Fish Scales as Non-Lethal Biosensors of Surface Water Contaminants

The Need
Recent nationwide surveys report a wide spectrum of xenobiotics in US surface waters, including toxic metals, chlorinated organics, polynuclear aromatic hydrocarbons and pharmaceuticals. Pharmaceuticals are of particular concern because of their extraordinary potency at very low concentrations, with aquatic organisms at the greatest risk because of their chronic, lifelong exposure to these chemicals. Fish-based, non-lethal biosensors that detect trace levels of both legacy and emerging chemicals (e.g. pharmaceuticals) and could be used with threatened and endangered species would provide powerful first-pass tools for rapid evaluation of potential water quality issues.

Program Overview & Objectives
This proposal evaluates the potential of fish scales to act as ‘biosensors’ of surface water contaminants. Current in vitro bioassays typically use tissue sections, cells derived from internal organs (e.g. liver, gonad), or tumor-derived cell-lines, none of which reflect realistic environmental exposure conditions. In contrast, fish scales are naturally exposed to water-borne substances, including contaminants. The strength of a fish scale assay is that it at once provides an in vitro screening tool (effects can be evaluated in microplates of scales) and an in vivo biosensor of fish response (scales from wild-caught or caged fish can be used as first-pass sensors to evaluate water quality in a given habitat). This project has strong potential to improve the tools available for water quality assessment by providing rapid, non-lethal and biologically relevant toxicant biosensors that would allow sampling by a broad variety of researchers. Many agencies, including NOAA Fisheries and the Maine Department of Marine Resources, routinely collect scales for aging and other purposes, a subset of which can be stored cryogenically for later analysis of contaminant exposure. Because scale biosensors could be used with any scale-bearing fish, they would allow rapid identification of which fish species are being exposed to contaminants, in what part of their geographic range, and, for diadromous fishes, whether exposure is occurring during migration to-, or return from-, the sea. Such information would allow managers to select specific locations and species as ‘hot-spots’ and target these, as needed, for more expensive chemical analyses.

Project Plan
We will evaluate the response of scales collected non-lethally from an endangered Maine species, Atlantic salmon (Salmo salar), to three classes of aquatic contaminants commonly found in surface waters in the US: mercury, ethinylestradiol, and the anti-depressant drug fluoxetine. We will test a range of doses, exposure durations and mixtures to assess the utility of fish scales as non-lethal xenobiotic biosensors. As chemical-specific biomarkers do not currently exist for any pollutant, our aim is to detect inappropriate upregulation of genes by different classes of chemicals as an indicator of potential water quality issues. If proven to be reliable and sensitive, the scale biosensor assay will provide a non-lethal screening tool for use in assessing both water quality and contaminant exposure in threatened and endangered fish species.

Contact Information
Adria Elskus
US Geological Survey
School of Biology & Ecology
University of Maine
5751 Murray Hall
Orono, ME 04469
aelskus@usgs.gov

Rebecca Van Beneden
School of Marine Sciences
University of Maine
306 Murray Hall
Orono, ME 04469
rebeccav@maine.edu

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