Tuesday, December 4, 2012

Study: our oceans are so acidic they're dissolving snails

More than a hundred thousand marine species build their bodies using calcium carbonate, including snails, oysters, sea stars, coral, and plenty of planktonic animals.
This incredible diversity of life evolved over millions of years, as animals figured out ways to pull calcium and carbonate ions from the water to build shells and skeletons so robust that they remain intact long after the animals perish.
But all of this is changing.
Our addiction to fossil fuels and the billions of tons of carbon dioxide we're pumping into the atmosphere each year may be undoing millions of years of evolution in a geological blink of time.

From TheAtlantic

Problem :
In 2008, a U.S. scientist predicted the corrosive effects that ocean acidification could have on tiny shellfish called pteropods, also known as marine snails, also known as sea butterflies, and sometimes referred to as "the potato chips of the oceans."
She warned they would not only be the "canaries in the coal mine" of climate change, but that the impact of losing a snail the size of a lentil would undoubtedly creep its way up the food chain.

The pteropod (marine snail) Limacina helicina antarctica (Nina Bednarsek/British Antarctic Survey)
The full study in Nature GeoScience journal

Methodology :
Turns out, this hypothetical disaster was already happening.
Also in 2008, during what should have been a relaxing trip in the Antarctic seas (or at least, that's what the phrase "science cruise" evokes for me), researchers from British Antarctic Survey, the University of East Anglia, the US Woods Hole Oceanographic Institution, and the National oceanic and Atmospheric Administration collected pteropods from the top 200m of the ocean's surface, where they tend to live, and examined them for shell damage.

Planktonic snails known as sea butterflies build fragile shells.
Will they survive an acidifying ocean? Plankton Chronicles Project by CNRS

Results :
The sea snail's shells were found to be "severely dissolved."
Part of the acidity in the water sample was due to upswelling, a natural occurrence in which cold water from the depths of the ocean is pushed up to the surface by heavy winds.
Upwelled water itself can be corrosive, and it's expected to occur more frequently as climate change intensifies.
But the ocean's pH is also decreasing at least in part because of atmospheric carbon dioxide attributed to the burning of fossil fuels.

Conclusion :
The impact of ocean acidification is, as predicted, significant, and is affecting marine ecosystems and food systems.

Implications :
"The tiny snails do not necessarily die as a result of their shells dissolving," said co-author (and science cruise leader) Geraint Tarling, "however it may increase their vulnerability to predation and infection."
This can go on to affect bigger fish, and from there, penguins and polar bears.
The snails are also the only food source of the "Sea Angel," another pretty name for something that's really just a slug, but is no less important for it.
And these little guys are only the first to start dissolving -- if ocean acidification continues at its current rate, the consequences can extend even further. First it's the sea butterflies, then it's everything else.

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