Ancient Ocean 'Dead Zone' Delayed Life After Mass Extinction

A flood of nutrients may have created an oxygen-starved ocean about 250 million years ago, preventing life from bouncing back for a few million years after a mass extinction wiped out 90 percent of marine species, a new study indicates.

The enriched, yet oxygen-starved ocean would have been similar to today's dead zones that appear in the modern ocean often as a result of agricultural runoff, as in the Gulf of Mexico.

The Permian-Triassic extinction, which hit about 250 million years ago, is believed to have been the result of widespread volcanic eruptions in what is now Siberia, which poured carbon dioxide into the atmosphere. Although the dates are inexact so far, it seems that life took an unusually long time to recover — possibly as much as 5 million years. [Oceans in Peril: Primed for Mass Extinction?]

Too much of a good thing

Chemical evidence from limestone deposited on the ocean floor during this time indicates that too much of a particular kind of life — tiny photosynthetic organisms, like certain bacteria and possibly algae — may have kept other marine species from recovering and diversifying.

"There was actually a lot of life in the ocean, but the life was not the typical life you would expect to find in oceans today," said lead researcher hydrogen sulfide. It's not clear whether or not algae — which need oxygen — were present, Meyer said.

Here's how it may have happened: The elevated carbon dioxide resulted in acid rain, which weathered the land (eroding sediments), releasing nutrients such as phosphorus, which were carried into the oceans with runoff. The extra nutrients fed these tiny organisms, causing them to flourish in the sunny surface waters. But when they died and sank to the seafloor, their decomposition sucked oxygen out of the water, creating what is called an anoxic, or oxygen-free, environment. The oceans also became sulfurous.

At other points in Earth's history, life has recovered more quickly from major setbacks. For instance, it took most animal groups hundreds of thousands of years to rebound after the Cretaceous-Tertiary extinction wiped out the dinosaurs, according to Lee Kump, a geoscientist at Pennsylvania State University who was not directly involved with the research, although he did provide feedback to the researchers and is Meyer's former adviser. 

"Scientists have argued about causes, either it was just in the nature of evolution, when it gets set back so abruptly and so intensely… Or it could signal more persistent, inimical oceanic conditions that delayed recovery," Kump said.
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Two Christmas Pups Found Abandoned In Snow

While others will be tucking into their turkey dinner on Christmas Day staff at Dogs Trust Newbury will be working around the clock caring for this Christmas’s first canine casualties – two little twelve-week-old puppies abandoned three days before Christmas in Reading.
Staff at the rehoming centre have given the pups suitably festive names – Brandy and Pudding. Brandy, a Staffordshire Bull Terrier, was cruelly abandoned on a street in Reading, while Pudding, a Boxer cross, was dumped in snowy woodland during the night on Tuesday (21st December). Both pups had been left to fend for themselves in the snow as temperatures dropped below freezing.
The puppies, discovered by a local dog warden, were understandably frightened and extremely cold but are making good progress at the rehoming centre. Pudding is underweight but has a distended abdomen, suggesting she had been poorly for some time. The two are now receiving round-the-clock care from Dogs Trust staff and although not litter-mates have already become firm canine chums and share a kennel together.
The pups will remain in the care of Dogs Trust until they have fully recovered and are ready to find a loving new home in the New Year.
Dogs Trust Newbury Rehoming Centre Manager, Maureen Iggleden, comments: “We suspect Brandy and Pudding may have been bought as Christmas presents and dumped when their owners realised the work involved in looking after a puppy. Our centre looks after hundreds of abandoned and unwanted dogs every year but it still shocks us to think that someone could so callously abandon a puppy, especially in these weather conditions.”
Clarissa Baldwin, Dogs Trust CEO who coined the famous slogan “A dog is for life not just for Christmas®”, adds:
“Sadly there are still people out there who think pets are as disposable as Christmas wrapping paper. Our research this year revealed that 1 in 5 parents would still consider buying their child a dog for Christmas, even though most presents are discarded by their bored recipients after just four weeks.
We’re urging people to ’think life’ before taking on a dog.”
To help discourage people from thoughtlessly buying dogs as Christmas presents, the charity’s 17 Rehoming Centres has put a hold on rehoming dogs from 19th December to 2nd January 2011. People are still able to visit the centres and reserve a dog, but will not be able to take it home until the New Year.
Anyone interested in rehoming Brandy or Pudding should contact Dogs Trust Newbury directly on 01488 658391 or visit the centre at Plumb’s Farm, Hamstead Marshall, Newbury, Berks RG20 0HR.
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