Zooplankton community composition in summers of 2021 and 2022 in the northern East China Sea and Yellow Sea, and their linkage with abiotic and biotic factors
摘要
The northern East China Sea and Yellow Sea are highly dynamic marginal seas, serving as important fishing grounds and primary areas for aquaculture. The zooplankton community structure, including abundance, biovolume, and normalized biovolume size spectra (NBSS) within this ecosystem in summers 2021 and 2022 was assessed through ZooScan digital imaging system. The abundances of zooplankton in summers 2021 and 2022 were 3 364.22±2 190.53 and 4 435.52±2 520.06 inds./m3, respectively, whereas the corresponding biovolumes were 649.10±519.63 and 1 064.86±1 254.87 mm3/m3, respectively. Small copepods as the dominant zooplankton functional group in terms of abundance in both years, while chaetognath and medusae were the dominant groups in terms of biovolume. The dominance of medusae and chaetognath in terms of biovolume, along with the flatter slopes of NBSS compared to a stable community, indicated that more energy accumulated in gelatinous organisms within the study area. There were significant positive relationships between temperature and tunicates or medusae, with a significantly higher population size observed in summer 2022 than in 2021. The lower abundance and biovolume of zooplankton, mainly of small copepods, in summer 2021 may be related to the larger population size of the large jellyfish and the proliferation of green tides. The investigation provided basic data and fundamental insights for achieving a comprehensive understanding of zooplankton community structure and their long-term dynamics.