Patricia M. Harris

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.

SURVIVAL IN AIR OF MYTILUS TROSSULUS FOLLOWING LONG-TERM EXPOSURE TO SPILLED EXXON VALDEZ CRUDE OIL IN PRINCE WILLIAM SOUND

Mussels, Mytilus trossulus, were sampled in 1996 from beaches in Prince William Sound (PWS) which contained residual oil resulting from the Exxon Valdez oil spill of March 1989, and from one beach which had been lightly oiled in 1989, but contained no residual oil in 1996. The latter mussels served as un-oiled references. Mussels were also collected from Tee Harbor, Southeast Alaska, to be used as an additional reference group. Where the size of the individuals in the resident population would permit, two size groups were sampled, 32-35 and 18-20 mm in length. Polynuclear aromatic hydrocarbon (PAH) concentrations in mussel tissue, and air survival time were determined for each group of mussels. Total PAH concentrations were significantly greater in tissue of mussels from oiled beds (0.6-2.0 micrograms g-1) than from references (0.01-0.12 microgram g-1) (P < 0.01). Oil-exposed mussels had significantly lower LT50 values (P < 0.05) for air survival than reference groups. Tolerance of small mussels to air exposure was significantly greater (P < 0.01) than large mussels in both the unoiled reference and oil exposed groups.

Fish Assemblages in Nearshore Habitats of Prince William Sound, Alaska

Abstract We sampled fish at eight locations in western Prince William Sound (PWS), Alaska, in April, July, and September 2006, and July 2007, to identify species assemblages and habitat use. At each location, fish were sampled with a 37-m long variable mesh beach seine in three nearshore habitats: bedrock outcrops, eelgrass meadows, and cobble beaches with kelp. A total of 49,060 fish representing 45 species were captured in 95 beach seine hauls. Catch-per-unit-effort (CPUE, all species) did not differ by season but did differ by habitat type—CPUE was greater in eelgrass and kelp than in bedrock. Seasonal pulses in catch were evident for some species; pink salmon were captured only in spring and summer, Pacific herring only in summer and fall, and capelin only in fall. Species richness was greater in summer (34) than in spring (23) or fall (28), and greater in eelgrass (34) than in bedrock (22) or kelp (33). Species that were good discriminators among seasonal collections were pink salmon, saffron cod, crescent gunnel, and Pacific herring, whereas species that were good discriminators among habitat collections were crescent gunnel, tubesnout, bay pipefish, saffron cod, and Arctic shanny. Of the most abundant species captured, most were juveniles based on estimated size at maturity. The summer fish assemblage in western PWS has changed over the last 20 years, especially with the appearance in large numbers of saffron cod. Sites in this study can be monitored periodically to track future changes in fish assemblages and habitat that may result from local and regional human disturbance.