Royal Netherlands Institute for Sea Research
Phone number
+31 (0)222 36 9493
Ocean Systems (OCS)
Tenure track Scientist
  • Marine geochemistry
  • Paleoceanography
  • Paleoclimatology
  • XRF core scanning and LA-ICP-MS on sediments
  • Trace metal cycling in restricted basins
Trouw 9 november: Interview Rick Hennekam over kantelpunten zuurstofgebrek zeeen.

Dr. Rick Hennekam

Tenure track Scientist

Past climate and environmental change on short time scales

Paleoceanographer Rick Hennekam studies past changes in Earth’s climate and environment. “This kind of research may go back 2,5 billion years, through samples from ancient sea floors, that are now piled up on land in South Africa or Australia. I generally look at samples that are slightly younger of age and use ocean sediments as climatological and environmental archives. The cores we take by ship are often shorter than 20 metres, which limits the time interval within these archives to about a million year or so.”

Focused view on geological archives

“One of the aspects that I am interested in is the variability of dissolved oxygen concentrations over time. Large algal blooms result in oxygen loss. When these organisms die and decay within the water column it consumes oxygen and may cause anoxic (oxygen-free) conditions, especially in water bodies that have a layered structure. This so-called stratification happens when relatively warm and/or freshwater lies on top of relatively cold and/or saltwater. The different densities of these water masses cause stratification and hamper oxygen exchange between the top and lower water layers. The transition from oxygenated to oxygen-free conditions can be rather quick and, hence, it is important to know how, why, and where anoxic conditions occur. You’d even like to predict upcoming anoxic events.”

“Such research benefits from new technological advances that allow reconstructions of past oxygen conditions with unprecedented sampling resolutions. Only with enough “focus” on our geological records, you will be able to extract information that may help predict upcoming anoxic events. We recently discovered that dissolved oxygen levels start to sway slower and wider over time as an anoxic event approaches. Back in the day, a big volume of sediment sample allowed to reconstruct past oxygen levels with only a resolution of hundreds to even thousands of years. Now, with new analysis methods, we can take a much closer look and make reconstructions on much shorter time scales. We literally look at layers of millimetres thick, or even less, and reconstruct past oxygen levels from year to year.”

Human time scales

“With our novel analytical techniques, we introduced a more 'human time scale' in our research. We reconstruct the climate and environment on time intervals that we as humans can relate to, such as years to decades.  I also reconstruct conditions on short time scales in our more recent past. Not only the climate of thousands or millions of years ago but also the climate during our great, great, great grandfathers’ lives is worth reconstructing. These relatively recent climate and environmental archives often overlap with real instrumental data, allowing to produce reconstructions with unmatched fidelity. For example, I also look at the layers of corals that, like tree rings, tell us from season to season what the environmental conditions at a particular reef were. By trying to understand this recent past, we hope to better predict and understand the future.”

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Research interests

I'm a marine geochemist with a passion for paleoceanography and paleoclimatology. I am specialized in high-resolution geochemical analysis techniques: XRF core scanning of sediment cores and LA-ICP-MS line-scanning (e.g. of resin-embedded sediments). Topics of interest (selection): oxygen-depleted marine environments, Quaternary climate variability, anthropogenic climate change (with corals), ocean currents (e.g., Indonesian Throughflow), and sea level variability.

Getting ready to cut a piston core into several sections on R/V Pelagia.

