Seaweeds and the Exxon Valdez Oil Spill

Abstract

ABSTRACT A three-year study, initiated in 1989, has evaluated the response of subtidal and intertidal seaweed communities to the Exxon Valdez oil spill and subsequent cleanup activities. The project was part of the coastal habitat injury assessment research sanctioned under the natural resource damage assessment program. A stratified random design was used to select oiled sites for the study. Paired control (unoiled) sites were then matched to the oiled sites. The most consistent effect found in subtidal populations in Prince William Sound was the higher relative abundance of small-size classes of kelps at the oiled sites, indicating the prior disappearance of larger plants. This disappearance was possibly caused by activities associated with the cleanup operations. Intertidal populations of algae were affected by the spill and cleanup in all three major areas studied: Prince William Sound, Cook Inlet-Kenai, and Kodiak-Alaskan Peninsula. The most obvious effect was a significant removal of the dominant intertidal plant Fucus gardneri from the mid and upper intertidal zones. The limited dispersal of this plant combined with the relatively harsh conditions of the upper intertidal will cause a slow recovery of the upper intertidal zone in the affected areas. Effects of the spill extended to other algal species. Species such as Cladophora, Myelophycus, Odonthalia, Palmaria, and Polysiphonia showed decreases in their percent cover at oiled sites. Only Gloiopeltis populations appeared to increase in percent cover in oiled areas. In both the Cook Inlet-Kenai and the Kodiak-Alaskan Peninsula areas Fucus populations appeared to be enhanced in the lower intertidal zone—between 2 and 3 meters below the high-tide mark—in 1991.