The Microtox® system is a screening tool used for a variety of toxicity testing applications. The advantages of this toxicity bioassay are its speed, simplicity, and relatively low cost, when compared to the cost of chemical analysis. The bioassay's strongest attribute is its usefulness as a primary screening test for a broad spectrum of toxicants and its monitoring capability over time. The Microtox® procedure can be used for testing either water (marine or fresh) or associated sediments.

The Microtox® assay uses freeze dried luminescent bacteria (Photobacterium phosphoreum) as the test organisms. The bacteria's light-producing mechanism is tied to the metabolic processes of the cell. If these processes are changed or damaged by a toxic substance, a reduction in light output results. The bioassay is based on detecting these changes in light output. Results can be obtained within 5 to 30 minutes. The light output readings are then used to calculate an EC5O for each sample. The ECSO is defined as the median effective concentration, and is a calculated toxicity value representing the sample concentration (%) estimated to cause a 50% response by the exposed test organisms. The EC50's are then compared against a control sample to evaluate relative toxicity.

The Environment and Natural Resources Institute (ENRI), University of Alaska, Anchorage, has the capability and expertise to run water or sediment samples using the Microtox® bioassay. The staff at ENRI analyze and evaluate results obtained from Microtox® bioassays to estimate potential toxicity of a sample. Elaine Major is available to provide technical assistance to Native organizations. She is interested in partnering with Native groups to collaborate on grant and contract applications for proposals. You may contact Elaine by phone at (907) 257-2731, or by e-mail at anebg@uaa.alaska.edu .