Few would disagree that bacteria play a pivotal role in the continued functioning of our biosphere. While the biogeochemical cycles involved in the production of organic matter have deservedly received considerable attention, the obverse cycles in which that organic matter is degraded are equally important. We know a great deal about the tremendous metabolic diversity of bacteria, and the pathways of the chemical reactions they perform. Outside of simple laboratory systems, however, we cannot predict with any certainty the rates at which bacteria grow, metabolize, and mineralize organic matter. This project is about understanding, at a mechanistic, quantitative level, what affects the activity of bacteria in nature. While initially the problem seems straightforward, we believe a solution has been elusive because there are complex processes involved, which operate at and intersect with several levels of biological organization: individuals (equivalent to the cell for bacteria and protozoa, the organisms of concern here), populations (whose dynamics both reflect and affect fluxes of organic substrates and electron acceptors), and the community (where ecological processes such as competition and predation occur).

Our ultimate goal is to develop and test models of coupled biogeochemical cycles and ecological community dynamics that predict the rates of organic matter cycling in natural systems. Such models must include the physical and chemical factors controlling the availability of resources (reactants) to bacteria, interactions (potentially competitive) among different bacterial populations, and interactions between bacteria and their predators. The explicit goal of this project is to focus on one type of environment - estuarine sediments - and one category of organic matter - polycyclic aromatic hydrocarbons (PAHs). This project is not about bioremediation per se; we use PAHs as model compounds that can be quantified against a background of heretofore poorly characterized natural organic matter (NOM). While we focus on PAHs, our research will also incorporate new empirical and modeling approaches for unraveling the complexities of NOM cycling, and thus has broader implications for biogeochemical cycles in other types of environments.

Our project relies on a tight integration of modeling and empiricism. We view modeling as an essential step towards understanding complex systems, but only when models interact with "reality" in the form of empirical data. Furthermore, we strongly believe that complex systems must be examined from an interdisciplinary viewpoint. The expertise of the research group encompasses ecology, chemical engineering, environmental geochemistry, and microbiology. Our research is funded by the National Science Foundation's Biocomplexity in the Environment program.