Friday, May 23, 2008

Can We Live Without Clams?

[Fishermen on Puget Sound. Some day, there may not be anything there to catch. Image credit: Cujo359]

I read a rather disturbing article in my home town newspaper today:

Climate models predicted it wouldn't happen until the end of the century.

So a team led by Seattle researchers was stunned to discover that vast swaths of acidified seawater already are showing up along the Pacific Coast as greenhouse-gas emissions upset the oceans' chemical balance.

In surveys from Vancouver Island to the tip of Baja California, reported Thursday in the online journal Science Express, the scientists found the first evidence that large amounts of corrosive water are reaching the continental shelf — the shallow sea margin where most marine creatures live.

Off Northern California, the acidified water was only four miles from shore.

"What we found ... was truly astonishing," said oceanographer Richard Feely, of the National Oceanic and Atmospheric Administration's (NOAA) Pacific Marine Environmental Laboratory in Seattle. "This means ocean acidification may be seriously impacting marine life on the continental shelf right now."

Acidified seawater showing up along coast ahead of schedule

The culprit, apparently, is carbon dioxide (CO2). When CO2 is introduced into cold water, which is abundant in the northern and southern regions of the Atlantic and the Pacific, it forms carbonic acid, a weak acid used in soda:

It has long been recognized that it is impossible to obtain pure hydrogen bicarbonate at room temperatures (about 20 °C or about 70 °F). However, in 1991 scientists at NASA's Goddard Space Flight Center (USA) succeeded in making the first pure H2CO3 samples. They did so by exposing a frozen mixture of water and carbon dioxide to high-energy radiation, and then warming to remove the excess water. The carbonic acid that remained was characterized by infrared spectroscopy. The fact that the carbonic acid was prepared by irradiating a solid H2O + CO2 mixture has given rise to suggestions that H2CO3 might be found in outer space, where frozen ices of H2O and CO2 are common, as are cosmic rays and ultraviolet light, to help them react.

Wikipedia: Carbonic Acid

So, colder is better for carbonic acid. The oceans in the arctic and antarctic stay near freezing (0 C, 32 F) for much of the year. It can be formed at higher temperatures, too, but not as readily. Water near the bottom of the oceans is similarly cold.

As you might imagine from what folks have been doing to create it, there's a good deal of discussion going on about just how much of a danger it is in the oceans:

The idea is not without controversy. Some scientists still cling to the idea that the buffering capacity of the oceans, by virtue of their sheer size, will counter any acidification effects. Others insist that carbonate inputs from dissolving rocks on land will counteract any reduction in alkalinity in the oceans. Still others argue that a feedback loop between oceans and atmosphere would dampen the effect; others argue that even a significantly lowered pH would not send any marine species to extinction and organisms would adapt to the changes. And even those who are most vocal about the possible effects of ocean acidification acknowledge the uncertainties, and the lack of in situ empirical proof that elevated carbon dioxide in the atmosphere lowers pH and causes significant ecological impact.

Dropping pH in the Oceans Causing a Rising Tide of Alarm

It would appear that the expedition the Seattle Times article covers is demonstrating that it may be as bad as anyone feared. The problem with carbonic acid, as with acid of any sort, is that it dissolves calcium. Calcium, of course, is what makes the shells of shellfish hard:

SHELLFISH, crabs, lobsters and a host of other familiar species could become extinct around Britain and Europe because our seas are becoming steadily more acidic.

An official report is to warn that carbon dioxide generated by human activity, already linked to climate change, is also sharply altering the chemistry of the oceans. The gas forms carbonic acid when it dissolves into sea water.

Some species, such as corals and certain plankton, are so sensitive to the rising acidity that they could be in rapid decline within decades. Others, such as crabs, mussels and lobsters, are more resistant, but they too will be in danger by the end of the century. All the affected organisms build their shells or skeletons from calcium carbonate, a mineral they extract from sea water but which is attacked by carbonic acid.


One of its authors, Carol Turley, of Plymouth Marine laboratory, said: “This issue is emerging as one of the most serious environmental threats humanity has faced. The oceans are acidifying very rapidly and many marine organisms are at risk.” Turley and her colleagues have carried out experiments measuring how marine organisms cope when sea water becomes more acidic. They tried growing a range of plankton and animal species in water that had been slightly acidified with extra carbon dioxide. Although the findings are not yet formally published, she said: “We had some very alarming results. Just a small change in acidity saw some of these creatures unable to grow or reproduce properly.

