In mid- and high-latitude oceans, winter surface cooling and strong winds drive turbulent mixing that carries phytoplankton to depths of several hundred metres, well below the sunlit layer. This downward mixing, in combination with low solar radiation, drastically limits phytoplankton growth during the winter, especially that of the diatoms and other species that are involved in seeding the spring bloom. Here we present observational evidence for widespread winter phytoplankton blooms in a large part of the North Atlantic subpolar gyre from autonomous profiling floats equipped with biogeochemical sensors. These blooms were triggered by intermittent restratification of the mixed layer when mixed-layer eddies led to a horizontal transport of lighter water over denser layers. Combining a bio-optical index with complementary chemotaxonomic and modelling approaches, we show that these restratification events increase phytoplankton residence time in the sunlight zone, resulting in greater light interception and the emergence of winter blooms. Restratification also caused a phytoplankton community shift from pico- and nanophytoplankton to phototrophic diatoms. We conclude that transient winter blooms can maintain active diatom populations throughout the winter months, directly seeding the spring bloom and potentially making a significant contribution to over-winter carbon export.
Subscribe to Journal
Get full journal access for 1 year
only $4.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Sverdrup, H. U. On conditions for the vernal blooming of phytoplankton. J. Cons. Int. pour l’exploitation la mer 18, 287–295 (1953).
Backhaus, J. O. et al. Convecion and primary production in winter. Mar. Ecol. Progr. Ser. 251, 1–14 (2003).
Dale, T., Rey, F. & Heimdal, B. R. Seasonal development of phytoplankton at a high latitude oceanic site. Sarsia 84, 419–435 (1999).
Große, F., Lindemann, C., Pätsch, J. & Backhaus, J. O. The influence of winter convection on primary production: a parameterisation using a hydrostatic three-dimensional biogeochemical model. J. Mar. Syst. 147, 138–152 (2015).
Behrenfeld, M. J. Abandoning Sverdrup’s critical depth hypothesis on phytoplankton blooms. Ecology 91, 977–989 (2010).
Behrenfeld, M. J., Doney, S. C., Lima, I., Boss, E. S. & Siegel, D. A. Annual cycles of ecological disturbance and recovery underlying the subarctic Atlantic spring plankton bloom. Glob. Biogeochem. Cycles 27, 526–540 (2013).
Boccaletti, G., Ferrari, R. & Fox-Kemper, B. Mixed layer instabilities and restratification. J. Phys. Oceanogr. 37, 2228–2250 (2007).
Fox-Kemper, B., Ferrari, R. & Hallberg, R. Parameterization of mixed layer eddies. Part I: theory and diagnosis. J. Phys. Oceanogr. 38, 1145–1165 (2008).
Mahadevan, A., D’Asaro, E., Lee, C. & Perry, M. J. Eddy-driven stratification initiates North Atlantic spring phytoplankton blooms. Science 337, 54–58 (2012).
Callies, J., Ferrari, R., Klymak, J. M. & Gula, J. Seasonality in submesoscale turbulence. Nat. Commun. 6, 6862 (2015).
Huisman, J. & Weissing, F. J. Biodiversity of plankton by species oscillations and chaos. Nature 402, 407–410 (1999).
Taylor, J. R. & Ferrari, R. Shutdown of turbulent convection as a new criterion for the onset of spring phytoplankton blooms. Limnol. Ocean. 56, 2293–2307 (2011).
Ferrari, R., Merrifield, S. T. & Taylor, J. R. Shutdown of convection triggers increase of surface chlorophyll. J. Mar. Syst. 147, 116–122 (2015).
Brainerd, K. E. & Gregg, M. C. Surface mixed and mixing layer depths. Deep-Sea Res. I 42, 1521–1543 (1995).
Franks, P. J. S. Has Sverdrup’s critical depth hypothesis been tested? Mixed layers vs. turbulent layers. ICES J. Mar. Sci. 72, 1897–1907 (2015).
