The Antagonistic Effect of Raised Salinity on the Aerobic Performance of a Rocky Intertidal Gastropod Nassarius deshayesianus (Issel, 1866) Exposed to Raised Water Temperature

Rocky intertidal organisms are facing pronounced fluctuations in environmental conditions even at small spatial and temporal scales. This heterogeneous habitat is a proper model system to investigate effects of physical parameters and their interactions on physiological performances of marine organisms. In the intertidal zone (especially in tidal pools), the temperature and salinity usually increase in concert during the daytime low tides. In this study, we used a rocky intertidal scavenger gastropod, Nassarius deshayesianus, as a model to test if high salinity can affect the metabolic performance of rocky intertidal mobile ectotherms at high temperatures. In August 2009, specimens were exposed to normal and elevated temperatures and salinities for 50 minutes and their specific metabolic rates were evaluated (N=12). At the high temperature treatment, metabolic rates were significantly lower when the salinity was high. Considering the concept of oxygen- and capacity- limited thermal tolerance, we will discuss that this antagonistic effect of increased salinity on the aerobic performance at the high temperature may lower thermal tolerance of intertidal ectotherms. Also N. deshayesianus showed high mortality after a few days of exposure to 36°C water temperature. This signifies that they may currently live close to the maximum limit of thermal tolerance in the hottest sea of the world, the Persian Gulf.