Linked news

Thursday 29 June 2023
Vidi grants for regional sea levels and ocean tipping points
[Dutch follows English] Two NIOZ researchers will receive Vidi grants of 800,000 euros. The laureates are Dr Aimée Slangen, for solving the regional sea-level puzzle and Dr Rick Hennekam, for investigating tipping points in climate and ocean…
Thursday 30 March 2023
Rise of oxygen in early ocean due to wobbling Earth's axis
Nearly 2.5 billion years ago, seas on our planet alternately contained more or less oxygen, due to the slow "wobble" of the rotating Earth. This writes an international team of scientists, some affiliated with NIOZ and Utrecht University. "The fact…
Monday 28 November 2022
NWO grant for research project to understand Sargassum inundations in the Caribbean
Climate change or Natural Range Expansion? As of 2011, the Caribbean Sea regularly suffers from washed-up masses of seaweed, called Sargassum, that rot if left to accumulate on beaches and in harbors. As part of an international call, a Dutch-led…
Friday 29 July 2022
How coastal seas help the ocean in absorbing carbon dioxide from the atmosphere
The biologically productive North Sea impacts the global climate through exchange of carbon and nutrients with the Atlantic Ocean. A Dutch consortium of scientists will investigate how big this role of the North Sea really is. Under the leadership of…
Tuesday 07 June 2022
World Ocean Day 8th June 2022 | Thank you sea, and five challenges
June 8th is World Oceans Day: declared 30 years ago by the United Nations to draw attention to the importance of healthy oceans for a habitable planet Earth. In this short video from the Royal Netherlands Institute for Sea Research (NIOZ), we present…
Wednesday 24 January 2018
Koralen van 'Darwin' verklaren schommelingen in mondiale opwarmingssnelheid
De aarde warmt snel op door de menselijke uitstoot van broeikasgassen, maar ook natuurlijke factoren spelen een rol bij variaties in de opwarmingssnelheid. Metingen van de mondiale oppervlaktetemperaturen laten soms onderbrekingen zien in de…

Linked blogs

Monday 22 May 2023
NoSE expedition to the Norwegian Trench 26 May - 14 June 2023
The biologically productive North Sea impacts the global climate through exchange of carbon and nutrients with the Atlantic Ocean. The North Sea is a very productive coastal sea. A lot of carbon dioxide (CO2) can be taken up through physical,…
Monday 28 June 2021
NIOZ@SEA | IceAGE_KR Kolbeinsey Ridge expedition to hydrothermal vents near Iceland
The marine environment around Iceland with its submarine ridges provides an area perfectly suited for investigating evolution, ecological resilience, and the impact of climate change. The hydrothermal vent fields along the ridges are biologically and…
Tuesday 04 February 2020
NIOZ@SEA | GoM2020 expedition in the northern Gulf of Mexico
The mighty Mississippi river and its Atchafalaya branch bring in vast amounts of sediment material and dissolved nutrients into the northern Gulf of Mexico. By doing so, these rivers have an enormous impact on the chemistry and biology in the water…
Tuesday 26 February 2019
NIOZ@SEA | FUNAMOX expedition in the southeast Atlantic
Off the coast of southwest Africa, currents force cold deep waters full of essential elements required for ocean life to the surface. This so-called upwelling has enormous impacts on the chemistry and biology of the water and sediment. We are sailing…
Wednesday 29 March 2017
NIOZ@Sea: Black Sea cruise
This edition of NIOZ@Sea is a series of blogs from the Black Sea cruise of our scientists on board research vessel Pelagia. The Black Sea is the largest permanently stratified sea in the world. This is ideal to study the structure of microbial…

