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Will giant polar amphipods be first to fare badly in an oxygen-poor ocean? Testing hypotheses linking oxygen to body size

Abstract.

"It has been suggested that giant Antarctic marine invertebrates will be particularly vulnerable to declining O2 levels as our ocean warms in line with current climate change predictions. Our study provides some support for this oxygen limitation hypothesis, with larger body sizes being generally more sensitive to O2 reductions than smaller body sizes. [...]"

Source: Philosophical Transactions of the Royal Society B
Authors: John I. Spicer  and Simon A. Morley
DOI: 10.1098/rstb.2019.0034

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The complex fate of Antarctic species in the face of a changing climate

"Researchers have presented support for the theory that marine invertebrates with larger body size are generally more sensitive to reductions in oxygen than smaller animals, and so will be more sensitive to future global climate change. However, evolutionary innovation can to some extent offset any respiratory disadvantages of large body size. [...]"

Source: Science Daily / University of Plymouth

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Variations in ocean deoxygenation across Earth System Models: Isolating the role of parametrized lateral mixing

Abstract.

"Modern Earth System Models (ESMs) disagree on the impacts of anthropogenic global warming on the distribution of oxygen and associated low‐oxygen waters. A sensitivity study using the GFDL CM2Mc model points to the representation of lateral mesoscale eddy transport as a potentially important factor in such disagreement. Because mesoscale eddies are smaller than the spatial scale of ESM ocean grids, their impact must be parameterized using a lateral mixing coefficient AREDI. [...]"

Source: Global Biogeochemical Cycles
Authors: A. Bahl, A. Gnanadesikan and M.‐A. Pradal
DOI: 10.1029/2018GB006121

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Vision is highly sensitive to oxygen availability in marine invertebrate larvae

Abstract.

"For many animals, evolution has selected for complex visual systems despite the high energetic demands associated with maintaining eyes and their processing structures. The metabolic demands of visual systems therefore make them highly sensitive to fluctuations in available oxygen. In the marine environment, oxygen changes over daily, seasonal, and inter-annual time scales and there are large gradients of oxygen with depth. [...]"

Source: Journal of Experimental Biology
Auhtors: Lillian R. McCormick, Lisa A. Levin and Nicholas W. Oesch
DOI: 10.1242/jeb.200899

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Assessment of time of emergence of anthropogenic deoxygenation and warming: insights from a CESM simulation from 850 to 2100 CE

Abstract.

"Marine deoxygenation and anthropogenic ocean warming are observed and projected to intensify in the future. These changes potentially impact the functions and services of marine ecosystems. A key question is whether marine ecosystems are already or will soon be exposed to environmental conditions not experienced during the last millennium. Using a forced simulation with the Community Earth System Model (CESM) over the period 850 to 2100, we find that anthropogenic deoxygenation and warming in the thermocline exceeded natural variability in, respectively, 60 % and 90 % of total ocean area. [...]"

Source: Biogeosciences
Authors: Angélique Hameau, Juliette Mignot Fortunat Joos
DOI: 10.5194/bg-16-1755-2019

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Small zooplankton rings the alarm for oxygen loss in big oceans

"Hypoxia, a low level of oxygen that limits the physiological functions of animals, is a topic that fascinates many biologists. As climate change progresses, the frequency of hypoxic episodes in aquatic environments is increasing, putting fish species under stress and even reducing populations in some cases. But it is not only fish that suffer the ill effects of hypoxia. [...]"

Source: Journal of Experimental Biology
Author: Yangfan Zhang
DOI: 10.1242/jeb.199141

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The influence of decadal oscillations on the oxygen and nutrient trends in the Pacific Ocean

Abstract.

"A strong oxygen deficient layer is located in the upper layer of the tropical Pacific Ocean and at deeper depths in the North Pacific. Processes related to climate change (upper ocean warming, reduced ventilation) are expected to change ocean oxygen and nutrient inventories. In most ocean basins, a decrease in oxygen (‘deoxygenation’) and an increase of nutrients has been observed in subsurface layers. Deoxygenation trends are not linear and there could be other influences on oxygen and nutrient trends and variability. Here oxygen and nutrient time series since 1950 in the Pacific Ocean were investigated at 50 to 300 m depth, as this layer provides critical pelagic habitat for biological communities. [...]"

Source: Biogeosciences
Authors: Lothar Stramma et al.
DOI: 10.5194/bg-2019-91

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The Ocean Is Running Out of Breath, Scientists Warn

Widespread and sometimes drastic marine oxygen declines are stressing sensitive species—a trend that will continue with climate change

"Escaping predators, digestion and other animal activities—including those of humans—require oxygen. But that essential ingredient is no longer so easy for marine life to obtain, several new studies reveal.

In the past decade ocean oxygen levels have taken a dive—an alarming trend that is linked to climate change, says Andreas Oschlies, an oceanographer at the Helmholtz Center for Ocean Research Kiel in Germany, whose team tracks ocean oxygen levels worldwide. “We were surprised by the intensity of the changes we saw, how rapidly oxygen is going down in the ocean and how large the effects on marine ecosystems are,” he says. [...]"

Source: Scientific American
Author: Laura Poppick

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Isotopic evidence for complex biogeochemical cycling of Cd in the eastern tropical South Pacific

Abstract.

"Over the past decades, observations have confirmed decreasing oxygen levels and shoaling of oxygen minimum zones (OMZs) in the tropical oceans. Such changes impact the biogeochemical cycling of micronutrients such as Cd, but the potential consequences are only poorly constrained. Here, we present seawater Cd concentrations and isotope compositions for 12 depth profiles at coastal, nearshore and offshore stations from 4°S to 14°S in the eastern tropical South Pacific, where one of the world's strongest OMZs prevails. [...]"

Source: Earth and PLanetary Science Letters
Authors: Ruifang C. Xie et al.
DOI: 10.1016/j.epsl.2019.02.001

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Deep‐sea oxygen depletion and ocean carbon sequestration during the last ice age

Abstract.

"Enhanced ocean carbon storage during the Pleistocene ice ages lowered atmospheric CO2 concentrations by 80 to 100 ppm relative to interglacial levels. Leading hypotheses to explain this phenomenon invoke a greater efficiency of the ocean's biological pump, in which case carbon storage in the deep sea would have been accompanied by a corresponding reduction in dissolved oxygen. We exploit the sensitivity of organic matter preservation in marine sediments to bottom water oxygen concentration to constrain the level of dissolved oxygen in the deep central equatorial Pacific Ocean during the last glacial period (18,000 – 28,000 years BP) to have been within the range of 20‐50 μmol/kg, much less than modern value of ca. 168 μmol/kg. [...]"

Source: Global Biogeochemical Cycles
Authors: Robert F. Anderson et al.
DOI: 10.1029/2018GB006049

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