Survival in air of Mytilus trossulus following long-term exposure to spilled Exxon Valdez crude oil in Prince William Sound

Effect of dispersed crude oil on the feeding activity, retention efficiency, and filtration rate of differently sized blue mussels (Mytilus edulis)

The use of physiological response endpoints in environmental monitoring represents an opportunity to provide an integrated picture of health status and ecological fitness of individuals, and may provide an indication of potential longer term effects on aquatic organisms in the environment. The feeding behavior response sensitivity of blue mussels (Mytilus edulis) of differing size to dispersed crude oil (DCO) was investigated in a lab exposure experiment. The ability of mussels to recover following a single exposure was also investigated, as well as the response to consecutive exposures, in order to assess the utility of employing the same individuals in chronic environmental monitoring. Feeding physiology was assessed by measuring retention efficiency and filtration rate of individual mussels in a live-algae feeding assay. In addition, the percentage of mussels actively filtering during testing was calculated. The feeding physiology parameters were sensitive and able to discriminate exposed mussels from controls. Further, data indicated that larger mussels appear more suitable in environmental monitoring, as these animals showed both sensitivity and an ability to adapt and recover from exposure while remaining sensitive to subsequent treatments. Smaller mussels were also sensitive to the measured endpoints, even if these animals suffered higher rates of mortality during the exposure. Finally, when exposed to the high concentration of DCO, mussels displayed a tendency to close the valves and terminate filtration.

Persistence of oiling in mussel beds after the Exxon Valdez oil spill

Persistence and weathering of Exxon Valdez oil in intertidal mussel (Mytilus trossulus) beds in Prince William Sound (PWS) and along the Gulf of Alaska was monitored from 1992 to 1995. Beds with significant contamination included most previously oiled areas in PWS, particularly within the Knight Island group and the Kenai Peninsula. In sediments, yearly mean concentrations of total petroleum hydrocarbons ranged from < 60 micrograms/g in reference beds to 62,258 micrograms/g wet wt., or approximately 0 to 523 micrograms/g dry wt. total polynuclear aromatic hydrocarbons (TPAHs). In mussels, mean TPAH concentrations ranged up to 8.1 micrograms/g dry wt. Hydrocarbon concentrations declined significantly with time in some, but not all mussels and sediments, and should reach background levels within three decades of the spill in most beds. In 1995, mean hydrocarbon concentration was greater than twice background concentration in sediments from 27 of 34 sites, and in mussels from 18 of 31 sites.