On the Nutrient distribution and phytoplankton biomass in the Gulf of Guinea equatorial band as inferred from In-situ measurements

Nubi, Olubunmi Ayoola; Edokpayi, CA; Hounkonnou, Mahouton Norbert

doi:10.5897/joms2016.0124

Cited by 4 publications

(24 citation statements)

References 19 publications

(30 reference statements)

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“…2a-c. Results are close to the distributions during the cold and warm seasons described along 4 • W in the 1970s and 1980s (Voituriez and Herbland, 1977;Oudot, 1983;Monger et al, 1997) and along 10 • W during the June and September 2005 EGEE cruises (Nubi et al, 2016). During the warm and low-productivity season, the low-chlorophyll ( Fig.…”

Section: Observed Seasonal Cyclessupporting

confidence: 81%

“…The coincidence of high chlorophyll concentrations with meridional oscillations of currents associated with an anticyclonic eddy observed during a summer cruise in the equatorial Atlantic (Morlière et al, 1994) strongly suggests that TIWs may also influence ecosystems. This was further settled with synoptic observations of physical (temperature, salinity, current) and ecosystem (nitrate, chlorophyll, zooplankton, micronekton) tracers in a tropical instability vortex (Menkes et al, 2002): their horizontal and vertical structures were highly coherent.…”

Section: Intraseasonal Processesmentioning

confidence: 97%

“…The impact of tropical instability waves (TIWs) on the ecosystem of the Atlantic cold tongue was proposed by Morlière et al (1994) and Menkes et al (2002). Although there is a debate about the influence of TIWs on the nutrient budget in the equatorial Pacific (Strutton et al, 2001;Gorgues et al, 2005), no such study is available in the equatorial Atlantic where TIWs dominate the intraseasonal variability in the western and central basins and wind-forced waves dominate in the east (Athié and Marin, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Radenac¹,

Jouanno²,

Tchamabi³

et al. 2020

Biogeosciences

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Abstract. Ocean color observations show semiannual variations in chlorophyll in the Atlantic cold tongue with a main bloom in boreal summer and a secondary bloom in December. In this study, ocean color and in situ measurements and a coupled physical–biogeochemical model are used to investigate the processes that drive this variability. Results show that the main phytoplankton bloom in July–August is driven by a strong vertical supply of nitrate in May–July, and the secondary bloom in December is driven by a shorter and moderate supply in November. The upper ocean nitrate balance is analyzed and shows that vertical advection controls the nitrate input in the equatorial euphotic layer and that vertical diffusion and meridional advection are key in extending and shaping the bloom off Equator. Below the mixed layer, observations and modeling show that the Equatorial Undercurrent brings low-nitrate water (relative to off-equatorial surrounding waters) but still rich enough to enhance the cold tongue productivity. Our results also give insights into the influence of intraseasonal processes in these exchanges. The submonthly meridional advection significantly contributes to the nitrate decrease below the mixed layer.

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Section: Observed Seasonal Cyclessupporting

confidence: 81%

Section: Intraseasonal Processesmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Radenac¹,

Jouanno²,

Tchamabi³

et al. 2020

Biogeosciences

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“…Atlantic equatorial upwelling has been considered of great significance for the important role it plays in biological productivity of this region (Voituriez and Herbland, 1977;Grodsky et al, 2008;Nubi et al, 2016). In the boreal summer, equatorial upwelling is associated with the Atlantic cold tongue (ACT) that appears near 10°W (Caniaux et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Thermocline shoals dramatically in the equatorial tropical Atlantic in response to seasonal intensification of the trade winds in the western tropical Atlantic, and the dynamic uplift of the thermocline combined with mixing by local winds has been suggested to be the principal mechanism controlling vertical nutrient fluxes (Longhurst, 1993;Bourlès et al, 2002;Nubi et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Spatial variability in autumnal equatorial upwelling intensity within the Gulf of Guinea as inferred from in situ measurements

