An acidic ocean that disintegrates microscopic sea life might sound like "The Horror from the Deep," the plot of a bad 1950s science fiction movie. It's a scenario with chilling effects, including the destruction of pteropods, the zooplankton which feed salmon, cod, herring, mackerel and baleen whales.Along with rising sea levels, warmer temperatures and shrinking glaciers, ocean acidification is another effect of increased carbon dioxide in the earth's atmosphere. Only recently have scientists begun to study the change in ocean chemistry caused by human-caused carbon emissions."This is a very young field," said Dr. Jeff Short, an environmental chemist and adviser to the Alaska Marine Conservation Council. "It has only been widely appreciated in the last five years."The AMCC sponsored Short's talk on ocean acidification March 15 at the Alaska Islands and Ocean Visitor Center. He did an overview of recent studies on the relationship between the atmosphere and the ocean. By the year 2100, acidity in the oceans could increase to a level that hasn't been seen for hundreds of thousands of years, Short said.The world's oceans today are slightly alkaline, and saturated in terms of calcium carbonate, one of the chemicals mollusks like oysters and clams use to make their shells - and corals use to make marine reefs. Calcium carbonates in the ocean actually need to be supersaturated - at the maximum of how much of the chemical a fluid can hold - for animals to make shells.As humans burn carbon fuels and pump more carbon dioxide into the atmosphere, the ocean absorbs much of the CO2. A chemical reaction in sea water leads to an increase in acid, which then causes the amount of calcium carbonate in the ocean to drop."Minor changes in acidity can result in huge changes in carbonates," Short said.One effect is on pteropods, microscopic sea animals whose shells are made of aragonite, a form of calcium carbonate. Short said the shells of pteropods in more acidic water can show dramatic dissolution within days. Would the shells eventually disintegrate? Short was asked."You can consider that as plausible," he said.Other mollusk shells might not dissolve, but the animal could spend more energy rebuilding its shell. Plankton like copopods that make their shells from silica - sand - wouldn't be affected by acidification.Short didn't know what the effect of ocean acidification would be on Kachemak Bay oysters - but he said that would be worth studying."That's a good idea," he said.Warmer oceans can affect calcium carbonate saturation, with colder oceans having lower saturations of chemicals. Polar oceans and deeper waters might be the first oceans to feel the affects of acidification, with the Antarctic Ocean getting hit worst - and the Gulf of Alaska getting hit second worst.Carbon dioxide levels between the atmosphere and the ocean will eventually come back into balance, Short said."'Eventually' meaning millennia," he added.More water in the oceans from melting glaciers won't decrease acidification. The mass of the upper 630 feet of ocean is 73 times 1015 - a 10 followed by 15 zeroes, Short said. Adding chemicals like antacids - the common treatment for an upset stomach - would need to be done on a huge scale."That would a tremendous amount of bicarbonate soda," Short said.So how to avoid harmful effects from acidification? Short looked at the options, and said there's only one: reduce human-produced carbon emissions by between 80 and 90 percent. The solution is to reduce burning carbon fuels, said Alan Parks, Homer outreach director for the Alaska Marine Conservation Council."There's still time to do all this stuff," Short said. "There's not much time."Short said more research needs to be done on ocean acidification. Many questions remain, such as why the ocean's surface has tended to stay supersaturated with calcium carbonate and what the extent of acidification will be.
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