NIOZ publications

  • 2023
    Clarkson, M.O.; Sweere, T.C.; Chiu, C.F.; Hennekam, R.; Bowyer, F.; Wood, R.A. (2023). Environmental controls on very high δ238U values in reducing sediments: Implications for Neoproterozoic seawater records. Earth-Sci. Rev. 237: 104306.
    Frieling, J.; Mather, T.A.; März, C.; Jenkyns, H.C.; Hennekam, R.; Reichart, G.-J.; Slomp, C.P.; van Helmond, N.A.G.M. (2023). Effects of redox variability and early diagenesis on marine sedimentary Hg records. Geochim. Cosmochim. Acta 351: 78-95.
    Lantink, M.L.; Lenstra, W.K.; Davies, J.H.F.L.; Hennekam, R.; Martin, D.M.; Mason, P.R.D.; Reichart, G.-J.; Slomp, C.; Hilgen, F.J. (2023). Precessional pacing of early Proterozoic redox cycles. Earth Planet. Sci. Lett. 610: 118117.
    van Kemenade, Z.R.; Cutmore, A.; Hennekam, R.; Hopmans, E.C.; van der Meer, M.T.J.; Mojtahid, M.; Jorissen, F.; Bale, N.; Reichart, G.-J.; Sinninghe Damsté, J.S; Rush, D. (2023). Marine nitrogen cycling dynamics under altering redox conditions: Insights from deposition of sapropels S1 and the ambiguous S2 in the Eastern Mediterranean Sea. Geochim. Cosmochim. Acta 354: 197-210.
  • 2022
    Chiu, C.F.; Sweere, T.C.; Clarkson, M.O.; de Souza, G.F.; Hennekam, R.; Vance, D. (2022). Co-variation systematics of uranium and molybdenum isotopes reveal pathways for descent into euxinia in Mediterranean sapropels. Earth Planet. Sci. Lett. 585: 117527.
    Grant, K.M.; Amarathunga, U.; Amies, J.D.; Hu, P.; Qian, Y.; Penny, T.; Rodriguez-Sanz, L.; Zhao, X.; Heslop, D.; Liebrand, D.; Hennekam, R.; Westerhold, T.; Gilmore, S.; Lourens, L.J.; Roberts, A.P.; Rohling, E.J. (2022). Organic carbon burial in Mediterranean sapropels intensified during Green Sahara Periods since 3.2 Myr ago. Commun. Earth Environ. 3(1).
    Hennekam, R.; Grant, K.M.; Rohling, E.J.; Tjallingii, R.; Heslop, D.; Roberts, A.P.; Lourens, L.J.; Reichart, G.-J. (2022). Accurately calibrated X-ray fluorescence core scanning (XRF-CS) record of Ti ∕ Al reveals Early Pleistocene aridity and humidity variability over North Africa and its close relationship to low-latitude insolation. Clim. Past 18(11): 2509-2521.
    Wu, J.; Liu, Z.; Michard, A.; Tachikawa, K.; Filippidi, A.; He, Z.; Hennekam, R.; Yang, S.; Davies, G.R.; de Lange, G.J. (2022). Effect of barite-bound Sr on detrital Sr isotope systematics in marine sediments. Chem. Geol. 587: 120613.
  • 2021
    Clarkson, M.O.; Hennekam, R.; Sweere, T.C.; Andersen, M.B.; Reichart, G.-J.; Vance, D. (2021). Carbonate associated uranium isotopes as a novel local redox indicator in oxidatively disturbed reducing sediments. Geochim. Cosmochim. Acta 311: 12-28.
    Goldberg, T.; Hennekam, R.; Wasch, L.; Reichart, G.-J.; Rach, O.; Stammeier, J.A.; Griffioen, J. (2021). Suitability of calibrated X-ray fluorescence core scanning for environmental geochemical characterisation of heterogeneous sediment cores. Appl. Geochem. 125: 104824.
    Hagemans, K.; Nooren, K.; de Haas, T.; Córdova, M.; Hennekam, R.; Stekelenburg, M.C.A.; Rodbell, D.T.; Middelkoop, H.; Donders, T.H. (2021). Patterns of alluvial deposition in Andean lake consistent with ENSO trigger. Quat. Sci. Rev. 259: 106900.
    Sweere, T.; Hennekam, R.; Vance, D.; Reichart, G.-J. (2021). Molybdenum isotope constraints on the temporal development of sulfidic conditions during Mediterranean sapropel intervals. Geochemical Perspectives Letters 17: 16-20.
    van der Bilt, W.G.M.; Barr, I.D.; Berben, S.M.P.; Hennekam, R.; Lane, T.; Adamson, K.; Bakke, J. (2021). Late Holocene canyon-carving floods in northern Iceland were smaller than previously reported. Commun. Earth Environ. 2: 86.
  • 2020
    Dunlea, A.G.; Murray, R.W.; Tada, R.; Alvarez-Zarikian, C.A.; Anderson, C.H.; Gilli, A.; Giosan, L.; Gorgas, T.; Hennekam, R.; Irino, T.; Murayama, M.; Peterson, L.C.; Reichart, G.-J.; Seki, A.; Zheng, H.B.; Ziegler, M. (2020). Intercomparison of XRF core scanning results from seven labs and approaches to practical calibration. Geochem. Geophys. Geosyst. 21(9): e2020GC009248.
