"A Chemical Imbalance" - (Part 5 - LAT - Altered Oceans series)

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A Chemical Imbalance
Growing seawater acidity threatens to wipe out coral, fish and other crucial species worldwide.

By Usha Lee McFarling
August 3, 2006

...Scientists report that the seas are more acidic today than they have been in at least 650,000 years. At the current rate of increase, ocean acidity is expected, by the end of this century, to be 2 1/2 times what it was before the Industrial Revolution began 200 years ago. Such a change would devastate many species of fish and other animals that have thrived in chemically stable seawater for millions of years.

Less likely to be harmed are algae, bacteria and other primitive forms of life that are already proliferating at the expense of fish, marine mammals and corals.

In a matter of decades, the world's remaining coral reefs could be too brittle to withstand pounding waves. Shells could become too fragile to protect their occupants. By the end of the century, much of the polar ocean is expected to be as acidified as the water that did such damage to the pteropods aboard the Discoverer.

Some marine biologists predict that altered acid levels will disrupt fisheries by melting away the bottom rungs of the food chain — tiny planktonic plants and animals that provide the basic nutrition for all living things in the sea....

The oceans have been a natural sponge for carbon dioxide from time immemorial. Especially after calamities such as asteroid strikes, they have acted as a global safety valve, soaking up excess CO2 and preventing catastrophic overheating of the planet.

If not for the oceans, the Earth would have warmed by 2 degrees instead of 1 over the last century, scientists say. Glaciers would be disappearing faster than they are, droughts would be more widespread and rising sea levels would be more pronounced....<more>

http://www.latimes.com/news/local/oceans/la-me-ocean3aug03,0,3589668.story

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3. More numbers, etc. from the article...

"By comparing these measurements to past levels of carbon dioxide preserved in ice cores, the researchers determined that the average pH of the ocean surface has declined since the beginning of the Industrial Revolution by 0.1 units, from 8.16 to 8.05.

Geological records show that such a change has not occurred in 650,000 years, Feely said....

If CO2 emissions continue at their current pace, the pH of the ocean is expected to dip to 7.9 or lower by the end of the century — a 150% change.

The last time ocean chemistry underwent such a radical transformation, Caldeira said, "was when the dinosaurs went extinct.


.....Zachos' international team analyzed sediments from a series of cores taken from the floor of the Atlantic Ocean 750 miles west of Namibia. At the bottom of the cores, the team found normal sediments, rich in calcium carbonate from shells — the sign of a healthy ocean.

But higher up, at a point in geologic history when the last major global warming event occurred, the whitish, carbonate-rich ooze gave way to a dark red clay layer free of shells. That condition, the researchers concluded, was caused by a highly acidified ocean. This state of affairs lasted for 40,000 or 50,000 years. It took 60,000 years before the ocean recovered and the sediments appeared normal again."

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