The benthic infaunal mudflat community of Boston Harbor’s Savin Hill Cove was sampled every other week from January though December 1986. Eighty replicate samples per date allowed precise estimates of the abundances of juvenile and adult stages of all macrofaunal taxa and many meiofaunal taxa. We describe the multivariate structure of the seasonal succession of this community with a faunal distance metric approach. There were three groups of species that produced a three‐stage or triangular succession pattern. Stage 1 is defined by a March bloom of harpacticoid copepods that closely follows a benthic diatom bloom. Harpacticoid copepod abundance rapidly declines in late spring and is followed by the recruitment of four opportunistic annelids, marking the break between stages 1 and 2. Stage 2 is a dense assemblage of four surface‐deposit feeding and shallow subsurface‐deposit‐feeding annelids that reach peak abundance in June and decline in late summer, marking the break between stages 2 and 3. Stage 3 populations are more diverse than stage 2, reach peak abundance in fall, and decline in late fall. The infaunal community structure of December resembles that of the community the previous January. Succession on this mudflat is a fast‐paced and dynamic process affected by epipelic diatom production, the timing and duration of juvenile recruitment, and the ability of the infauna to survive in dense assemblages of tube builders.

Abstract14C-labeling of chlorophyll a and subsequent extraction by high-pressure liquid chromatography (HPLC) was adapted for field measurement of both specific growth rate and biomass of diatom films found on muddy intertidal sediments of Savin Hill Cove, a small embayment of northwest Dorchester Bay, Boston Harbor.