Dissolving brittle stars hint at implications of ocean acidification

Aug 16, 2013 by Chelsea Leu
Dissolving brittle stars hint at implications of ocean acidification
At the GeoSoilEnviroCARS beamline at the Advanced Photon Source, scientists mapped slices of 24 brittle starfish skeletons in 3 dimensions using X-ray tomography to find out how much volume the eroded skeletons had lost, and to reconstruct their structures. Credit: Shawn Harper

(Phys.org) —Under the sea ice of Explorers Cove, Antarctica, is a startling array of life. Brittle stars, sea urchins and scallops grow in profusion on the seafloor, a stark contrast to the icy moonscape on the continent's surface. This distant, frigid ecosystem may serve as a microcosm for the health of the entire ocean. And the plentiful brittle stars that dot the seafloor can act as a harbinger of aquatic trouble.

Scientists at Vanderbilt University and the New York Health Department say that these cold-water communities may be especially vulnerable to the effects of ocean acidification. The group has established the rate at which seawater is dissolving brittle star skeletons, and note that ocean acidity may be close to a tipping point. Surpassing that threshold may threaten the growth of and upset entire ecosystems.

Using high-energy X-rays at the Advanced Photon Source at the U.S. Department of Energy's Argonne National Laboratory, the team published in the May 2013 issue of the journal Palaios a baseline for further monitoring ocean acidification. The paper is titled "Dissolution of ophiuroid ossicles on the shallow Antarctic shelf: implications for the fossil record and ocean acidification."

Brittle star skeletons are made of calcite, which dissolves more readily in . With increasing levels of carbon dioxide and rising acidity in the ocean, brittle stars and other invertebrates may have more difficulty secreting calcite, affecting their skeletal formation and their ability to survive.

The researchers set out to establish the rate at which these skeletal parts, or ossicles, were dissolving.

"Marine invertebrates like brittle stars can signify the effects of ocean acidification, and may be used to track its effects on vulnerable organisms," said Beverly Walker, lead author of the paper and supervisor of the Crary Science Lab in McMurdo Station, Antarctica.

To find this rate, the researchers compared eroded ossicles to pristine ones, inspecting them with a scanning electron microscope for microstructural damage and fractures. Then, at the GeoSoilEnviroCARS beamline at the APS, the team mapped 24 ossicles in 3 dimensions using X-ray tomography to find out how much volume the eroded ossicles had lost, and to reconstruct the structure of the ossicles.

Scientists found that at the current rates, the ossicles need six to 105 years to dissolve completely. But they also noted that with acidity levels rising, the calcite in brittle stars is likely to be even less stable in the future. "The fact that ophiuroid ossicles show signs of initial dissolution after only two years of contact with seawater," the researchers wrote, "suggests that they are close to a threshold of dissolution."

To obtain these eroded ossicles, scuba divers collected brittle stars from the seafloor, and the researchers then placed the bagged remains of brittle stars directly on the or suspended more than a meter above it. These samples were subjected to the ocean's currents for two years.

Before this study, data on the dissolution rates of brittle stars was scarce. Now that this baseline rate is established, further research can build on this data to track the effects of on these highly specialized communities.

Explore further: Coastal Antarctic study identifies large acidic change

More information: palaios.sepmonline.org/content/28/5/317.short

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2.1 / 5 (21) Aug 16, 2013
"...these cold-water communities may be especially vulnerable to the effects of ocean acidification."

Since the 1700s the ocean surface has changed in pH from 8.25 to 8.14. Neutral water has a pH of 7 so pH has changed 1.3% towards neutrality. Alas "neutralization" wont net a half billion dollars for your buddy's electric car company:


"The fact that ophiuroid ossicles show signs of initial dissolution after only two years of contact with seawater suggests that they are close to a threshold of dissolution."

Brittle stars evolved after branching out from normal starfish 500 million years ago, 250 million years before dinosaurs, back when CO₂ was a whopping 10X today's concentration. They make their bony shells from a derivative of CO₂ called calcite, which is CaCO₃.

Here they sunk *dead* bristle star skeletons and measured how fast they re-dissolved, making no rate comparison to lower CO₂ eras. Now re-read the mealy-mouthed headline!
3.2 / 5 (14) Aug 16, 2013
Since the 1700s the ocean surface has changed in pH from 8.25 to 8.14. Neutral water has a pH of 7 so pH has changed 1.3% towards neutrality

Aren't you supposed to know something about chemistry? Heck, I'm an electrical enginer, and even I know that pH is based on the (log) concentration of H-plus atoms - and that even at pH values greater than 7 you have H-plus atoms in the water (i.e. you still have acids - even in pH regions which are above 7 ...just as you have bases forming in solutions at pH below 7).

A shift towards lower pH ALWAYS means more acids. You really need someone to tell you this? Really? Go back to school.

Brittle stars evolved after branching out from normal starfish 500 million years ago, 250 million years before dinosaurs, back when CO₂ was a whopping 10X today's concentration.

And guess what: they haven't stopped adapting to the changes in pH since then. But now it's changing so fast that they don't have time to adapt.
2.1 / 5 (21) Aug 16, 2013
Since the main beach is already strewn with Global Warming syringes, antialias now pees in our pool as his buddies demean Holocaust survivors by shouting "deniers!" at our buff crew, down here in wild paradise:


More "acid" is what the world needs, actually, to help young people see through Establi$hment bull.

