Leading Indicators: Marine Microbial Community Gene Expression Responses to Ocean Alkalinity Enhancement

Ocean alkalinity enhancement (OAE) is one of the most promising approaches for removing carbon dioxide (CO₂) from the atmosphere, with the potential to mitigate both carbon emissions and ocean acidification. OAE works by adding strongly alkaline chemicals (such as hydroxides or carbonates, either dissolved or as solid particles) to the surface ocean. This raises the pH of seawater and reduces the concentration of dissolved CO₂. As the ocean rebalances chemically, CO₂ is absorbed from the atmosphere and stays dissolved in the ocean.

One of the most compelling aspects of OAE as a negative-emissions strategy is the size of the reservoir: the ocean contains more than 40 times as much carbon as the atmosphere. So, in principle, much of the accumulated human-produced CO₂ could be stored in the ocean without requiring a large proportional change in the natural reservoir size. However, deploying OAE at the scale needed to meaningfully influence climate change faces massive engineering, economic and governance obstacles. But even if those technical and implementation challenges are solved, a better understanding of the impacts of OAE on ocean ecosystems is needed to deploy it responsibly. Wherever OAE is deployed, it will inevitably impact oceanic life—and will be felt immediately and most strongly by the microorganisms that form the base of marine ecosystems. Microbes’ most sensitive and specific biological responses to environmental changes like OAE – “leading indicators” of the whole-ecosystem effects – are patterns of gene expression. This is the process by which information encoded in an organism’s DNA genome is first transcribed into RNA and finally translated into the proteins that are the molecular agents driving most biological metabolism.

In this project, we are exploring the gene expression responses of marine microbes to simulated OAE additions at a range of scales, from cultured isolates in the laboratory, to shipboard experiments with natural microbial communities, to pilot-scale OAE deployments. Our goal is to identify which elements of marine microbial community metabolism are most sensitive to OAE, so that we can use these molecular responses as benchmarks to compare the biological impacts of different OAE methods as they scale up.

Co-investigators: Maureen Coleman, B. B. Cael, Manon Duret.