THREE-DIMENSIONAL CONNECTIVITY BETWEEN SHALLOW AND DEEP CORAL ECOSYSTEMS ALONG THE COASTAL AREA OF OKINAWA ISLAND

Abstract

 In light of the ongoing global coral bleaching crisis, the mesophotic zone (MPZ) at depths of 30 to 150 meters, where water temperatures are relatively stable, is expected to serve as both a refuge and a resupply source for shallow-water coral genetics. To facilitate the establishment of a desirable coral ecosystem, this study employed a high-resolution ocean model for the coastal area around Okinawa Island, Japan, to investigate the advection-dispersion processes of coral larvae. A Lagrangian statistical analysis was conducted to evaluate the three-dimensional transport and population connectivity of the modeled virtual coral larvae between shallow areas and MPZs. The findings indicate that the degree of coral connectivity varies significantly depending on topographical features. Notable observations include asymmetry in coral connectivity between the east and west coasts, driven by the residual clockwise current around the island. Enhanced selfrecruitment was evident in shallow areas around the semi-enclosed Kin and Nakagusuku Bays, while significant accumulation occurred in both shallow and deep MPZ areas of the more open Nago Bay.