Characterization of Ribbed Mussel Geukensia demissa (Dillwyn, 1817) Habitat in Relation to Tidal Elevation and Salinity in a South Carolina Estuary


The distribution of sessile intertidal organisms depends on many different environmental and biological variables. Of these, elevation and salinity are particularly relevant, especially for organisms that occur in salt marsh–dominated estuaries in the Southeastern United States. The ribbed mussel Geukensia demissa is a mytilid bivalve, which is an ecologically important foundation species. Despite experiencing commercial harvesting pressure in South Carolina, G. demissa currently lacks speciesspecific regulations in terms of minimum harvest size and harvest limits. Furthermore, the distribution of G. demissa within its habitat, although well described in the Northeastern United States, has not been studied in South Carolina. The goal of the present study was to develop a methodology that could be used to characterize the distribution of G. demissa using elevation and salinity data to improve the understanding of the distribution of this species at the landscape scale and to support consideration of improved management measures. Transect grid surveys for the presence or absence of G. demissa were performed at stations along a salinity gradient in the Ashley River, a tributary of the Charleston Harbor, SC, in the spring of 2017. The presence or absence of G. demissa was explained by both elevation and salinity data using a logistic regression model, and G. demissa was predicted to be most likely to occur at a high position in the intertidal zone (0.17mbelow mean high water) and at an intermediate salinity of 18. In addition, the tidal inundation period for G. demissa in this study ranged from 45 min to 6 h, and averaged 3.5 h per high tide, highlighting the physiological challenges of its typical habitat distribution.

Journal of Shellfish Research, 38:53-61