Science Serving Maryland's Coasts

Patrick Spain, Suffolk University

Class Year: 
2001

Project Title: 

The Ability of Various Sized Oyster Spat to Withstand Increasing Degrees of Dessication

Abstract: 

It was hypothesized that desiccation will cause mortality in Crassostrea virginica (Eastern oyster) spat; small oyster spat are more susceptible to desiccation than larger spat; misting with ambient Choptank river water will reduce spat mortality; covering spat (thus reducing exposure to solar radiation) will decrease mortality; and decreased temperature/increased humidity will decrease mortality. These hypotheses were tested by subjecting spat of varying sizes and known ages to desiccation under various stressors. These included: direct exposure to atmospheric ambient weather conditions; exposure to the atmosphere while covered by a tarp thus preventing exposure to solar radiation; and exposure to ambient conditions with lessoned desiccation by providing a constant mist of Choptank River water flowing over the spat. The exposure times for each stressor ranged from 2-48 hrs. During the entire exposure time data loggers recorded the temperature, humidity, and solar radiation of the ambient conditions the spat were being exposed to. The results showed that desiccation did cause mortality in spat, and that the larger the individual spat, the longer it could to survive under any stressor. Positive correlations between decreased solar radiation, increased humidity, and decreased temperature were found. The spat positioned under the tarp faired slightly better than those under the mist of river water and both faired significantly better than those exposed to ambient conditions.
It was hypothesized that the mortality rate of Crassostrea virginica spat exposed to ambient conditions will decrease as their size increases and as their exposure time decreases was tested by subjecting spat of varying sizes and known ages to desiccation under various stressors. These stressors included direct exposure to ambient weather (sunny) conditions; exposure to the atmosphere while covered by a tarp thus preventing exposure to solar radiation; and exposure to ambient conditions with lessoned desiccation by providing a constant mist of Choptank River water flowing over the spat. The exposure times for each stressor ranged from 2-48 hrs. These stressors determined if various other factors (solar radiation, time of day, humidity, temperature, and a constant mist of sea water as compared to complete desiccation) would have any effect on the survival rate of the spat once removed from their natural environment. The results showed that the larger the individual spat, the longer it could to survive under any stressor. Positive correlations between decreased solar radiation, increased humidity, and decreased temperature were found. It was also determined that time of day did play a significant role in spat survival. The spat positioned under the tarp faired slightly better than those under the mist of river water and both faired significantly better than those exposed to ambient conditions.