Biodiversity and distribution patterns of blooming jellyfish in the Bohai Sea revealed by eDNA metabarcoding

Mass occurrences of scyphozoan jellyfish severely affect marine ecosystems and costal economy, thus increased the emergency in the population dynamics survey of the blooming jellyfish. However, traditional ecological survey methods have difficulties in cryptic life stages detection and population dynamics survey, due to high spatio-temperal variations in their occurrence. Environmental DNA (eDNA) technique is a effective tool to overcome this limitation. Here, investigate the biodiversity and spatial distribution characteristics of the blooming jellyfish in the Bohai sea of China using eDNA metabarcoding approach, covering surface, middle and bottom seawater, and sediments. Six jellyfish taxa were identified, among which Aurelia coerulea, Nemopilema nomurai and Cyanea nozakii were dominant blooming jellyfish species. These three blooming jellyfish presented significant vertical distribution pattern in the offshore regions. A. coerulea and C. nozakii mainly distributed in the upper-middle layer, whereas N. nomurai showed a middle-bottom aggregation. Horizontally, A. coerulea and C. nozakii were more abundant in the inshore regions, while N. nomurai mainly distributed in offshore areas. Spearman correlation analysis revealed a significant correlation between the eDNA of three dominant blooming jellyfish species and temperature, salinity and nutrients. Our study confirms the availability of eDNA approach in the biodiverstiy evaluation and broad spatial distribution investigation of the blooming jellyfish, that can be applied as a supplementary tool of traditional survey.