In press / In Revision / Submitted

Mayot, N., P. Matrai, A. Arjona, S. Bélanger, C. Marchese, T. Jaegler, M. Ardyna and M. Steele. Springtime export of Arctic sea ice shapes the phytoplankton production in the Greenland Sea | Submitted to Global Biogeochemical Cycles


Mayot, N., P. Matrai, I. H. Ellingsen, M. Steele, K. Johnson, S. C. Riser and D. Swift (2018). Assessing Phytoplankton Activities in the Seasonal Ice Zone of the Greenland Sea Over an Annual Cycle | Journal of Geophysical Research: Oceans | 123(11), 8004-8025 | PDF


In seasonal ice zones (SIZs), such as the one of the Greenland Sea, the sea ice growth in winter and subsequent melting in summer influence the phytoplankton activity. However, studies assessing phytoplankton activities over complete annual cycles and at a fine temporal resolution are lacking in this environment. Biogeochemical‐Argo floats, which are able to sample under the ice, were used to collect physical and biogeochemical data along vertical profiles and at 5‐day resolution during two complete annual cycles in the Greenland Sea SIZ. Three phytoplankton activity phases were distinct within an annual cycle: one under ice, a second at the ice edge, and a third one around an open‐water subsurface chlorophyll maximum. As expected, the light and nitrate availabilities controlled the phytoplankton activity and the establishment of these phases. On average, most of the annual net community production occurred equally under ice and at the ice edge. The open‐water subsurface chlorophyll maximum phase contribution, on the other hand, was much smaller. Phytoplankton biomass accumulation and production thus occur over a longer period than might be assumed if under ice blooms were neglected. This also means that satellite‐based estimates of phytoplankton biomass and production in this SIZ are likely underestimated. Simulations with the Arctic‐based physical‐biologically coupled SINMOD model suggest that most of the annual net community production in this SIZ results from local processes rather than due to advection of nitrate from the East Greenland and Jan Mayen Currents.

Ayata, S-D., J-O. Irisson, A. Aubert, L. Berline, J-C. Dutay, N. Mayot, A-E. Nieblas, F. D’Ortenzio, J. Palmieri, G. Reygondeau, V. Rossi, and C. Guieu (2018). Regionalisation of the Mediterranean basin, a MERMEX synthesis | Progress in Oceanography | 163, 7-20 | PDF

Taillandier, V., T. Wagener, F. D’Ortenzio, N. Mayot, H. Legoff, J. Ras, L. Coppola, O. Pasqueron de Fommervault1, C. Schmechtig, E. Diamond, H. Bittig, D. Lefevre, E. Leymarie, A. Poteau and L. Prieur (2018). Hydrography in the Mediterranean Sea during a cruise with RV Tethys 2 in May 2015 | Earth System Science Data | 10(1), 627-641 | PDF

Testor, P., A. Bosse, L. Houpert, F. Margirier, L. Mortier, H. Le Goff, D. Dausse, M. Labaste, J. Karstensen, D. Hayes, A. Olita, E. Heslop, F. D’Ortenzio, N. Mayot, H. Lavigne, O. Pasqueron de Fommervault, L. Coppola, L. Prieur, V. Taillandier, X. Durrieu de Madron, F. Bourrin, G. Many, P. Damien, C. Estournel, P. Marsaleix, I. Taupier-Letage, P. Raimbault, R. Waldman, M-N. Bouin, H. Giordani, G. Caniaux, S. Somot, V. Ducrocq and P. Conan (2018). Dense water formations in the North Western Mediterranean: from the physical forcings to the biogeochemical consequences | Journal of Geophysical Research: Oceans | 123(3), 1745-1776 | PDF


Mayot, N., F. D’Ortenzio, J. Uitz, B. Gentili, D. Antoine and H. Claustre (2017). Influence of the phytoplankton community structure on the spring and annual primary production in the North-Western Mediterranean Sea | Journal of Geophysical Research: Oceans | 122(12), 9918-9936 | PDF


Satellite ocean color observations revealed that unusually deep convection events in 1999, 2005, 2006, 2010 and 2013 led to an increased phytoplankton biomass during the spring bloom over a large area of the North-Western Mediterranean Sea (NWM). Here we investigate the effects of these events on the seasonal phytoplankton community structure, we quantify their influence on primary production, and we discuss the potential biogeochemical impact. For this purpose, we compiled in situ phytoplankton pigment data from five ship surveys performed in the NWM and from monthly cruises at a fixed station in the Ligurian Sea. We derived primary production rates from a light-photosynthesis model applied to these in situ data. Our results confirm that the maximum phytoplankton biomass during the spring bloom is larger in years associated with intense deep convection events (+ 51%). During these enhanced spring blooms, the contribution of diatoms to total phytoplankton biomass increased (+ 33 %), as well as the primary production rate (+ 115 %). The occurrence of a highly productive bloom is also related to an increase in the phytoplankton bloom area (+ 155 %), and in the relative contribution of diatoms to primary production (+ 63 %). Therefore, assuming that deep convection in the NWM could be significantly weakened by future climate changes, substantial decreases in the spring production of organic carbon and of its export to deep waters can be expected.

