News

Increased biofilm formation due to high-temperature adaptation in marine Roseobacter

Abstract.

"Ocean temperatures will increase significantly over the next 100 years due to global climate change. As temperatures increase beyond current ranges, it is unclear how adaptation will impact the distribution and ecological role of marine microorganisms. To address this major unknown, we imposed a stressful high-temperature regime for 500 generations on a strain from the abundant marine Roseobacter clade. High-temperature-adapted isolates significantly improved their fitness but also increased biofilm formation at the air–liquid interface.  [...]"

Source: Nature Microbiology
Authors: Alyssa G. Kent et al.
DOI: 10.1038/s41564-018-0213-8

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Scientists draw new connections between climate change and warming oceans

"Earth scientists exploring how ocean chemistry has evolved found similarities between an event 55 million years ago and current predicted trajectories of planet temperatures, with regards to inputs of CO2 into the atmosphere and oxygen levels in the oceans. As the oceans warm, oxygen decreases while hydrogen sulfide increases, making the oceans toxic and putting marine species at risk."

Source: Science Daily (University of Toronto)

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Middle Eocene greenhouse warming facilitated by diminished weathering feedback

Abstract.

"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.
DOI: 10.1038/s41467-018-05104-9

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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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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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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

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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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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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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."

Source: Nature
Authors: Laure Resplandy
DOI: 10.1038/d41586-018-05034-y

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The possible roles of algae in restricting the increase in atmospheric CO2 and global temperature

Abstract.

"Anthropogenic inputs are increasing the CO2 content of the atmosphere, and the CO2 and total inorganic C in the surface ocean and, to a lesser degree, the deep ocean. The greenhouse effect of the increased CO2 (and, to a lesser extent, other greenhouse gases) is very probably the major cause of present global warming. The warming increases temperature of the atmosphere and the surface ocean to a greater extent than the deep ocean, with shoaling of the thermocline, decreasing nutrient flux to the surface ocean where there is greater mean photosynthetic photon flux density. [...]"

Source: European Journal of Phycology 
Author: John A. Raven
DOI: 10.1080/09670262.2017.1362593

Read the full article online.


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