Principal Investigator: Terry Snell (Georgia Institute of Technology)
Principal Investigator: Nancy Walls (Georgia Institute of Technology)
Principal Investigator: David Dusenbery (Georgia Institute of Technology)
Principal Investigator: Lloyd Dunn (Georgia Institute of Technology)
Sponsor: GWRI
Start Date: 1992-04-01; Completion Date: 1993-04-01;
Keywords: sediment toxicity, biomarkers, rapid toxicity assessment, enzyme inhibition, ingestion rate, fluorescence
Description:
Sediment samples were collected from 23 sites in Utoy Creek and its tributaries over a distance of about 12 km. Toxicity tests were performed on sediment elutriates using the freshwater rotifer Brachionus calyciflorus and the nematode Caenorabditis elegans. Several endpoints were evaluated in the rotifer tests including mortality, swimming activity, enzyme activity and ingestion rate. For nematodes, LC50s were estimated using mortality as endpoint. Toxicity was detected at several sites in an industrial area near two former wood treatment plants. 80% of the stations sampled in a small tributary draining this site contained sediments with significant toxicity. Some sediment elutriates were quite toxic, requiring 97% dilution to remove toxic effects. A toxicity identification evaluation was performed on elutriates from station 6. About 50% of the toxicity was removed by passage over a XAD-2 or activated charcoal column, both of which remove organics. Passage of elutriate over an Amberlite-200 column that removes cations eliminated virtually all of the toxicity. Addition of 50 μm EDTA likewise removed most of the toxicity. Analysis of extracts from the XAD-2 column with GC-mass spectroscopy revealed the presence of several non-polar organic compounds including derivatives of pentanone, benzene, dimethylstyrene, napthalene, and cyclohexane. In addition to the sediment samples, the toxicity of 10 pure chemicals was investigated using rotifer esterase and PLA2 inhibition and ingestion rate tests to develop a data base for comparison to other species. Ingestion rate NOEC was consistently more sensitive than LC50s by a factor of 3-35, depending on the chemical. Reproductive rate NOEC was usually more sensitive than ingestion rate NOEC by a factor of 2-10 times. The relative sensitivity of esterase and PLA2 enzyme inhibition compared to ingestion rate varied with each chemical. Relative sensitivity could not be predicted a priori for broad classes of toxicants like metals, organics and pesticides. Ceriodaphnia and B. calyciflorus had identical LC50s for station 6 elutriate, however, rotifer ingestion rate NOEC was 12 times lower. The LC50 of nematodes exposed to whole sediments was a less sensitive measure of toxicity than rotifer ingestion or enzyme inhibition tests. Use of the rapid toxicity tests described here could