Role of the ctenophore Mnemiopsis leidyi in nutrient cycling in Long Island Sound, New York, USA

Abstract

The population dynamics of the ctenophore Mnemiopsis leidyi are often characterized by a substantial build-up and demise in abundance in coastal and estuarine waters, a pattern that may have a significant impact on nutrient cycling. Since many coastal ecosystems are experiencing negative impacts of eutrophication, there is great interest in quantifying nutrient loading sources. Still, the ability to calculate robust nutrient budgets in many coastal systems has been hampered by a poor understanding of the contribution of gelatinous zooplankton to nutrient pools. Long Island Sound is a highly productive, urban estuary within which M. leidyi occurs, but the role of this species in nutrient cycling was unknown. In 2011, the population biomass and nutrient remineralization rates (i.e. NH4 +, PO4 3?) of M. leidyi in the estuary were evaluated. Ctenophores remineralized NH4 + and PO4 3? at rates up to 0.62 and 0.13 ?mol ind.?1 h?1, respectively, and were capable of substantial release of nutrients upon population demise (39.32 ?mol m?3 d?1 of NH4 + and 20.02 ?mol m?3 d?1 of PO4 3?). However, in both cases, these rates were not in quantities sufficient to support a major fraction of primary production (<1% d?1). This study suggests that ctenophores may contribute only in a minor way to nutrient pools in highly eutrophic ecosystems.