OOS 72

Microbial Efficiency: Perspectives on the Fate of Metabolized Organic Carbon in a Changing World

Defining and measuring microbial efficiency (i.e., ME - the proportion of carbon directed towards biosynthesis during microbial metabolism) is a difficult challenge faced by ecologists and ecological modelers alike. Our current understanding of this variable has developed from numerous valuable, yet unstandardized, approaches (e.g., physiological, ecological, mathematical). Because ME has the potential to tip the balance between ecosystem-level sequestration and net release of carbon, it is both timely and necessary that the ecological community develop an integrated understanding of this topic. For example, existing techniques for measuring ME (e.g., 13- or 14-C uptake, calorespirometry) are inherently limited by various methodological assumptions and recognizing these limitations will help to explain the range of ME estimates regularly published. The sensitivity of ME to environmental (e.g. temperature, carbon substrate diversity), physiological (e.g. growth rate), and community (e.g. r vs. K strategist) parameters is also of primary importance. The goal of this session is to review the current state of inquiry surrounding microbial efficiency from a variety of approaches in both soil and aquatic environments. We will cover 1) new and traditional methods for estimating ME and their inherent advantages/disadvantages for addressing specific questions, 2) existing terminology used in ME research and efforts towards a universal, integrated conceptual framework, 3) the response of ME to various stressors, 4) the sensitivity to ME of model projections for future scenarios of carbon cycling, and 5) future directions for examining ME that can provide direct and immediate insights towards mitigation of human-induced environmental change.