Distribution Patterns of Large Jellyfish and Their Effects on the Zooplankton Community in the Northern Chinese Coastal Seas during the Summer of 2021

The northern Chinese coastal seas have been observed to constitute a large jellyfish blooming hotspots during the las decades. The spatial distribution of the abundance and biomass of large jellyfish was investigated in this area through a bottom trawl survey during the summer of 2021. Nemopilema nomurai, Cyanea spp., Aurelia coerulea, Aequorea spp., and Ulmaridae (undefined sp.) were identified during the investigation. The realized niches of the three most abundant species (N. nomurai, Cyanea spp., and A. coerulea) were measured through the maximum entropy (MaxEnt) model to explain their spatial distribution patterns. Nemopilema nomurai was used as a representative species to estimate the feeding rate and feeding pressure of large jellyfish on the zooplankton. During N. nomurai blooms, the potential consumption of zooplankton by N. nomurai was enormous and even exceeded the zooplankton productivity in regions where N. nomurai assembled in this study. Reductions in absolute and relative abundance were noted in small copepods at mid-bloom and bloom stations compared to non-bloom stations. The realized niches of large jellyfish and their relationships with the zooplankton in this study would be helpful for understanding their biogeographic distribution and ecological roles in the northern Chinese coastal seas under future climate change scenarios.