Impact of the climate change on Ecklonia cava-dominated kelp forest in South Korea

Sun Kyeong Choi¹, Anna B. Jöst¹, Taihun Kim¹, Seul Yi¹, Baek Son¹, Sang Rul Park²

¹Korea Institute of Ocean Science and Technology, Korea - ²Jeju National University, Korea

The impacts of climate change are global, with significant regional variations and water temperature is a strong indicator. South Korea, located in the northern part of the East China Sea, has been reported as one of most rapidly warming areas globally. Kelp forests predominantly consisted in Ecklonia cava, a perennial endemic macroalga, which provides ecologically diverse habitats and constitutes economically significant ecosystems in Korea and Japan. In this study, we examined the variability characteristics of E. cava as a result of the impact of climate change. When cultivated under temperature-specific conditions, E. cava exhibited the most rapid growth at 15°C, with growth inhibited as water temperature escalated. This suggests that the growth of the natural population may be negatively affected, given that the minimum water temperature of winter in the southern part of Korea is increasingly above 15°C. Moreover, we identified the indiscriminate feeding activity of tropical fish herbivores from the study area with the significant increase in water temperature in November 2023, and confirmed E. cava with severe damage (i.e., reduced blade length and bite marks). However, September to November has been identified as the only annual reproductive peak for this kelp species. The results of this study suggest that the decline of native E. cava in Korean waters is anticipated due to the synergistic impacts of water temperature and non-indigenous herbivores by climate change.