Effects of long-term exposure to low salinity on the brackish-water Amphiurid Brittlestar Ophiophragmus Filograneus (Lyman, 1875) from the Indian River Lagoon System, Florida

Abstract

Previous studies on salinity tolerance of Ophiophragmus filograneus have documented its ability to acclimate to a wide range of salinities in the laboratory and to acclimatize to short-term natural reductions in salinity. In all cases, salinities below 10% were lethal within a few weeks of exposure. Recent long-term changes in hydrology have exposed a dense population of O. filograneus in the Banana River lagoon to 3 yr of salinities between 10% and 20%. The burrowing response of animals subjected to acute exposure was tested in the present study at salinities of 8, 10, 12, 14 (ambient), 19, and 24%. After almost 6 wk of continuous exposure, animals at 14%, 19%, and 24%had fully acclimated, although all animals showed signs of stress. Those at 12% still had elevated burrowing times after 6 wk. Animals at 10% survived, but many did not burrow within the allotted time (7 min) for each trial. None at 8% burrowed nor survived more than 15 d. Long-term exposure to low salinity does not extend the tolerance of O. filograneus: it has a lower lethal limit of about 8%, a limit that might produce local extirpation if current approaches to lagoon management do not change.