Brody, S. R. & Lozier, M. S. Changes in dominant mixing length scales as a driver of subpolar phytoplankton bloom initiation in the North Atlantic. Geophys. Res. Lett. 41, 3197–3203 (2014).
Behrenfeld, M. J. & Boss, E. S. Resurrecting the ecological underpinnings of ocean plankton blooms. Annu. Rev. Mar. Sci. 6, 167–194 (2014).
Lindemann, C. & St. John, M. A. A seasonal diary of phytoplankton in the North Atlantic. Front. Mar. Sci. 1, 37 (2014).
Johnson, L., Lee, C. M. & D’Asaro, E. A. Global estimates of lateral springtime restratification. J. Phys. Oceanogr. 46, 1555–1573 (2016).
Litchman, E. Growth rates of phytoplankton under fluctuating light. Freshwat. Biol. 44, 223–235 (2000).
Walter, B., Peters, J., Van Beusekom, J. E. E. & St. John, M. A. Interactive effects of temperature and light during deep convection: a case study on growth and condition of the diatom Thalassiosira weissflogii. ICES J. Mar. Sci. 72, 2061–2071 (2015).
Cetinić, I. et al. A simple optical index shows spatial and temporal heterogeneity in phytoplankton community composition during the 2008 North Atlantic Bloom Experiment. Biogeosciences 12, 2179–2194 (2015).
Smetacek, V. S. Role of sinking in diatom life-history cycles: ecological, evolutionary and geological significance. Mar. Biol. 84, 239–251 (1985).
McQuoid, M. R. & Hobson, L. A. Diatom resting stages. J. Phycol. 32, 889–902 (1996).
Caron, D. A. Mixotrophy stirs up our understanding of marine food webs. Proc. Natl Acad. Sci. USA 113, 2806–2808 (2016).
Smayda, T. J. & Mitchell-Innes, B. Dark survival of autotrophic, planktonic marine diatoms. Mar. Biol. 25, 195–202 (1974).
Barton, A. D., Lozier, M. S. & Williams, R. G. Physical controls of variability in North Atlantic phytoplankton communities. Limnol. Oceanogr. 60, 181–197 (2014).
Gardner, W. D., Chung, S. P., Richardson, M. J. & Walsh, I. D. The oceanic mixed-layer pump. Deep-Sea Res. II 42, 757–775 (1995).
Dall’Olmo, G. & Mork, K. A. Carbon export by small particles in the Norwegian Sea. Geophys. Res. Lett. 41, 2921–2927 (2014).
Koeve, W., Pollehne, F., Oschlies, A. & Zeitzschel, B. Storm-induced convective export of organic matter during spring in the northeast Atlantic Ocean. Deep-Sea Res. I 49, 1431–1444 (2002).
We thank N. Briggs, M. J. Perry, E. D’Asaro, B. Gentili, E. Boss and F. Benedetti for fruitful discussions, C. Schmechtig for BGC-Argo float data management and J. Ras for proofreading the manuscript. We also thank S. Wright for sharing the CHEMTAX software v.1.95, and C. de Boyer Montégut for providing the MLD climatology. This work represents a contribution to the remOcean project (REMotely sensed biogeochemical cycles in the OCEAN, GA 246777) funded by the European Research Council, the ATLANTOS EU project (grant agreement 2014-633211) funded by H2020 program and the Italian Flagship Program RITMARE.
The authors declare no competing financial interests.
About this article
Cite this article
Lacour, L., Ardyna, M., Stec, K. et al. Unexpected winter phytoplankton blooms in the North Atlantic subpolar gyre. Nature Geosci 10, 836–839 (2017). https://doi.org/10.1038/ngeo3035
Global Biogeochemical Cycles (2021)
Scientific Reports (2021)
Sensing the ocean biological carbon pump from space: A review of capabilities, concepts, research gaps and future developments
Earth-Science Reviews (2021)
Journal of Geophysical Research: Oceans (2020)
Frontiers in Marine Science (2020)