The carbonate system variability and acidification process remain little understood in the coastal ocean of Cameroon. The aim of this study was to assess the variability of the carbonate system in a portion of the southern coast of Cameroon, and the influence of local seawater physicochemical and biological properties on keys parameters of this system. The study was carried out at three fixed sampling stations (Bp, Kb, and Eb), from September 2021 to August 2022 involving all the seasons encountered in the study area. The carbonate system was determined from Total alkalinity (TA), pH, temperature and salinity, using the CO2SYS_xls program. In addition, nutrients (nitrate, nitrite, phosphate and nitrogen ammonia) and chlorophyll-a data were collected simultaneously at each station. The results showed a high variability of the carbonate system parameters on both temporal and spatial scale. TA and bicarbonate ions (
) were significantly different between the large rainy season (LRS) and small rainy season (SRS), while
and
partial pressure (
) were significantly different between Kb and Eb sampling stations (p-value < 0.05). The critical thresholds for ocean acidification (OA) seems to not been reached in the southern coastal ocean of Cameroon, given the means values of pH (8.14 ± 0.17), aragonite (3.31 ± 1.3 ?) and calcite (5.3 ± 2.05 ?) saturation states obtained. Salinity appears as the main driver of the variability of TA in the study area, while, nitrogen ammonia and the dissolved carbon dioxide from the degradation of organic matter, respiration and atmospheric absorption, appears as the drivers of pH variation. The large rainy season (LRS) seems to be the most critical period for OA sensitive organisms, while the Bp station looks most vulnerable.
References
[1]
Millero, F.J. (2000) The Carbonate System in Marine Environments. In: Gianguzza, A., Pelizetti, E. and Sammartano, S., Eds., Chemical Processes in Marine Environments, Springer, 9-41. https://doi.org/10.1007/978-3-662-04207-6_2
[2]
Cai, W., Xu, Y., Feely, R.A., Wanninkhof, R., Jönsson, B., Alin, S.R., etal. (2020) Controls on Surface Water Carbonate Chemistry along North American Ocean Margins. NatureCommunications, 11, Article No. 2691. https://doi.org/10.1038/s41467-020-16530-z
[3]
IOC-UNESCO (2022) State of the Ocean Report, Pilot Edition. IOC-UNESCO, Report No. IOC Technical Series, 173.
[4]
Von Schuckmann, K., Moreira, L., Grégoire, M., Marcos, M., Staneva, J., Brasseur, P., et al. (2024) 8th Edition of the Copernicus Ocean State Report (OSR8). Copernicus GmbH. https://doi.org/10.5194/sp-4-osr8
[5]
Gattuso, J.P. and Hansson, L. (2011) Ocean Acidification. Oxford University Press. https://doi.org/10.1093/oso/9780199591091.001.0001
[6]
Stark, J.S., Roden, N.P., Johnstone, G.J., Milnes, M., Black, J.G., Whiteside, S., etal. (2018) Carbonate Chemistry of an In-Situ Free-Ocean CO2 Enrichment Experiment (antFOCE) in Comparison to Short Term Variation in Antarctic Coastal Waters. ScientificReports, 8, Article No. 2816. https://doi.org/10.1038/s41598-018-21029-1
[7]
Aze, T., Barry, J., Bellerby, R. and Secretariat of the Convention on Biological Diversity (2014) An Updated Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. CBD Technical Series No. 75.
