Gulf Dead Zone Looms Large in 2019
"In 2019, predictions indicate that the Gulf of Mexico will retain the dubious distinction of having the second-largest low-oxygen dead zone on Earth (the Baltic Sea remains firmly in first place). By the end of the summer, the hypoxic region on the seafloor at the mouth of the Mississippi River is expected to occupy over 22,000 square kilometers—an area the size of the state of Massachusetts. [...]
Source: Earth & Space Science News
Author: Mary Caperton Morton
The far-future ocean: Warm yet oxygen-rich
"The oceans are losing oxygen. Numerous studies based on direct measurements in recent years have shown this. Since water can dissolve less gas as temperatures rise, these results were not surprising. In addition to global warming, factors such as eutrophication of the coastal seas also contribute to the ongoing deoxygenation. [...]"
Loss of fixed nitrogen causes net oxygen gain in a warmer future ocean
"Oceanic anoxic events have been associated with warm climates in Earth history, and there are concerns that current ocean deoxygenation may eventually lead to anoxia. Here we show results of a multi-millennial global-warming simulation that reveal, after a transitory deoxygenation, a marine oxygen inventory 6% higher than preindustrial despite an average 3 °C ocean warming. [...]"
Source: Nature Communications
Authors: Andreas Oschlies et al.
Will giant polar amphipods be first to fare badly in an oxygen-poor ocean? Testing hypotheses linking oxygen to body size
"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
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
Variations in ocean deoxygenation across Earth System Models: Isolating the role of parametrized lateral mixing
"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
Vision is highly sensitive to oxygen availability in marine invertebrate larvae
"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
Assessment of time of emergence of anthropogenic deoxygenation and warming: insights from a CESM simulation from 850 to 2100 CE
"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. [...]"
Authors: Angélique Hameau, Juliette Mignot Fortunat Joos
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
The influence of decadal oscillations on the oxygen and nutrient trends in the Pacific Ocean
"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. [...]"
Authors: Lothar Stramma et al.