Influence of larval exposure to salinity and cadmium stress on juvenile performance of two marine invertebrates (Capitella sp I and Crepidula fornicata)

Delayed metamorphosis and short-term food limitation reduce juvenile or adu lt fitness in a number of marine invertebrate species. In this study, we te sted the ability of pollutant and salinity stress to bring about similar ef fects on juvenile or adult performance. Larvae of the polychaete Capitella sp. I were exposed to sublethal cadmium stress (up to 2000 mug l(-1)) or sa linity stress (down to 10 parts per thousand) for 24 and 48 h at 23 degrees C. Following exposure, we induced surviving larvae to metamorphose and moni tored the subsequent survival, growth, and reproductive output of juveniles reared under control conditions (no added cadmium, 32 parts per thousand s alinity). Similarly, larvae of the gastropod Crepidula fornicata were expos ed for 24 and 48 h to cadmium in seawater (up to a nominal concentration of 20,000 mug l(-1)). Surviving larvae were reared to metamorphic competence in the absence of cadmium, induced to metamorphose, and maintained under co ntrol conditions for an additional 5 days to monitor juvenile growth rates and survival. Exposing larvae of Capitella sp. I to low salinity (10-12 par ts per thousand) for 48 h generally did not affect adult fecundity, but str essing the larvae for as little as 24 h significantly reduced post-settleme nt survival and juvenile growth rates (P < 0.05). In contrast, exposing lar vae of this species to cadmium for even 48 h had no significant effects on post-settlement survival or fecundity, and no consistent effect on mean juv enile growth rate. Similarly, cadmium exposure did not significantly affect mean juvenile growth rates for C fornicata, even when larvae were severely stressed (i.e., when larval mortality exceeded 50% during exposures). We s uggest that heavy metal stressors do not act through the same mechanism as the stresses of inadequate food supply, reduced salinity, and delayed metam orphosis. (C) 2001 Elsevier Science B.V. All rights reserved.