Differences in the crab community structure between pristine and degraded Suaeda marshes after Spartina invasion

The degradation of coastal wetlands often threatens the diversity of native species. In addition to human activities, alien plant invasion is a major cause of local habitat degradation. Spartina alterniflora invasion results in extensive degradation of native Suaeda salsa marshes, and the difference in the macrobenthos between pristine and degraded S. salsa marshes remains unclear. Here, we compared the crab community structures of two S. salsa marsh sites on the Yellow Sea coast. One of the sites was coastal and experienced periodic tidal flooding, while the other site had migrated inland due to the encroachment of alien S. alterniflora onto the mudflat, which blocked the tide. A total of seven crab species were found in the two sites, and three and seven species were identified in the S. salsa marshes with and without tidal flooding, respectively. The S. salsa marsh that did not experience tidal flooding had the highest Shannon–Wiener index, while the S. salsa marsh that experienced tidal flooding had the highest total density. Our study highlighted that even if S. salsa marshes are preserved in nature reserves, there should be conspicuous differences in the crab communities between pristine and degraded S. salsa marshes after S. alterniflora invasion. Future conservation studies should assess the ecological value of different S. salsa marshes by paying increased attention to changes in the faunal groups of the habitats.