| Microbial communities are crucial to the health of ecological systems. Yet, little is known about the impacts of contaminants, such as metals, to these populations, particularly in anaerobic environments. The work described herein examines impacts of metal contamination on microbial communities in anaerobic freshwater sediments. The objectives of the research included obtaining statistical evidence for correlation among metal concentrations and parameters indicative of microbial community health, such as biomass, diversity, and respiration. Additionally, impacts to microbial community structure, as well as individual populations, were considered. A field-based experimental design was used to allow evaluation of native microbial communities exposed to metal stress in a contaminated lake, Lake DePue, Illinois. My experimental approach combined ecological experimental design and molecular analytical methods. Studies of the ecological toxicology of contaminants to microbial communities, such as this one, enhance our understanding of ecological impacts of contaminants and facilitate improved design of systems for bioremediation.; The resulting study, which included monitoring impacts of metals on microbial biomass, microbial community structure, and select population's activities, has established that anaerobic microbial communities were stressed by metal contamination and followed many trends predicted by established ecological models for stress-response. Microbial biomass concentrations decreased in negative correlation with pore water zinc and arsenic concentrations in the lake sediments. Further, an important result of this work has been the discovery of elevated biologic sulfate reduction rates in conjunction with metal contamination. While, microbial communities were similar irregardless of metal concentration, correlation was established between metal concentrations and several microbial populations. Of particular interest were data suggesting that some mesophilic crenarchaeota---a recently established sub-division of crenarchaeota kingdom may be selectively enriched in metal stressed sediments. |
