News

Earth's oxygen increased in gradual steps rather than big bursts

"A carbon cycle anomaly discovered in carbonate rocks of the Neoproterozoic Hüttenberg Formation of north-eastern Namibia follows a pattern similar to that found right after the Great Oxygenation Event, hinting at new evidence for how Earth's atmosphere became fully oxygenated.

By using the Hüttenberg Formation, which formed between a billion and half a billion years ago, to study the time between Earth's change from an anoxic environment (i.e. one lacking oxygen) to a more hospitable environment that heralded the animal kingdom, a team of researchers led by Dr. Huan Cui of the NASA Astrobiology Institute at the University of Wisconsin–Madison discovered a sustained, high level of carbon. This influx of carbon, coupled with changes in other elements, indicates how changing levels of oceanic oxygen may have lent a helping hand to early animal evolution. [...]"

Source: Phys.org

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Acid coastal seas off US putting common fish species at risk

"Scientists have shown that coastal waters and river estuaries can exhibit unique vulnerabilities to acidification than offshore waters. This acidification, detected in waters off the United States West Coast and the Gulf of Mexico, can lead to disorientation and cognitive problems in some marine fish species, such as salmon, sharks, and cod. This work is presented at the Goldschmidt Conference in Boston.
 

Scientists have recently discovered that marine creatures can be adversely affected by hypercapnia, a condition of too much dissolved CO2 in seawater (CO2 partial pressure, or pCO2). When this level rises above 1000 micro atmospheres (1000 μatm), some fish species suffer cognitive problems and disorientation, such as losing their way or even swimming towards predators. Surface ocean CO2 partial pressures tend to be around 400 μatm, so until now scientists have thought that hypercapnia was a problem which would only become apparent over time in subsurface waters. [...]"

Source: Phys.org

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Back to the future of climate change

Summary:

Researchers are looking to the geologic past to make future projections about climate change. Their research focuses on the ancient Tethys Ocean (site of the present-day Mediterranean Sea) and provides a benchmark for present and future climate and ocean models.

Source: Science Daily

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How nutrients are removed in oxygen-depleted regions of the ocean

"In the course of global climate change, scientists are observing the increase of low-oxygen areas in the ocean, also termed oxygen minimum zones (OMZs). Large-scale OMZs exist, for example, in the Pacific off the coast of South America or in the Indian Ocean. Since little to no oxygen is present in these regions - depending on the depth of the water - organisms whose metabolisms is independent of oxygen have a distinct advantage. These organisms include some representatives of the foraminifera: unicellular, shell-forming microorganisms, which have a nucleus and thus belong to the eukaryotes. Their life style involves a particular metabolic pathway termed anaerobic respiration. In the absence of oxygen, they convert nitrate present in the water into molecular nitrogen. [...]"

Source: Kiel University

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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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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.

Source: phys.org

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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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Nitrogen – ocean plastics pollution’s forgotten neighbour

"Tremendous – and deserved - attention has been paid for the last few years to the scourge of ocean plastics pollution, which we now know reaches the farthest depths of the ocean and can have impacts on ocean life from the smallest plankton to the largest whales.  We know (Jambeck et al., 2015) that some 4.8 million to 12.7 million metric tonnes of plastic enter the ocean each year. UN Environment has estimated the socio-economic costs of ocean plastics pollution at about US$13 billion per year.  We are only beginning to explore and understand the potential human health impacts of plastics in the oceanic food chain. [...]"

Source: United Nations Development Programme
Author: Andrew Hudson

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Chesapeake Bay: Larger-than-average summer 'dead zone' forecast for 2018 after wet spring

"Ecologists from the University of Michigan and the University of Maryland Center for Environmental Science are forecasting a larger-than-average Chesapeake Bay "dead zone" in 2018, due to increased rainfall in the watershed this spring.
 

This summer's Chesapeake Bay hypoxic or dead zone, an area of low to no oxygen that can kill fish and other aquatic life, is expected to be about 1.9 cubic miles (7.9 cubic kilometers), according to the forecast released today by the two universities. [...]"

Source: Phys.org

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Gulf of Mexico 'dead zone' forecasted to exceed the size of Connecticut

"Scientists have predicted the dead zone, or area with little to no oxygen in the northern Gulf of Mexico, will become larger than the state of Connecticut by the end of July. The dead zone will cover about 6,620 square miles of the bottom of the continental shelf off Louisiana and Texas. While there are more than 500 dead zones around the world, the northern Gulf of Mexico dead zone is the second largest human-caused coastal hypoxic area in the world."

Source: Phys.org

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