Bristol Bay hosts the largest salmon fishery in the world, as well as a number of other important fisheries. We are studying sediment conditions that influence biodiversity and the distribution of benthic organisms, as well as contaminant concentrations in resident organisms. The sediment and tissue samples are being analyzed for over 150 chemical contaminants, toxicity, and seafloor community health. Resource managers in the area need a clear assessment of the health of the bay.

Why We Care
Many of the contaminant stressor inputs to coastal Alaska ecosystems are driven by long range oceanic currents and atmospheric transport from lower latitudes. However, in Bristol Bay, the proposed “Pebble Mine” in the watershed constitutes the most significant pollution threat to the water and habitat quality in the Bay. Despite boasting one of the largest commercial and subsistence salmon fisheries in the world, environmental studies in the area are few, resulting in a lack of adequate baseline data and information to assess future trends in the Bay. Our goal is to provide sediment chemistry, benthic community characterization, and sediment toxicity baseline data that can be used for ecological characterization of the Bay.

What We Are Doing
We are working in collaboration with the University of Alaska Fairbanks Bristol Bay Ecosystem Health program, and U.S. Fish and Wildlife Service Becharof National Wildlife Refuge to conduct the study. The National Status and Trends Bioeffects program uses a stratified random design for its bottom habitat characterization. The study area includes the near-shore and coastal waters of Nushagak and Kvichak Bays, plus Dillingham Harbor and the lower reaches of the Naknek River.

The area was subdivided into eight strata for field collections, which we conducted in the summer 2013 and 2014. In each stratum, in addition to water quality parameters (dissolved oxygen, salinity, turbidity, and temperature), we collected multiple sets of surficial sediment samples for sediment contaminant concentration assessment, sediment grain size determination, sediment benthic community characterization, and sediment toxicity measurements. As part of this study, we also collected resident fish (rainbow smelt and starry flounders) in open waters of Nushagak and Kvichak Bays, and in Dillingham Harbor and the Naknek River. We are analyzing these fish samples for contaminant body burdens and for histopathology characterization.

Laboratory analyses are in progress, including:

1. Quantification of over 150 organic and inorganic contaminants in the sediment and tissue samples.
2. Sediment toxicity assessments using sea urchin fertilization and development, and the Microtox® response bioassays.
3. Sediment benthic community characterizations involving enumeration of density, species richness, and diversity. In addition, pattern analysis and classification will also be analyzed to delineate taxa assemblages.
4. Fish histopathology characterization includes the determination of prevalence and intensity of parasites, diseases, and lesions in tissues.

What We Found
The sediment parameters, histological, and infauna data from the 2013 samples have been completed, but analysis is still pending for the 2014 samples. These data will be integrated with the chemical analytical results and the data from 2013 samples.

Partnering with us on this project are the University of Alaska Fairbanks Bristol Bay, and the U.S. Fish and Wildlife Service National Wildlife Refuges. The North Pacific Research Board (NPRB) is providing major funding support.

Next Steps
Data will be analyzed using linear and multivariate statistical methods, community analysis, and compared to applicable sediment and tissue guidelines. In addition to comprehensive final reports, education and outreach materials will also be completed in coordination with the NPRB outreach coordinator.