There are multiple facets to Contaminant Immune Function studies at the WERC Davis Field Station, two of which are work on biomarkers of immune function to exposure to PAH's in seaducks and differential gene expression as a result of contaminant exposure in avian and otter species.

Project Details

Seaducks:

During oil spill response and natural resource damage preassessment activities, recovery of oiled carcasses and observations of oiled individuals established that certain bird species were acutely exposed to oil from the Selendang shipwreck at Dutch Harbor. Research has shown that chronic exposure to oil can have long-term deleterious effects on survival of harlequin ducks (Histrionicus histrionicus) (Esler et al. 2002).  Accordingly, chronic exposure to sub-lethal levels of oil may have negative effects on population recovery following an oil spill.

 

Sea Otters:

Populations of certain Northern (Enhydra lutris kenyoni) sea otters have experienced recent declines (Bodkin 2002).  Suggested causes for these declines are complex and have been attributed to a variety of ecological or anthropogenic pressures. Major disasters such as oil spills are usually noted for their sudden dramatic impact on marine and coastal species. The acute effects of a spill are evaluated by mortality estimations, clinical evaluation, and necropsy examinations (Lipscomb et al. 1993, Monson et al. 2000). The long-term effects of these tragedies are more difficult to document, and studies often are restricted to demographic modeling, estimations of reproductive efficiency, or time-differential, age-specific survival rates. While several recent studies have eloquently shown that many species face long term oil-related effects after a spill (Monson et al. 2000, Mazet et al. 2000, Mazet et al. 2001), biological markers that identify oil-induced sublethal pathology in susceptible species are urgently needed.  The goal of the proposed study is to identify specific, sensitive genetic markers that signify persistent pathological and physiological injury associated with either acute or chronic hydrocarbon exposure.

            Crude petroleum oil has multiple aromatic and aliphatic hydrocarbon constituents, and the toxic effects of exposure and ingestion understandably can be diverse and extensive within the body (Rebar et al. 1995, Mazet et al. 2000, Mazet et al. 2001). Under these circumstances, the molecular investigation of subtle alterations of expressed genes indicative of multiple physiological processes at the cellular level is particularly useful. Further, samples required for molecular investigations are minimally invasive or stressful to the subject animals. Gene expression technologies have the exciting potential of providing methods for monitoring the long-term effects of oil exposure in federally listed, free-ranging sea otters. An added benefit is that these methods may elucidate the mechanisms by which oil can deleteriously affect an individual sea otter over a long period, and thereby aid in the design of therapeutic and preventative strategies to treat and protect susceptible individuals and populations at risk from oil exposure.

            We have demonstrated that characteristic and specific patterns of gene expression are reflective of oil exposure (Bowen et al., in preparation), and thus provide an ideal basis for evaluating immunologic vigor and health of the population.  Since phenotypic evidence of petroleum oil-induced changes to sea otters can be slow to emerge, measurement of differential expression of selected genes can potentially provide real-time evidence of health perturbations.

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