Impact of moderately energetic fine-scale dynamics on the phytoplankton community structure in the western Mediterranean Sea

Abstract. Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only a few in situ-based studies at fine scales have been performed, and most of them concern western boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea (WMS), in the region south of the Balearic Islands. Taking advantage of near-real-time satellite information, we defined a sampling strategy in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the research vessel, on a towed vehicle and on an ocean glider were used to sample physical and biogeochemical variables at a high spatial resolution. Particular attention was given to adapting the sampling route in order to estimate the vertical velocities in the frontal area also. This strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different concentrations of chlorophyll a and O2. Here, we focus on moderately energetic fronts induced by fine-scale circulation. Moreover, we explore physical–biological coupling in an oligotrophic region. Our results show that the fronts induced by the fine-scale circulation, even if weaker than the fronts occurring in energetic and nutrient-rich boundary current systems, maintain nevertheless a strong structuring effect on the phytoplankton community by segregating different groups at the surface. Since oligotrophic and moderately energetic regions are representative of a very large part of the world ocean, our results may have global significance when extrapolated.

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Impact of moderate energetic ﬁne-scale dynamics on the phytoplankton community structure in the western Mediterranean Sea

10.5194/bg-2021-38 ◽

2021 ◽

Author(s):

Roxane Tzortzis ◽

Andrea M. Doglioli ◽

Stéphanie Barrillon ◽

Anne A. Petrenko ◽

Francesco d'Ovidio ◽

...

Keyword(s):

Mediterranean Sea ◽

Phytoplankton Community ◽

Sampling Strategy ◽

Western Mediterranean ◽

Water Masses ◽

Ocean Dynamics ◽

Fine Scale ◽

Boundary Current ◽

Western Mediterranean Sea

Abstract. Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only few in situ samplings have been performed and most of them in boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea, in the southern region of the Balearic Islands. Taking advantage of near-real time satellite information, a sampling strategy was defined in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the vessel, on a towed fish and on an ocean glider were used to sample at high spatial resolution both physical and biogeochemical variables. A particular attention was put in adapting the sampling route, in order to also estimate the vertical velocities in the frontal area. Such a strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different contents in chlorophyll a and O2. Our study shows that the Lagrangian fronts induced by the fine-scale circulation, even if much weaker than the fronts occurring in boundary current systems, maintain a strong structuring effect on phytoplankton community by segregating different taxa at the surface.

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Climatological distribution of dissolved inorganic nutrients in the Western Mediterranean Sea (1981–2017)

10.5194/essd-2021-149 ◽

2021 ◽

Author(s):

Malek Belgacem ◽

Katrin Schroeder ◽

Alexander Barth ◽

Charles Troupin ◽

Bruno Pavoni ◽

...

Keyword(s):

Mediterranean Sea ◽

World Ocean ◽

Western Mediterranean ◽

Inorganic Nutrients ◽

Data Product ◽

Western Mediterranean Sea ◽

Dissolved Inorganic Nutrients ◽

In Situ Observations ◽

Nutrient Variability

Abstract. The Western MEDiterranean Sea BioGeochemical Climatology (BGC-WMED) presented here is a product derived from in situ observations. Annual mean gridded nutrient fields for the period 1981–2017, and its sub-periods 1981–2004 and 2005–2017, on a horizontal 1/4° × 1/4° grid have been produced. The biogeochemical climatology is built on 19 depth levels and for the dissolved inorganic nutrients nitrate, phosphate and orthosilicate. To generate smooth and homogeneous interpolated fields, the method of the Variational Inverse Model (VIM) was applied. A sensitivity analysis was carried out to assess the comparability of the data product with the observational data. The BGC-WMED has then been compared to other available data products, i.e. the medBFM biogeochemical reanalysis of the Mediterranean Sea and the World Ocean Atlas18 (WOA18) (its biogeochemical part). The BGC-WMED product supports the understanding of inorganic nutrient variability in the western Mediterranean Sea, in space and in time, but can also be used to validate numerical simulations making it a reference data product.

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Climatological distribution of dissolved inorganic nutrients in the western Mediterranean Sea (1981–2017)

Earth System Science Data ◽

10.5194/essd-13-5915-2021 ◽

2021 ◽

Vol 13 (12) ◽

pp. 5915-5949

Author(s):

Malek Belgacem ◽

Katrin Schroeder ◽

Alexander Barth ◽

Charles Troupin ◽

Bruno Pavoni ◽

...

Keyword(s):

Mediterranean Sea ◽

World Ocean ◽

Western Mediterranean ◽

Inorganic Nutrients ◽

Data Product ◽

Western Mediterranean Sea ◽

Dissolved Inorganic Nutrients ◽

World Ocean Atlas ◽

Nutrient Variability

Abstract. The Western MEDiterranean Sea BioGeochemical Climatology (BGC-WMED, https://doi.org/10.1594/PANGAEA.930447) (Belgacem et al., 2021) presented here is a product derived from quality-controlled in situ observations. Annual mean gridded nutrient fields for the period 1981–2017 and its sub-periods 1981–2004 and 2005–2017 on a horizontal 1/4∘ × 1/4∘ grid have been produced. The biogeochemical climatology is built on 19 depth levels and for the dissolved inorganic nutrients nitrate, phosphate and orthosilicate. To generate smooth and homogeneous interpolated fields, the method of the variational inverse model (VIM) was applied. A sensitivity analysis was carried out to assess the comparability of the data product with the observational data. The BGC-WMED was then compared to other available data products, i.e., the MedBFM biogeochemical reanalysis of the Mediterranean Sea and the World Ocean Atlas 2018 (WOA18) (its biogeochemical part). The new product reproduces common features with more detailed patterns and agrees with previous records. This suggests a good reference for the region and for the scientific community for the understanding of inorganic nutrient variability in the western Mediterranean Sea, in space and in time, but our new climatology can also be used to validate numerical simulations, making it a reference data product.

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Interactive comment on “In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013” by Jean-Baptiste Renard et al.

10.5194/acp-2017-720-rc2 ◽

2017 ◽

Author(s):

Anonymous

Keyword(s):

Mediterranean Sea ◽

Western Mediterranean ◽

In Situ Measurements ◽

Dust Particles ◽

Desert Dust ◽

Western Mediterranean Sea ◽

Aerosol Counter

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Coupling physics and biogeochemistry thanks to high resolution observations of the phytoplankton community structure in the North-Western Mediterranean Sea

10.5194/bg-2017-343 ◽

2017 ◽

Cited By ~ 1

Author(s):

Pierre Marrec ◽

Andrea M. Doglioli ◽

Gérald Grégori ◽

Mathilde Dugenne ◽

Alice Della Penna ◽

...

Keyword(s):

High Resolution ◽

Surface Waters ◽

Phytoplankton Community ◽

Western Mediterranean ◽

Fine Scale ◽

Phytoplankton Community Structure ◽

The North ◽

Cold Core ◽

North Western

Abstract. Fine-scale physical structures and ocean dynamics strongly influence and regulate biogeochemical and ecological processes. These processes are particularly challenging to describe and understand because of their ephemeral nature. The OSCAHR (Observing Submesoscale Coupling At High Resolution) campaign has been conducted in fall 2015 in which, a fine-scale structure in the North Western Mediterranean Ligurian subbasin was pre-identified using both satellite and numerical modeling data. Along the ship track, various variables were measured at the surface (temperature, salinity, chlorophyll-a and nutrients concentrations) with ADCP current velocity. We also deployed a new model of CytoSense automated flow cytometer (AFCM) optimized for small and dim cells, for near real-time characterization of surface phytoplankton community structure of surface waters with a spatial resolution of few km and a hourly temporal resolution. For the first time with this type of AFCM we were able to resolve Prochlorococcus and Synechococcus picocyanobacteria. The vertical physical dynamics and biogeochemical properties of the studied area were investigated by continuous high resolution CTD profiles thanks to a moving vessel profiler (MVP) during the vessel underway associated to a 1-m vertical resolution pumping system deployed during fixed stations. The observed fine-scale feature presented a cyclonic structure with a relatively cold core surrounded by warmer waters. Surface waters were totally depleted in nitrate and phosphate. In addition to the doming of the isopycnals by the cyclonic circulation, an intense wind event induced Ekman pumping. The upwelled subsurface cold nutrient-rich water fertilized surface waters, characterized by an increase in Chl-a concentration. Prochlorococcus, pico- and nano-eukaryotes were more abundant in cold core waters while Synechococcus dominated in warm boundary waters. Nanoeukaryote were the main contributors (> 50 %) in terms of pigment content (FLR) and biomass. Biological observations based on the mean cell's red fluorescence recorded by AFCM combined with physical properties of surface waters suggest a distinct origin for two warm boundary waters. Finally, the application of a matrix growth population model based on high-frequency AFCM measurements in warm boundary surface waters provides estimates of in-situ growth rate and apparent net primary production for Prochlorococcus (μ = 0.21 d−1, NPP = 0.11 mgC m−3 d−1) and Synechococcus (μ = 0.72 d−1, NPP = 2.68 mgC m−3 d−1), which corroborate their opposite surface distribution pattern. The innovative adaptive strategy applied during OSCAHR with a combination of several multidisciplinary and complementary approaches involving high-resolution in-situ observations and sampling, remote-sensing and model simulations provided a deeper understanding of the marine biogeochemical dynamics through the first trophic levels.

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Inventory and the biogeographical affinities of Annelida Polychaeta in theAlgerian coastline (Western Mediterranean)

Mediterranean Marine Science ◽

10.12681/mms.20408 ◽

2020 ◽

Vol 21 (1) ◽

pp. 157

Author(s):

ALI BAKALEM ◽

PATRICK GILLET ◽

JEAN-PHILIPPE PEZY ◽

JEAN-CLAUDE DAUVIN

Keyword(s):

Mediterranean Sea ◽

World Ocean ◽

Aegean Sea ◽

Western Mediterranean ◽

The Black Sea ◽

Polychaete Species ◽

Western Mediterranean Sea ◽

Atlantic Origin ◽

Algerian Coast ◽

The Mediterranean

The data analyzed to inventory of all polychaetes in Algerian waters make it possible to estimate the diversity of this group to 534 species. The most diversified families are Syllidae (66 species), Spionidae (37 species) and Terebellidae (27 species).The presence of these listed species along the Algerian coast is compared with their occurrence in nine other areas of the Mediterranean Sea, in the Black Sea and in four other areas of the World Ocean. Comparison are also made with respect to the indications of the biogeographical origin for each species. The polychaete fauna of the Algerian coast is among the richest of the Mediterranean Sea and comparable to that reported for the French Mediterranean continental shelf and the Aegean Sea, but higher that that found in the bordering coastlines of Morocco and Tunisia. Most of the species have an Atlantic origin and are present in the western Mediterranean Sea; this inventory includes eight Non-Indigenous Polychaete Species in the Algerian waters.

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