Response of Hydrobia ventrosa (Montagu) to Environmental Stress: Effects of Salinity Fluctuations and Cadmium Exposure on Growth

Abstract

As estuarine environments are often rich in both natural and man-induced stresses, estuarine species may provide important insights into the study of how organisms respond to stress. Exposure to cadmium concentrations of 100200 [Lg 1-1 significantly reduced growth rate of the estuarine gastropod, Hydrobia ventrosa (Montagu). Snails acclimated to 23%o salinity sea-water (S) showed reduced growth rates at 13 and 33%o S relative to snails grown at 23%o S. At 13%o S snails did not grow, and any additional effects of cadmium exposure on growth were masked. The results are not consistent with expectations based on estimated cadmium bioavailability as the relative reduction in growth in response to cadmium increased with increasing salinity. The growth trajectory of H. ventrosa at 23%o S (no cadmium) fitted a logistic growth model. Changing salinity and exposure to cadmium altered daily specific growth rates (% day-1) in a size(or time-) dependent manner such that a logistic model no longer described the growth trajectory of this species. Maximum growth rates occurred at a higher salinity than expected, based on reports of the natural distribution of H. ventrosa, and the results suggest substantial intraspecific variability in salinity tolerance in this species. Key-words: Cadmium, growth, Hydrobia, salinity