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Large-scale ocean deoxygenation during the Paleocene-Eocene Thermal Maximum

Abstract.

"The consequences of global warming for fisheries are not well understood, but the geological record demonstrates that carbon cycle perturbations are frequently associated with ocean deoxygenation. Of particular interest is the Paleocene-Eocene Thermal Maximum (PETM) where the CO2 input into the atmosphere was similar to the IPCC RCP8.5 emission scenario. Here we present sulfur-isotope data which record a positive 1 ‰ excursion during the PETM. Modeling suggests that significant parts of the ocean must have become sulfidic. The toxicity of hydrogen sulfide will render two of the largest and least explored ecosystems on Earth, the mesopelagic and bathypelagic zones, uninhabitable by multi-cellular organisms. This will affect many marine species whose eco-zones stretch into the deep ocean. [...]"

Source: Science  
Authors: Weiqi Yao, Adina Paytan, Ulrich G. Wortmann
DOI: 10.1126/science.aar8658

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Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem

Abstract.

"Hypoxia is one of the most important stressors affecting the health conditions of coastal ecosystems. In highly productive ecosystems such as the Humboldt Current ecosystem, the oxygen minimum zone is an important abiotic factor modulating the structure of benthic communities over the continental shelf. Herein, we study soft-bottom macrobenthic communities along a depth gradient–at 10, 20, 30 and 50 m–for two years to understand how hypoxia affects the structure of shallow communities at two sites in Mejillones Bay (23°S) in northern Chile. [...]"

Source: PLoS ONE
Authors: Maritza Fajardo et al.
DOI: 10.1371/journal.pone.0200349

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The Ocean is losing its breath: declining oxygen in the world's ocean and coastal waters; summary for policy makers

"Oxygen is critical to the health of the ocean. It structures aquatic ecosystems, impacts the biogeochemical cycling of carbon, nitrogen and other key elements, and is a fundamental requirement for marine life from the intertidal zone to the greatest depths of the ocean." [...]

Source: UNESCO (UNESDOC)
Authors: Denise Breitburg et al.

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North Pacific freshwater events linked to changes in glacial ocean circulation

Abstract.

"There is compelling evidence that episodic deposition of large volumes of freshwater into the oceans strongly influenced global ocean circulation and climate variability during glacial periods. In the North Atlantic region, episodes of massive freshwater discharge to the North Atlantic Ocean were related to distinct cold periods known as Heinrich Stadials. [...]"

Source: Nature
Authors: E. Maier et al.
DOI: 10.1038/s41586-018-0276-y

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Single cell genomic and transcriptomic evidence for the use of alternative nitrogen substrates by anammox bacteria

Abstract.

"Anaerobic ammonium oxidation (anammox) contributes substantially to ocean nitrogen loss, particularly in anoxic marine zones (AMZs). Ammonium is scarce in AMZs, raising the hypothesis that organic nitrogen compounds may be ammonium sources for anammox. Biochemical measurements suggest that the organic compounds urea and cyanate can support anammox in AMZs. [...]"

Source: The ISME Journal
Authors: Sangita Ganesh et al.
DOI: 10.1038/s41396-018-0223-9

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Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing

Abstract.

"The evolution of burrowing animals forms a defining event in the history of the Earth. It has been hypothesised that the expansion of seafloor burrowing during the Palaeozoic altered the biogeochemistry of the oceans and atmosphere. However, whilst potential impacts of bioturbation on the individual phosphorus, oxygen and sulphur cycles have been considered, combined effects have not been investigated, leading to major uncertainty over the timing and magnitude of the Earth system response to the evolution of bioturbation. [...]"

Source: Nature Communications
Authors: Sebastiaan van de Velde et al.
DOI: 10.1038/s41467-018-04973-4

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Coupling of ocean redox and animal evolution during the Ediacaran-Cambrian transition

Abstract.

"The late Ediacaran to early Cambrian interval witnessed extraordinary radiations of metazoan life. The role of the physical environment in this biological revolution, such as changes to oxygen levels and nutrient availability, has been the focus of longstanding debate. Seemingly contradictory data from geochemical redox proxies help to fuel this controversy. As an essential nutrient, nitrogen can help to resolve this impasse by establishing linkages between nutrient supply, ocean redox, and biological changes. [...]"

Source: Nature Communications
Authors: Dan Wang et al.
DOI: 10.1038/s41467-018-04980-5

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Oxygen minimum zones in the early Cambrian ocean

Abstract.

"The relationship between the evolution of early animal communities and oceanic oxygen levels remains unclear. In particular, uncertainty persists in reconstructions of redox conditions during the pivotal early Cambrian (541-510 million years ago, Ma), where conflicting datasets from deeper marine settings suggest either ocean anoxia or fully oxygenated conditions. By coupling geochemical palaeoredox proxies with a record of organic-walled fossils from exceptionally well-defined successions of the early Cambrian Baltic Basin, we provide evidence for the early establishment of modern-type oxygen minimum zones (OMZs). [...]"

Source: Geochemical Perspectives Letters 
Authors: R. Guilbaud et al.
DOI: 10.7185/geochemlet.1806

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Ecology and evolution of seafloor and subseafloor microbial communities

Abstract.

"Vast regions of the dark ocean have ultra-slow rates of organic matter sedimentation, and their sediments are oxygenated to great depths yet have low levels of organic matter and cells. Primary production in the oxic seabed is supported by ammonia-oxidizing archaea, whereas in anoxic sediments, novel, uncultivated groups have the potential to produce H2 and CH4, which fuel anaerobic carbon fixation. [...]"

Source: Nature Reviews Microbiology
Authors: William D. Orsi
DOI: 10.1038/s41579-018-0046-8

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Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing

Abstract.

"The evolution of burrowing animals forms a defining event in the history of the Earth. It has been hypothesised that the expansion of seafloor burrowing during the Palaeozoic altered the biogeochemistry of the oceans and atmosphere. However, whilst potential impacts of bioturbation on the individual phosphorus, oxygen and sulphur cycles have been considered, combined effects have not been investigated, leading to major uncertainty over the timing and magnitude of the Earth system response to the evolution of bioturbation. [...]"

Source: Nature Communications
Authors: Sebastiaan van de Velde et al.
DOI: 10.1038/s41467-018-04973-4

Read the full article here.


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