Research interests

A Graduate Assistantship is available for work with Dr. Robert Findlay, beginning January 2007 or August 2007. See this page for more information. Three major themes or interests tie my research activities together. These are the community and ecosystem ecology of microorganisms, the applied ecology of microbial communities and the development of methods for the determination of microbial biomass, activity, community structure and trophic interactions. I also have a strong interest in independent and collaborative research.

My major focus is on aquatic microbial communities and their role within ecosystems, first in marine sediments and more recently in freshwater and groundwater sediments. I have often investigated factors that control the distribution and abundance of microorganisms and structure their communities. Factors include predation, light, flow, food resource, temperature, and sediment disruption. Several of the factors (light, temperature and predation) combine to produce a seasonal pattern of change in benthic microbial community structure. A current Ph.D. student is extending this line of research to the role of underlying geology (see Jen Mosher's webpage). A current student opportunity in the laboratory is supported by a grant from the National Science Foundation (see Ad for Research Assistantship ) and will investigate energy flow in streams. Complex dissolved organic matter (DOM) in stream water supports, in part, microbial communities in sediments and on rock surfaces. As part of a multidisciplinary team, we are interested in understanding if scaling rules describing the relationship between stream size and nutrient utilization hold for DOM. We have produced 13C-labeled DOM and using Stable Isotope Probing (SIP) will determine which microorganisms are important to DOM processing in streams and if they process DOM in the same manner as they process nutrients. A second NSF-funded grant has provided for the purchase of a gas-source stable isotope mass spectrometer that is fitted with both an elemental analyzer and a gas chromatograph and allows compound specific stable isotope analysis. This capacity is driving a renewed effort within the laboratory to determine the role of microorganisms as a food resource for animals.

I include studies of the impacts of human society on the environment among my research activities. Studies have included organic pollution and bacterial contamination in groundwater, effects of fishing activity on marine sediments, introduction of drilling fluids in the marine environment, the environmental impacts of salmonid net-pen culture in both marine and freshwater systems and various aspects of lipophilic pollutants in marine and freshwater systems. A current Ph.D. student is focusing on the impacts of regulation of flood-plain rivers via dams on ecosystem function (see Andrew Rypel's webpage).

Throughout all the described projects, effort is directed toward the development, evaluation and application of state-of-the-art biogeochemical and microbiological methods. Past efforts include detection of bacterial cell wall components as a measure of bacterial biomass, detection of phospholipid as a measure of microbial biomass, quantification of the bacterial storage lipid polymeric beta-hydroxyalkanoates as a measure of nutritional status, measuring the rate of incorporation of 14C-labeled substrates into structural and storage lipids as a determination of activity and nutritional status and the use of phospholipid fatty acid analysis to quantify microbial community structure. All these efforts were directed toward complex sedimentary communities. In addition, I have investigated using the response of microbial communities to detect nutrient enrichment, anthropogenic stress and have adapted the phospholipid method to simultaneously determine lipophilic pollutant concentration. Current method development efforts include development of quantitative competitive PCR for determining degradative gene frequencies in sediment communities, adapting the phospholipid fatty acid technique to detect Archaea by assaying for their membrane phospholipid fatty alcohols and, application of compound-specific stable isotope ratios of fatty acids to both foodweb analysis and organic matter utilization using the recently acquired stable isotope mass spectrometer.

Opportunities for undergraduate and graduate research in my laboratory are open to any of the above questions or to new questions supported by the array of techniques available within the laboratory. I am particularly interested in recruiting a qualified student to fill the Research Assistantship available on a current NSF grant (see above).

Selected publications

Levy, J., K. Sun, R.H. Findlay, F.T. Farruggia, J.A. Porter, K.L. Mumy, J.M. Brannock, and A.T. Tomaras. In Press. Transport of Escherichia coli bacteria through laboratory columns of glacial outwash sediments: estimating model parameter values with sediment characteristics. Journal of Contaminant Hydrology.

Mosher, J.J., R.H. Findlay, C.G. Johnston. 2006. Physical and chemical factors affecting microbial biomass and activity in contaminated subsurface riverine sediments. Canadian Journal of Microbiology 52: 397-403.

Abboud, R., R. Popa, V. Souza-Egipsy, C.S. Giometti, S. Tollaksen, J.J. Mosher, R.H. Findlay, and K.H. Nealson. 2005. Low-Temperature Growth of Shewanella oneidensis MR-1. Applied and Environmental Microbiology 71: 811-816.

Findlay RH. 2004. Determination of microbial community structure using phospholipid fatty acid profiles. In: GA Kowalchuk, FJ De Bruijn, IM Head, ADL Akkermans, JD Van Elsas (eds) Molecular Microbial Ecology Manual, 2nd edition. Kluwer Academic Publishers, Dordrecht, The Netherlands. Chapter 4.8.

Mumy, K.L. and R.H. Findlay. 2004. Convenient determination of DNA extraction efficiency using an external DNA recovery standard and quantitative competitive PCR. Journal of Microbiological Methods 57: 259-268

Christian, A.D., B.N. Smith, D.J. Berg, J.C. Smoot, and R.H. Findlay. 2004. Trophic position and potential food sources of two species of unionid bivalves (Mollusca: Unionidae) in two small Ohio streams. J. N. Am. Benthol. Soc. 23:101-113.

Sutton, S.D. and R.H. Findlay. 2003. Sedimentary microbial community dynamics in a regulated stream: East Fork Little Miami River, Ohio. Environmental Microbiology 5: 256-266.

Smoot, J.C., L.Mayer, M. Bock, P.C. Wood, and R.H. Findlay. 2003. Structures and concentrations of surfactants in gut fluid of the marine polychaete Arenicola marina. Marine Ecology Progress Series 258: 161-169.

Langworthy, D.E., R.D. Stapleton, G.S. Sayler and R.H. Findlay. 2002. Lipid analysis of the response of a sedimentary microbial community to polycyclic aromatic hydrocarbons. Microbial Ecology 43:189-198.