SFB 754:
Climate - Biogeochemistry Interactions in the Tropical Ocean
Subject Area
Geosciences
Biology
Medicine
Term
from 2008 to 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 27542298
Final Report Year
2020
Final Report Abstract
The overall goal of the SFB 754 was to understand the coupling of tropical ocean circulation and climate
variability with the ocean’s oxygen and nutrient budgets, to quantitatively evaluate the functioning of
oxygen-sensitive microbial processes and their impact on biogeochemical cycles, and to assess potential
consequences for the ocean’s future. Oxygen dissolved in seawater was the central chemical element of
the project. It is not only essential for higher forms of marine life, but it also controls remineralisation
processes and thereby interacts with major nutrient cycles in the ocean and Earth system. This is most
prominent in so-called - (OMZs) where low oxygen levels act as “switch” from aerobic to anaerobic
processes, such as denitrification and associated loss of fixed nitrogen from the ocean, or the release of
the nutrients phosphate and iron from sediments and the associated gain of these nutritive elements
upon sediments turning anoxic. OMZs are located in the tropical oceans. The SFB 754 targeted two
contrasting regions, the generally anoxic OMZ off Peru and the OMZ off Mauretania, where oxygen
concentrations are low, but generally well above the thresholds for switches from aerobic to anaerobic
processes.
Major scientific findings of the SFB 754 include the identification and detailed quantitative understanding
of oxygen supply by small-scale physical processes, in particular temporally varying zonal current bands
that transport oxygen to the tropical OMZs. Coarse-resolution climate models cannot resolve these
small-scale features and thus tend to systematically underestimate the oxygen supply – and hence
overestimate the volume of OMZs. New high-resolution biogeochemical models and parameterizations
developed for coarse-resolution models developed within the SFB 754 have helped to considerably
improve the representation of OMZs in state-of-the-art climate models. An unexpected finding of the
dedicated field work was the discovery of anoxic eddies in the tropical Atlantic. These form regularly in
the Cape Verde region and for their many month long lifetime provide stable environments for anoxic
microbial processes and special food webs that were not previously thought to occur in the North
Atlantic.
Novel biogeochemical processes for cycling nutrients in the sediments and in the water column were
identified in the quasi-permanent low-oxygen conditions off Peru, and their often substantial role in the
nutrient budgets of the OMZs and the overlying productive surface waters was quantified to derive, for
the first time, a closed nitrogen budget. Some processes drive feedbacks that may accelerate marine
oxygen loss under climate change, and, via the production of greenhouse gases such as nitrous oxide,
may also accelerate climate change under expanding anoxia. Parameterisations of these processes
were developed and employed in climate models to yield realistic representations of past oceanic
anoxic events in Earth’s history. These models also suggest that positive oxygen-climate feedbacks for
expected future warming are relatively small compared to uncertainties in other components of current
climate models.
Perhaps the single most surprising finding of the SFB 754 was the identification of the rapid decline
of the marine oxygen inventory, called ocean deoxygenation, a term coined by the SFB 754 and now
widely used in science and environmental assessments. Interestingly, our estimate of a 2 % oxygen
decline during the past 50 years is 2 to 3 times larger than simulated by current climate models. This
discrepancy between observational estimates and model results poses a major challenge for both
modellers and observationalists, which is now addressed by a number of research groups worldwide.
The comprehensive data set of oxygen and additional biogeochemical and physical parameters obtained
by the SFB 754 will continue to help the international scientific community in better understanding the
processes and consequences of ocean deoxygenation.
Publications
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(2008) Expanding oxygen-minimum zones in the Tropical oceans. Science, 320, 655-658
Stramma, L., Johnson, G. C., Sprintall, J. and Mohrholz, V.
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(2008) Simulated 21st century’s increase in oceanic suboxia by CO2-enhanced biological carbon export. Global Biogeochem. Cycles, 22(4), GB4008
Oschlies, A., Schulz, K. G., Riebesell, U. and Schmittner, A.
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(2010) Changes in the ventilation of the oxygen minimum zone of the tropical North Atlantic, J. Phys. Oceanogr., 40, 1784-1801
Brandt, P., Hormann, V., Körtzinger, A., Visbeck, M., Krahmann, G., Stramma, L., Lumpkin, R. and Schmid, C.
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(2011) Benthic nitrogen cycling traversing the Peruvian oxygen minimum zone. Geochim. Cosmochim. Acta 75, 6094-6111
Bohlen, L., Dale, A. W., Sommer, S., Mosch, T., Hensen, C., Noffke, A., Scholz, F. and Wallmann, K.
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(2011) Sensitivity of simulated extent and future evolution of marine suboxia to mixing intensity. Geophysical Research Letters, 38 (6). L06607
Duteil, O. and Oschlies, A.