    Hennekam, R.; Bolt, B.; van Nes, E.H.; de Lange, G.J.; Scheffer, M.; Reichart, G.-J. (2020). Early‐warning signals for marine anoxic events. Geophys. Res. Lett. 47(20): e2020GL089183.
    Le Houedec, S.; Mojtahid, M.; Bicchi, E.; de Lange, G.J.; Hennekam, R. (2020). Suborbital hydrological variability inferred from coupled benthic and planktic foraminiferal‐based proxies in the southeastern Mediterranean during the last 19 ka. Paleoceanography and Paleoclimatology 35(2): e2019PA003827.
    Ménot, G.; Pivot, S.; Bouloubassi, I.; Davtian, N.; Hennekam, R.; Bosch, D.; Ducassou, E.; Bard, E.; Migeon, S.; Revel, M. (2020). Timing and stepwise transitions of the African Humid Period from geochemical proxies in the Nile deep-sea fan sediments. Quat. Sci. Rev. 228: 106071.
    Qian, Y.; Roberts, A.P.; Liu, Y.; Hu, P.; Zhao, X.; Heslop, D.; Grant, K.M.; Rohling, E.J.; Hennekam, R.; Li, J. (2020). Assessment and integration of bulk and component‐specific methods for identifying mineral magnetic assemblages in environmental magnetism. JGR: Solid Earth 125(8): e2019JB019024.
    Weiss, G.M.; Massalska, B.; Hennekam, R.; Reichart, G.-J.; Sinninghe Damsté, J.S; Schouten, S.; van der Meer, M.T.J. (2020). Alkenone distributions and hydrogen isotope ratios show changes in haptophyte species and source water in the Holocene Baltic Sea. Geochem. Geophys. Geosyst. 21(2): e2019GC008751.
  • 2019
    Bale, N.J.; Hennekam, R.; Hopmans, E.C.; Dorhout, D.; Reichart, G.-J.; Van der Meer, M.T.J.; Villareal, T.A.; Sinninghe Damsté, J.S; Schouten, S. (2019). Biomarker evidence for nitrogen-fixing cyanobacterial blooms in a brackish surface layer in the Nile River plume during sapropel deposition. Geology (Boulder Colo.) 47(11): 1088-1092.
    Dirksen, J.P.; Hennekam, R.; Geerken, E.; Reichart, G.-J. (2019). A novel approach using time-depth distortions to assess multicentennial variability in deep-sea oxygen deficiency in the Eastern Mediterranean Sea during sapropel S5. Paleoceanography and Paleoclimatology 34(5): 774-786.
    Hennekam, R.; Sweere, T.; Tjallingii, R.; de Lange, G.J.; Reichart, G.-J. (2019). Trace metal analysis of sediment cores using a novel X-ray fluorescence core scanning method. Quaternary International 514: 55-67.
    Mojtahid, M.; Hennekam, R.; de Nooijer, L.J.; Reichart, G.-J.; Jorissen, F.; Boer, W.; Le Houedec, S.; de Lange, G.J. (2019). Evaluation and application of foraminiferal element/calcium ratios: Assessing riverine fluxes and environmental conditions during sapropel S1 in the Southeastern Mediterranean. Mar. Micropaleontol. 153: 101783.
  • 2018
    Hennekam, R.; Zinke, J.; van Sebille, E.; ten Have, M.; Brummer, G.-J. A.; Reichart, G.-J. (2018). Cocos (Keeling) corals reveal 200 years of multidecadal modulation of southeast Indian Ocean hydrology by Indonesian throughflow. Paleoceanography and Paleoclimatology 33: 48-60.
    Zwiep, K.L.; Hennekam, R.; Donders, T.H.; van Helmond, N.A.G.M.; de Lange, G.J.; Sangiorgi, F. (2018). Marine productivity, water column processes and seafloor anoxia in relation to Nile discharge during sapropels S1 and S3. Quat. Sci. Rev. 200: 178-190.
  • 2017
    Korte, L.F.; Brummer, G.-J. A.; van der Does, M.; Guerreiro, C.V.; Hennekam, R.; van Hateren, J.A.; Jong, D.; Munday, C.I.; Schouten, S.; Stuut, J-B W. (2017). Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic. Atmos. Chem. Phys. 17(9): 6023-6040.
    Rohling, E.J.; Hibbert, F.D.; Williams, F.H.; Grant, K.M.; Marino, G.; Foster, G.L.; Hennekam, R.; de Lange, G.J.; Roberts, A.P.; Yu, J.; Webster, J.M.; Yokoyama, Y. (2017). Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions. Quat. Sci. Rev. 176: 1-28.

Linked projects

UUNIOZ_The origin and diversification of eukaryotic metabolisms
Anja Spang
Utrecht University
Project duration
1 Jan 2021 - 31 Dec 2025
UUNIOZ_Harmful Algal Blooms
Laura Villanueva
Utrecht University
Project duration
1 Jan 2021 - 31 Dec 2025
NoSE_North Sea Atlantic Exchange
Matthew Humphreys
Netherlands Organization for Scientific Research
Project duration
1 Oct 2022 - 31 Dec 2027