Macroalgal Community at Floristic Boundary Area between South and West Sea in Korea

This study was conducted to provide marine algal community and floristic boundary of Gageo-do and nearby islands in the southwest coast of Korea from August 2013 to March 2015. There were 136 marine algae species collected in this study, including 11 green algae (8.09%), 30 brown algae (22.06%), and 95 red algae (69.85%). This study confirms that the current number of marine algae species in 277. According to the functional form group and ESG analysis, the ESG II ratio for sheet-like species, filamentous species, and coarsely-branched species was 86.03%, in which most functional groups were composed of opportunistic species. The value of C/P, R/P, and (R+C) /P were 0.44, 2.54 and 2.99, respectively, indicating the characteristics of a temperate mixed marine algal flora. Based on the species reported in this study and previous studies, the appearance rates of subtropical and warm tolerant benthic marine algae showed no correlations an increase of water temperature. The cluster analysis of marine algae of 13 islands divided the West Sea and South Sea at a similarity of 40% in species composition. Notably, the presence of Ecklonia cava, Rugulopteryx okamurae, and Corallina crassissima was important to distinguish the marine algae of the West Sea and South Sea. It is assumed that the southwestern coastal area acts as a transition zone between the West Sea and South Sea floristic regions. Therefore, marine ecological research and monitoring of the change in water temperature and marine organisms at Gageo-do are urgently needed, as the island is important not only for its geography but also in relation to its surrounding ocean currents, water temperature, and marine biodiversity.