1Helmholtz Zentrum Geesthacht Center for Materials and Coastal Research, Max-Planck Str. 1, 21502 Geesthacht, Germany
2Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
3Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany
4Scottish Association for Marine Science, Oban, Argyll, PA37 1QA, UK
5GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstrasse 1–3, 24148 Kiel, Germany
6A. O. Kovalevskiy Institute of Biology of Southern Seas, Nakhimov Av. 2, 99011 Sevastopol, Ukraine
7Istanbul Technical University, EMCOL and Department of Geological Engineering, Maslak Sar\i yer, 34469 Istanbul, Turkey
8Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, Via di Vigna Murata 605, 143 Rome, Italy
9Faculty of Environmental Science and Engineering, Babes-Bolyai University, Cluj-Napoca, Romania
10Laboratory of Marine Geology and Physical Oceanography, Department of Geology, University of Patras, 26504, Greece
11ETH Zurich, Geological Institute, Sonneggstrasse 5, 8092 Zurich, Switzerland
12National Institute of Marine Geology and Geoecology, 304 Mamaia Boulevard, 8700 Constanta, Romania
13University of Gothenburg, Dept. of Chemistry and Molecular Biology, Marine Chemistry, 412 96, Gothenburg, Sweden
14Swedish Institute for the Marine Environment, Seminariegatan 1F, 405 30, Gothenburg, Sweden
15Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters – Research and Management, Seestrasse 79, 6047 Kastanienbaum, Switzerland
16Marine Hydrophysical Institute, Dept. Marine Biogeochemistry, Kapitanskaya St. 2, 99011 Sevastopol, Ukraine
17Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Water Resources and Drinking Water, Überlandstrasse 133, 8600 Dübendorf, Switzerland
18Leibniz Institute for Baltic Sea Research Warnemünde, Seestr. 15, 18119 Rostock, Germany
19Bremen University/MARUM, Leobener Str., 28359 Bremen, Germany
aJoint first authorship (these authors have contributed equally to the manuscript).
bpresent address: GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstrasse 1–3, 24148 Kiel, Germany
cpresent address: University of Kiel, Institute of Geosciences, Ludewig-Meyn-Str. 10, 24118 Kiel, Germany
dpresent address: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
epresent address: Curtin University, WA-Organic and Isotope Geochemistry Center, G.P.O.~Box U1987, Perth, WA 6845, Australia
fpresent address: Helmholtz Zentrum Geesthacht Center for Materials and Coastal Research, Max-Planck Str. 1, 21502 Geesthacht, Germany
Received: 12 Jul 2013 – Discussion started: 05 Aug 2013
Abstract. In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", http://www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences.
Revised: 16 Dec 2013 – Accepted: 28 Dec 2013 – Published: 27 Feb 2014
Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of water-column oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.
Friedrich, J., Janssen, F., Aleynik, D., Bange, H. W., Boltacheva, N., Çagatay, M. N., Dale, A. W., Etiope, G., Erdem, Z., Geraga, M., Gilli, A., Gomoiu, M. T., Hall, P. O. J., Hansson, D., He, Y., Holtappels, M., Kirf, M. K., Kononets, M., Konovalov, S., Lichtschlag, A., Livingstone, D. M., Marinaro, G., Mazlumyan, S., Naeher, S., North, R. P., Papatheodorou, G., Pfannkuche, O., Prien, R., Rehder, G., Schubert, C. J., Soltwedel, T., Sommer, S., Stahl, H., Stanev, E. V., Teaca, A., Tengberg, A., Waldmann, C., Wehrli, B., and Wenzhöfer, F.: Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon, Biogeosciences, 11, 1215-1259, doi:10.5194/bg-11-1215-2014, 2014.