Faunal communities on restored oyster reefs: effects of habitat complexity and environmental conditions

Wild oyster populations have suffered >85% global loss, and in Chesapeake Bay, only 1% of the historic oyster population remains. In response, efforts to restore oysters and the services they provide, such as water filtration and habitat, have increased. A critical step towards restoring these services is understanding the role of restored reefs in marine ecosystems and determining the factors that affect how species utilize them. In a field survey, we embedded benthic settling trays into restored reefs that varied in structural complexity in 4 rivers in Chesapeake Bay. We retrieved trays after 7 wk to estimate species diversity, density, and biomass of macro-fauna; these metrics were then related to structural indices and environmental conditions at each reef. A total of 66 macrofaunal species inhabited restored oyster reefs across all the samples, and reefs supported on average 75.6 g AFDW m(-2) and 6356 ind.m(-2). Species composition differed significantly among the rivers, and salinity best explained the differences. Salinity and rugosity were significantly and positively related to macrofaunal diversity, while negatively related to fish density. Salinity was also significantly and negatively related to macrofaunal density and biomass, whereas live oyster volume was significantly and positively related to total macrofaunal biomass and density, as well as densities of specific taxa (fish, polychaete, mud crab, mussel). Restored oyster reefs can be productive habitats with this potential varying with both salinity and habitat complexity. Our results suggest that habitat quality and utilization of reefs will be enhanced when habitat complexity of restored oyster reefs is high.