Diversity, Abundance and Community Structure of Soft-Bottom Macrobenthic Fauna in the Maryland Coastal Bays, USA

Maryland coastal bays have undergone changes in the past few decades. Phytoplankton and macroalgae biomasses have increased, especially in the northern parts of the bays due to nutrient enrichment. The response of benthic macroinvertebrate community to these changes is not well documented. The composition and abundance of macrobenthic fauna were investigated at 24 stations in the lagoons, based on samples collected in May 2017 with a Van Veen grab. A total of 25,481 macroinvertebrates were recorded, belonging to seven phyla, 55 families, 76 genera, and 96 species. Polychaetes were the most abundant group (86%), followed by crustaceans (6%), and nematodes (3%). Families with the highest species richness were Spionidae (9 spp.), Capitellidae (6 spp.), Paraonidae (5 spp.), Phyllodocidae (4 spp.), and Haustoriidae (4 spp.). The species with the highest (>4%) relative abundance were Mediomastus sp. (6,073 ind 0.052 m^-2), Streblospio benedicti (3,790 ind 0.052 m^-2), Capitella cf. teleta (2,602 ind 0.052 m^-2), Polydora sp. (2,151 ind 0.052 m^-2), Mediomastus ambiseta (1,723 ind 0.052 m^-2), and Clymenella torquata (1,030 ind 0.052 m^-2). The abundance of macroinvertebrates ranged from 4,185 ind 0.052 m^-2 (station 11 in Assawoman Bay) to 67 ind 0.052 m^-2 (station 14 in Saint Martin River). Assawoman Bay had the highest mean abundance of macroinvertebrates (2251.7 ± 966.7 ind 0.052 m^-2) whereas the lowest mean abundance of macroinvertebrates occurred in Isle of Wight Bay (663.0 ± 582.0 ind 0.052 m^-2). The highest abundance of macroinvertebrates occurred in the northern bays, and the lowest abundance was in the southern bays. Overall, there were no significant correlations between the density of macroinvertebrates and abiotic factors (i.e. organic matter (%), temperature, salinity, Dissolved Oxygen, and pH). Studies are continuing to assess seasonal and spatial changes in the macroinvertebrate community in relation to environmental factors.