M.A. Freilich, C. Poirier, M. Dever, E. Alou-Font, J. Allen, A. Cabornero, L. Sudek, C.J. Choi, S. Ruiz, A. Pascual, J.T. Farrar, T.M.S. Johnston, E.A. D’Asaro, A.Z. Worden, & A. Mahadevan,

3D intrusions transport active surface microbial assemblages to the dark ocean, Proc. Natl. Acad. Sci. U.S.A. 121 (19) e2319937121

https://doi.org/10.1073/pnas.2319937121 (2024).

Particulate organic carbon (POC) formed by photosynthesis in the sunlit surface ocean fuels the ecosystems in the dark ocean below. We show that mesoscale fronts and eddies, which are ubiquitous physical features in subtropical oceans, generate three-dimensional intrusions connecting the surface to deep ocean. Intrusions are enriched in total POC due to enhancement of small, nonsinking photosynthetic plankton and free-living bacteria that resemble surface microbial communities. Flow-driven export of POC, estimated using an approximation of eddy physics, is the same order of magnitude as export by sinking POC, which was previously thought to dominate export. These observations reveal coupling of surface and deep ocean productivity and biodiversity and give insight into mechanisms by which the ocean transports carbon to depth.

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