[8]
Hurd, C.L., Lenton, A., Tilbrook, B. and Boyd, P.W. (2018) Current Understanding and Challenges for Oceans in a Higher-CO2 World. NatureClimateChange, 8, 686-694. https://doi.org/10.1038/s41558-018-0211-0
[9]
Leung, J.Y.S., Zhang, S. and Connell, S.D. (2022) Is Ocean Acidification Really a Threat to Marine Calcifiers? A Systematic Review and Meta‐analysis of 980+ Studies Spanning Two Decades. Small, 18, Article ID: 2107407. https://doi.org/10.1002/smll.202107407
[10]
Intergovernmental Panel on Climate Change (IPCC) (2019) The Ocean and Cryosphere in a Changing Climate: Special Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. https://doi.org/10.1017/9781009157964
[11]
McGarry, K., Siedlecki, S.A., Salisbury, J. and Alin, S.R. (2021) Multiple Linear Regression Models for Reconstructing and Exploring Processes Controlling the Carbonate System of the Northeast US from Basic Hydrographic Data. JournalofGeophysicalResearch:Oceans, 126, e2020JC016480. https://doi.org/10.1029/2020jc016480
[12]
McCutcheon, M.R., Yao, H., Staryk, C.J. and Hu, X. (2021) Temporal Variability and Driving Factors of the Carbonate System in the Aransas Ship Channel, TX, USA: A Time Series Study. Biogeosciences, 18, 4571-4586. https://doi.org/10.5194/bg-18-4571-2021
[13]
Cai, W., Hu, X., Huang, W., Murrell, M.C., Lehrter, J.C., Lohrenz, S.E., etal. (2011) Acidification of Subsurface Coastal Waters Enhanced by Eutrophication. NatureGeoscience, 4, 766-770. https://doi.org/10.1038/ngeo1297
[14]
Morrell, B. (2019) Coastal Ocean Acidification: Carbonate Chemistry and Ecosystem Effects. EncyclopediaofOceanSciences, 1, 671-674. https://doi.org/10.1016/b978-0-12-409548-9.11289-8
[15]
Grear, J.S., Rynearson, T.A., Montalbano, A.L., Govenar, B. and Menden-Deuer, S. (2017) pCO2 Effects on Species Composition and Growth of an Estuarine Phytoplankton Community. Estuarine, CoastalandShelfScience, 190, 40-49. https://doi.org/10.1016/j.ecss.2017.03.016
[16]
Pajusalu, L., Dupont, S., Lainela, S. and Martin, G. (2019) Ocean Acidification Research in Estonia: Challenges and Opportunities. ProceedingsoftheEstonianAcademyofSciences, 68, 22-31. https://doi.org/10.3176/proc.2019.1.05
Lefèvre, N. (2009) Low CO2 Concentrations in the Gulf of Guinea during the Upwelling Season in 2006. MarineChemistry, 113, 93-101. https://doi.org/10.1016/j.marchem.2009.01.001
[19]
Koffi, K.U., Konan, E.S., Hassoun, A.E.R. and Kouadio, Y. (2024) Relationship between the Carbonate System and Phytoplankton Community in the Gulf of Guinea-Africa. FrontiersinMarineScience, 11, Article 1286338. https://doi.org/10.3389/fmars.2024.1286338
[20]
Koffi, K.U. (2014) Distribution des paramètres du carbone et du flux de CO2 à l’interface air-mer dans l’Est de l’Atlantique tropical. Université Pierre et Marie Curie-Paris VI, Université de Cocody Abidjan. Université De Cocody Abidjan.
[21]
Kwame Kpaliba, R. and Bawa, M. (2022) Variability of Carbonate Chemistry of Seawater of the Central Atlantic Coastline of Ghana. Journal of Phase Change Material, 2, 12-23.
[22]
Tilbrook, B., Jewett, E.B., DeGrandpre, M.D., Hernandez-Ayon, J.M., Feely, R.A., Gledhill, D.K., etal. (2019) An Enhanced Ocean Acidification Observing Network: From People to Technology to Data Synthesis and Information Exchange. FrontiersinMarineScience, 6, Article 337. https://doi.org/10.3389/fmars.2019.00337
[23]
Bilounga, U.J.F., Onana, F.M. and Efole E., T. (2022) Potential Impacts of Ocean Acidification in Cameroon Marine and Coastal Ecosystems (Central Africa). AcademiaLetters. https://doi.org/10.20935/al1482
[24]
Molua, E. (2006) Climatic Trends in Cameroon: Implications for Agricultural Management. ClimateResearch, 30, 255-262. https://doi.org/10.3354/cr030255
[25]
Pouokam, G. and Lemnuy, W.B. (2012) Cameroon Climate Compatible Development: Cameroon Case Study. https://doi.org/10.13140/RG.2.1.2202.0326
[26]
climate-data.org (2019) Kribi Climate: Average Temperature, Weather by Month, Kribi Water Temperature.
