Interactive effects of multiple stressors on the physiological performance of the invasive mussel Mytilus galloprovincialis

The invasive mussel Mytilus galloprovincialis is a heat-tolerant species relative to its competative congener M. trossulus, that dominates warm seawater environments but it is unknown how multiple stressors (MS) may affect its physiology. Our study determined the effects of MS on the metabolic rate (MR), superoxide dismutase (SOD) antioxidant enzyme activity, and clearance rate (CR) of M. galloprovincialis. Mussels were exposed for 7 d to hyposalinity (20, 28, 34 ppt) then to heat shock (17, 20, 25 ?) after which MR and SOD activity were determined. CR was quantified following a 30 min MS exposure. We found a significant influence of MS on MR, SOD, and CR. We identified synergistic effects on MR under the most extreme treatment. SOD activity was the greatest under 20 C exposure while CR declined under heat shock. Thus, our study suggests that mussels experiencing MS may become energy limited as MR increases and feeding rates decrease.