Effect of Environmental Variables on the Inter- and Subtidal Macrobenthic Communities in the Iwon Dike Area

摘要

Spatial patterns in the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike and environmental variables were examined in August 2001. In total, 156 macrobenthic species (123 intertidal species and 90 subtidal species) were recorded during this study, predominately polychaetes (40%), bivalves (22%), and crustaceans (22%). Polychaetes made up less than 40% of the intertidal community, but more than 50% of the subtidal community. The mean density during this studywas 1,456 ind./m. Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among four regions: near the Iwon dike (Bl), the high and middle intertidal zone (B2), low intertidal zone (Al), and subtidal zone(A2). The number of species, total density, and diversity (H1) varied significantly among the four regions. The distribution of macrobenthic community was affected by environmental variables, such as % silt/clay content, total sulfide, lose of ignition,and chemical oxygen demand. These environmental variables were negatively correlated with the dominant species (Nephtys polybranchia, Umbonium thomasi, and Scoloplos armiger) in the intertidal area, but positively correlated with the dominant species (Lumbrineris cruzensis, Notomastus latericeus, and Moerella sp.) in the subtidal area. Environmental variables (% silt/clay content and total sulfide) were positively correlated with the dominant species (Heteromastus filiformis) in region Bl, but negatively correlated with the dominant species (Umbonium thomasi and Scoloplos koreanus) in region B2. Amphipods Urothoe spp. and Monoculodes koreanus were the dominant species in region Al. Umbonium thomasi, the dominant species in region B2, was not found inregions Bl or Al. We suggest that the inter-specific competition for territory and exposure to seawater may be important factors controlling the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike.