Impact of open-ocean convection on nutrients, phytoplankton biomass and activity

Séverin, Tatiana; Conan, Pascal; Madron, Xavier Durrieu de; Houpert, Loïc; Oliver, Matthew J.; Oriol, L.; Caparros, Jocelyne; Ghiglione, J. F.; Pujo‐Pay, Mireille

doi:10.1016/j.dsr.2014.07.015

Cited by 47 publications

(71 citation statements)

References 59 publications

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“…A previous study on a secondary convection event in the NWM showed that the nutrient supply by a single event was equivalent to the annual supply by the Gulf of Lions rivers, even for an event limited in space (1000 km 2 ) and time (8 days) during which the MLD only reached the WMDW [ Severin et al ., ]. The convection event of March 2011 was preceded by a first deep convection event in February 2011 that reached the bottom.…”

Section: Discussionmentioning

confidence: 99%

“…Several studies showed that the deep convection process is responsible for the introduction of a large amount of nutrients to the surface layer [ Marty and Chiavériny , ; Estrada et al ., ; Severin et al ., ; Ulses et al ., ], which directly influences the intensity of the spring bloom [ Lévy et al ., ; Taylor and Ferrari , ; Backhaus et al ., ; Heimbürger et al ., ; Ulses et al ., ]. A monitoring of phytoplankton pigments in March 2005 and from mid‐March to September 2009 in the NWM revealed the heterogeneity of the spring bloom related to mesoscale processes, and the phytoplankton populations succession from spring (diatoms and haptophyte) to late summer (dinoflagellate and coccolithophores) [ Estrada et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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Open‐ocean convection process: A driver of the winter nutrient supply and the spring phytoplankton distribution in the Northwestern Mediterranean Sea

et al. 2017

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This study was a part of the DeWEX project (Deep Water formation Experiment), designed to better understand the impact of dense water formation on the marine biogeochemical cycles. Here, nutrient and phytoplankton vertical and horizontal distributions were investigated during a deep open‐ocean convection event and during the following spring bloom in the Northwestern Mediterranean Sea (NWM). In February 2013, the deep convection event established a surface nutrient gradient from the center of the deep convection patch to the surrounding mixed and stratified areas. In the center of the convection area, a slight but significant difference of nitrate, phosphate and silicate concentrations was observed possibly due to the different volume of deep waters included in the mixing or to the sediment resuspension occurring where the mixing reached the bottom. One of this process, or a combination of both, enriched the water column in silicate and phosphate, and altered significantly the stoichiometry in the center of the deep convection area. This alteration favored the local development of microphytoplankton in spring, while nanophytoplankton dominated neighboring locations where the convection reached the deep layer but not the bottom. This study shows that the convection process influences both winter nutrients distribution and spring phytoplankton distribution and community structure. Modifications of the convection's spatial scale and intensity (i.e., convective mixing depth) are likely to have strong consequences on phytoplankton community structure and distribution in the NWM, and thus on the marine food web.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Open‐ocean convection process: A driver of the winter nutrient supply and the spring phytoplankton distribution in the Northwestern Mediterranean Sea

et al. 2017

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“…An important interannual variability on the intensity of the winter deep convection has been observed, for the most part related to the variability of atmospheric and hydrodynamic forcing (Mertens and Schott, 1998;L'Hévéder et al, 2013). In response to this oceanic and atmospheric variability, significant interannual differences in the biological response were also reported (Marty et al, 2002;Herrmann et al, 2013;Severin et al, 2014).…”

Section: The "Bloom" Trophic Regimementioning

confidence: 91%

“…Such temporal coincidence suggests that deep convection events could impact the phytoplankton phenology of the region, by inducing a stronger phytoplankton bloom (i.e., a higher amplitude, 0.82 mg m −3 for the "Bloom #5" trophic regime and 1.09 mg m −3 for the "Anomalous #1" trophic regime) and a delay of the spring peak of a few weeks. This stronger NWM spring bloom induced by the intense deep convection events could be the result of either an increased nutrient concentration, or a modified nutrient stoichiometry, and/or of an enhanced zooplankton dilution, all these mechanisms being triggered by the deep convection (Herrmann et al, 2013;Severin et al, 2014). In summary, the presence of the "Anomalous #1" bioregion appears as a clear indicator of the phenological and ecological changes induced by deep convection events.…”

Section: The "Bloom" Trophic Regimementioning

confidence: 99%

Interannual variability of the Mediterranean trophic regimes from ocean color satellites

et al. 2016

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Abstract. D'Ortenzio and Ribera d'Alcalà (2009, DR09hereafter) 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.

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“…2a) corresponds with their ability to use light as an additional energy source (Béjà et al 2000, Giovannoni et al 2005a, DeLong & Béjà 2010, Iverson et al 2012. Vertical mixing also enhances availability of phytoplanktonderived particulate and dissolved organic matter (Heimbürger et al 2013, Gogou et al 2014, Severin et al 2014). This organic matter supports the development of bacteria regularly inhabiting the euphotic zone, such as Oceanospirillales and Flavobacteriales (Severin et al 2016).…”

Section: Population Composition and Transcriptional Activitymentioning

confidence: 99%

Winter mixing impacts gene expression in marine microbial populations in the Gulf of Aqaba

Miller¹,

Pfreundt²,

Hou³

et al. 2017

Aquat. Microb. Ecol.

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In aquatic systems, changes in temperature and irradiance fundamentally characterize the water column and regulate microbial population structure and function. In systems with stable thermal stratification, the warm surface mixed layer is typically nutrient impoverished, limiting biological production. In periods of destratification, convective mixing of the water column exposes the microorganisms inhabiting these mixed systems to rapid variations in light availability and spectra. We explored the impact of winter deep-mixing (500 m deep mixed layer) on microbial communities from the surface (2.5 m) and the aphotic waters (440 m) in the Gulf of Aqaba by examining changes in both population composition and function via DNA and RNA sequencing. The greatest fraction of 16S sequences was assigned to Euryarchaeota, while metatranscriptomes were dominated by Synechococcus transcripts. Community composition was highly similar at both depths, yet transcription profiles differed. Phototrophic organisms found at the photic surface overexpressed genes related to catabolism and energy metabolism, while genes affiliated with biosynthesis were overexpressed at the aphotic depth. Similar transcriptional trends were observed in the non-photoautotrophs SAR11, Euryarchaeota, and Thaumarchaeota, with niche partitioning based on differential utilization of nitrogen and phosphorus occurring between the 2 archaeal groups. We did not detect upregulated expression of cyanobacterial genes indicative of mixotrophy or glycogen metabolism in the aphotic zone, suggesting they survive the aphotic period by utilizing photosynthates produced in the photic zone. Indications for a mixotrophic lifestyle were observed for prasinophytes, with genes related to phagocytosis overexpressed at the aphotic depth compared with the surface.

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Impact of open-ocean convection on nutrients, phytoplankton biomass and activity

Cited by 47 publications

References 59 publications

Open‐ocean convection process: A driver of the winter nutrient supply and the spring phytoplankton distribution in the Northwestern Mediterranean Sea

Open‐ocean convection process: A driver of the winter nutrient supply and the spring phytoplankton distribution in the Northwestern Mediterranean Sea

Interannual variability of the Mediterranean trophic regimes from ocean color satellites

Winter mixing impacts gene expression in marine microbial populations in the Gulf of Aqaba

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