Overview:  This award addresses the chemical and biological processes affecting watersoluble alkanes in the ocean, using natural seeps to study their fluxes, partitioning between ocean and atmosphere, and the bacterial response to their input.

Intellectual Merit: Hydrocarbons enter the Ocean through a combination of natural seepage, anthropogenic discharge and biological production, with profound impacts on Ocean biogeochemistry, ecology, and the atmosphere. Impacts can be viewed from two perspectives - where hydrocarbons in the marine setting can act as both an energy-rich food substrate and as a toxic substance—with impacts modulated by the activity of hydrocarbon-degrading bacteria.  The transport, fate, and effects of marine hydrocarbons have been the subject of numerous studies, and the importance of petroleum hydrocarbons in the sea has been reiterated through an ongoing series of reports published by the National Academy of Sciences (i.e., Oil in the Sea).  These efforts have led to significant advances toward understanding the behavior of liquid phase oil in the ocean, with a focus on the long chain alkanes and multicyclic compounds. However, the behavior of highly volatile hydrocarbons - a class that is abundant in petroleum reservoirs and many crude and refined products—is less studied and is poorly understood.  Such hydrocarbons display distinct behaviors compared with traditional oil in that they will partition to seawater or the atmosphere depending on their molecular structure and the context by which they enter the ocean, a combination of characteristics unsuitable for traditional fate and transport models that govern our understanding of liquid oil. The current research proposal addresses this gap in knowledge and describes a plan to study volatile, water-soluble hydrocarbons in the context of natural seepage, focusing on key questions about their transport and fate, and the Ocean’s microbial response. Two key questions include: 1) What factors control the partitioning of water-soluble alkanes between water and the atmosphere at natural seeps, and how does this affect their availability to microbes? 2) What genomic and metabolic factors enable the microbial response to the input of water-soluble alkanes and how does the microbial response vary with regional oceanographic and geologic factors such as proximity and flux of natural seepage? The hypotheses that result from these questions will be tested through a series of oceanographic and laboratory-based experiments designed around natural oil seeps in the Pacific and in the Gulf of Mexico. The results of these studies promise to inform our understanding of the transport, fate, and effects of water-soluble alkanes in the ocean.

Broader Impacts: The broader impacts of this research include both educational opportunities and broader societal relevance. Toward educational opportunities, the proposed research includes training of multiple undergraduate and graduate students. The requested research expedition would be leveraged to provide the capstone experience driving a field studies course—a proven mechanism by which ~8 undergraduate and ~4 graduate students will directly engage in oceanographic research. An additional ~10 undergraduate students from a primarily undergraduate institution will gain hands on experience with atmospheric sampling and data analysis as part of their senior capstone course. The results of this research will inform policy and public debate, insomuch as they will provide a scientific foundation to understand the transport and fate of water-soluble alkanes in the ocean - an issue of direct societal relevance. Such basic scientific knowledge is especially prudent in the context of numerous scenarios that involve large scale discharge of water soluble alkanes to the ocean. Lastly, the PIs of this proposal are actively engaged in the public discussion about hydrocarbons and Ocean health - with industry, Government officials, policy makers and NGOs—a discussion which will be informed by this research.