NSF Award
2421365
The carbon cycle plays a critical role in regulating the earth’s climate. Carbon in different forms can be found everywhere on the planet and there is a large and dynamic pool of carbon in the ocean. The fate of carbon in the ocean influences other parts of the global carbon cycle such as the atmosphere and is regulated by a range of biological and physical processes. This study examines the role of marine microorganisms in producing and consuming highly abundant small carbon-containing molecules called osmolytes. Many of these molecules have never been measured in the ocean or have only been measured in limited instances. Microorganisms may change how they cycle and store osmolytes in response to environmental fluctuations in temperature and nutrient availability. This study will culture marine microorganisms under nutrient-limiting conditions and measure osmolytes across a gradient of nutrient limitation in the ocean. This new information will show how environmental conditions impact the abundances of these molecules and the rates at which they are cycled. These challenging measurements will contribute to constraining one aspect of the carbon cycle and will enable better predictions of how cycling of these molecules will change under future climate conditions. The project will be led by three early career female scientists and will provide training opportunities for several undergraduate students, a PhD student and a postdoc. In addition, members of the research team will provide training on mass spectrometry data analysis at an annual summer school in Africa.<br/><br/>In a changing ocean it is critical to quantify labile carbon flux and predict its role in future climates. Each year, half of all marine primary production (25 Pg C) is remineralized by microorganisms. Organic osmolytes, which regulate osmotic pressure and thus may accumulate at millimolar concentrations inside cells, likely comprise a significant, but unconstrained, component of this carbon flux. Given their high intracellular concentrations and small size, these labile compounds are valuable carbon substrates as well as sources of nitrogen and sulfur. This study will produce mechanistic insights into this component of the labile carbon flux by direct quantification of the cycling of organic osmolytes with implications for nitrogen and sulfur cycling as well. Objective 1 will identify differential production of osmolytes by different taxa responding to nitrogen stress by coupling osmolyte measurements and transcriptomics. Objective 2 will measure rates of osmolyte assimilation and the fate of different osmolytes within metabolism. Objective 3 will quantify osmolyte cycling across a coastal to oligotrophic transect in the Mid-Atlantic that encompasses a gradient of natural communities and nitrogen availability. Standing stocks, assimilation rates, and metabolic fate of osmolytes in a natural community will be measured using mass spectrometry and linked to microbial activity via metatranscriptomics. The resulting budget of osmolyte cycling will constrain the contributions of osmolytes to the labile dissolved organic matter flux and inform future efforts to quantify microbial rates of individual labile molecule production and uptake. This project will provide student and postdoc training opportunities in advanced laboratory and analytical skills. As part of a broader effort to<br/>build capacity in oceanography globally, mass spectrometry data generated for this project will be used as a training tool at the Coastal Ocean Environment Summer School in Nigeria and Ghana.<br/><br/>This project is funded by the Chemical Oceanography and Biological Oceanography Programs in the Division of Ocean Sciences.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
