Effects of natural and anthropogenic stressors on lysosomal destabilization in oysters Crassostrea virginica

Lysosomal destabilization indices (based on a neutral red retention assay) were evaluated for digestive gland cells of oysters Crassostrea virginica. Laboratory studies were conducted to evaluate the effects of variable salinity regimes (a natural stressor) and copper exposures (a pollutant stressor) on lysosomal destabilization. Field studies were also conducted with native oysters and hatchery-reared juvenile oysters deployed in situ at reference and polluted sites. Lysosomal integrity was not affected by either short-term or longer-term variations in salinity during laboratory experiments, and the destabilization indices were similar to those of deployed and native oysters from reference sites characterized by a range of salinities. However, laboratory Cu exposures (ranging from 2.5 to 20 mu g Cu l(-1)) caused significant adverse effects on lysosomal destabilization after only 18 h, and the effects were sustained or worsened with increasing exposure time and concentration. Hatchery-reared oysters deployed at or native oysters collected from polluted sites had significantly higher lysosomal destabilization indices. Estuarine habitats are characterized by variable salinity regimes, so cellular responses that are sensitive to salinity stress as well as contaminant stress would be difficult to interpret if salinity effects cannot be distinguished from pollutant effects. A robust biomarker of anthropogenic effects should be insensitive to natural stressors such as salinity, but should be sensitive to pollutants. The salinity and contaminant studies described in this paper indicate that lysosomal destabilization responses in oysters are insensitive to salinity variations and sensitive to pollutants, and are therefore potentially valuable biomarkers of anthropogenic stress.