Cordgrass Spartina alterniflora acts as a key carbon source to support macrozoobenthos in the salt marsh and nearby mudflat communities

Exotic cordgrass Spartina can influence the trophic interaction and functioning of coastal ecosystems by altering the availability or palatability of carbon sources utilized by macrozoobenthos. Previous studies focused mainly on the trophic dynamics in Spartina-invaded mangroves or marshes, but the effect of Spartina on the diet of macrozoobenthos inhabiting the nearby unvegetated mudflat remains largely unexplored. By analyzing carbon and nitrogen stable isotopes, we compare the trophic contribution of an exotic cordgrass Spartina alterniflora to the macrozoobenthos between the dense S. alterniflora area (DSA) and adjacent tidal bare mudflat (TBM) in the Hepu coast, Guangxi province. Macrozoobenthic species were more abundant in TBM than in DSA, but the difference in carbon and nitrogen stable isotopes was insignificant for the seven conspecifics between two sampling areas, where similar organic carbon sources and trophic levels for macrozoobenthos were found. The MixSIAR mixing model revealed that S. alterniflora acted as the most important carbon source for many macrozoobenthic species and all guilds in DSA and TBM. This study showed that S. alterniflora can benefit the adjacent bare mudflat by supplying detritus as the carbon source for macrozoobenthos, which is favorable for maintaining the biodiversity and trophic dynamics of macrozoobenthic communities in coastal ecosystems.