The distribution characteristics of medusozoans (Cnidaria) related to environmental factors in cold source water intake area of the Fangchenggang Nuclear Power Plant based on eDNA metabarcoding technology

The free-swimming gelatinous stage of medusozoans, generally called 'jellyfish', frequently swarms around the intake area of the Fangchenggang Nuclear Power Plant, posing a noticeable risk to its operational safety. Traditional ecological survey methods have limitations in rapidly and effectively assessing the diversity and spatiotemporal distribution of medusozoans, particularly during their early life stages, such as planulae, polyps, and ephyrae. To compensate for these limitations, we employed environmental DNA (eDNA) metabarcoding technology-a non-invasive, efficient, and broadly applicable approach-to conduct targeted surveys during the winter and summer seasons. The findings revealed notable seasonal variations in medusozoan community composition, with 29 and 56 species identified in winter and summer, respectively (<i>p</i> < 0.05). A higher abundance of Hydrozoa and relatively fewer Scyphozoa were observed in both seasons. Horizontally, no significant differences were identified among the defined zones (<i>p</i> > 0.05); however, specific sites such as estuarine, water intake, and drainage areas exhibited unique environmental features influencing the distribution of medusozoans. Vertically, within the 3-8 m depth range, no significant differences in the distribution of them were observed, likely due to the limited depth range and enhanced vertical mixing of the water column (<i>p</i> > 0.05). These observations underscore the utility of eDNA metabarcoding for the rapid detection and assessment of medusozoan diversity and spatiotemporal distribution. As a valuable supplement to traditional survey techniques, this method enhances medusozoan monitoring in marine areas adjacent to Fangchenggang Nuclear Power Plant. Moreover, it enables the investigation of how temperature, salinity, dissolved oxygen, and chlorophyll <i>α</i> variations-driven by both climate change and human activities-influence medusozoan distribution patterns around coastal infrastructures globally.