Polycyclic aromatic hydrocarbon levels in mussels from prince william sound, ALASKA, USA, document the return to baseline conditions

Abstract

Abstract-Bioavailable hydrocarbons in the Exxon Valdez oil spill zone in Prince William Sound (PWS; AK, USA) shorelines were at or near background levels in 2002, as indicated by low concentrations of polycyclic aromatic hydrocarbons (PAHs) in mussels (Mytilus trossulus) collected from sites throughout PWS. Total PAH (TPAH) minus parent naphthalene concentrations in mussels collected in 1998 to 2002 from sites oiled in 1989 were at or near reference-site values. Both oiled and reference sites included locations associated with past human and industrial activity (HA). Inclusion of the unoiled HA sites in the range of reference sites that define prespill conditions is consistent with federal regulations. For the period from 1998 to 2002, the geometric mean of TPAH concentrations for 218 mussel samples collected from 72 sites, including four HA sites that had been heavily oiled in 1989, is 54 ng/g dry weight (range, 2-1,190 ng/g). The maximum mussel TPAH concentrations are equivalent to a weatheredoil exposure dose to intertidal foragers that is one to three orders of magnitude less than the doses shown to cause sublethal effects in surrogate species. The geometric mean of TPAH concentrations for mussel samples from 28 locations not oiled in 1989 and unaffected by human use (NHA sites) is 28 ng/g (range, 3-355 ng/g), whereas the geometric mean of TPAH concentrations for mussel samples from 14 locations not oiled in 1989 and affected by human use (HA sites) is 106 ng/g (range, 2-12,056 ng/g). The range of data for the unoiled HA and NHA sites defines the background of bioavailable PAHs to mussels on western PWS shorelines that would have prevailed if the oil spill had not occurred. The low PAH concentrations in mussels from sites known to have subsurface oil residues demonstrates the low bioavailability of these spill remnants and, thus, are a low additional risk to foraging wildlife. The present study shows continuous exposure from four-to six-ring PAHs originating at HA sites in western PWS. At low concentrations, these PAHs are known to cause adverse biological effects. However, in the context of PWS, oiled and HA sites represent a small percentage (ϳ0.1-0.2%) of the total PWS shoreline.

Semipermeable membrane devices link site-specific contaminants to effects: Part 1 – Induction of CYP1A in rainbow trout from contaminants in Prince William Sound, Alaska

“…These 562 impacts were distributed over more than a century and their cumulative total affects less than 563 0.2% of the present day shoreline in PWS (Boehm et al, 2004). These small scale impacts, 564 coupled with a low population density, results in fewer and more localized contaminant sources.…”

Hypotheses concerning the decline and poor recovery of Pacific herring in Prince William Sound, Alaska

“…2). and suggest that no one early life stage is the ''key'' to year class strength in PWS herring, and the above observations suggest that, at least in the case at hand, nutritional state, low zooplankton densities, and warmer water temperatures at age-1 were associated with an extremely weak year class (Brown 2004;.…”

“…Mussel tissues have been used extensively in determining levels of total TPAH in the waters of PWS (Short and Harris 2006;Boehm et al 2004Boehm et al , 2007. For Marty et al (2010).…”

“…Direct water-column sampling was discontinued several years after the EVOS because TPAH concentrations were at background or below method detection limits. Boehm et al (2004Boehm et al ( , 2007 produced an extensive database of the concentrations of TPAH in mussel samples collected from 1989 to 2005 from oiled and unoiled shorelines including sites of past human activity (e.g., mines, canneries) in PWS. Figure 5 shows the arithmetic means of TPAH water concentrations derived from analyses of mussel tissues from oiled and unoiled shorelines using the conversion of Neff and Burns (1996).…”

“…Based on sonar surveys and scat analysis, the majority of the potential prey in PWS during the summer were euphausiids, but herring and sand lance also were present (Matkin and Hobbs 1999). Based on observations of the winter distribution of herring and humpbacks, Matkin and Hobbs (1999) and Brown (2004) have inferred that the overwintering whales are feeding on herring. However, studies have shown that high euphausiid abundance leads to aggregations of humpback and other whales (Hjort andRuud 1929 cited in Sverdrup et al 1942;Everson 2000).…”