Ocean acidification drives community shifts towards simplified non-calcified habitats in a subtropical−temperate transition zone
"Rising atmospheric concentrations of carbon dioxide are causing surface seawater pH and carbonate ion concentrations to fall in a process known as ocean acidification. To assess the likely ecological effects of ocean acidification we compared intertidal and subtidal marine communities at increasing levels of pCO2 at recently discovered volcanic seeps off the Pacific coast of Japan (34° N). This study region is of particular interest for ocean acidification research as it has naturally low levels of surface seawater pCO2 (280–320 µatm) and is located at a transition zone between temperate and sub-tropical communities. [...]"
Source: Scientific Reports
Authors: Sylvain Agostini et al.
Generality in multispecies responses to ocean acidification revealed through multiple hypothesis testing
"Decades of research have demonstrated that many calcifying species are negatively affected by ocean acidification, a major anthropogenic threat in marine ecosystems. However, even closely related species may exhibit different responses to ocean acidification and less is known about the drivers that shape such variation in different species. Here, we examine the drivers of physiological performance under ocean acidification in a group of five species of turf‐forming coralline algae. [...]"
Source: Global Change Biology
Authors: Allison K. Barner et al.
Stratifying ocean sampling globally and with depth to account for environmental variability
"With increasing depth, the ocean is less sampled for physical, chemical and biological variables. Using the Global Marine Environmental Datasets (GMED) and Ecological Marine Units (EMUs), we show that spatial variation in environmental variables decreases with depth. This is also the case over temporal scales because seasonal change, surface weather conditions, and biological activity are highest in shallow depths. [...]"
Source: Scientific Reports
Authors: Mark John Costello et al.
Middle Eocene greenhouse warming facilitated by diminished weathering feedback
"The Middle Eocene Climatic Optimum (MECO) represents a ~500-kyr period of global warming ~40 million years ago and is associated with a rise in atmospheric CO2 concentrations, but the cause of this CO2 rise remains enigmatic. Here we show, based on osmium isotope ratios (187Os/188Os) of marine sediments and published records of the carbonate compensation depth (CCD), that the continental silicate weathering response to the inferred CO2 rise and warming was strongly diminished during the MECO—in contrast to expectations from the silicate weathering thermostat hypothesis. [...]"
Source: Nature Communications
Authors: Robin van der Ploeg et al.
Large-scale ocean deoxygenation during the Paleocene-Eocene Thermal Maximum
"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. [...]"
Authors: Weiqi Yao, Adina Paytan, Ulrich G. Wortmann
Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem
"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.
Expanding 'dead zone' in Arabian Sea raises climate change fears
In the waters of the Arabian Sea, a vast "dead zone" the size of Scotland is expanding and scientists say climate change may be to blame. In his lab in Abu Dhabi, Zouhair Lachkar is labouring over a colourful computer model of the Gulf of Oman, showing changing temperatures, sea levels and oxygen concentrations.His models and new research unveiled earlier this year show a worrying trend.Dead zones are areas of the sea where the lack of oxygen makes it difficult for fish to survive and the one in the Arabian Sea is "is the most intense in the world," says Lachkar, a senior scientist at NYU Abu Dhabi in the capital of the United Arab Emirates.
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.
How ocean warmth triggers glacial melting far away
"The melting of glaciers on one side of the globe can trigger disintegration of glaciers on the other side of the globe, as has been presented in a recent paper by a team of AWI scientists, who investigated marine microalgae preserved in glacial deposits and subsequently used their findings to perform climate simulations. The study highlights a process with alerting consequences for modern ice sheets: continuous warming of the ocean can result in a massive loss of polar ice mass, and consequently to rapid sea level rise."
Source: Science Daily
North Pacific freshwater events linked to changes in glacial ocean circulation
"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. [...]"
Authors: E. Maier et al.
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