JARRETT, J.N.; RUSSELL, G.; O’DRISCOLL, M.; SULLIVAN, D.: Impact of Short-term Salinity Fluctuations on Larvae and Juveniles of Crepidula fornicata and C. plana

The adult stages of most estuarine organisms are well adapted to environmental fluctuations characteristic of this habitat. However, larval stages of some marine invertebrates reared under constant or short-term conditions of low salinity exhibit reduced rates of larval growth and development and higher mortality. The capacity for larvae to recover from salinity stress and the long-term impact of larval salinity stress on juvenile growth are poorly understood. We exposed larvae of two prosobranch gastropods, Crepidula fornicata and Crepidula plana, to short-term (2 d) reductions in salinity (22o/oo, 20o/oo, 15o/oo or 10o/oo) either immediately after larvae hatched or at ages 1 d through 6 d and examined larval growth, mortality, and juvenile growth. In general, larval mortality was higher and larvae grew considerably more slowly when exposed to 10o/oo or 15o/oo seawater regardless of age at exposure. Larvae of several low salinity treatments did not recover to control growth when returned to optimal conditions. For most treatments, larvae exposed to 22o/oo or 20o/oo seawater grew at rates similar to control rates or recovered to control growth rates when returned to optimal conditions. Juvenile growth rates did not differ among treatments or controls for C. fornicata but, for C. plana, juvenile growth rates were significantly lower for some low salinity treatments compared to controls. These results suggest that the impact of short-term salinity stress on larvae and subsequent impacts on juvenile performance vary with the severity of the stress, larval age (developmental stage), and species being examined.