EAGER: Perturbation of eukaryotic dynamics in a biostimulated groundwater aquifer

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1007476 MattesWhereas the effects of pollution on aboveground ecosystems are well studied (e.g. eutrophication of water bodies), comparatively little is known about the effects of pollution on subsurface ecosystems. This is partly because eukaryotic community ecology in groundwater aquifers is seldom studied and generally underappreciated for its importance in biogeochemical processing. In general, there currently exists a gap between what is known about eukaryotes and the consequences of engineering activities on their activity, community dynamics, and persistence in contaminated groundwater systems undergoing bioremediation. The PI has been investigating microbial community structure in an aquifer in southeastern Iowa contaminated with the explosive RDX as it is undergoing biostimulation with acetate as a means to effect RDX reduction. His objective in this proposal is to identify specific consequences of aquifer biostimulation by simple carbon addition to the eukaryotic communities present therein. His central hypothesis is that eukaryote dynamics in the RDX-contaminated aquifer, when perturbed by acetate injections, will be governed by the ecological principles of competitive exclusion and secondary succession with endemic eukaryotes being replaced by cosmopolitan generalist eukaryotes. To test the central hypothesis, he proposes the following specific aims: (1) perform a census of eukaryotes in pristine and carbon amended portions of the aquifer to identify qualitative differences in populations. His working hypothesis, based on PASCALIS studies and his own preliminary data, is that eukaryote composition in an unpolluted region of the aquifer will be dominated by crustaceans and other obligate groundwater eukaryotes while composition in a portion amended with acetate will be dominated by generalists such as cosmopolitan protists and fungi. (2) Ascertain quantitative changes of eukaryotes due to the addition of organic carbon, the time following perturbation, and the changes in redox state by comparative environmental sampling. His working hypothesis here, based on biological dispersal mechanics and secondary succession theory, is that eukaryotic lineages displaced by excessive organic carbon and subsequent anaerobic conditions will not re-populate affected aquifer portions during the course of the study (1 year).Because engineering as a discipline considers prokaryotes in aquifers almost exclusively without addressing the consequences of remedial actions to eukaryotic organisms, the proposed activities could lead to the creation of a new paradigm in aquifer biology with respect to remediation activities and a bridge between engineering practice and current understanding of eukaryotes in aquifers. A better understanding of the intra-aquifer linkages between biological processes and nonbiological factors could be used to evaluate whether or not groundwater remediation by carbon amendment will permanently affect aquifer ecosystem structure and to hypothesize potential consequences. Because the data we collect will be concurrent with data collected during bioremediation management activities, the proposed studies could also shed light on the possibility that eukaryotes are useful indicators of aquifer state and/or bioremediation process performance. The proposed activities represent a potential benefit to society by providing a basis for the understanding of effects in aquifers from carbon pollution. One graduate and one undergraduate engineering student will be trained during this project and results will be disseminated among the scientific community and the general public. This work will also strengthen the existing collaboration between an academic entity and an industry partner and serve to advance research, education, and practice in the bioremediation field.