Oil stranded by the 1989 Exxon Valdez spill has persisted in subsurface sediments of exposed shores for 16 years. With annualized loss rates declining from ∼68% yr -1 prior to 1992 to ∼4% yr -1 after 2001, weathering processes are retarded in both sediments and residual emulsified oil ("oil mousse"), and retention of toxic polycyclic aromatic hydrocarbons is prolonged. The n-alkanes, typically very readily oxidized by microbes, instead remain abundant in many stranded emulsified oil samples from the Gulf of Alaska. They are less abundant in Prince William Sound samples, where stranded oil was less viscous. Our results indicate that, at some locations, remaining subsurface oil may persist for decades with little change.
We followed long-term dynamics of a conspicuous intertidal brown alga, Fucus gardneri, for seven years after the 1989 Exxon Valdez oil spill (EVOS) in Prince William Sound, Alaska, USA. We compared percent cover of Fucus over time at sites that had been oiled, some of which were washed with high-pressure hot water, relative to sites that had experienced neither oil nor cleanup activities (reference sites). Fucus cover at spill-disturbed sites was initially reduced due to toxic effects of oil and cleanup but rapidly increased to above normal levels and then subsequently dropped in 1994-1995. The changes in cover at spill-disturbed sites were dramatic (Ն50% decline year-to-year) and synchronous across all quadrats at a site. In contrast, reference sites demonstrated little synchrony. We examined two possible mechanisms that could generate synchronous fluctuations at spilldisturbed sites, i.e., (1) plant-herbivore coupling, in which limpet or snail grazing would reduce Fucus populations (hypothesis tested by analyzing abundances from 1990 to 1996), and (2) a single cohort of Fucus recruiting soon after the spill that would monopolize space for several years before declining synchronously (hypothesis tested by analyzing size frequency in 1996). We found no evidence for the first mechanism but support for the latter. The persistent patterns in size structure and dynamics in Fucus after EVOS suggest that full recovery had not occurred by 1996, even though Fucus cover at spill-disturbed sites was similar to reference areas within a few years of the spill.
Several studies conducted in Prince William Sound during 1989 were directed at assessing short term biological effects of treatment methods considered or employed for treating oil contaminated beaches. The four treatment alternatives evaluated in this paper are: low pressure warm water wash (LP-WW); high pressure hot water wash (HP-HW); the dispersant Corexit 7664; and the beach cleaner Corexit 9580 M2. Effects on the biota were assessed primarily on the basis of changes in the abundance of dominant taxa and the magnitude of selected community attributes (such as percent cover by algae or animals, and number of taxa). Significant reductions in one or more community or population attributes, and increases in the percent of dead mussels were observed in response to all types of treatment but the strongest and most consistent effects were observed following high pressure hot water treatment, which was also accompanied by heavy mortality in rockweed. Generally, the programs were not designed to discriminate among the potential causes of damage. However, available data suggest that neither chemical nor LP-WW treatments caused significant thermal impacts in the intertidal biota. In contrast, temperature appeared to cause significant mortality in the dominant plants and grazing and filter-feeding animals in HP-HW treatment sites. Observations of displacement and mortality for clams and mussels suggest that physical effects may be substantial in some cases. Of the types of treatment examined, dispersant and beach cleaner treatments appeared to be accompanied with the smallest number of significant changes in abundance; however, this conclusion is weak because the LP-WW wash accompanying chemical applications during the tests was sometimes less rigorous than when performed by itself. LP-WW treatment was accompanied by an intermediate level of changes whereas HP-HW treatment was accompanied with the highest percentage of changes, nearly all of which were decreases. Based upon long term surveys in the area, HP-HW treatment caused severe and persistent effects that remained conspicuous as late as July 1992. The long term consequences of dispersant and beach cleaner applications have not been evaluated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.