Subscribe to our free daily newsletters
  Space Travel News  




Subscribe to our free daily newsletters



EARLY EARTH
ASU graduate student leads study estimating oxygen loss in ancient global ocean
by Staff Writers
Tempe AZ (SPX) Aug 16, 2017


Adding nutrients to the ocean causes increased production of organic matter such as phytoplankton. When these die, they sink to the bottom as "marine snow" and decompose, consuming oxygen in the process. This is thought to be primarily responsible for large-scale oxygen loss in ancient oceans, leading to mass extinctions in the marine environment. The modern ocean exhibits similar symptoms. Image courtesy Natalie Renier, Woods Hole Oceanographic Institution.

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.

Their research was published August 9, 2017, in the journal Science Advances.

"The project began when I was an undergraduate Summer School Fellow at Woods Hole," says Ostrander, a PhD student at ASU's School of Earth and Space Exploration. His coauthors on the paper are Jeremy Owens at Florida State and Sune Nielsen at Woods Hole.

"We were able to track changes to the oxygen content of ancient seawater by measuring isotopes of thallium in ancient seafloor sediments," Ostrander explains. "Since the oxygen in the rocks we measure wouldn't really give any valuable information, we use thallium and other elements as stand-ins, or proxies."

Sediments preserve the thallium isotope composition of seawater, which changes depending on the amount of oxygen in the deep ocean at the time they were deposited. The sediments pile up over time, with deeper levels corresponding to times further in the past.

The sediments the team studied were organic-rich black shales collected as core samples by deep ocean drilling in 2003. The site was the Demerara Rise, a submarine plateau in the Atlantic Ocean off the coasts of Surinam and French Guyana.

"We dissolved the rocks in our lab," explains Ostrander, "and then chemically separated everything but thallium, the element we needed for analysis."

Then using mass spectrometry, the team measured variations in thallium within sedimentary rocks as a proxy for changes in oxygen levels over tens of thousands of years.

Based on the analysis, the researchers suspect that up to half of the deep ocean had become oxygen-depleted during Oceanic Anoxic Event 2, and remained so for about half a million years before it recovered.

"The loss of oxygen took 43,000 years to occur, plus or minus about 11,000," says Ostrander. "Call it 50,000 years or less."

The primary cause of Oceanic Anoxic Event 2 may have been increased nutrient delivery to the oceans, the researchers say. An increase in nutrients fuels the production of organic matter, and subsequent remineralization by bacteria feeding on it.

"It's this remineralization that is specifically responsible for the oxygen loss, because these bacteria consume oxygen in order to oxidize the organic, or carbon-bearing, matter," Ostrander says. "We see a similar scenario in the modern ocean, again due to increased nutrient delivery, but largely driven by fertilizers used in farming."

In fact, he says, "the largest 'dead zone' observed in the Gulf of Mexico is occurring right now for this very reason."

The researchers draw a distinct parallel between the rate of deoxygenation back then and modern trends in oceanic oxygen loss.

Says co-author Nielsen, "Our results show that marine deoxygenation rates prior to the ancient event were likely occurring over tens of thousands of years, and are surprisingly similar to the two percent oxygen depletion trend we're seeing induced by human-related activity over the last 50 years."

He adds, "We don't know if the ocean is headed toward another global anoxic event, but the trend is, of course, worrying."

Ostrander says, "At this point, we are only just beginning to understand how oxygen levels in the ocean have changed in the past. But with our new tool, we've already learned that one of the most extreme climate events in the sedimentary record provides an uncomfortably reasonable analog for possible future ocean oxygen loss and subsequent ecological shifts."

He adds, "We hope to use this information to gain a better look into the short-, medium- and long-term future for oxygen content in today's oceans."

EARLY EARTH
Scientists unearth largest dinosaur species in Patagonia
Washington (UPI) Aug 9, 2017
Paleontologists have unearthed a new species of titanosaur in Agentina's Patagonia. Researchers believe it is the largest dinosaur species ever discovered. Titanosaurs are a diverse group of plant-eating sauropods. The group's newest member is Patagotitan mayorum. Its name is an homage to the dino's origins and size - "mayorum" is the Greek word for titan. Scientists first disco ... read more

Related Links
Arizona State University
Explore The Early Earth at TerraDaily.com


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

EARLY EARTH
EARLY EARTH
For Moratorium on Sending Commands to Mars, Blame the Sun

Tributes to wetter times on Mars

Opportunity will spend three weeks at current location due to Solar Conjunction

Curiosity Mars Rover Begins Study of Ridge Destination

EARLY EARTH
Florida startup boldly sets sights on moon

Moon could be wetter than thought, say scientists

How Light Looks Different on the Moon and What NASA Is Doing About It

United Launch Alliance to launch Astrobotic mission to the Moon

EARLY EARTH
New Horizons Video Soars over Pluto's Majestic Mountains and Icy Plains

Juno spots Jupiter's Great Red Spot

New evidence in support of the Planet Nine hypothesis

Twilight observations reveal huge storm on Neptune

EARLY EARTH
A New Search for Extrasolar Planets from the Arecibo Observatory

Gulf of Mexico tube worm is one of the longest-living animals in the world

Molecular Outflow Launched Beyond Disk Around Young Star

Unexpected life found at bottom of High Arctic lakes

EARLY EARTH
ISRO Develops Ship-Based Antenna System to Track Satellite Launches

SpaceX Sets August 14 Launch Date for Next US Resupply Mission to ISS

Dragon to be packed with new experiments for International Space Station

NASA taps BWXT for reactor design for future Mars missions

EARLY EARTH
China develops sea launches to boost space commerce

Chinese satellite Zhongxing-9A enters preset orbit

Chinese Space Program: From Setback, to Manned Flights, to the Moon

Chinese Rocket Fizzles Out, Puts Other Launches on Hold

EARLY EARTH
SwRI part of international team identifying primordial asteroids

Supernova-Hunting Team Finds Comet with Aid of Amateur Astronomer

Asteroid Flyby Will Benefit NASA Detection and Tracking Network

Upcoming asteroid flyby will help Planetary Defense Network




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement