Habitat Primarily Structures Seagrass Epifaunal Communities: a Regional-Scale Assessment in the Chesapeake Bay

Abstract

Epifaunal invertebrates play an important role in seagrass systems, both by grazing epiphytic algae from seagrass blades and by acting as a major food source for higher trophic levels. However, while many studies have described epifaunal community properties at small spatial scales (1–10 m2) and across very large gradients (from continental coastlines to the entire globe), few have examined regional-scale (100–1000 km2) patterns or, more importantly, disentangled the drivers of these patterns. Here, we synoptically sampled the epifaunal invertebrates of 16 sites dominated by eelgrass (Zostera marina) across the lower Chesapeake Bay estuary to describe differences in epifaunal community abundance, biomass, richness, and composition. We then used complementary spatial and environmental data to identify potential drivers of these patterns. We found no significant associations between any variable and epifaunal abundance or biomass, but differences in epifaunal species richness correlated most strongly with water temperature, and differences in community composition were best explained by seagrass cover and the biomass of algal resources. Further exploration revealed the relationship between cover and community structure was driven by three specific species of peracarid crustaceans. Furthermore, when only species with direct development were included in the analysis, geographic distance, rather than seagrass cover, became a significant predictor of community composition, suggesting that species with particular traits (i.e., direct developers) are more likely to be found closer together in space.