Macroinfauna of a Southern New England salt marsh: Seasonal dynamics and production

The animal-habitat relationships and seasonal dynamics of the benthic macroinfauna were investigated from November 1986 to October 1988 in the Great Sippe-wissett salt marsh (Massachusetts, USA). Total macrofaunal abundance varied seasonally, displaying a peak in late spring and early summer, then declining sharply during late summer and recovering briefly in fall before collapsing in winter. Three macroinfaunal assemblages were found in the marsh, distributed along gradients of environmental factors. These included a sandy non-organic sediment assemblage, a sandy organic sediment assemblage and a muddy sediment assemblage. The species groups characteristic of unstable sandy non-organic sediments included the polychaetes Leitoscoloplos fragilis, Aricidea jefreyssi, Magelona rosea and Streptosyllis verrilli, the oligochaete Paranais litoralis, and the crustacean Acanthohaustorius millsi. Sandy organic sediments were characterized by the polychaetes Marenzelleria viridis, Capitella capitata, Neanthes succinea, N. arenaceodonta, Polydora ligni and Heteromastus filiformis, the oligochaete Lumbricillus sp., and the mollusc Gemma gemma. In muddy sites, the polychaete Streblospio benedicti and the oligochaetes Paranais litoralis and Monopylephorus evertus were the dominant species. Secondary production of benthic macroinfauna in each of these habitats was estimated. The highest values of biomass and production were recorded in the sandy organic sediments. Secondary production was estimated to be 1850 kJ m-2 yr-1 in sandy organic areas, but only 281 kJ m-2 yr-1 in sandy non-organic areas and 113 kJ m-2 yr-1 in muddy areas. This results in an area-weighted average production of 505 kJ m-2 yr-1 for the unvegetated areas of the marsh. The Great Sippewissett salt marsh has an area of 483800 m2, the total secondary production of the macroinfauna for the whole unvegetated area of the marsh was estimated as 4651 kg dry wt yr-1, expressed as somatic growth. This production value seems consistent with production data obtained for other intertidal North Atlantic environments.