Effect of salinity reduction on oxygen consumption by larval estuarine invertebrates

Unpredictable events can cause rapid sizable changes in environmental condi tions. 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 la rval oxygen consumption. Two species of larval invertebrates were exposed t o salinity reduction, the marine polychaete Arenicola cristata Stimpson and the mud snail Ilyanassa obsoleta (Say). In experimental treatments, salini ty was reduced to 10 or 15 parts per thousand; control individuals were mai ntained at 30 parts per thousand. 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 par ts per thousand S compared with controls and with salinity reduction to 15 parts per thousand; larvae eventually died at 10 parts per thousand. After salinity reduction ceased, larvae exposed to a salinity reduction to 15 par ts per thousand consumed more (A. cristata) or the same (I. obsoleta) amoun t of oxygen as individuals maintained at 30 parts per thousand. We have sho wn in previous experiments that salinity reduction results in significant r eductions 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) lar vae. Taken in conjunction with the results of our present study on larval o xygen consumption, the results suggest that salinity reduction has a large impact on estuarine invertebrates.