Award: OCE-1658030

In this project we successfully studied the proteins produced by microbial community in the North Atlantic Ocean using metaproteomic samples collected by the new autonomous underwater vehicle (AUV) Clio. Clio is the first AUV designed specifically for studying ocean biogeochemistry - the integrated study of elemental cycles and the influence of biology, chemistry and geological processes on them. With support from this project, Clio has completed nearly 30 dives to date, dived to more than 4000m depth, and collected thousands of samples. The analysis of the proteins from microbes collected on these expeditions showed the presence of sophisticated biochemical systems deployed in response to nutrient and micronutrient scarcity and the export of organic matter. On the Bermuda Atlantic Time Series expeditions, Clio typically conducted three dives per cruise, including acquiring high resolution vertical profiles through the chlorophyll maximum with 5m resolution. The metaproteomic datasets from the Clio expeditions have yielded surprising and important insights into the biogeochemical processes occuring in the North Atlantic oligotrophic gyre. In the euphotic zone, a layering of nutrient stressors is evident, and that seasonal deepening of the thermocline is represented within the nitrogen and phosphorus transporters and element sparing systems becoming more prevalent through the summer period. In contrast, within the chlorophyll maximum iron stress proteins become increasingly pronounced, which is surprising in the heavy dust deposition Atlantic environment, but indicates isolation of the chlorophyll maximum from surface waters. In addition transporters for organic forms of these nutrients is seen within all of these profiles, implying DON and DOP sources are key to this ecosystem's functioning. Together these results imply a layering of multiple nutrient stressors, rather than typical model parameterizations for productivity control by single nutrient limitation. This project contributed to the development of technology for AUV sampling, improvements in methods for measurement of ocean proteins using metaproteomic mass spectrometry analyses, and broader impact efforts including submissions and upgrades to the Ocean Protein Portal for ocean biochemical research and education and to the training of a graduate student and postdoc. Last Modified: 07/09/2020 Submitted by: Mak A Saito