Changes of coastal environment from typhoon impacts in Jeju Island, Korea: From population to community levels

Abstract

Jeju Island, the northern part of the East China Sea, have been identified as one of most rapidly warming areas globally. Jeju Island is acknowledged as a forefront of climate change impacts, particularly concerning ocean warming in Korea, but there are relatively few long-term studies of marine ecosystems in relation to climate change and environmental change. In this study, we collected environmental factors such as nutrients, water temperature, and salinity in seawater from the coast of Jeju Island since 2017 and identified the characteristics of seawater temperature fluctuations caused by typhoons. We also analyzed the characteristics of macroalgal community and Ecklonia cava population fluctuations before and after typhoons. In Moonseom of Jeju Island, the seawater temperatures on 10-m depth were found to fluctuate rapidly during typhoon approaches. In the benthic biodiversity changes by depth analyzed in the waters of Moonseom since 2016, the number of species did not change significantly before and after the typhoon, but the changes in the community index varied from year to year depending on the intensity and extent of the typhoon's impact. In some cases, the loss of the canopy by the kelps due to the typhoon resulted in a more diverse community with a higher diversity index, while the corals were less affected by the typhoon due to their deeper habitat depths. A case-specific transient model study of typhoon impacts found that the number of E. cava fluctuate significantly with and without typhoon impacts. The results of this study suggest that the rocky marine ecosystem in Jeju's waters, which is continuously affected by typhoons every year due to the effects of recent climate change, is shifting from algae-dominated communities to coral-dominated communities.