Zooplankton of lower Narragansett Bay, 1972–1973

Abstract

From January 1972 through December 1973 weekly zooplankton samples were taken in lower Narragansett Bay in connection with a phytoplankton study. Fifty percent (by numbers) of the zooplankton were calanoid copepods, the dominant species beingAcartia clausi. In 1973, individuals of summer-fall zooplankton species were much more numerous than in 1972, butAcartia clausi, the dominant winter-spring species, was equally abundant both years. Release of grazing pressure by zooplankton did not appear to trigger the winter-spring flowering of 1973, but a definite relationship was seen between ctenophores, herbivorous zooplankton and phytoplankton in the summer and fall of 1973. Moderate numbers of zooplankton were present in the winter around the time of the phytoplankton bloom, but the major peaks of biomass and numbers occurred in the spring when water temperatures were on the increase. Zooplankton biomass dropped to near zero in late summer and fall.