MACROINFAUNA OF A SOUTHERN NEW-ENGLAND SALT-MARSH - SEASONAL DYNAMICSAND PRODUCTION

The animal-habitat relationships and seasonal dynamics of the benthic macroinfauna were investigated from November 1986 to October 1988 in t he Great Sippewissett salt marsh (Massachusetts, USA), Total macrofaun al abundance varied seasonally, displaying a peak in late spring and e arly summer, then declining sharply during late summer and recovering briefly in fall before collapsing in winter. Three macroinfaunal assem blages were found in the marsh, distributed along gradients of environ mental 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 sedim ents included the polychaetes Leitoscoloplos fragilis, Aricidea jefrey ssi, Magelona rosea and Streptosyllis verrilli, the oligochaete Parana is litoralis, and the crustacean Acanthohaustorius millsi. Sandy organ ic sediments were characterized by the polychaetes Marenzelleria virid is, Capitella capitata, Neanthes succinea, N. arenaceodonta, Polydora ligni and Heteromastus filiformis, the oligochaete Lumbricillus sp., a nd 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 mac roinfauna 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 san dy organic areas, but only 281 kJ m(-2) yr(-1) in sandy non-organic ar eas and 113 kJ m(-2) yr(-1) in muddy areas. This results in an area-we ighted average production of 505 kJ m(-2) yr(-1) for the unvegetated a reas of the marsh. The Great Sippewissett salt marsh has an area of 48 3 800 m(2), the total secondary production of the macroinfauna for the whole unvegetated area of the marsh was estimated as 4651 kg dry wt y r(-1), expressed as somatic growth. This production value seems consis tent with production data obtained for other intertidal North Atlantic environments.