Understanding large-scale geographical patterns of marine biodiversity and their underlying drivers remains a key objective in marine ecology. The marginal seas of the western Pacific, encompassing the world's most complex marine biogeographic transition zone and the biodiversity core of the Coral Triangle, offer an ideal system for studying global marine biodiversity dynamics. Here we surveyed fish diversity along a 4500 km transect from the Yellow Sea to the Java Sea by combining continuous ship-track seawater collection with environmental DNA (eDNA) metabarcoding. We detected 225 fish taxa, with members of the family Engraulidae both broadly distributed and numerically dominant, and we recorded four protected cartilaginous fishes. Compared with historical records, continuous ship-track eDNA sampling more effectively recovered planktivorous and upper-pelagic taxa that traditional gear typically underrepresents due to their mobility and low catchability. Importantly, fish diversity followed a distinct three-phase pattern along the transect, characterized by an initial increase from the Yellow Sea to the South China Shelf, a sharp decline toward the South China Sea Islands, and a gradual recovery approaching the Sunda Shelf. These shifts were consistently associated with abrupt geomorphological transitions along the continental shelf and with topographic variables such as bottom depth and coastal distance. This study highlights the transformative potential of eDNA for global-scale ocean monitoring and provides compelling evidence that topographic variables play a dominant role in shaping macro-scale marine biodiversity patterns in this region, surpassing the influence of other natural and anthropogenic factors. • Large-scale underway eDNA sampling enables cost-effective, global marine monitoring. • Compared to traditional methods, eDNA uniquely detects taxon-specific species. • Fish diversity in the Western Pacific is shaped mainly by topography, with regional human impacts.
Li et al. (Wed,) studied this question.