Trophic Consistency of Benthic Invertebrates Among Diversified Vegetational Habitats in a Temperate Coastal Wetland of Korea as Determined by Stable Isotopes

The relative importance of different organic matter sources to macrobenthic consumers was investigated at two vegetational habitats (Phragmites australis and Suaeda japonica) and at a bare intertidal flat in Suncheon Bay in May and August 2010, using stable carbon and nitrogen isotope tracers. The delta C-13 of consumers was much narrower in range than that of potential food sources (microphytobenthos, marsh plants, and riverine and marine particulate organic matter), and values were similar between sites. However, cluster analysis based on the consumer's isotope values showed that they are divided according to functional groups rather than habitat type and taxonomical group, suggesting that the exploitation of different dietary sources depends on feeding strategy. Except for two suspension feeders and nonselective deposit feeders at the Phragmites bed, most consumers had similar delta C-13 to those of microphytobenthos. An isotopic mixing model calculation revealed the consistent importance of microphytobenthos to the nutrition of benthic invertebrates among wetland habitats in different seasons. In contrast, very little contribution of marsh plant-derived organic matter to consumer nutrition was detected at all sites. Furthermore, our results suggest that the summer monsoon event does not lead to a seasonal shift in dietary sources of consumers in this coastal wetland system.