Effects of Residual Exxon Valdez Oil on Intertidal Protothaca staminea: Mortality, Growth, and Bioaccumulation of Hydrocarbons in Transplanted Clams

Effects of residual Exxon Valdez oil on the intertidal clam, Protothaca staminea, were studied using reciprocal experimental transplants of clams between unoiled and oiled sites. Individually tagged clams were transplanted in 1994 and collected in 1995 and 1996. Mortality, growth, and tissue chemistry data were collected from reference unoiled and oiled clams, clams transplanted from an oiled to unoiled site, and clams moved from an unoiled to oiled site. Greatest mortality occurred in clams originating from the oiled site. Best growth occurred in clams moved from the oiled site to the unoiled area. Largest tissue burdens of hydrocarbons occurred in oiled site clams. There was indication of depuration of hydrocarbons when oiled site clams were transplanted to the unoiled site. Clams transplanted from the unoiled site to oiled site accumulated hydrocarbons after one year. Our results indicate that residual oil, 5–6 years following the EV oil spill, affected survival and growth rates of clams.