Description
In 2006-2008, Forester Creek, CA underwent a significant restoration project to remove its concrete lining and restore its wetlands/riparian ecosystem. In 2010, Forester Creek was listed as impaired for selenium on the 303D list of water quality impaired waters. This study investigated the removal and bioaccumulation of selenium by the restored wetlands on Forester Creek, in San Diego County, CA. Specific aims of this study were to determine the concentration of dissolved selenium in surface waters using ICP/MS, and the efficiency of Se removal by the restored wetlands, by comparing the levels of dissolved Se both upstream and downstream of the restoration, and by measuring total selenium levels in crayfish (Procambarus clarkii) living in the restored wetlands. Among all the water samples taken from Forester Creek for this study, none exceeded the U.S. EPA criteria of 3.1 μg/L for dissolved selenium in flowing waters. A Mann Whitney test showed that during dry weather levels of dissolved Se (mean = 2.28 μg/L) were significantly (p < 0.05) higher upstream of the restored wetlands as compared to downstream (mean = 1.87 μg/L). Moreover, the mean levels of total Se in muscle tissue of the indicator crayfish species analyzed was 10.87 mg/kg (dry weight), which was in the same range as levels in Se-contaminated environments. Overall, this evidence indicates the bioaccumulation in the crayfish in the Forester Creek restored wetlands is occurring and raises an alarm that selenium is accumulating to what may be considered levels of ecological concern. This finding is somewhat surprising considering that our results also showed that dissolved Se levels in the inflowing waters to the wetlands meets the U.S. EPA water quality criteria.
