Jaehyeon Kim1,2, Jaeseok Chung1,2, Jae Seong Lee2,1, Taihun Kim1,2
1Korea Institute of Ocean Science & Technology, Republic of Korea - 2University of Science & Technology, Republic of Korea
Jeju Island, the southernmost island of South Korea, is characterized by its volcanic rocky shores harboring a high marine biodiversity, ranging from temperate seaweeds to tropical corals. Due to recent rapid increases in seawater temperature, Jeju’s temperate coastal ecosystems have concurrently experienced a decline in temperate macroalgal species (e.g., Ecklonia cava) and an increase in tropical hard coral species (e.g., Alveopora japonica, Montipora millepora, Psammocora albopicta). This shift is causing spatial competition between macroalgal and coral species, potentially transforming the whole structure of the temperate coastal rocky ecosystem in Jeju Waters. The purpose of our study was to investigate the optimal temperature ranges for the survival and growth of macroalgal and coral species by measuring their physiological parameters. During incubation experiments, the predominant macroalgal species in Jeju Waters, E. cava, and the rapidly expanding coral species A. japonica, M. millepora, and P. albopicta, were exposed to temperatures ranging from 7°C to 34°C. To evaluate physiological responses to temperature, Photosynthesis to Respiration (P:R) ratio was measured as a metabolic indicator, and buoyant weight was measured to yield the growth rate of each species. As results, E. cava exhibited the highest production and growth rates at a temperature range of 15–18°C. A. japonica showed peak production and growth rates between 22–25°C, and M. millepora and P. albopicta, respectively, between 22–30°C. Therefore, the species-specific physiological responses to seawater temperature offer an explanation for the decline of E. cava populations and the increase of tropical hard coral coverages. Our experiment also provides crucial data for predicting the potential expansion ranges of hard corals along the Korean Peninsula. Furthermore, our results can be applied to predict overall ecosystem changes according to future climate change scenarios.
Biography
Jaehyeon Kim is Master’s student from the Korea Institute of Ocean Science & Technology (KIOST) School of the University of Science & Technology, major in ocean science. His main focus is physiological responses to environmental changes in shallow marine organisms, such as macroalgae, corals, invertabrates, fishes etc.