Effect of salinity reduction on oxygen consumption by larval estuarine invertebrates

Unpredictable events can cause rapid sizable changes in environmental conditions. Storm events are an example of an unpredictable event; in estuarine habitats, storms can bring about drastic changes in salinity levels within several hours. This study focused on the effect of salinity reduction on larval oxygen consumption. Two species of larval invertebrates were exposed to salinity reduction, the marine polychaete Arenicola cristata Stimpson and the mud snail Ilyanassa obsoleta (Say). In experimental treatments, salinity was reduced to 10 or 15‰; control individuals were maintained at 30‰. Salinity was reduced for 3 d when larvae were between the ages of 1 and 4 d, post-hatch. Oxygen consumption was the same among treatments during salinity reduction for I. obsoleta larvae. The oxygen consumption of A. cristata larvae was significantly lower at 10‰S compared with controls and with salinity reduction to 15‰; larvae eventually died at 10‰. After salinity reduction ceased, larvae exposed to a salinity reduction to 15‰ consumed more (A. cristata) or the same (I. obsoleta) amount of oxygen as individuals maintained at 30‰. We have shown in previous experiments that salinity reduction results in significant reductions in larval growth in A. cristata and I. obsoleta larvae as well as in changes in developmental rates of A. cristata (but not I. obsoleta) larvae. Taken in conjunction with the results of our present study on larval oxygen consumption, the results suggest that salinity reduction has a large impact on estuarine invertebrates.