Prokaryotes play a fundamental role in decomposing organic matter in the ocean, but little is known about how microbial metabolic capabilities vary at the global ocean scale and what are the drivers causing this variation. We aimed at obtaining the first global exploration of the functional capabilities of prokaryotes in the ocean, with emphasis on the under-sampled meso- and bathypelagic layers. We explored the potential utilization of 95 carbon sources with Biolog GN2 plates® in 441 prokaryotic communities sampled from surface to bathypelagic waters (down to 4,000 m) at 111 stations distributed across the tropical and subtropical Atlantic, Indian, and Pacific oceans. The resulting metabolic profiles were compared with biological and physico-chemical properties such as fluorescent dissolved organic matter (DOM) or temperature. The relative use of the individual substrates was remarkably consistent across oceanic regions and layers, and only the Equatorial Pacific Ocean showed a different metabolic structure. When grouping substrates by categories, we observed some vertical variations, such as an increased relative utilization of polymers in bathypelagic layers or a higher relative use of P-compounds or amino acids in the surface ocean. The increased relative use of polymers with depth, together with the increases in humic DOM, suggest that deep ocean communities have the capability to process complex DOM. Overall, the main identified driver of the metabolic structure of ocean prokaryotic communities was temperature. Our results represent the first global depiction of the potential use of a variety of carbon sources by prokaryotic communities across the tropical and the subtropical ocean and show that acetic acid clearly emerges as one of the most widely potentially used carbon sources in the ocean.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank all the participants in the Malaspina expedition, in particular, Iñigo G. Zarandona for help with sampling and laboratory analysis, Marta Estrada for help with statistics, the physical oceanography team for processing the CTD data, the microbiology team for determination of microbial abundances and activity, the chemical oceanography team for determination and processing of dissolved organic matter fluorescence, the staff of the Marine Technology Unit (CSIC-UTM), and the captain and crew of R/V Hespérides for their support during the Expedition. Funding. This research was funded by the Spanish Ministry of Economy and Competitiveness under projects Malaspina-2010 Circumnavigation Expedition (grant number CSD2008-00077) and partly by projects ANIMA (CTM2015-65720-R), and MIAU (RTI2018-101025-B-I00). CR-G was supported by a Juan de la Cierva fellowship and the GRAMMI project (IJCI-2015-23505 and RTI2018-099740-J-I00, MICINN, Spain).