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(2011) Simulating the biogeochemical effects of volcanic CO2 degassing on the oxygen-state of the deep ocean during the Cenomanian/Turonian Anoxic Event (OAE2). Earth Planet. Sci. Lett., 305 (3-4), 371-384
Flögel, S., Wallmann, K., Poulsen, C. J., Zhou, J., Oschlies, A., Voigt, S. and Kuhnt, W.
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(2012) Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone. Limnology and Oceanography, 57 (3), pp. 851-867
Noffke, A., Hensen, C., Sommer, S., Scholz, F., Bohlen, L., Mosch, T., Graco, M. and Wallmann, K.
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(2012) Diapycnal oxygen supply to the Tropical North Atlantic oxygen minimum zone. Biogeosciences, 10, 5079-5093
Fischer, T., Banyte, D., Brandt, P., Dengler, M., Krahmann, G., Tanhua, T. and Visbeck, M.
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(2012) Doubling of marine dinitrogen-fixation rates based on direct measurements. Nature 488(7411): 361-364
Großkopf, T., Mohr, W., Baustian, T., Schunck, H., Gill, D., Kuypers, M. M. M., Lavik, G., Schmitz, R. A., Wallace, D. W. R. and LaRoche, J.
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(2012) Dynamics and stoichiometry of nutrients and phytoplankton in waters influenced by the oxygen minimum zone in the tropical South East Pacific. Deep-Sea ResearchPart I, 62, 20-31
Franz, J., Krahmann, G., Lavik, G., Grasse, P., Dittmar, T. and Riebesell, U.
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(2012) Production of oceanic nitrous oxide by ammonia-oxidizing archaea. Biogeosciences, 9, 2419-2429
Löscher, C. R., Kock, A., Könneke, M., LaRoche, J., Bange, H. W. and Schmitz, R. A.
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(2012) The distribution of neodymium isotopes and concentrations in the Eastern Equatorial Pacific: Water mass advection versus particle exchange. Earth and Planetary Science Letters, 353-354, 198-207
Grasse, P., Stichel, T., Stumpf, R., Stramma, L. and Frank, M.
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(2013) Changes in silicate utilisation and upwelling intensity off Peru since the Last Glacial Maximum – insights from silicon and neodymium isotopes. Quaternary Science Reviews 72, 18-35
Ehlert, C., Grasse, P. and Frank, M.
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(2013) The influence of water mass mixing on the dissolved Si isotope composition in the Eastern Equatorial Pacific. Earth and Planetary Science Letters, 380, 60-71
Grasse, P., Ehlert, C. and Frank, M.
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(2014) Facets of diazotrophy in the oxygen minimum zone waters off Peru. ISME Journal 8(11): 2180-92
Löscher, C. R., Großkopf, T., Desai, F. D., Gill, D., Schunck, H., Croot, P. L., Schlosser, C., Neulinger, S. C., Pinnow, N., Lavik, G., Kuypers, M. M. M., LaRoche, J. and Schmitz, R. A.
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(2014) Major role of the equatorial current system in setting oxygen levels in the eastern tropical Atlantic Ocean: A high-resolution model study. Geophys. Res. Lett., 41, 2033-2040
Duteil, O., Schwarzkopf, F. U., Böning, C. W. and Oschlies, A.
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(2014) The impact of ocean deoxygenation on iron release from continental margin sediments. Nat. Geosci. 7, 433-437
Scholz F., McManus, J., Mix, A. C., Hensen, C. and Schneider, R. R.
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(2015) A revised global estimate of dissolved iron fluxes from marine sediments. Glob. Biogeochem. Cy. 29
Dale, A.W., Nickelsen, L., Scholz, F., Hensen, C., Oschlies, A. and Wallmann, K.
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(2015) Hidden biosphere in an oxygendeficient Atlantic open ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic. Biogeosciences, 12, 7467-7482
Löscher, C. R., Fischer, M. A., Neulinger, S. C., Fiedler, B., Philippi, M., Schütte, F., Singh, A., Hauss, H., Karstensen, J., Körtzinger, A., Künzel, S. and Schmitz, R. A.
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(2015) Massive nitrous oxide emissions from the tropical South Pacific Ocean. Nature Geoscience, 8, 530-533
Arévalo-Martínez, D. L., Kock, A., Löscher, C. R., Schmitz, R. A. and Bange, H. W.
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(2015) Organic carbon production, mineralization and preservation on the Peruvian margin. Biogeosciences 12, 1537-1559
Dale, A. W., Sommer, S., Lomnitz, U., Montes, I., Treude, T., Gier, J., Hensen, C., Dengler, M., Stolpovsky, K., Bryant, L. D. and Wallmann, K.
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(2015) Oxygen minimum zone variations in the tropical Pacific during the Holocene. Geophysical Research Letters, 42, 8530-8537
Xu, X., Segschneider, J., Schneider, B., Park, W. and Latif, M.
