Differences in Subtidal Macrobenthic Community Structures and Influencing Factors Between Jindo and Jeju Islands in South Korea.

Although islands in South Korea have been significantly impacted by human activities, marine ecological studies focusing on island coasts have been limited. Due to their distinct characteristics, macrobenthos is extensively utilized to assess the impact of anthropogenic influences on the marine environment. In August 2010, August 2011, and September 2012, samples of macrobenthic communities, bottom water, and sediment were collected from the subtidal zones around southern Jindo and northern Jeju islands in South Korea. Macrobenthos was identified to the species level using a stereomicroscope. Bottom seawater quality was evaluated, with a focus on dissolved heavy metal concentrations (As, Cr, Cd, Cu, Pb, and Zn). Additionally, we measured the organic matter content and mean grain size of the sediment. There were marked differences in macrobenthic community structures between the two islands, including the number of species, species abundance, species richness index, and Pielou's evenness index ( < 0.05). Cluster analysis, non-metric analysis, permutational multivariate analysis of variance (PERMANOVA), and permutational analysis of multivariate dispersion (PERMDISP) revealed variations in macrobenthic communities between the two islands and over the years 2010, 2011, and 2012. According to the Biota-Environment Matching (BIO-ENV), distance-based redundancy analysis (dbRDA), and distance-based linear model analyses (DistLM), the principal environmental variables influencing the distribution of macrobenthic communities are Cd and As. These variations likely result from different levels of human activity on each island. Moreover, interannual variations in macrobenthic communities, especially in 2012, were predominantly influenced by Pb and Cr, likely due to alterations in the influence of the Changjiang (Yangtze River) diluted water.