Carbon is the basic building block of life. Most of our energy, including the food we eat and the fossil fuels we burn, are composed of carbon (C). Carbon is the cause of global climate change, one of the biggest challenges we face today. Knowing how and why C flows through different “pools” on Earth (e.g., air, water, rock, soil, living organisms) is key to understanding how and how fast climate will change. As C moves between different pools on Earth, it cycles between its different forms: organic carbon (i.e., organic matter), and inorganic carbon (e.g., carbon dioxide, CO2, a greenhouse gas). Processes such as photosynthesis, respiration, or weathering control the conversion of C from one form to another and the flow of C between pools. Any change in the cycle that moves C out of one pool, for example the combustion of dead organic matter in fossil fuels, puts more C in other pools such as CO2 released to the atmosphere that results in warmer temperatures on Earth. Although we generally know the fundamentals of the C cycle, specific biogeochemical processes and their timescales are too poorly constrained to allow a predictive understanding of how human alteration of the C cycle will change our climate. My research examines how and how fast dissolved organic matter (DOM) is converted to CO2 within the context of the modern C cycle (Fig. 1).
All water on Earth contains DOM from the breakdown of once-living organic matter (e.g., organic matter from plants and microbes). The DOM pool on Earth is similar in size to the amount of C contained in the atmosphere; it is the largest pool of organic C in the ocean, and it is the largest flux of organic C from land to oceans worldwide. These large pools of DOM link organic C with CO2 and drive the global C cycle because the short- to medium-term fate of DOM is conversion to greenhouse gases (i.e., CO2; Fig. 1). Each of my three main research directions (described below) focuses on understanding the controls on DOM fluxes and degradation. As an organic matter geochemist and photochemist I lead these three research directions in collaboration with hydrologists, chemists, and microbiologists as described in more detail under reach research direction.
- Sunlight: The study of sunlight in the degradation of DOM in the Arctic, and interactions between bacterial and photochemical degradation of DOM. Supported by NSF Polar Programs.
- Bacteria: The study of how the chemical composition of DOM controls bacterial respiration of this C to CO2. Supported by NSF Earth Sciences.
- Iron: The study of how linkages between DOM and iron may play a pivotal role in the conversion of DOM to CO2 in arctic soils and surface waters. Supported by NSF CAREER, Camille & Henry Dreyfus Foundation, and EMSL.