Award: OCE-1756337

Phosphorus (P) is required for life, and in the ocean, phosphorus supply in bioavailable forms can control the rate of primary production and carbon cycling by marine microbes in surface water. Phosphate can be taken up directly into cells, but in regions where it is in short supply, such as the western North Atlantic, cells switch to using less preferable forms of dissolved organic phosphorus (DOP). Despite the importance of DOP, the composition and bioavailability of DOP is poorly constrained. The overarching goal of this work was to provide foundational information on the way DOP molecular characteristics translate into P bioavailability to marine microorganisms, and in turn how microorganisms growing under different conditions make different amounts and forms of DOP. This research addressed the following questions using both field- and laboratory-based approaches: Does DOP composition and bioavailability vary across gradients in phosphate concentration in the surface ocean? Do photosynthetic marine microbes (phytoplankton) which produce organic matter make DOP of different composition and bioavailability under different conditions? This project focused on developing a new method to screen the composition (size) of DOP and its bioavailability. The new method was then used to screen DOP composition and bioavailability in laboratory experiments and samples from an oceanographic cruise in the western North Atlantic, sampling from the north eastern coast of the US, a region rich in nutrients, to a region near Bermuda, in the low nutrient Sargasso Sea. We found that DOP composition and bioavailability differ substantially across samples with different concentrations of phosphate. This demonstrates that DOP is compositionally variable in the ocean and that this influences its bioavailability and cycling. The DOP data and experimental studies suggest that these compositional differences result from changes in both the composition DOP that is produced, and the composition of DOP that is used by microbes. DOP is typically input into ecosystem models with a set bioavailability which is invariant by region. This study shows that including variations in DOP bioavailability is a prerequisite to building ecosystem models that capture the influence of P biogeochemistry on primary production and carbon cycling in aquatic systems. In addition to the outcomes noted above, we used the goals of this project to promote awareness that marine microbes play an important role in the habitability of our planet by cycling resources like carbon and phosphorus and other key aspects of the ocean science literacy principles. To do this, we used a suite of activity platforms to engage the public and diverse learners (e.g., card games, hands-on science kits, public lectures,etc.). Some highlights include participation in the SUBMERGE Marine Science Festival, which drew over 7000 attendees from the New York City metro area, Girls in Science & Engineering Day at the Intrepid Sea, Air & Space Museum which brought together organizations from all over New York City in honor of Womens month to celebrate the role of women in STEM, the Lamont-Doherty Earth Observatory Open House, which attracted thousands of New York City and tri-state families.We also used this project, and our activity platforms, to engage students from diverse backgrounds. Our hands-on science kits were loaned to and used extensively by Black Girls Dive, a WOC-founded non-profit that empowers young women to explore their STEM identity through marine science and SCUBA diving. In addition to these efforts with informal learning, this project also supported formal mentoring of early career researchers in a post-baccalaureate Bridge to Ph.D. program. Collectively, this project offered a rich opportunity to advance ocean literacy for all, increasing the publics understanding of oceanography and providing advancement opportunities for early career researchers. Last Modified: 05/27/2024 Submitted by: SonyaTDyhrman