Influence of zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis) mussel invasions on benthic nutrient and oxygen dynamics

摘要

Although invasive zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis) mussels are known to increase water column concentrations of nitrogen and phosphorus, the relative roles of direct nutrient release by the mussels and mussel-induced alterations to sediment fluxes are little understood. In short-term microcosm experiments comparing the presence and absence of mussels on sediments from Oneida Lake, New York, USA, both dreissenid species approximately doubled benthic oxygen consumption and fluxes of ammonium. The impact on soluble reactive phosphate (SRP) flux varied from 40% to 140% depending on whether mussels were located in the water column or directly on sediments. The additional flux was attributable directly to release by the mussels, with fluxes from the sediments remaining largely unchanged. However, mussels located directly on sediment surfaces released twice as much SRP as mussels located higher in the water column, with a molar N:P ratio as low as 4:1. The high rate of SRP release by mussels on sediment, possibly caused by mobilization of iron-bound phosphorus from sediment particles in the anoxic guts of the mussels, could contribute to observed increases in SRP, abundance of nuisance algae such as Cladophora, and abundance and toxicity of the cyanobacteria Microcystis in dreissenid invaded ecosystems.