Project: Microorganism control of organic matter production and degradation

In the open sea, resources supporting the energetic and nutritional demands of organisms are persistently in short supply, and input of these resources to ocean ecosystems is a function of complex biological-physical feedbacks. Competition for such limiting resources has been a major factor shaping extant microbial diversity. In the well-lit waters of the upper ocean, biological harvesting of sunlight fuels synthesis of organic matter with concomitant consumption of nutrients. However, the vertical transition from the well-lit euphotic zone to the dimly-lit waters of the ocean's interior represents a major energetic threshold, and is accompanied by sharp biogeochemical and microbiological gradients. In these waters, microorganisms derive energy from oxidization of diverse chemical substrates. Compared to the relatively easily sampled and well-studied upper ocean, we have considerably less information on the microbial oceanography of the deep sea. It remains unclear how variability in the supply, form (e.g. dissolved and particulate phases), and composition (e.g. elemental and molecular) of organic matter influences contemporaneous microbial diversity, and conversely how changes in microorganism diversity influences organic matter turnover.

Through a combination of experimental approaches and in situ ocean measurements, this collaborative project will evaluate temporal and spatial coupling in organic matter production and its consumption by microorganisms. The work will focus on quantifying rates of organic matter degradation in the dimly-lit waters of the ocean's interior, and identifying the microorganisms that catalyze the various steps of decomposition. Moreover, through collaborative efforts, the project will elucidate feedbacks between processes occurring in the upper ocean (e.g. photosynthesis, nitrogen fixation) and vertical and temporal variability in microbial metabolism and diversity in the deep sea.

Bio

Matthew Church is an Associate Professor at the University of Montana and works as a resident scientist at the Flathead Lake Biological Station on the shores of Flathead Lake. He received his B.S. degree from The Evergreen State College and his Ph.D. from The College of William and Mary's School of Marine Science. His research interests focuses on the biogeochemistry and ecology of microorganisms in aquatic environments. Much of his work to date has focused on ocean ecosystems, but more recently he's become interested in microbial ecology in lakes and streams. Members of his lab group work on diverse projects that typically couple molecular and biogeochemical methodological approaches to gain insights into the distributions and metabolic activities of microorganisms controlling specific ecosystem processes. For example, for the past 10 years he has worked on quantifying the importance of nitrogen fixation to open ocean nutrient budgets and examining how the ecology of nitrogen-fixing microorganisms shapes nitrogen cycling in aquatic systems. He has long-standing interests in examining how ecosystems respond to climate-driven changes. He is a big proponent of the power of sustained time-series observations in helping to understand ecological and biogeochemical change. He recently served as the lead principal investigator of the Hawaii Ocean Time-series (HOT) program (2009-2016).