Headline Sep 25, 2014/



An Omega value for aragonite of one  is the level of acidity where calcium carbonate dissolves out of the mineral as easily as it precipitates into it.

In other words, the system is in equilibrium and shells made of aragonite  will not tend to dissolve.

Merely creeping above that value does not, however, get you out of the woods. Shell formation is an active process, and low omega values even above one make it hard. 

Corals, for example, require an omega value as high as three to grow their stony skeletons prolifically.

But that could be a problem by 2100. Low omega values are spreading from the poles  (whose colder water dissolve carbon dioxide more easily } towards the tropics.

The Monterey report suggests that the rate of erosion of  reefs could outpace reef building by the middle of the century, and that all reef formation will cease by the end of it.
Other species will suffer, too. A study published in Nature last year, for example, looked at the shells of planktonic snails called pteropods. 

In Antarctic waters, which already have an omega value of one, their shells were weak and badly formed when compared with those:

Of similar species found in warmer, more northerly waters. Earlier work on other molluscs has come to similar conclusions. Not everything suffers from more dissolved CO2, though. 

The Monterey report cites studies which support the idea that algae, cyanobacteria and sea grasses will indeed benefit.

One investigation also suggests acidification may help cyanobacteria fix nitrogen and turn it into protein. 

Since a lack of accessible nitrogen keeps large areas of the ocean relatively sterile, this, too could be good for productivity.

The Monaco report attempts to identify fisheries that will be particularly affected by these changes.

These include the Southern Ocean  (one of the few areas not already heavily fished)  and the productive fishery off the coast of Peru and northern Chile, where upwelling from the deep brings nutrients to the surface, but which is already quiet acidic.

The principal threat here, and to similar fisheries, such as that off the west coast of North America, is to planktonic larvae that fish eat.

Oysters and clam beds around the world are also likely to be effected -again,  the larvae of these animals are at risk.

The report does not, though, investigate the possibility of increases  in algal plankton raising the oceans' overall productivity.

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''' Acid Test '''

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