Bioturbation as a novel method to characterize the toxicity of aquatic sediment.
Abstract (Summary)Bioturbation, the biological process through which many species of infaunal benthic invertebrates suspend bottom sediments into the water column through their burrowing, feeding, respiratory, and locomotor activities, may be a sub-lethal endpoint that can be exploited to assess the toxicity of aquatic sediments. Therefore, we developed a novel test method that used bioturbation (BioTurbTox test) generated by the activities of second in-star Chironomus tentans larvae as the toxicity endpoint (Chapter 2). To validate this method, copper (Cu) and fluoranthene were individually spiked into relatively uncontaminated aquatic sediment to assess changes in bioturbation and mobilization of the chemicals into the overlying water. Turbidity production responded to the chemicals in the sediment in a concentration-dependent manner and was an excellent indicator of sediment toxicity. Moreover, substantial concentrations of Cu were released into the overlying water from the Cu-spiked sediment, whereas little fluoranthene was mobilized into the overlying water from the fluoranthene-spiked sediment. Sediment samples were then collected from the field and used to evaluate the similarity of response of the BioTurbTox test to other more standardized toxicity tests. In the summer of 2003, sediment samples were collected at six sites in the Neuse River of North Carolina tested for toxicity, and analyzed for chemical contaminants (Chapter 3). Atrazine was the most frequently detected current-use pesticide and pyrene and fluoranthene were measured at relatively high concentrations from the Neuse River sites. Concentrations of fluoranthene were correlated with results from the Ceriodaphnia dubia porewater and BioTurbTox tests. We concluded that the new BioTurbTox test was useful as a rapid screening method for sediment toxicity information, but required normalization to the clay content or to the total organic carbon content of field collected sediments. In Chapter 4, the toxicity of environmental pharmaceuticals and personal care products (PPCPs) were evaluated with the BioTurbTox and C. dubia reproductive tests. Fluoxetine and bisphenol A significantly affected bioturbation caused by C. tentans, especially at high concentrations (1-2 mg/L), and the turbidity change induced by caffeine, fluoxetine, and bisphenol A showed a concentration-response relation. Triclosan affected reproduction of C. dubia at relatively low concentrations (IC50: 85.4 ?Ýg/L). However, most of the tested PPCPs were not acutely toxic at environmentally relevant concentrations, but were relatively toxic at high concentrations. In Chapter 5, two sediment-spiking methods (extract mixing vs. whole sediment dilution methods) were compared with the BioTurbTox test and a gradient response was observed from both methods. Based on the similarity of the toxic response, we determined that either of the spiking methods was appropriate for estimating the toxicity of aquatic sediments in screening level assessments. The overall conclusion from this research was that the newly developed BioTurbTox test shows promise as a tool to assess the toxicity and mobilization of contaminants from aquatic sediments.
Advisor:W. Gregory Cope
School Location:USA - North Carolina
Source Type:Master's Thesis
Date of Publication:02/28/2005