Community Structure and Abundance of Benthic Infaunal Invertebrates in Maine Fringing Marsh Ecosystems

Abstract

Fringing marshes are abundant ecosystems that dominate the New England coastline. Despite their abundance, very little baseline data is available from them and few studies have documented the ecosystems services that they provide. This information is important for conservation efforts as well as for an increased understanding of how fringing marshes function compared to larger marsh meadow systems. Benthic infaunal invertebrates were sampled from cores collected from Spartina alterniflora-dominated low marsh, Spartina patens-dominated high marsh, and Phragmites australis-invaded high marsh zones of nine fringing marsh ecosystems in Casco Bay, Maine, USA. Infaunal densities and biomass were generally higher in low marsh than high marsh or P. australis cores. Invertebrate community structure was significantly different between low marsh and high marsh and P. australis cores, which was attributed to significantly higher pore water salinity, lower organic matter, total plant percent cover, and S. patens cover in low marsh zones. There were no differences in invertebrate densities, biomass, or community structure when high marsh and P. australis cores were compared. Invertebrate densities and community structure were dominated by oligochaetes in all zones. Oligochaetes were also an important component of infaunal biomass, but the less abundant and larger invertebrates such as green crabs, tanaids, and bivalves were also large contributors to biomass in the low marsh zone. Low marsh invertebrate communities were characterized by significantly higher densities of nematodes, Nereis virens, an unidentified oligochaete, the bivalves Gemma gemma and Mya arenaria, and Leptochelia rapax. High marsh invertebrate communities were characterized by higher densities of insects, specifically Culicoides sp. ceratopogonid larvae and Anurida maritima, as well as an unidentified species of mite. Our results revealed a diverse and abundant infaunal invertebrate community that likely supports similar ecosystem services in fringing marshes as invertebrates in larger marsh meadows.