The purposes for tissue sampling in biological specimens are: 1. to assess the potential for adverse biological impacts to fish and wildlife resources; and, 2. to assess public health risks. For the GBP monitoring plan, food chain (aquatic plants, invertebrates, and whole body fish) samples will be analyzed for contaminant residues to assess impacts to fish and wildlife resources, while gamefish fillet samples will be analyzed for contaminant residues to assess human health risks. Established ecological risk guidelines for selenium can be used to interpret selenium body burdens in assessing impacts to fish and wildlife resources.

Collecting food chain samples for analysis is important since post-project contaminant levels along the Mud Slough corridor may be expected to reach the established ecological risk guidelines toxicity thresholds for selenium in represented biota. Biota contaminant residues in food chain compartments can be used to evaluate ecosystem health. For example, since selenium is bioacccumulative, elevated concentrations at lower trophic levels can be an indicator of elevated concentrations at higher trophic levels. Effects of elevated selenium at higher trophic levels are well documented, such as teratogenic effects on avian embryos. Collecting edible portions (fillets) of gamefish to evaluate the potential for adverse public health risks is important, since recreational and subsistence fishing are known to occur in the GBP.