The response of ecosystems to heavy-metal contamination occurs over decades to centuries as the biological communities adapt to persistent toxicity. For example, in the Clark Fork River Valley, Montana, an area contaminated nearly 100 years ago by mine wastes containing heavy metals such as lead and zinc, critical ecosystem processes (e.g. biomass production) are suppressed while the diversity of microbial communities is not. It is hypothesized that the energetic cost of tolerating toxins leads to suppressed ecosystem functioning even where adapted organisms do not suffer lethal effects of contaminants. New and classical microbiological methods will be employed to compare the energetic cost of metal tolerance in closely related pairs of organisms cultured from contaminated and uncontaminated rivers. Analysis of the genetic elements - metal-resistant molecules of DNA separate from chromosome DNA - responsible for differences in metal tolerance between the pairs will lend insight into the role of gene transfer among species in maintaining community diversity in contaminated ecosystems, a process that may represent a fundamental difference in the community ecology of microorganisms and higher organisms.
This research will increase understanding of the long term effects of contaminants on ecosystems and potentially lead to improved methods for quantifying natural resource damage under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Also, Native American students from Chief Dull Knife Community College in Lame Deer, Montana, will participate in field and laboratory projects geared toward transferring knowledge to their college.
