Effects of salt marsh restoration on eukaryotic microbenthic communities in the Yangtze Estuary

To fight invasion of Spartina alterniflora and conserve biodiversity of migratory shorebirds, several S. alterniflora marshes and bare mudflats have been restored back to Scirpus mariqueter marshes in the Yangtze River estuary in recent years. Although it is known that changes in plant cover in salt marshes alters the physical environment, findings on its effects on benthic communities are inconsistent and site-specific. In the present study, we tested how ciliates were influenced by a recent restoration. Ciliated protozoa play a key role in wetland benthic food webs and are useful bioindicators. We investigated 3 habitats: restored S. mariqueter meadow, S. alterniflora-invaded meadow, and bare mudflats, where we quantified environmental conditions, community composition (species and traits), and 3 aspects of biodiversity (classic, taxonomic, and functional diversity) over 4 seasons. CAP and ANOSIM were used to determine the differences among samples, while RDA and GLMs were used to reveal potential driving factors. We found that, although changes in the type of vegetation due to restoration or invasion significantly modified the sediment properties and ciliate species composition, it had limited influence on functional trait composition as well as on diversity, especially on functional diversity. These results indicate that the conversion of mudflats to S. mariqueter meadow did not affect ciliate community functions at the time scale of this study. However, biomonitoring based on microbenthic communities should be included when evaluating the long-term success of coastal wetland restoration.