EFFECTS OF SALINITY ON THE CONDITION AND SURVIVAL OF ZEBRA MUSSELS (DREISSENA-POLYMORPHA)

The objectives of this study were to determine the tolerance of variou s life stages of zebra mussels to salinity; determine the extent to wh ich acclimation events in estuarine systems affect tolerance of zebra mussels; and determine the effects of salinity on health or condition of adult zebra mussels. At high temperatures (18-20 degrees C), the co ndition of zebra mussels is reduced at salinities above 1 parts per th ousand. However, at lower temperatures (3-12 degrees C), the optimum s alinity for zebra mussels is 2-4 parts per thousand. The incipient let hal salinity of post-veligers is near 2 parts per thousand, of larger adults (5-15 mm) between 2 parts per thousand and 4 parts per thousand , and of veliger larvae near 4.5 parts per thousand. Zebra mussels are able to acclimate to slowly changing salinities (i.e., 1 parts per th ousand d(-1)) such that the time to 50% mortality of a population shou ld be greater than 1 yr at temperatures near 20 degrees C and saliniti es up to 8 parts per thousand.