Hydrocarbons and Fisheries Habitat in Berners Bay, Alaska: Baseline Monitoring Associated with the Kensington Gold Mine

Purpose Of Study

Several projects associated with development of the Kensington Gold Mine have been proposed in Berners Bay, Alaska. Daily ferry service would transport workers from marine terminals to be built at Cascade Point and Slate Creek Cove across Berners Bay (Fig. 1). Construction of these terminals and other infrastructure (e.g., access roads) could directly affect as many as 80 ha within the Berners Bay watershed (U.S. Department of Agriculture 2004). Degradation of marine waters could occur from fuel spills, chronic pollution from vessels, and parking lot runoff near the terminal facilities.

Among contaminants that could enter the watershed from boats and parking lot runoff, polynuclear aromatic hydrocarbons (PAHs) are some of the most toxic to aquatic life and the most persistent. Released into the environment through either combustion or weathering of oil products, some PAHs are known carcinogens and mutagens. Particularly sensitive to these large molecular weight hydrocarbons are eggs and larvae of fish such as Pacific herring (Clupea pallasii) and pink salmon (Oncorhynchus gorbuscha); weathered PAHs at concentrations less than or equal to 1.0 ppb may damage herring larvae and pink salmon embryos (Carls et al. 1999; Heintz et al. 1999). Thus, potential oil contamination of intertidal spawning areas for herring, salmon (Oncorhynchus spp.), eulachon (Thaleichthys pacificus), and capelin (Mallotus villosus) is a concern.

Methods & Preliminary Findings

To establish a baseline of information for long-term monitoring associated with development of the Kensington Gold Mine near Juneau, Alaska, we measured hydrocarbon concentrations in seawater, sediment, and blue mussel (Mytilus trossulus) tissue near proposed marine terminal facilities in Berners Bay and at a control site outside of Berners Bay (Bridget Cove) in 2004. In addition, fish assemblages in eelgrass (Zostera marina) and understory kelp (e.g., Laminaria spp.) habitats were sampled with a beach seine at each site. Areas of eelgrass beds and shoreline extent of kelp beds were mapped with global positioning system technology. Hydrocarbon concentrations were very low or not detectable in most of the samples; only concentrations of pristane, a biogenic compound, were elevated.

Summary Of Results

Twelve seine hauls yielded 9,653 fish comprising 24 species; 86% of the total catch was in Bridget Cove.

Total fish catch was greater in eelgrass (6,993 fish) than in kelp (2,660 fish).

Based on percent of total catch, the most abundant species were juvenile chum salmon (Oncorhynchus keta; 87%), juvenile coho salmon (O. kisutch; 6%), crescent gunnel (Pholis laeta; 3%), and Dolly Varden (Salvelinus malma; 1%). Other species captured that are important in sport or commercial fisheries were juvenile pink salmon (O. gorbuscha), Pacific herring (Clupea pallasii), and cutthroat trout (O. clarkii).

The only eelgrass beds in Berners Bay are in Echo Cove. Total area of eelgrass mapped along the eastern shore of Echo Cove was 0.81 ha. Total area of eelgrass mapped in Bridget Cove was 7.08 ha.

Our initial findings after one year of baseline studies identify Berners Bay as a pristine environment with respect to hydrocarbons, and provides quality habitat for juvenile fish of many species. At least one more year of baseline sampling is planned in 2005.