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2015) On the role of circulation and mixing in the ventilation of oxygen minimum zones with a focus on the eastern tropical North Atlantic. Biogeosciences, 12, 489-512
Brandt, P., Bange, H. W., Banyte, D., Dengler, M., Didwischus, S.-H., Fischer, T., Greatbatch, R. J., Hahn, J., Kanzow, T., Karstensen, J., Körtzinger, A., Krahmann, G., Schmidtko, S., Stramma, L., Tanhua, T. and Visbeck, M.
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(2016) Centennial to millennial-scale changes in oxygenation and productivity in the Eastern Tropical South Pacific during the last 25 000 years. Quaternary Science Reviews, 131, 102-117
Salvatteci, R., Gutierrez, D., Sifeddine, A., Ortlieb, L., Druffel, E., Boussafir, M. and Schneider, R.
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(2016) Dead zone or oasis in the open ocean? Zooplankton distribution and migration in low-oxygen modewater eddies. Biogeosciences, 13:1977- 1989
Hauss, H., Christiansen, S., Schütte, F., Kiko, R., Edvam Lima, M., Rodrigues, E., Karstensen, J., Löscher, C. R., Körtzinger, A. and Fiedler, B.
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(2016) Depletion of oxygen, nitrate and nitrite in the Peruvian oxygen minimum zone cause an imbalance of benthic nitrogen fluxes. Deep-Sea Research, 112, 113-122,
Sommer, S., Gier, J., Treude, T., Lomnitz, U., Dengler, M., Cardich, J. and Dale, A. W.
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(2016) Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions. Earth and Planetary Science Letters, 454, pp. 272-281
Scholz, F., Löscher, C. R., Fiskal, A., Sommer, S., Hensen, C., Lomnitz, U., Wuttig, K., Göttlicher, J., Kossel, E., Steininger, R. and Canfield, D. E.
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(2016) Occurrence and characteristics of mesoscale eddies in the tropical northeastern Atlantic Ocean. Ocean Science, 12, 663-685
Schütte, F., Brandt, P. and Karstensen, J.
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(2017) Biological and physical influences on marine snowfall at the equator. Nature Geoscience, 10(11), 852-858
Kiko, R., Biastoch, A., Brandt, P., Cravatte, S., Hauss, H., Hummels, R., Kriest, I., Marin, F., McDonnell, A. M. P., Oschlies, A., Picheral, M., Schwarzkopf, F. U., Thurnherr, A. M. and Stemmann, L.
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(2017) Calibrating a global three-dimensional biogeochemical ocean model (MOPS-1.0). Geosci. Model Dev., 10, 127-154
Kriest, I., Sauerland, V., Khatiwala, S., Srivastav, A. and Oschlies, A.
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(2017) Decline in global oxygen content during the past five decades. Nature, 542, 335-339
Schmidtko, S., Stramma, L. and Visbeck, M.
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(2017) Nutrient co-limitation at the boundary of an oceanic gyre. Nature 551(7679): 242-24
Browning, T. J., Achterberg, E. P., Rapp, I., Engel, A., Bertrand, E. M., Tagliabue, A. and Moore, M.
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(2017) Patterns of deoxygenation – sensitivity to natural and anthropogenic drivers. Phil. Trans. R. Soc. A, 375
Oschlies, A., Duteil, O., Getzlaff, J., Koeve, W., Landolfi, A. and Schmidtko, S.
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(2017) Unraveling the onset of Cretaceous Oceanic Anoxic Event 2 in an extended sediment archive from the Tarfaya-Laayoune Basin, Morocco. Paleoceanography, 32(8), 923-946
Kuhnt, W., Holbourn, A. E., Beil, S., Aquit, M., Krawczyk, T., Flögel, S., Chellai, E. H. and Jabour, H.
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(2018) A novel eukaryotic denitrification pathway in foraminifera. Current Biology, 28, 2536-2543
Woehle, C., Roy, A.-S., Glock, N., Wein, T., Weissenbach, J., Rosenstiel, P., Hiebenthal, C., Michels, J., Schönfeld, J. and Dagan, T.
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(2018) Coupling of oceanic carbon and nitrogen cycling facilitates spatially resolved quantitative reconstruction of nitrate inventories. Nature Communications, 9, 1217
Glock, N., Erdem, Z., Wallmann, K., Somes, C., Liebetrau, V., Schönfeld, J., Gorb, S. and Eisenhauer, A.
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(2018) Drivers and mechanisms of ocean deoxygenation. Nat. Geosci., 11, 467-473
Oschlies, A., Brandt, P., Stramma, L. and Schmidtko, S.