[27]
Onguene, R., Pemha, E., Lyard, F., Du-Penhoat, Y., Nkoue, G., Duhaut, T., etal. (2015) Overview of Tide Characteristics in Cameroon Coastal Areas Using Recent Observations. OpenJournalofMarineScience, 5, 81-98. https://doi.org/10.4236/ojms.2015.51008
[28]
Yuan, X., Zhang, B., Liang, R., Wang, R. and Sun, Y. (2020) Environmental Impact of the Natural Gas Liquefaction Process: An Example from China. AppliedSciences, 10, Article 1701. https://doi.org/10.3390/app10051701
[29]
Ayissi, I., Aksissou, M., Tiwari, M. and Fretey, J. (2014) Caractérisation des habitats benthiques et ponte des tortues marines autour du parc national de Campo-Ma’an (Cameroun). InternationalJournalofBiologicalandChemicalSciences, 7, 1820-1828. https://doi.org/10.4314/ijbcs.v7i5.3
[30]
Esri National Geographic (2025) NatGeo_World_Map (MapServer).
[31]
Dickson, A.G., Sabine, C.L., Christian, J.R. and Bargeron, C.P. (2007) Guide to Best Practices for Ocean CO2 Measurements. North Pacific Marine Science Organization.
[32]
Pimenta, A. and Grear, J. (2018) Guidelines for Measuring Changes in Seawater pH and Associated Carbonate Chemistry in Coastal Environments of the Eastern United States. EPA/600/R-17/483, 59.
[33]
Dickson, A. (2010) Standards for Ocean Measurements. Oceanography, 23, 34-47. https://doi.org/10.5670/oceanog.2010.22
[34]
Fassbender, A.J., Sabine, C.L. and Feifel, K.M. (2016) Consideration of Coastal Carbonate Chemistry in Understanding Biological Calcification. Geophysical Research Letters, 43, 4467-4476. https://doi.org/10.1002/2016gl068860
[35]
Dickson, A.G. (2010) Part 1: Seawater Carbonate Chemistry. Guide to Best Practices for Ocean Acidification Research and Data Reporting. Publications Office of the European Union, 36.
[36]
ICOS (Ocean Thematic Centre) (2018) Calculation Uncertainty of pCO2 from Discrete Samples of TA, DIC, and pH.
[37]
Pierrot, D., Lewis, E. and Wallace, D.W.R. (2006) MS Excel Program Developed for CO2 System Calculations. Carbon Dioxide Information Analysis Center (CDIAC) Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee.
[38]
Millero, F.J., Graham, T.B., Huang, F., Bustos-Serrano, H. and Pierrot, D. (2006) Dissociation Constants of Carbonic Acid in Seawater as a Function of Salinity and Temperature. MarineChemistry, 100, 80-94. https://doi.org/10.1016/j.marchem.2005.12.001
[39]
Dickson, A.G. (1990) Standard Potential of the Reaction: AgCl(s) + 12H2(g) = Ag(s) + HCl(aq), and and the Standard Acidity Constant of the Ion HSO4− in Synthetic Sea Water from 273.15 to 318.15 K. TheJournalofChemicalThermodynamics, 22, 113-127. https://doi.org/10.1016/0021-9614(90)90074-z
[40]
Uppström, L.R. (1974) The Boron/Chlorinity Ratio of Deep-Sea Water from the Pacific Ocean. DeepSeaResearchandOceanographicAbstracts, 21, 161-162. https://doi.org/10.1016/0011-7471(74)90074-6
[41]
R Core Team (2024) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing.
