In-situ experimental evidence revealing how ocean warming promotes Aurelia coerulea polyps mediated by benthic...

Harmful jellyfish blooms are widely believed to be associated with global warming; however, direct in-situ evidence at an ecosystem level to explain bloom mechanisms is lacking. This study focused on Aurelia coerulea polyps and the local benthic ecosystem and applied field temperature manipulation to explore responses of polyps and benthic ecosystems to global warming, community changes, and polyp survival strategies. In our experiment, local heating (+1.5 °C and +3 °C) led to significant changes in benthic community structure (p < 0.001), a decline in biodiversity, and the proliferation of opportunistic dominant organisms. Aurelia coerulea polyps achieved remarkable expansion, with their coverage percentage reaching 79.73 % in the +3 °C group at the final sampling, significantly higher than the 53.30 % at ambient temperature. During the transition of the benthic ecosystem from stability to instability, jellyfish polyps expanded colonization by virtue of diversified asexual reproduction modes such as budding, longitudinal fission, stolonic budding, which were enhanced under warming, and their rapid responses to environmental change and strong adaptability to warming environments. Our study revealed direct effects on organisms and indirect effects mediated by ecosystems of global warming in the process of jellyfish polyp blooms and emphasized the importance of considering the comprehensive effect of global warming at the local benthic ecosystem level through in-situ experiments when explaining the proliferation of opportunistic and hazardous species with complex life cycles such as jellyfish.