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(2019) Diapycnal dissolved organic matter supply into the upper Peruvian oxycline. Biogeosciences, 16, 2033-2047
Loginova, A. N., Thomsen, S., Dengler, M., Lüdke, J. and Engel, A.
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(2019) Interannual variability of the Atlantic North Equatorial Undercurrent and its impact on oxygen. Journal of Geophysical Research: Oceans, 124 (4). pp. 2348-2373
Burmeister, K., Lübbecke, J. F., Brandt, P. and Duteil, O.
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(2019) Metabolic preference of nitrate over oxygen as electron acceptor in Foraminifera from the Peruvian oxygen minimum. PNAS, 116 (8), 2860-2865
Glock, N., Roy, A.-S., Romero, D., Wein, T., Weissenbach, J., Revsbech, N.-P., Høgslund, S., Clemens, D., Sommer, S. and Dagan, T.
DFG Programme
Collaborative Research Centres
Completed projects
-
A01 - Modelling oceanic oxygen change from the Holocene into the Anthropocene
(Project Heads
Latif, Mojib
;
Schneider, Birgit
)
-
A02 - High-resolution modelling of physical-biogeochemical interactions in the tropical ocean: determination of potential future trends
(Project Heads
Böning, Claus
;
Oschlies, Andreas
)
-
A03 - A tracer release experiment (POSTRE) to quantify benthic-pelagic exchanges in the Peruvian oxygen minimum zone (OMZ), and constraining the age-spectrum of the OMZ with transient tracers
(Project Heads
Tanhua, Toste
;
Visbeck, Martin
)
-
A04 - Trends and variability of oxygen inventory, supply and consumption in the eastern tropical North Atlantic (ETNA) oxygen minimum zone
(Project Heads
Brandt, Peter
;
Körtzinger, Arne
)
-
A05 - Water mass structure in the eastern tropical Pacific Ocean: Relationship to oxygen variability and geochemical properties
(Project Heads
Frank, Martin
;
Stramma, Lothar
)
-
A06 - Centennial to millennial scale climate change and low-latitude oxygen minimum conditions
(Project Heads
Frank, Martin
;
Schneider, Ralph
)
-
A07 - Unraveling the Onset and Spread of Cretaceous Anoxia
(Project Heads
Kuhnt, Wolfgang
;
Wallmann, Klaus
)
-
A08 - Transports and fluxes across the bottom boundary layer
(Project Heads
Dengler, Marcus
;
Scholten, Jan
)
-
A09 - Circulation mechanisms for decadal time scale changes in oxygen minimum zones
(Project Heads
Greatbatch, Richard
;
Lübbecke, Joke
)
-
B01 - A global model of redox-dependent biogeochemical cycles
(Project Heads
Dale, Andrew
;
Oschlies, Andreas
)
-
B02 - Influence of nutrient stoichiometry on pelagic ecosystem dynamics in the Peru upwelling zone
(Project Heads
Pahlow, Markus
;
Riebesell, Ulf
)
-
B03 - Sensitivity of oceanic biological nitrogen fixation to changes in dissolved oxygen
(Project Heads
La Roche, Ph.D., Julie
;
Schmitz-Streit, Ruth Anne
)
-
B04 - N-losses and nutrient regeneration in oxygen minimum zone waters with emphasis on micro-niches
(Project Heads
Bange, Hermann W.
;
Kuypers, Marcel
;
Schmitz-Streit, Ruth Anne
)
-
B05 - Biogeochemical cycling of iron and phosphorus under low oxygen conditions
(Project Heads
Hensen, Christian
;
Wallmann, Klaus
)
-
B06 - Benthic-pelagic N-cycling under shifting redox conditions and hydro-dynamical forcing
(Project Heads
Dengler, Marcus
;
Sommer, Stefan
)
-
B07 - Foraminiferal nitrate respiration in oxygen minimum zones (OMZ) - past and present
(Project Heads
Dagan, Tal
;
Eisenhauer, Anton
;
Gorb, Stanislav N.
)
-
B08 - The role of zooplankton in N-, P- and C- cycling and for the oxygen budget of tropical oxygen minimum zones
(Project Heads
Kriest, Iris
;
Melzner, Frank
;
Sommer, Ulrich
)
-
B09 - Supply of organic matter to oxygen minimum zones
(Project Heads
Achterberg, Eric
;
Engel, Anja
;
Karstensen, Johannes
)
-
B10 - Pelagic transfer of iron and nutrients in the Peruvian oxygen minimum zone
(Project Heads
Achterberg, Eric
;
Gledhill, Martha
)
-
Z01 - Central Activities of the Collaborative Research Projekt
(Project Head
Oschlies, Andreas
)
-
Z02 - Expedition costs for the SFB research cruises
(Project Heads
Körtzinger, Arne
;
Stramma, Lothar
)
-
Ö - SFB Outreach
(Project Head
Dengg, Joachim
)