The Intertidal Macrobenthic Community along an Artificial Structure

Abstract

Artificial structures were designed as pilot structures to promote the creation and restoration of tidal flats. However, little information is available as to whether such artificial construction affects the macrobenthic community structure. We monitored the variation of the macrobenthic community structure and species composition at two artificial structures (seaweed and a timber fence) on the tidal flats near the Iwon Dike, Korea. In total, 137 macrobenthic species were recorded during this study, predominately crustaceans (47%), polychaetes (18%), and molluscs (27%). The density of polychaetes comprised over 50% of the total density, followed by gastropods (38%) and crustaceans (11%). Macrobenthic species composition was similar between the artificial and natural areas, with several common dominant species found at the beginning of the experiment, but differing after 7 months. The gastropod Umbonium thomasi, the most dominant species, appeared at all sites within 1 month after the start of the experiment, but disappeared in the artificial sites after 7 months, suggesting disturbance by the environmental factors. The number of species and diversity (H') varied significantly within the sites at the beginning of the experiment, but no difference was observed after 7 months. Multivariate analysis (multidimensional scaling) revealed significant differences in community structure between the artificial and the natural areas after 7 months after the start of the experiment, except from 18 to 21 months. The community structures were mainly influenced by U. thomasi. The community structures in the artificial sites were affected by environmental variables, such as carbon, COD/IL sulfide, lose of ignition, kurtosis and silt, which changed over time. We observed no significant correlations between environmental variables and the dominant species, except in the case of Spio sp. and Macrophthalmus dilatatus, suggesting that the biological interactions and the temporary disturb