Acid seas threaten to make British shellfish extinct (PDF)

The fact that this was a problem for shellfish appears to have been discovered by accident:

Like all significant and surprising scientific discoveries, many great minds may have simultaneously converged on the idea that loading up the atmosphere with carbon emissions would begin to affect the ocean environment, and in turn its ability to further sequester carbon and maintain environmental parameters in balance. The story of one such scientist playing a key role in uncovering the phenomenon of ocean acidification was Victoria Fabry. According to New Scientist magazine, Fabry was doing shipboard experiments on small pteropod mollusks she kept in sealed jars, when she began to notice that their shells were dissolving. She surmised that the carbon dioxide respired by the pteropods was making the seawater more acidic and dissolving the calcium carbonate of their shells.

The fate of the delicate pteropods in her jars made Fabry join other scientists in wondering whether increasing the carbon dioxide concentration of the atmosphere could have a similar effect on sea life in the oceans. There had already been publications and reports on the increasing acidification -- technically, decreasing alkalinity since seawater is has an average pH of more than 8.0, and the predicted drop in pH will not take seawater below the neutral pH of 7. Most notable was perhaps the 2003 Nature paper calculating that absorption of fossil CO2 would make the oceans more acidic than they had been in 300 million years. But it was only in 2005, when the Royal Society of UK launched an investigation into the effects of acidification on marine life, that significant attention was drawn to the consequences of this "other CO2 problem".

Dropping pH in the Oceans Causing a Rising Tide of Alarm

The problem is that the shellfish can't gather enough calcium to build their shells:

A change of 0.1 units sounds small but represents a huge shift in ocean chemistry. Crucially, it represents a 30% decrease in the amount of dissolved carbonate — which marine creatures must extract from water to build their shells.

Acid seas threaten to make British shellfish extinct (PDF)

Which brings us back to the Seattle Times article, and why maritime scientists find this latest discovery so disturbing:

On the pH scale, which measures acidity, strongly alkaline materials such as oven cleaner measure about 13. Hydrochloric acid has a pH of 1. Seawater usually measures around 8.1. The most acidic water the scientists found off the Pacific Coast measured 7.6 on the pH scale. The numerical difference may seem slight, but it represents a threefold increase in acidity, Hales said.

Acidified seawater showing up along coast ahead of schedule

That's an increase of 0.5, five times the amount of acidity the Plymouth Marine Lab's report said could adversely affect shellfish survival rates. What's worse, apparently carbonic acid isn't just for cold water any more:

Until now, researchers believed the most acidified water was confined to the deep oceans. Cold water, which holds more carbon dioxide, sinks. Deep waters also are naturally high in carbon dioxide, which is a byproduct of the decay of plankton.

Feely and his NOAA colleague Christopher Sabine previously have shown that zones of acidified water are growing and moving closer to the surface as the oceans absorb more man-made carbon dioxide.

During surveys on the Pacific Coast last year, a team including Feely and Sabine discovered the natural upwelling that occurs along the West Coast each spring and early summer is pulling the acidified water onto the continental shelf.

Acidified seawater showing up along coast ahead of schedule

Shellfish aren't the only sea life that could be endangered:

We already know that warmer water is bleaching the coral of the Great Barrier Reef, but just recently it was discovered that there’s a new threat to the reef’s survival ... carbonic acid.

It’s only been in the science journals for the last few years but ocean acidification is a time bomb. It could not only destroy the Great Barrier Reef but it could wreak havoc on marine life around the world and, ultimately, affect land dwellers like ourselves.

Ocean Acidification – The BIG global warming story

A collapse of coral reefs could lead to the collapse of any number of fish populations. They often feed off the things that live in or on the reefs. To say this could be a disaster is probably an understatement.

My guess is that in the years to come, we will be reading about other effects that will either have been discovered or observed in the oceans.

What can be done about it? It's hard to say. If the problem were confined to a small pond, dumping fertilizer into it might do the trick:

Low pH can be increased easily by applying agricultural limestone. The amount of lime required can be determined by sending samples of the mud from the pond bottom to the NCDA Soil Analysis Laboratory for analysis.

Effects of High and Low pH Levels in Water on Fish

Unfortunately, scaling this sort of solution up to something the size of an ocean could prove impractical. The International Symposium On Effects of Climate Change On The World's Oceans was just held in Spain. One of the subjects was mitigation strategies. Covering all the suggested strategies would require another article, but they seem to come down to three categories of suggestions:

  1. Study specific aspects of the problem, including the rate of evolutionary change that can be expected in ocean life, and the spread of acidification and warming

  2. Regulatory responses

  3. Better management of natural resources

In short, no fixes, only mitigation strategies seem to be under consideration. This isn't too surprising. We barely understand the problem, so suggesting solutions is basically a fool's game.

So, the next time someone suggests that he doesn't see a problem with climate change, in addition to asking him if he thinks we can do without New York City and Florida, now you can ask him if he can live without shellfish. Or fish of any sort.

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