Marine phytoplankton account for approximately half of global primary productivity1, making their fate an important driver of the marine carbon cycle. Viruses are thought to recycle more than one-quarter of oceanic photosynthetically fixed organic carbon2, which can stimulate nutrient regeneration, primary production and upper ocean respiration2 via lytic infection and the ‘virus shunt’. Ultimately, this limits the trophic transfer of carbon and energy to both higher food webs and the deep ocean2. Using imagery taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite, along with a suite of diagnostic lipid- and gene-based molecular biomarkers, in situ optical sensors and sediment traps, we show that Coccolithovirus infections of mesoscale (~100 km) Emiliania huxleyi blooms in the North Atlantic are coupled with particle aggregation, high zooplankton grazing and greater downward vertical fluxes of both particulate organic and particulate inorganic carbon from the upper mixed layer. Our analyses captured blooms in different phases of infection (early, late and post) and revealed the highest export flux in ‘early-infected blooms’ with sinking particles being disproportionately enriched with infected cells and subsequently remineralized at depth in the mesopelagic. Our findings reveal viral infection as a previously unrecognized ecosystem process enhancing biological pump efficiency.
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We thank the captain and crew of the RV Knorr for assistance and cooperation at sea, as well as Marine Facilities and Operations at the Woods Hole Oceanographic Institution for logistical support. We thank R. Fernandes and S. Prakya (University of the Azores) and I. Bashmachnikov (Saint Petersburg University) for daily downloading and sending MODIS and AVISO altimetry data to the RV Knorr for onboard processing. We also thank B. Edwards for logistical help with sediment trap deployments and recoveries. R. Stevens (College of Charleston) and A. Neeley (NASA) provided assistance with the dilution experiments and CHEMTAX analyses, respectively. This study was supported by grants from the National Science Foundation to K.D.B. (OCE-1061876, OCE-1537951 and OCE-1459200), M.J.L.C., G.R.D., A.V. and B.A.S.V.M. (OCE-1050995), and R.J.C. and E.J.H. (OCE-1325258), and from the Gordon and Betty Moore Foundation to K.D.B. (GBMF3789) and B.A.S.V.M. (GBMF3301).
The authors declare no competing interests.
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Laber, C.P., Hunter, J.E., Carvalho, F. et al. Coccolithovirus facilitation of carbon export in the North Atlantic. Nat Microbiol 3, 537–547 (2018). https://doi.org/10.1038/s41564-018-0128-4
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