Dreissenid metabolism and ecosystem-scale effects as revealed by oxygen consumption

Respiration rates of the quagga mussel (Dreissena rostriformis bugensis) were determined for the shallow and profunda morph phenotypes from in situ and laboratory experiments under a range of temperature (4-20°C), shell size, and food and oxygen availability conditions. Temperature-normalized oxygen consumption was significantly lower for the hypolimnetic profunda phenotype than for the shallow type. Mass-normalized respiration rates were inversely related to mussel size. Mussels adjusted their oxygen consumption in response to food enhancement and deprivation, lowering their respiration to a basal metabolic rate 18 hours after food deprivation. In response to decreasing ambient oxygen, quagga mussels exhibited first-order reaction kinetics, with mass-normalized respiration rate at a dissolved oxygen concentration of 0.002 mol L− 1 being 1% of that at saturation. Using published data on quagga mussel energy budgets and respiratory quotients, oxygen consumption rates were converted to organic carbon consumption rates. Using these values, along with data on mussel density and size frequency distribution, it is estimated that quagga mussels consume 54% of annual phytoplankton production, from 1.4-4.1 times the offshore annual settled organic carbon in the southern basin of Lake Michigan, and from 2.4-5.5% of offshore areal particulate carbon in the water column. Dreissenids appear to exert significant direct influences on benthic oxygen dynamics, and consume enough organic carbon to have a significant effect on energy flow in the Lake Michigan ecosystem.