Award: OCE-1558506

The overall project goal was to examine how single-celled marine photosynthetic microbes, called diatoms, thrive across different environments, from the coast to the open ocean. Diatoms generate about 20% of global photosynthetic carbon fixation which converts carbon dioxide into the organic building blocks of biomass – a process that forms the base of marine food webs. Diatoms are also key contributors to the cycling of major elements like carbon through the earth system. Thus, understanding the factors that control their distribution and activities are critical for understanding ocean ecosystem structure and function both at present and in the future. We asked the following questions: 1) How variable is diatom community composition in the coastal ocean compared to the open ocean? 2) How do diatom species change their cellular activities in different environments? This project focused on samples from two oceanographic cruises in the 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 some diatom species were located primarily in coastal regions while others were found only in the open ocean, suggesting that they are adapted to different environmental conditions. A subset of species were found in both types of environments suggesting that these species are 'flexible' and able to cope with a wide range of environmental conditions. Novel genetic tools were used to identify the cellular activities of diatoms by examining each diatom’s expressed gene compliment (gene expression) in cruise samples. This is essentially tracking which genes are turned on or off under different conditions. Genes encode the proteins that control cellular activities, so this is a way of tracking what diatoms are doing in the environment. To use this approach we generated a custom database of diatom gene expression patterns using diatoms isolated during the cruises that we then grew in the laboratory. We found that gene expression differed between diatom species in the same environment, suggesting that species-specific adaptations may help many diatom species co-exist in diverse environments. The availability of resources like nitrogen and phosphorus also drove changes in the diatom gene expression patterns, highlighting the ways in which individual diatoms shift their activities to maintain growth in different environments. Taken together this project provides fundamental new insight into the ecology and activities of these microbes. Building this knowledge base is critical for understanding the structure and function of current and future ocean ecosystems. This project provides a lasting resource of new diatom isolates in culture in the laboratory that can be used for future study. The gene expression data also represents a lasting resource that can be re-used, and used as a reference database for future diatom studies. In addition, this project supported outreach and education broadly related to increasing ocean literacy. Specifically, we used the goals of this project to promote awareness that marine microbes play an important role in the habitability of our planet. To do this, we used a suite of activity platforms (e.g., card games, hands-on science kits, virtual presentations and videos, in-person tours and orientations, etc) to engage diverse learners. Some highlights include participation in the SUBMERGE Marine Science Festival, which drew over 7000 attendees from the NYC metro area, Girls in Science & Engineering Day at the Intrepid Sea, Air & Space Museum which brought together organizations from all over NYC in honor of Women’s month to celebrate the role of women in STEM, the Sun & Earth Day at the American Museum of Natural History, and the Lamont-Doherty Earth Observatory Open House, which attracted thousands of NYC and tri-state families. We also used this project, and our activity platforms, to engage students from diverse backgrounds. This project supported a student in Columbia University’s Bridge to the PhD Program, María Hernández Limón. María is now finishing up her PhD at the University of Chicago in Microbial Ecology. We also hosted students from the McNair Scholars Program at Mercy College, which targets low-income, first-generation students and those who are from groups underrepresented in graduate education. 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. Collectively, this project offered a rich opportunity to advance ocean literacy for all, increasing the public’s understanding of microbial oceanography, and mentoring, both formally and informally, young women and underrepresented groups towards careers in science. Last Modified: 11/30/2022 Submitted by: Sonya T Dyhrman