[42]
McGrath, T., McGovern, E., Gregory, C. and Cave, R.R. (2019) Local Drivers of the Seasonal Carbonate Cycle across Four Contrasting Coastal Systems. RegionalStudiesinMarineScience, 30, Article ID: 100733. https://doi.org/10.1016/j.rsma.2019.100733
[43]
Jones, E.M., Renner, A.H.H., Chierici, M., Wiedmann, I., Lødemel, H.H. and Biuw, M. (2020) Seasonal Dynamics of Carbonate Chemistry, Nutrients and CO2 Uptake in a Sub-Arctic Fjord. ElemSciAnth, 8, Article 41. https://doi.org/10.1525/elementa.438
[44]
Baldry, K., Hardman-Mountford, N. and Greenwood, J. (2017) Estimating Total Alkalinity for Coastal Ocean Acidification Monitoring at Regional to Continental Scales in Australian Coastal Waters. Biogeosciences Discussions.
[45]
Jiang, Z., Tyrrell, T., Hydes, D.J., Dai, M. and Hartman, S.E. (2014) Variability of Alkalinity and the Alkalinity‐Salinity Relationship in the Tropical and Subtropical Surface Ocean. GlobalBiogeochemicalCycles, 28, 729-742. https://doi.org/10.1002/2013gb004678
[46]
Koziorowska-Makuch, K., Szymczycha, B., Thomas, H. and Kuliński, K. (2023) The Marine Carbonate System Variability in High Meltwater Season (Spitsbergen Fjords, Svalbard). ProgressinOceanography, 211, Article ID: 102977. https://doi.org/10.1016/j.pocean.2023.102977
[47]
Fassbender, A.J., Alin, S.R., Feely, R.A., Sutton, A.J., Newton, J.A. and Byrne, R.H. (2016) Estimating Total Alkalinity in the Washington State Coastal Zone: Complexities and Surprising Utility for Ocean Acidification Research. EstuariesandCoasts, 40, 404-418. https://doi.org/10.1007/s12237-016-0168-z
[48]
Millero, F.J., Lee, K. and Roche, M. (1998) Distribution of Alkalinity in the Surface Waters of the Major Oceans. MarineChemistry, 60, 111-130. https://doi.org/10.1016/s0304-4203(97)00084-4
[49]
Wallace, R.B., Baumann, H., Grear, J.S., Aller, R.C. and Gobler, C.J. (2014) Coastal Ocean Acidification: The Other Eutrophication Problem. Estuarine, Coastal and ShelfScience, 148, 1-13. https://doi.org/10.1016/j.ecss.2014.05.027
[50]
Friedrich, T., Timmermann, A., Abe-Ouchi, A., Bates, N.R., Chikamoto, M.O., Church, M.J., etal. (2012) Detecting Regional Anthropogenic Trends in Ocean Acidification against Natural Variability. NatureClimateChange, 2, 167-171. https://doi.org/10.1038/nclimate1372
[51]
Thor, P. and Dupont, S. (2017) Ocean Acidification. In: Salomon, M. and Markus, T., Eds., HandbookonMarineEnvironmentProtection, Springer, 375-394. https://doi.org/10.1007/978-3-319-60156-4_19
[52]
Ebango Ngando, N., Regis Christian, M.N., Song, L.M., Achille, N.P., Li, C.H. AND Minette, T.E. (2021) Catch Statistics from Artisanal Marine Fishing: A Case of the South Coast. AfricanJournalofFisheriesSciences, 9, 1-13.
[53]
Le Quesne, W.J.F. and Pinnegar, J.K. (2011) The Potential Impacts of Ocean Acidification: Scaling from Physiology to Fisheries: Potential Acidification Impacts on Fisheries. FishandFisheries, 13, 333-344. https://doi.org/10.1111/j.1467-2979.2011.00423.x
[54]
Mostofa, K.M.G., Liu, C., Zhai, W., Minella, M., Vione, D., Gao, K., etal. (2016) Reviews and Syntheses: Ocean Acidification and Its Potential Impacts on Marine Ecosystems. Biogeosciences, 13, 1767-1786. https://doi.org/10.5194/bg-13-1767-2016
[55]
Widdicombe, S., Isensee, K., Artioli, Y., Gaitán-Espitia, J.D., Hauri, C., Newton, J.A., et al. (2023) Unifying Biological Field Observations to Detect and Compare Ocean Acidification Impacts across Marine Species and Ecosystems: What to Monitor and Why. OceanScience, 19, 101-119. https://doi.org/10.5194/os-19-101-2023