Will ocean zones with low oxygen levels expand or shrink?

"Computer simulations show that areas of the ocean that have low levels of dissolved oxygen will expand, but then shrink, in response to global warming — adding to an emerging picture of the finely balanced processes involved.

Global warming has reduced the amount of dissolved oxygen in the ocean by 2% since 1960. A major concern is that the rate of loss of dissolved oxygen has already increased by up to 20% in tropical waters, expanding the volume of regions called oxygen minimum zones (OMZs), where levels of dissolved oxygen are already very low. [...]"


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Oxygenation of the Mesoproterozoic ocean and the evolution of complex eukaryotes


"The Mesoproterozoic era (1,600–1,000 million years ago (Ma)) has long been considered a period of relative environmental stasis, with persistently low levels of atmospheric oxygen. There remains much uncertainty, however, over the evolution of ocean chemistry during this period, which may have been of profound significance for the early evolution of eukaryotic life. [...]"

Source: Nature Geoscience
Authors: Kan Zhang
DOI: 10.1038/s41561-018-0111-y

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Tiny microenvironments in the ocean hold clues to global nitrogen cycle

"Nitrogen is essential to marine life and cycles throughout the ocean in a delicately balanced system. Living organisms--especially marine plants called phytoplankton--require nitrogen in processes such as photosynthesis. In turn, phytoplankton growth takes up carbon dioxide from the atmosphere and helps regulate global climate. [...]"

Source: EruekAlert

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New Study in Oxygen-Deprived Black Sea Provides Insights on Future Carbon Budget

"Scientists are studying the oxygen-deprived waters of the Black Sea to help answer questions about the deepest parts of the ocean and Earth’s climate.


A new study led by researchers at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science found that even in the absence of oxygen, the chemical and biological processes occurring in the Black Sea resemble those in the oxygenated deep ocean. [...]"

Source: University of Miami Rosenstiel School of Marine & Atmospheric Science

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Local oceanographic variability influences the performance of juvenile abalone under climate change


"Climate change is causing warming, deoxygenation, and acidification of the global ocean. However, manifestation of climate change may vary at local scales due to oceanographic conditions. Variation in stressors, such as high temperature and low oxygen, at local scales may lead to variable biological responses and spatial refuges from climate impacts. We conducted outplant experiments at two locations separated by ~2.5 km and two sites at each location separated by ~200 m in the nearshore of Isla Natividad, Mexico to assess how local ocean conditions (warming and hypoxia) may affect juvenile abalone performance. [...]"

Source: Scientific Reports
Authors: C.A. Boch
DOI: 10.1038/s41598-018-23746-z

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Species distribution modeling of deep sea sponges in the North Pacific Ocean.


"Knowledge of deep-sea species and their ecosystems is limited due to the inaccessibility of the areas and the prohibitive cost of conducting large-scale field studies. My graduate research has used predictive modeling methods to map hexactinellid sponge habitat extent in the North Pacific, as well as climate-induced changes in oceanic dissolved oxygen levels and how this will impact sponges. [...]"

Authors: Fiona Davidson
DOI: 10.7287/peerj.preprints.26815v1

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Ocean deoxygenation: Time for action

"In their Review "Declining oxygen in the global ocean and coastal waters" [...] D. Breitburg et al. summarize evidence showing that oxygen has declined in the open ocean and in coastal waters over the past 50 years as a result of increased greenhouse gas emissions and nutrient discharges to coastal waters. We also urgently need more data on the role and speed of microbial engagement, including how deoxygenation is altering microbial pathways and rates of processes within the water column and the deep ocean. [...]" 

Source: Science
Authors: Sylvia A. Earle et al.
DOI: 10.1126/science.aat0167

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Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2


"Oceanic Anoxic Event 2 (OAE 2), occurring ∼94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE 2 remains unresolved. [...]"

Source: PNAS
Authors: Matthew O. Clarkson et al.
DOI: 10.1073/pnas.1715278115

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Oxygen loss could be a huge issue for oceans

"A major study into an ancient climate change event that affected a significant percentage of Earth’s oceans has brought into sharp focus a lesser-known villain in global warming: oxygen depletion. 

The study, just published in the prestigious Proceedings of the National Academy of Sciences (PNAS), examined a past period of global warming around 94 million years ago, when oceans became de-oxygenated.

This famous period in Earth’s geological history, known as an Oceanic Anoxic Event (OAE), was more severe and on much longer timescales than the current changes. But it has given the scientists studying this period an extreme case-study to help understand how the oceans are effected by high atmospheric CO2 emissions. [...]"

Source: University of Exeter News

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Earth’s Oceans Suffocate as Climate Change and Nutrient Loading Create “Dead Zones”

"A new research study from a Global Ocean Oxygen Network (GO2NE) team of scientists reveals that the number of low- and zero oxygen sites in the world’s oceans have increased dramatically in the past 50 years. The Intergovernmental Oceanographic Commission of the United Nations created the GO2NE working group to provide a multidisciplinary, global view of deoxygenation, with the end goal of advising policymakers on preserving marine resources by countering low oxygen. [...]"

Source: environmental monitor
Author: Karla Lant

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