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Study estimates oxygen loss in ancient global ocean

A loss of oxygen in global ocean seawater 94 million years ago led to a mass extinction of marine life that lasted for roughly half a million years.

Scientists have found several potential explanations for how the loss of oxygen happened. These could include enhanced volcanic activity, increased nutrients reaching the ocean, rising sea levels, and warming sea and surface temperatures. But to point a finger at any one cause (or several of them) requires knowing how fast the oxygen loss happened.

A new technique, developed by Arizona State University graduate student Chad Ostrander with colleagues at Wood Hole Oceanographic Institution (WHOI) and Florida State University (FSU), has put a timetable on the oxygen loss associated with this major ocean extinction event, which is known to science as Oceanic Anoxic Event 2.

Source: phys.org

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Meat industry blamed for largest-ever 'dead zone' in Gulf of Mexico

"The global meat industry, already implicated in driving global warming and deforestation, has now been blamed for fueling what is expected to be the worst “dead zone” on record in the Gulf of Mexico.

Toxins from manure and fertiliser pouring into waterways are exacerbating huge, harmful algal blooms that create oxygen-deprived stretches of the gulf, the Great Lakes and Chesapeake Bay, according to a new report by Mighty, an environmental group chaired by former congressman Henry Waxman. [...]"

Source: The Guardian

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Gulf of Mexico ‘dead zone’ is the largest ever measured

"Scientists have determined this year’s Gulf of Mexico “dead zone,” an area of low oxygen that can kill fish and marine life, is 8,776 square miles, an area about the size of New Jersey. It is the largest measured since dead zone mapping began there in 1985." 

Source: National Oceanic and Atmospheric Administration (NOAA)

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Fossil site shows impact of early Jurassic's low oxygen oceans

Summary:

Using a combination of fossils and chemical markers, scientists have tracked how a period of globally low ocean-oxygen turned an Early Jurassic marine ecosystem into a stressed community inhabited by only a few species.

Source: Science Daily

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Report: High seas in high danger as ecological tipping point nears

"As delegates convene at the United Nations to work out an international treaty to preserve the biodiversity of the high seas, a new report underscores the need to protect the remote ocean.

Scientists at Oxford University in the United Kingdom reviewed 271 research papers published between 2012 and 2017 and synthesized the latest data on the impact of climate change, fishing and pollution on the high seas. Their findings are not encouraging: Even the most distant reaches of the ocean are suffering from chemical and plastic contamination, a loss of biodiversity and the consequences of rising temperatures. [...]"

Source: UPI

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Massive Bloom Of Pickle-Shaped Sea Creatures Fills The Pacific

"Millions of tubular sea creatures called pyrosomes have taken over the Pacific Ocean in an unprecedented bloom that has scientists baffled.

These bumpy, translucent organisms look like sea cucumbers that range in size from six inches to more than two feet long. But they’re actually made up of hundreds of tiny animals knit together with tissue into a filter-feeding cylinder. [...]

No one knows what the effects of the bloom will be, but scientists worry that if all the creatures die off at once they could sink to the seafloor and suck up all the oxygen as they’re decomposing, creating a dead zone for marine life."

Source: OPB/EarthFix

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NOAA, USGS and partners predict larger summer ‘dead zone’ for the Chesapeake Bay

"Scientists expect this year’s summer Chesapeake Bay hypoxic or “dead zone” — an area of low to no oxygen that can kill fish and aquatic life — will be larger than average, approximately 1.89 cubic miles, or nearly the volume of 3.2 million Olympic-size swimming pools.

Measurements for the Bay’s dead zone go back to 1950, and the 30-year mean maximum dead zone volume is 1.74 cubic miles. [...]"

Source: U.S. Geological Survey

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Stormy waters: the salmon farmer trying to limit fishing and save the ocean

"There’s trouble brewing in Tasmania’s waterways once again.

In the 1980s, protests over the proposed Franklin River hydroelectric dam threw the Apple Isle’s conservation plight onto the national stage. This time, it is the state’s salmon farming industry that is under a cloud. The relatively young industry is worth over $700m a year and now outpaces all other farming activities on the island but environmental campaigners are worried about its impact on the region’s pristine waters. [...]"

Source: The Guardian

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As CO2 Goes Up, Ocean Health Goes Down

"June 8th is World Oceans Day, a day to raise awareness of the ocean’s importance to the planet. 93 percent of the excess heat absorbed by the climate system goes into our oceans, creating major consequences. While more extreme storms and rising sea levels are some of the impacts of warmer oceans, rising CO2 levels and the resulting warmer oceans are impacting ocean health itself. The most well­known effects are coral bleaching and ocean acidification, but an emerging issue is the decreasing oxygen levels in the warming waters. [...]"

Source: Climate Central

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Jurassic drop in ocean oxygen lasted a million years

"Dramatic drops in oceanic oxygen, which cause mass extinctions of sea life, come to a natural end - but it takes about a million years.

The depletion of oxygen in the oceans is known as "anoxia", and scientists from the University of Exeter have been studying how periods of anoxia end.

They found that the drop in oxygen causes more organic carbon to be buried in sediment on the ocean floor, eventually leading to rising oxygen in the atmosphere which ultimately re-oxygenates the ocean."

Source: University of Exeter
Contact: Alex Morrison

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