Mayot, N., F. D’Ortenzio, V. Taillandier, L. Prieur, O. Pasqueron de Fommervault, H. Claustre, A. Bosse, P. Testor and P. Conan (2017). Physical and biogeochemical controls of the phytoplankton blooms in North Western Mediterranean Sea: a multiplatform approach over a complete annual cycle (2012-2013 DEWEX experiment) | Journal of Geophysical Research: Oceans | 122(12), 9999-10019 | PDF


The North Western Mediterranean Sea exhibits recurrent and significant autumnal and spring phytoplankton blooms. The existence of these two blooms coincide with typical temperate dynamics. To determine the potential control of physical and biogeochemical factors on these phytoplankton blooms, data from a multiplatform approach (combining ships, Argo and BGC-Argo floats, and bio-optical gliders) were analyzed in association with satellite observations in 2012-2013. The satellite framework allowed a simultaneous analysis over the whole annual cycle of in situ observations of mixed layer depth, photosynthetical available radiation, particle backscattering, nutrients (nitrate and silicate) and chlorophyll-a concentrations. During the year 2012-2013, satellite ocean color observations, confirmed by in situ data, have revealed the existence of two areas (or bioregions) with comparable autumnal blooms but contrasting spring blooms. In both bioregions, the ratio of the euphotic zone (defined as the isolume 0.415 mol photons m-2 d-1, Z0.415) and the MLD identified the initiation of the autumnal bloom, as well as the maximal annual increase in [Chl-a] in spring. In fact, the autumnal phytoplankton bloom might be initiated by mixing of the summer shallowing deep chlorophyll maximum, while the spring restratification (when Z0.415/MLD ratio became > 1) might induce surface phytoplankton production that largely overcomes the losses. Finally, winter deep convection events that took place in one of the bioregions induced higher net accumulation rate of phytoplankton in spring associated with a diatom-dominated phytoplankton community principally. We suggest that very deep winter MLD lead to an increase in surface silicates availability, which favored the development of diatoms.

Bosse, A., P. Testor, N. Mayot, L. Prieur, F. D’Ortenzio, L. Mortier, H. Le Goff, C. Gourcuff, L. Coppola, H. Lavigne and P. Raimbault, A submesoscale coherent vortex in the Ligurian Sea: from dynamical barriers to biological implications | Journal of Geophysical Research: Oceans | 122(8), 6196–6217 | PDF

Séverin, T., F. Kessouri, M. Rembauville, E. Sanchéz-Pérez, L. Oriol, J. Caparros, M. Pujo-Pay, J-F. Ghiglione, F. D’Ortenzio, V. Taillendier, C. Ulses, C. Estournel, N. Mayot and P. Conan (2017). Open-ocean convection process: a driver of the winter nutrient supply and the spring phytoplankton distribution in the Northwestern Mediterranean Sea | Journal of Geophysical Research: Oceans | 122(6), 4587–4601 | PDF


Biard, T., L. Stemmann, M. Picheral, N Mayot, P. Vandromme, H. Hauss, G. Gorsky, L. Guidi, R. Kiko and F. Not (2016). In situ imaging reveals the biomass of giant protists in the global ocean | Nature | 532, 504-507 | PDF on ResearchGate


Planktonic organisms play crucial roles in oceanic food webs and global biogeochemical cycles. Most of our knowledge about the ecological impact of large zooplankton stems from research on abundant and robust crustaceans, and in particular copepods. A number of the other organisms that comprise planktonic communities are fragile, and therefore hard to sample and quantify, meaning that their abundances and effects on oceanic ecosystems are poorly understood. Here, using data from a worldwide in situ imaging survey of plankton larger than 600 µm, we show that a substantial part of the biomass of this size fraction consists of giant protists belonging to the Rhizaria, a super-group of mostly fragile unicellular marine organisms that includes the taxa Phaeodaria and Radiolaria (for example, orders Collodaria and Acantharia). Globally, we estimate that rhizarians in the top 200 m of world oceans represent a standing stock of 0.089 Pg carbon, equivalent to 5.2% of the total oceanic biota carbon reservoir. In the vast oligotrophic intertropical open oceans, rhizarian biomass is estimated to be equivalent to that of all other mesozooplankton (plankton in the size range 0.2–20 mm). The photosymbiotic association of many rhizarians with microalgae may be an important factor in explaining their distribution. The previously overlooked importance of these giant protists across the widest ecosystem on the planet changes our understanding of marine planktonic ecosystems.

Mayot, N., F. D’Ortenzio, M. Ribera d’Alcalà, H. Lavigne, and H. Claustre (2016). Interannual variability of the Mediterranean trophic regimes from ocean color satellites | Biogeosciences | 13, 1901–1917 | PDF


D’Ortenzio and Ribera d’Alcalà (2009, DR09 hereafter) divided the Mediterranean Sea into “bioregions” based on the climatological seasonality (phenology) of phytoplankton. Here we investigate the interannual variability of this bioregionalization. Using 16 years of available ocean color observations (i.e. SeaWiFS and MODIS), we analyzed the spatial distribution of the DR09 trophic regimes on an annual basis. Additionally, we identified new trophic regimes, exhibiting seasonal cycles of phytoplankton biomass different from the DR09 climatological description and named “Anomalous”. Overall, the classification of the Mediterranean phytoplankton phenology proposed by DR09 (i.e. “No Bloom”, “Intermittently”, “Bloom” and “Coastal”), is confirmed to be representative of most of the Mediterranean phytoplankton phenologies. The mean spatial distribution of these trophic regimes (i.e. bioregions) over the 16 years studied is also similar to the one proposed by DR09, although some annual variations were observed at regional scale. Discrepancies with the DR09 study were related to interannual variability in the sub-basin forcing: winter deep convection events, frontal instabilities, inflow of Atlantic or Black Sea Waters and river run-off. The large assortment of phytoplankton phenologies identified in the Mediterranean Sea is thus verified at the interannual scale, further supporting the “sentinel” role of this basin for detecting the impact of climate changes on the pelagic environment.