Environmental Services Program
One water quality concern in many rivers and lakes is toxicity to aquatic organisms. A variety of contaminants such as metals and pesticides are potential causes of toxicity. The Water Quality Monitoring Section uses the Microbics M500 Toxicity Analyzer to evaluate toxicity of samples. Toxicity analysis may be conducted on surface water grab samples, pore water extracted from sediment or sediments.
The Microtox method of toxicity analysis utilizes a bioluminescent bacteria, Vibrio fischeri, that produces light as a by-product of cellular respiration. Rate of luminescence is directly related to the amount of cell respiration. Any toxicity to the cell will reduce respiration and the amount of light produced by the bacteria will be subsequently decreased.
Some of the tests commonly used by staff include: the 90 percent Basic Test, the SOLO Test for toxicity screening, QC tests using a phenol or zinc sulfate standard, and the Basic Solid Phase Test. Results are typically reported as Effective Concentration/50 (EC/50), which means the concentration of a sample that causes a 50 percent reduction in bacterial light output.