How ocean deoxygenation enters the global agenda

A Story of the Collaborative Research Centre "Climate-Biogeochemistry Interactions in the Tropical Ocean"

After 12 years of intensive research, the Collaborative Research Centre 754 "Climate-Biogeochemical Interactions in the Tropical Ocean" ended in winter 2019 with a final symposium in Heiligenhafen.

More than 100 scientists involved in the large-scale project over its entire running time were able to gain numerous new insights into the processes of nutrient cycling, the interaction between ocean and atmosphere and the ecosystems in the tropical oceans. Above all, however, they drew attention to a phenomenon that affects the entire ocean: global oxygen loss and the spread of oxygen minimum zones in the ocean. With this video, the SFB 754 now draws a conclusion and at the same time points out the new research tasks that have resulted from its work. These include improved ocean observation and the question of how to prevent further oxygen loss.

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Additive impacts of deoxygenation and acidification threaten marine biota


"Deoxygenation in coastal and open‐ocean ecosystems rarely exists in isolation but occurs concomitantly with acidification. Here, we first combine meta‐data of experimental assessments from across the globe to investigate the potential interactive impacts of deoxygenation and acidification on a broad range of marine taxa. [...]"

Source: Global Change Biology
Authors: Alexandra Steckbauer et al.
DOI: 10.1111/gcb.15252

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Anammox bacteria generate energy from wastewater while taking a breath

"A type of anaerobic bacteria responsible for more than 50 percent of nitrogen loss from marine environments has been shown to use solid-state matter present outside their cells for respiration. The finding by KAUST researchers adds to knowledge of the global nitrogen cycle and has important energy-saving potential for wastewater treatment. [...]"


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Operationalizing Ocean Health: Toward Integrated Research on Ocean Health and Recovery to Achieve Ocean Sustainability


"Protecting the ocean has become a major goal of international policy as human activities increasingly endanger the integrity of the ocean ecosystem, often summarized as ‘‘ocean health.’’ By and large, efforts to protect the ocean have failed because, among other things, (1) the underlying socio-ecological pathways have not been properly considered, and (2) the concept of ocean health has been ill defined. Collectively, this prevents an adequate societal response as to how ocean ecosystems and their vital functions for human societies can be protected and restored. We review the confusion surrounding the term ‘‘ocean health’’ and suggest an operational ocean-health framework in line with the concept of strong sustainability. [...]"

Source: One Earth
Authors: Andrea Franke et al.
DOI: 10.1016/j.oneear.2020.05.013

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Slightly smaller-than-average 2020 ‘dead zone’ predicted for Chesapeake Bay

"Researchers from the University of Michigan, the Chesapeake Bay Program and the University of Maryland Center for Environmental Science are forecasting a slightly smaller-than-average Chesapeake Bay “dead zone” this year, due to reduced rainfall and less nutrient-rich runoff flowing into the bay from the watershed this spring. [...]"

Source: University of Michigan

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Larger-than-average ‘dead zone’ expected for Gulf of Mexico

"NOAA scientists are forecasting this summer’s Gulf of Mexico hypoxic area or “dead zone” – an area of low to no oxygen that can kill fish and other marine life – to be approximately 6,700 square miles, larger than the long-term average measured size of 5,387 square miles but substantially less than the record of 8,776 square miles set in 2017. The annual prediction is based on U.S. Geological Survey river-flow and nutrient data. [...]"

Source: NOAA

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Spatial variations in sedimentary N-transformation rates in the North Sea (German Bight)


"In this study, we investigate the role of sedimentary N cycling in the southern North Sea. We present a budget of ammonification, nitrification and sedimentary NO−3 consumption and denitrification in contrasting sediment types of the German Bight (southern North Sea), including novel net ammonification rates. [...]"

Source: Biogeosciences
Authors: Alexander Bratek et al.
DOI: 10.5194/bg-17-2839-2020

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Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea


"In the East China Sea, hypoxia (oxygen ≤ 62.5 mmol m−3) is frequently observed off the Changjiang (or Yangtze River) estuary covering up to about 15 000 km2. The Changjiang is a major contributor to hypoxia formation because it discharges large amounts of freshwater and nutrients into the region. However, modeling and observational studies have suggested that intrusions of nutrient-rich oceanic water from the Kuroshio Current also contribute to hypoxia formation.  [...]"

Source: Biogeosciences
Authors: Fabian Große et al.
DOI: 10.5194/bg-17-2701-2020

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Reconstructing N2-fixing cyanobacterial blooms in the Baltic Sea

beyond observations using 6- and 7-methylheptadecane in sediments as specific biomarkers


"Summer cyanobacterial blooms represent a threat to the Baltic Sea ecosystem, causing deoxygenation of the bottom water and the spread of the so-called dead zones. The history of the Baltic Sea cyanobacterial blooms is known from in situ and satellite observations since the early 1980s but is still not well understood. [...]"

Source: Biogeosciences
Authors: Jérôme Kaiser et al.
DOI: 10.5194/bg-17-2579-2020

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Chesapeake Bay water quality declines by four percentage points

"An estimated 38% of the Chesapeake Bay and its tidal tributaries met clean water standards for clarity, oxygen and algae growth between 2016 and 2018. This score is lower than the record high 42% from the previous reporting period, but is still the fifth highest estimate of water quality standards attainment since 1985. This four percentage point decrease is due in large part to a decline in dissolved oxygen in the open waters of the Bay, those areas beyond the shoreline and shallows. Dissolved oxygen is necessary for the survival of the Bay’s aquatic species, and is a factor in the annual dead zone. [...]"

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