Spatio-temporal assessment of the impacts of the trends in physical and biogeochemical parameters on the primary production of the Gulf of Guinea

Dahunsi, Adeola M.; Oyikeke, Tolulope S.; Abdulfatai, Mujeeb A.; Afolabi, Lateef A.

doi:10.1016/j.heliyon.2023.e13047

Cited by 3 publications

(1 citation statement)

References 56 publications

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“…Understanding the spatial and temporal variability in phytoplankton community structure is essential for assessing their ecological significance and their impact on the broader marine food web. Due to the ecological importance of phytoplankton populations in the marine environment, and given the harmful nature of certain species, several studies have been carried out to investigate these organisms and understand how their growth is influenced by their respective environment (Glibert et al, 2014;Edworthy et al, 2022;Dahunsi et al, 2023). Some studies, using model simulations, have predicted the increase of harmful algal blooms (HABs) in response to global warming (Glibert et al, 2014;Moore et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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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Unravelling nutrient dynamics and mixed layer depth variability in the equatorial Atlantic: insights from 10°W meridional section monitoring

Kouame,

N’Guessan,

Kouassi

et al. 2024

Front. Mar. Sci.

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The ocean, a pivotal component of the Earth’s climate system, exerts a profound global influence through intricate physical and biological interactions within its surface layer. This interplay centers around the mixed layer (ML), integral for energy exchange driven by oceanic currents. An essential regulatory function of the ocean involves orchestrating the distribution of chemical elements, with nitrate assuming a pivotal role in oceanic primary production. Nutrient availability, a cornerstone of primary production, hinges on the mixed layer depth (MLD) dynamics, modulated by many mechanisms, including upwelling and convection. This study unravels the interplay between nutrient variability and MLD depth, focusing on the Gulf of Guinea (GG) region in the equatorial Atlantic. Characterization of the study area reveals distinctive sea surface temperature (SST), salinity (SSS), and current patterns. The South Equatorial Undercurrent (SEUC) and Equatorial Undercurrent (EUC) play vital roles in surface nutrient transport. Nitrate distribution unveils latitudinal variations, exhibiting pronounced enrichment during boreal summer and winter. The equatorial region experiences a strengthening of MLDs from 10.5 to 35.33 m in summer, which increases the nitrate input from 0 to 2.06 mmol m-3 in the surface layers in the mixed layer. In contrast, boreal winters experience more intense MLDs that vary between 20.5 and 64.50 m, supporting high nitrate concentrations of 2.96 to 7.49 mmol m-3, challenging previous hypotheses. This equatorial enrichment is supported by low nitracline ranging from 5.47 to 46.19 m. Beyond the equator, the subequatorial and subtropical regions, despite the observed deepening of the ML, present low nitrate concentrations (less than 0.5 mmol m-3) with a nitracline that does not reach the ML. However, at 6°S and 9°S, a respective increase in nitrate content of 0.66 mmol m-3 and 1.2 mmol m-3 influenced by internal waves, advection and surface currents is observed. Temperature, salinity, and atmospheric fluxes shape nutrient distribution and primary production dynamics. These findings illuminate the intricate relationships between oceanographic processes, nutrient availability, and marine ecosystem productivity. A holistic understanding is crucial for sustainable resource management and fisheries in the equatorial Atlantic and beyond.

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Interannual and Seasonal Variability of CO2 Parameters in the Tropical Atlantic Ocean

Bonou,

Dossa,

Dahunsi

et al. 2024

JMSE

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This study examined the carbon cycling dynamics in the tropical Atlantic Ocean from 1985 to 2023, focusing on factors influencing the surface partial pressure of CO2 (pCO2), freshwater input, total alkalinity (ALK), total dissolved carbon (TCO2), and pH levels. The time series data revealed significant trends, with average pCO2 concentrations rising from approximately 350 μatm in the early 1990s to over 400 μatm by 2023. The TCO2 levels increased from about 2000 μmol/kg to 2200 μmol/kg, while ALK rose from approximately 2300 μmol/kg to 2500 μmol/kg. This increase highlights the ocean’s role as a carbon sink, particularly in areas with high biological productivity and upwelling where TCO2 also rose. This study employed Empirical Orthogonal Functions (EOFs) to identify variability modes and understand spatial patterns of pCO2. Freshwater dynamics significantly affect TCO2 concentrations, particularly in coastal regions, where pH can shift from 8.2 to 7.9, exacerbating acidification. Rising sea surface temperatures have been linked to elevated pCO2 values. These findings support the need for ongoing monitoring and effective management strategies to mitigate the impacts of climate change and ensure the sustainability of marine resources. This study documented the long-term trends in tropical Atlantic CO2 parameters linked to the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO).

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Spatio-temporal assessment of the impacts of the trends in physical and biogeochemical parameters on the primary production of the Gulf of Guinea

Cited by 3 publications

References 56 publications

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

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

Unravelling nutrient dynamics and mixed layer depth variability in the equatorial Atlantic: insights from 10°W meridional section monitoring

Interannual and Seasonal Variability of CO2 Parameters in the Tropical Atlantic Ocean

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