Depth- and Taxon-Specific Coral Bleaching of High-Latitude Marginal Coral Communities at Jeju Island During the 4th Global Coral Bleaching Event

Abstract

At Jeju Island, Republic of Korea, hard coral communities consisting of Alveopora, Montipora, and Psammocora represent some of the northernmost photosymbiotic Scleractinia in the Northwest Pacific. Here, we document taxon-specific, depth-specific bleaching conditions observed during the 2024 marine heatwave associated with the Fourth Global Coral Bleaching Event. Alveopora japonica and Montipora showed pronounced bleaching at shallower depths, whereas Psammocora appeared comparatively less affected. A follow-up survey two months later documented mortality, particularly among A. japonica colonies. These observations highlight heterogeneous bleaching responses among taxa and depths in a high-latitude marginal coral communities near the poleward distributional limit of photosymbiotic scleractinian corals. The depth-related pattern observed in A. japonica raises the hypothesis of possible bathymetric redistribution, although quantitative long-term observations are required to determine whether this represents a persistent shift.