Comparative trophic structures of macrobenthic food web in two macrotidal wetlands with and without a dike on the temperate coast of Korea as revealed by stable isotopes

Abstract

This study characterized trophic structures of the macrobenthic food webs in two contrasting estuarine wetlands, with and without a dike, on the southern coast of Korea, based on the δ¹³C and δ¹⁵N values of dominant macrobenthic consumers. The pelagic algal biomasses were similar in the upper Phragmites australis-covered and lower bare intertidal habitats partitioned by the dike, but the microphytobenthos (MPB) biomasses were extremely low in the Phragmites bed. The consumer δ¹³C values were more negative and their isotopic niche width was much narrower in the upper than in the lower habitat at the diked site. These dissimilar spatial patterns between sites suggest a simplified food-web structure, which reflects the reduced availability of MPB in the upper habitat in the dike-impacted site. Overall, our findings suggest that restriction of the tides by dike construction induces local changes in basal resource availability and faunal composition, leading to macrobenthic community trophic reorganization.

Keywords: Dike; Intertidal wetland; Macrobenthos; Phragmites australis beds; Stable isotopes; Trophic structure.