred to as Type Ⅱ net) was 30470 ind/m³ in spring and 24355 ind/m³ in autumn. The average biomass of zooplankton was 143 mg/m³ in spring and 190 mg/m³ in autumn, respectively. In the past decade, the average density and biomass of large planktonic animals have generally shown a downward trend. The average diversity index of zooplankton by Type Ⅰ net was 2.40 in spring and 2.80 in autumn ,meanwhile, by Type Ⅱ net 2.38 in spring and 2.66 in autumn, The average evenness index of zooplankton by Type Ⅰ net was 0.73 in spring and 0.78 in autumn, meanwhile, by Type Ⅱ net 0.69 in spring and 0.75 in autumn. The average richness index of zooplankton by Type Ⅰ net was 1.14 in spring and 1.57 in autumn, meanwhile, by Type Ⅱ net 0.73 in spring and 0.86 in autumn. The diversity of zooplankton was not high and overall showed a slight upward trend. Temperature, salinity, and ammonia nitrogen were the main environmental factors affecting the structure characteristics of zooplankton in Dalian Bay in the past decade. There was a negative correlation between temperature and the density of copepods, while salinity has a strong correlation with the density of Calanus sinicus. The research results may provide scientific basis for environmental protection and ecological assessment in Dalian Bay.