Articles | Volume 13, issue 12
Biogeosciences, 13, 3585–3606, 2016

Special issue: Low oxygen environments in marine, fresh and estuarine...

Biogeosciences, 13, 3585–3606, 2016

Reviews and syntheses 20 Jun 2016

Reviews and syntheses | 20 Jun 2016

Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific oceans

Carolin R. Löscher1,a, Hermann W. Bange1, Ruth A. Schmitz2, Cameron M. Callbeck3, Anja Engel1, Helena Hauss1, Torsten Kanzow1,b, Rainer Kiko1, Gaute Lavik3, Alexandra Loginova1, Frank Melzner1, Judith Meyer1, Sven C. Neulinger2,c, Markus Pahlow1, Ulf Riebesell1, Harald Schunck2, Sören Thomsen1, and Hannes Wagner1 Carolin R. Löscher et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • 2Institute of General Microbiology, Christian-Albrechts-Universität zu Kiel, Am Botanischen Garten 1–9, 24118 Kiel, Germany
  • 3Max Planck Institute for Marine Microbiology, Celsiusstraße 1, 28359 Bremen, Germany
  • anow at: Nordic Center for Earth Evolution, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
  • bnow at: AWI, Bremerhaven, Germany
  • cnow at: GbR, Kiel, Germany

Abstract. Recent modeling results suggest that oceanic oxygen levels will decrease significantly over the next decades to centuries in response to climate change and altered ocean circulation. Hence, the future ocean may experience major shifts in nutrient cycling triggered by the expansion and intensification of tropical oxygen minimum zones (OMZs), which are connected to the most productive upwelling systems in the ocean. There are numerous feedbacks among oxygen concentrations, nutrient cycling and biological productivity; however, existing knowledge is insufficient to understand physical, chemical and biological interactions in order to adequately assess past and potential future changes.

In the following, we summarize one decade of research performed in the framework of the Collaborative Research Center 754 (SFB754) focusing on climate–biogeochemistry interactions in tropical OMZs. We investigated the influence of low environmental oxygen conditions on biogeochemical cycles, organic matter formation and remineralization, greenhouse gas production and the ecology in OMZ regions of the eastern tropical South Pacific compared to the weaker OMZ of the eastern tropical North Atlantic. Based on our findings, a coupling of primary production and organic matter export via the nitrogen cycle is proposed, which may, however, be impacted by several additional factors, e.g., micronutrients, particles acting as microniches, vertical and horizontal transport of organic material and the role of zooplankton and viruses therein.

Short summary
The ocean loses oxygen due to climate change. Addressing this issue in tropical ocean regions (off Peru and Mauritania), we aimed to understand the effects of oxygen depletion on various aspects of marine biogeochemistry, including primary production and export production, the nitrogen cycle, greenhouse gas production, organic matter fluxes and remineralization, and the role of zooplankton and viruses.
Final-revised paper