Estuarine benthic invertebrates of Indian river and Rehoboth Bays, Delaware

Abstract

AbstractFrom 1968 to 1970, 273 quantitative samples of macroscopic benthic invertebrates were collected seasonally (winter and summer) from Indian River and Rehoboth Bays, Delaware. A total of 103, 485 individuals representing 11 phyla and 149 species was taken. Mobile carnivores comprised 30.9% (46 species) of the fauna, selective deposit feeders 28.2% (42 species), sedentary suspension feeders 18.1% (27 species), nonselective deposit feeders 3.4% (5 species), and sessile carnivores 2.7% (4 species). In terms of number of individuals, selective deposit feeders and sedentary suspension feeders comprised 49.2% (51,442 individuals) and 43.7% (44,647 individuals), respectively. The average density (no./m2) was generally significantly higher in Indian River than Rehoboth Bay. Maximum density for the former was 106,871/m2 and for the latter 60,192/m2. Evenness diversity was normally slightly higher in summer than winter and higher in Rehoboth Bay than in Indian River Bay. The top three species, ranked by density and frequency of occurrence, were Ampelisca abdita, Gemma gemma, and Tellina agilis. Annual and seasonal changes in density and dominance (exclusive of the top three species) were substantial. Biomass patterns were very similar to areas north (Moriches Bay, New York) and south (Beaufort, North Carolina). It was suggested that larger invertebrates have been deemphasized in biomass estimates in past studies. It was concluded that Rehoboth and Indian River Bays contained an Ampelisca — bivalve (Gemma gemma, Tellina agilis, Mercenaria mercenaria) community.