Nubi¹,

O.O²,

Bonou³

2019

J. Oceanogr. Mar. Sci.

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In attempt to study the spatial differences in autumnal equatorial upwelling intensity relative to bioproductivity in the eastern equatorial Atlantic, oceanographic in situ data along regions 10°W, 0°E, 2.5°E and 6°E, collected in the Gulf of Guinea during autumn cruise carried out in September 2007 were analyzed. The surface mean values for temperature along 10°W, 0°E, 2.5°E and 6°E are 25.02, 26.15, 26.88 and 25.60°C, respectively. There was eastward weakening of the equatorial undercurrent from 10°W until its complete disappearance at 6°E. The highest concentration of nitrate recorded at the surface at 10°W was attributed to the shoaling pycnocline observed at this region. The surface mean values for nitrate along 10°W, 0°E, 2.5°E and 6°E are 0.37, 0.09, 0.04 and 0.04 μmol.kg-1 , respectively. In response to the shoaling pycnocline at 10°W, corresponding to the highest concentration of chlorophyll fluorescence was recorded at this region. The surface mean values for chlorophyll fluorescence along 10°W, 0°E, 2.5°E and 6°E are 0.34, 0.05, 0.07 and 0.08 mg/m 3 , respectively. Contributions to equatorial upwelling by the equatorial undercurrent were the strongest and mostly expressed along 10°W. Profiles for apparent oxygen utilization and chlorophyll fluorescence gave indications that biological response to surface enrichments within the equatorial bands was highest at region 10°W. Vertical sections for studied parameters were unsuggestive of westward advection from 6°E to 10°W within the equatorial band, and this signifies the important role of vertical processes in equatorial enrichment at 10°W during boreal autumn.

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Relationship between the carbonate system and phytoplankton community in the Gulf of Guinea-Africa

Koffi,

Konan,

Hassoun

et al. 2024

Front. Mar. Sci.

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We carried out measurements of the CO2 system parameters to evaluate the impact of carbonate and nutrients’ chemistry on phytoplankton populations in the Gulf of Guinea (GoG). The seasonal variations of the CO2 system parameters (fCO2, DIC, pH and TA) along with nitrates and phosphates were quantified weekly at surface (between 0 and 5 m depth) (5.57°N - 4.57°W) in the GoG from May to December 2020. Seawater pH varied widely during the study period, ranging between 8.10-8.35 pH units; DIC and TA varied between 1810 and 2094 μmol kg-1, and between 2051 and 2216 μmol-1 respectively. DIC peaks coincided with the high upwelling period (August and September). For phytoplankton, a total of 60 species were found belonging to four taxonomic phyla: Bacillariophyta, Dinophyta, Chlorophyta and Dictyochophyta. The highest number of phytoplanktonic species were recorded for Bacillariophyta phylum with 36 species (60%). The phylum Dinophyta comprised 22 taxa (36%) and Chlorophyta and Dictyochophyta recorded only one species (2%). The highest specific diversities were observed in August and September with 29 and 26 taxa respectively and the lowest was found in October-November (5 taxa) and December (one taxa). Bacillariophyta and Dinophyta appeared throughout the entire study period. The only species for Chlorophyta phylum appeared in June and July and the Dictyochophyta’s one in May, July and August. In general, the physical (SST, SSS) and chemical (TA, DIC, pH) parameters influenced less than 50% of the phytoplankton population in the coastal area of the GoG. Our study shows that Bacillariophyta population grows up when the physicochemical parameters’ variability increase.

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On the Nutrient distribution and phytoplankton biomass in the Gulf of Guinea equatorial band as inferred from In-situ measurements

Cited by 4 publications

References 19 publications

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Spatial variability in autumnal equatorial upwelling intensity within the Gulf of Guinea as inferred from in situ measurements

Relationship between the carbonate system and phytoplankton community in the Gulf of Guinea-Africa

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