Large scale eDNA database reveals latitudinal diversity gradients with seasonal variations

The spatial and temporal distribution patterns of marine organism diversity are crucial for the sustainable exploitation of fishery resources, management and preservation of marine ecosystems. We investigated the latitudinal diversity gradients of fish genera in Japanese waters using an environmental DNA (eDNA) survey. The environmental DNA data for 2111 surveys across Japan were obtained from the All Nippon eDNA Monitoring Network (ANEMONE) database. We observed a negative correlation between diversity and latitude in Japanese waters. The latitudinal gradient differed between seasons (correlation was especially negative in summer), suggesting that the seasonal change in the latitudinal gradient may be associated with the incidence of vagrant fish from tropical seas, and not the commonly observed pattern of seasonal migration (i.e., southwards in winter and northwards in summer). Furthermore, we found that global warming may lead to a temporary increase in biodiversity by increasing the incidence of vagrant fish from outside regions; however, this increase is not substantial. Although we did not find significant differences between years, further long-term and systematic monitoring may reveal temporal changes in marine biodiversity over longer time-periods, thus reflecting climate changes. Overall, the continued operation of ANEMONE will be the key to the future conservation of biodiversity in Japanese waters. ### Competing Interest Statement The authors have declared no competing interest.