The impact of salinity changes associated with size on the wedge clam Donax trunculus Linnaeus, 1758 (Mollusca: Bivalvia): A laboratory assay

Abstract

Temperate zones have undergone intense rainfall in recent years, which may induce alterations in the salinity of estuarine and coastal areas and consequently on benthic communities. Donax trunculus Linnaeus, 1758, is a component of the macrofauna in shallow areas of sandy beaches and, because of its economic value, one of the most exploited clams. The sensitivity of D. trunculus to salinity changes and differences related to size were tested in this study. Adults and juveniles of D. trunculus were exposed to different salinity treatments and mortality was registered every 12 h during 21 days. In general, salinities below 14.2 were lethal to both populations, whereas the survival rate was 100% in salinities equal to or above 26.7. Differences in survival rates between the two size classes were detected, especially at intermediate salinities, where juvenile survival was higher. Median lethal salinity (LC50) was similar for both groups, although in juveniles the values were lower, whereas the median lethal time (LT50) values were higher in young clams. Therefore, the results of this study suggest that D. trunculus is a euryhaline species whose tolerance to low salinities varies between size classes. Juveniles resist lower salinities than adults, and can withstand sudden changes in salinity over a longer period.