Award: OCE-1151698

The overarching goal of this project was to understand how changes in ocean oxygen content affect the diversity and metabolism of microbial communities. Knowledge of these effects is important for predicting the flow of matter and energy through marine food webs. Changes in matter and energy flow at the microbial level may in turn affect levels (e.g., fish) that are of relevance to human economic and recreational activities. This project therefore contributes data that may enable more accurate predictions of how large shifts in ocean properties affect social and economic systems. The first sub-goal of this research was to characterize the microorganisms that use the essential elements of sulfur and nitrogen to generate energy. This work involved four field campaigns (research cruises) to two physically and chemically distinct low oxygen regions, the permanently anoxic (no detectable oxygen) oxygen minimum zone (OMZ) of the Eastern Tropical North Pacific off Mexico and the seasonally hypoxic (low but detectable oxygen) OMZ of the Gulf of Mexico (Figure 1). Our analyses involved experiments to assess how seawater microbes respond metabolically to shifts in oxygen, sulfur, and nitrogen content, as well as extensive computational analyses of microbial DNA and RNA sequences. The computational analyses were particularly important for identifying both novel organisms and metabolic processes. This work, for example, identified novel clades of OMZ bacteria that oxidize sulfur compounds or the greenhouse gas methane, and do so by linking this metabolism to the removal of nitrogen from the ecosystem. This work also identified previously unrecognized adaptations to low oxygen by the world's most abundant organism, a bacterium called SAR11. A secondary component of sub-goal 1 was to understand how these unique OMZ microbes are distributed in the environment. Specifically, we assessed how OMZ microbes, and the chemical processes they mediate, differ depending on whether microbes are living attached to the surfaces of marine particles (such as zooplankton or phytoplankton cells, or sediments) versus living freely as individual cells in the water column. Our work on this question identified significant differences in microbial cycling of nitrogen and sulfur between these environments. This finding helped identify ecological interactions (e.g., between microbes) and confirmed that, as in other ecosystems, we need to understand the microscale distribution of microorganisms in order to fully understand their contribution to chemical and nutrient cycling as oxygen levels change. This research has thus far produced 21 published journal articles and 2 published book chapters; trained 8 Georgia Tech undergraduates, 4 Georgia Tech graduate students, 4 postdocs, 2 high school teachers, and 5 summer Research Experiences for Undergraduates (REU) students from non-research institutions; and funded 4 research cruises, creating research opportunities for 12 different labs, including those of international collaborators. Data associated with this project are archived via the BCO-DMO website for award 1151698. The second major sub-goal of our project was to establish an educational framework that uses marine research to enhance science curricula in middle and high schools. This goal focused specifically on developing and running a teacher training workshop at Georgia Tech, the Summer Workshop in Marine Science (SWiMS) (Figure 2). The workshop involves a week of hands?on lab and learning activities at Georgia Tech and at the Georgia Marine Institute on Sapelo Island, followed by assessment of classroom outcomes throughout the following school year. SWiMS was developed using resources and personnel (including local high school teachers) associated with this grant, and was implemented for the first time in 2015. SWiMS has run consecutively for 5 summers and has provided training for over 90 Georgia educators (2015-2019), primarily in high?needs districts around Atlanta. The development of SWiMS also provided summer internships at Georgia Tech for 5 Atlanta-area high school science teachers. Plans are in place to continue offering SWiMS in conjunction with the Center for Education Integrating Science, Mathematics, and Computing (CEISMC) and the recently launched graduate program in Ocean Science and Engineering at Georgia Tech. Last Modified: 06/11/2020 Submitted by: Frank J Stewart