LIFE-CYCLE, DEMOGRAPHY, AND PRODUCTION OF MARENZELLERIA-VIRIDIS IN A SALT-MARSH OF SOUTHERN NEW-ENGLAND

Population dynamics and production of the spionid polychaete Marenzell eria viridis were studied at Great Sippewissett salt marsh (Massachuse tts, USA) for two years. Marenzelleria viridis was the main contributo r in biomass and production to the macroinfaunal assemblages of the sa ndy organic sediments of the marsh. Marenzelleria viridis spawned duri ng the cold part of the year and the appearance of settled larvae on s ediments was observed from January to May. The density of M. viridis r ose sharply from winter to late spring followed by a striking drop thr ough summer. The estimated mean annual production of M. viridis was 60 . 0 g dry weight m(2) during the first year and 26 . 3 g dry weight m (2) during the second year. The population of M. viridis is affected b y different processes during the year. The number of initial recruits seems to be largely governed by meteorological conditions. The numbers of recruits are then affected by competition for resources, and later , as predators become active, predation pressure determines the abunda nce of the population of M. viridis.