Articles | Volume 23, issue 9
https://doi.org/10.5194/bg-23-3253-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-23-3253-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
11 May 2026
Research article |
| 11 May 2026
| 11 May 2026
Benthic phosphorus cycling in the northern Benguela upwelling system: excess P supply and altered pelagic nutrient stoichiometry
Department of Ocean Systems, Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 4, 1797 SZ `t Horntje, the Netherlands
Kristin A. Ungerhofer
Department of Ocean Systems, Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 4, 1797 SZ `t Horntje, the Netherlands
Darci Rush
Department of Microbiology and Marine Biogeochemistry, Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 4, 1797 SZ `t Horntje, the Netherlands
Gert-Jan Reichart
Department of Ocean Systems, Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 4, 1797 SZ `t Horntje, the Netherlands
Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, the Netherlands
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Nora Richter, Ellen C. Hopmans, Danica Mitrović, Pedro M. Raposeiro, Vítor Gonçalves, Ana C. Costa, Linda A. Amaral-Zettler, Laura Villanueva, and Darci Rush
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Rick Hennekam, Katharine M. Grant, Eelco J. Rohling, Rik Tjallingii, David Heslop, Andrew P. Roberts, Lucas J. Lourens, and Gert-Jan Reichart
Clim. Past, 18, 2509–2521, https://doi.org/10.5194/cp-18-2509-2022, https://doi.org/10.5194/cp-18-2509-2022, 2022
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The ratio of titanium to aluminum (Ti/Al) is an established way to reconstruct North African climate in eastern Mediterranean Sea sediments. We demonstrate here how to obtain reliable Ti/Al data using an efficient scanning method that allows rapid acquisition of long climate records at low expense. Using this method, we reconstruct a 3-million-year North African climate record. African environmental variability was paced predominantly by low-latitude insolation from 3–1.2 million years ago.
Carolien M. H. van der Weijst, Koen J. van der Laan, Francien Peterse, Gert-Jan Reichart, Francesca Sangiorgi, Stefan Schouten, Tjerk J. T. Veenstra, and Appy Sluijs
Clim. Past, 18, 1947–1962, https://doi.org/10.5194/cp-18-1947-2022, https://doi.org/10.5194/cp-18-1947-2022, 2022
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The TEX86 proxy is often used by paleoceanographers to reconstruct past sea-surface temperatures. However, the origin of the TEX86 signal in marine sediments has been debated since the proxy was first proposed. In our paper, we show that TEX86 carries a mixed sea-surface and subsurface temperature signal and should be calibrated accordingly. Using our 15-million-year record, we subsequently show how a TEX86 subsurface temperature record can be used to inform us on past sea-surface temperatures.
Carolien M. H. van der Weijst, Josse Winkelhorst, Wesley de Nooijer, Anna von der Heydt, Gert-Jan Reichart, Francesca Sangiorgi, and Appy Sluijs
Clim. Past, 18, 961–973, https://doi.org/10.5194/cp-18-961-2022, https://doi.org/10.5194/cp-18-961-2022, 2022
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A hypothesized link between Pliocene (5.3–2.5 million years ago) global climate and tropical thermocline depth is currently only backed up by data from the Pacific Ocean. In our paper, we present temperature, salinity, and thermocline records from the tropical Atlantic Ocean. Surprisingly, the Pliocene thermocline evolution was remarkably different in the Atlantic and Pacific. We need to reevaluate the mechanisms that drive thermocline depth, and how these are tied to global climate change.
Zoë R. van Kemenade, Laura Villanueva, Ellen C. Hopmans, Peter Kraal, Harry J. Witte, Jaap S. Sinninghe Damsté, and Darci Rush
Biogeosciences, 19, 201–221, https://doi.org/10.5194/bg-19-201-2022, https://doi.org/10.5194/bg-19-201-2022, 2022
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Anaerobic ammonium oxidation (anammox) is an important nitrogen-removal process in the ocean. We assess the distribution of bacteriohopanetetrol-x (BHT-x), used to trace past anammox, along a redox gradient in the water column of the Benguela upwelling system. BHT-x / BHT ratios of >0.18 correspond to the presence of living anammox bacteria and oxygen levels <50 μmol L−1. This allows for a more robust application of BHT-x to trace past marine anammox and deoxygenation in dynamic marine systems.
Alice E. Webb, Didier M. de Bakker, Karline Soetaert, Tamara da Costa, Steven M. A. C. van Heuven, Fleur C. van Duyl, Gert-Jan Reichart, and Lennart J. de Nooijer
Biogeosciences, 18, 6501–6516, https://doi.org/10.5194/bg-18-6501-2021, https://doi.org/10.5194/bg-18-6501-2021, 2021
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The biogeochemical behaviour of shallow reef communities is quantified to better understand the impact of habitat degradation and species composition shifts on reef functioning. The reef communities investigated barely support reef functions that are usually ascribed to conventional coral reefs, and the overall biogeochemical behaviour is found to be similar regardless of substrate type. This suggests a decrease in functional diversity which may therefore limit services provided by this reef.
Indah Ardiningsih, Kyyas Seyitmuhammedov, Sylvia G. Sander, Claudine H. Stirling, Gert-Jan Reichart, Kevin R. Arrigo, Loes J. A. Gerringa, and Rob Middag
Biogeosciences, 18, 4587–4601, https://doi.org/10.5194/bg-18-4587-2021, https://doi.org/10.5194/bg-18-4587-2021, 2021
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Organic Fe speciation is investigated along a natural gradient of the western Antarctic Peninsula from an ice-covered shelf to the open ocean. The two major fronts in the region affect the distribution of ligands. The excess ligands not bound to dissolved Fe (DFe) comprised up to 80 % of the total ligand concentrations, implying the potential to solubilize additional Fe input. The ligands on the shelf can increase the DFe residence time and fuel local primary production upon ice melt.
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Short summary
Element cycles in oxygen-depleted areas such as upwelling areas inform future deoxygenation scenarios. The Benguela upwelling system shows strong decoupling of nitrogen and phosphorus cycling due to seasonal shelf anoxia. Anaerobic processes result in pelagic nitrogen loss as N2. At the same time, sediments are rich in fish-derived and bacterial phosphorus, with high fluxes of excess phosphate, altering deep-water nitrogen:phosphorus ratios. Such alterations can affect ocean functioning.
Element cycles in oxygen-depleted areas such as upwelling areas inform future deoxygenation...
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