Resident Crab Associations with Sedimentation on Restored Intertidal Oyster Reefs in South Carolina and the Implications for Secondary Consumers

Abstract

AbstractBenthic–pelagic coupling is an important habitat function provided by oyster reefs that is potentially affected by sedimentation impacts. In this study, the distributions of three resident crab species, the flat mud crab (also known as the flatback mud crab) Eurypanopeus depressus, the common mud crab (also known as the Atlantic mud crab) Panopeus herbstii, and the invasive green porcelain crab Petrolisthes armatus, were examined with respect to sedimentation on six restored intertidal eastern oyster Crassostrea virginica sites in South Carolina. Sedimentation among sites ranged from 4% to 60% cover and was composed of silty clay and sand. Crab associations with sedimentation differed among species. Common mud crabs and green porcelain crab densities were negatively correlated with percent sediment cover, whereas flat mud crab densities were not related to sediment cover. Flat mud crabs occupy the interstices of the reef, and their densities were positively correlated with scorched mussel Brachidontes exustus densities. Total crab biomass and individual body weight were converted to annual secondary production estimates, which ranged from 6.1 to 27.2 g/m2 (ash‐free dry weight) among sites. Sedimentation on oyster habitat reduced crab annual secondary production beyond a prediction made by a proportional inverse relationship between percent sediment cover and crab secondary production. As an example, at 50% sediment cover, crab annual secondary production was reduced by 68%. The discrepancy between observed and predicted (proportional) reductions in crab secondary production estimates were most pronounced when sedimentation levels were less than 60% cover. These results suggest the use of proportional loss estimates to mitigate for sedimentation impacts on oyster habitat, when quantified as percent sediment cover, do not adequately compensate for impacts to resident crabs and consequential energy loss to crustacean and fish predators that include many important recreational and commercial species.Received November 22, 2011; accepted May 10, 2012