The seasonal abundance and production of Oithona nana (Copepoda:Cyclopoida) in Southampton Water

Abstract

Recent studies indicate that Oithona spp. contribute significantly to total copepod biomass. Little is known, however, about their ecological significance, particularly in the case of the estuarine Oithona nana. A study comprising three sites within Southampton Water was conducted to evaluate the late-stage copepodite/adult (stages IV to VI) O. nana community, using 120 μm mesh nets. Although present throughout the estuary, there was a striking spatial gradient with O. nana most common in the upper estuary. A clear seasonal pattern was observed with O. nana as the most abundant copepod species from late-summer until early-winter. It comprised 61% of all copepods recorded, with a biomass of 757.22 mg C m -3 . Production estimates of O. nana were derived from the “instantaneous-growth” approach, using appropriate growth equations. The estimated production of O. nana ranged from 1.50 mg C m -3 yr -1 within the lower estuary to 146.77 mg C m -3