Brittlestars make their shells out of CO₂, and just like phytoplankton they are growing *faster* now exactly because of fossil fuel release of life giving CO₂ that has been buried for millions of years.

Plankton is blooming by a whopping 40% thanks to fossil fuels: "Lab. evidence is presented that calcification and net primary production in the coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass."

Alarm is not data!
2.5 / 5 (22) Aug 16, 2013
Nik,you are a prime example of our failed educational system.

Carbonic acid is bad for all of the oceans.It will take out the fragile ecosystems,then global economies,and humans shortly after.

See,we have cut down over 50% of the Earth's forests. This vastly increases our UNNATURAL CO2 emissions. When the oceans absorb our C02 from the atmosphere,it bonds with calcium carbonate in the oceans to form carbonic acid.

2.5 / 5 (19) Aug 16, 2013
All of mankind's factories emit more sulfur than all of the earth's volcanoes.

Satellites have already proven that man can indeed speed up natural climate change.
All thanks to thermal imaging like spectroscopy,X-rays,etc. All gases burn a certain color. Don't tell the American conservatives about that. it's a secret. lol!
1.6 / 5 (13) Aug 16, 2013
kevin's posts on Phys.org delight Joyce lovers.


"The circumflexuous wall of a singleminded men's asylum, accentuated by bi tso fb rok engl a ssan dspl itch ina, -Yark inquires pointed out - that they ad bîn provoked ay ^ fork, of à grave Brofèsor; àth é's Brèak - tast - table; ; acùtely profèssionally piquéd, to=introdùce a notion of time [ùpon à plane (?) sù fàç'e'] by pùnct! ingh oles (sic) in iSpace!" - James Joyce (Finnegans Wake, 1939)
1.6 / 5 (14) Aug 16, 2013
kevin parroted: "See,we have cut down over 50% of the Earth's forests. This vastly increases our UNNATURAL CO2 emissions."

Indeed, forests continued to be cut down for thousands of years for fuel, agriculture and wood until the Industrial Revolution allowed us to switch to long buried fuels, metal, and plastic and to use that extra energy to produce fertilizer that made a laughing stock of the old Reverend Thomas Malthus and his more recent supporter Paul Ehrlich of Stanford, until the likes of tobacco farmer and now petrodollar mogul Al Gore used his divinity school major to whip up a new religion which, like Scientology before it, got the attention of Hollywood and thus the mainstream media. Climatology members now enthusiastically control federal funding for both science R&D and technology business grants. Activists are actually attracted to politics, unlike still busy scientists.

As our carbon emissions threaten to restore even more of our long lost forests, cue Godzilla movie!
1.6 / 5 (14) Aug 16, 2013
Franklins posts yet another *dead* animal skeleton, placed not in a living, buffered and ionically rich ocean but in a beaker, with chemicals added. Dead shells do indeed dissolve away slowly as do dead skeletons of sunken ship captains and their crews. As waves crash on beaches, old shells and dead starfish indeed wear down, unlike living ones. Missing from the image is a control that shows the effect normal sea water on utterly dead animal shells..

The extremely thin shells of the millimeter sized sea butterfly that you posted evolved a mere 100 million years ago, back when CO₂ was only 3X that of today, so it certainly does make sense to worry about ocean neutralization by CO₂ but now that Global Warming is called off by satellite, weather balloon and Argo buoy falsification of the massive water vapor feedback that all climate models rely on to form the very backbone of climate alarm, we have a century to perfect nuclear power as fracking continues to cut CO₂ emissions.
4.6 / 5 (9) Aug 17, 2013
Nik, I really am surprised at how ignorant you actually are of systems.


The idea you appear to espouse of "more is better!" with regard to carbon dioxide - I have to ask if you've ever seen plankton blooms due to iron, or heard of what happens when you throw too many nutrients in one place on land, even taking your stance that "more is better." Microbial ecology alone argues against causing random blooms or nutrient excess. It tends to not be one resource that is the limiter on a community - you remember phosphates, the things we used to have in commercial detergents? Ended up suffocating everything else in the water as oxygen consumption ramped up where it was present.

Throw one extra resource in at abundance and it tends to upset the whole apple cart - a few are able to exploit the excess, but it almost invariably involves more consumption of other resources that otherwise were rate-limited in consumption by normal environmental nutrient ratios.
4.6 / 5 (9) Aug 17, 2013
Nik -
That is all besides the argument you appear to make against carbon dioxide as a bad thing otherwise, namely as a greenhouse gas.

It's not good to mess with nutrient ratios. It's not good to pump greenhouse gasses into our atmosphere. The two add up to even more of an argument for limiting carbon dioxide emissions.

It's all environmental change. The environment does vary naturally - but unless animal variation, reproduction, and adaptation occurs at a similar or the same rate, it risks environmental collapse.

And before the "oh boo hoo" comes out, I'm not religious about it at all. I just don't like the idea of only having rats and cockroaches as company: they aren't efficient at pollinating or taking care of roadside carrion or chewing on underbrush or a myriad of other activities that make it a bit more pleasant to live on earth.

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