Global warming is causing a silent storm in the oceans by acidifying waters at a record rate, threatening marine life from coral reefs to fish stocks, an international study showed on November 14, 2013. The report, by 540 experts in 37 nations, said the seas could become 170 percent more acidic by 2100 compared to levels before the Industrial Revolution. Carbon dioxide, the main greenhouse gas, can become a mild acid when mixed with water.
Many Issues Confront our Ocean
Acidification is combining with a warming of ocean waters, also caused by a build-up of greenhouse gases in the atmosphere, and other man-made factors such as higher pollution and overfishing, the report said.
“It is like the silent storm – you can’t hear it, you can’t feel it,” Carol Turley, a senior scientist at the Plymouth Marine Laboratory in England, told Reuters.
The study, released on the sidelines of a meeting of almost 200 nations in Warsaw on ways to slow global warming, estimated that acidity of the oceans had already increased by 26 percent since the Industrial Revolution in the 18th and 19th centuries.
OCEAN FOOD CHAIN
The oceans absorb an estimated 22 million tons of CO2 from the atmosphere every day. This buffers the greenhouse effect by drawing the planet-warming gas out of the atmosphere and storing it in water, but at a great cost to ocean life. This carbon mixes with the salt water to create carbonic acid, which immediately breaks down, forming bicarbonate and hydrogen. And this excess hydrogen increases the water’s acidity. Higher acidity, in turn, undermines the ability of everything from corals to crabs to build protective shells and skeletons and has knock-on effects on the food web.
Marine chemist Richard Feely, a senior scientist with the National Oceanic and Atmosphere Administration, has been collecting water samples in the North Pacific for over 30 years. He’s observed a decrease in pH at the upper part of the water column, notably the region where carbon dioxide from automobile exhaust, coal-fired power plants, and other human activities has collected. This surface water is now acidic enough to dissolve the shells of some marine animals such as corals, plankton, and mollusks in laboratory experiments.
But this not only hampers the ability of marine animals like corals and crabs to create shells and skeletons. There are microscopic organisms called phytoplankton and zooplankton who are made up of calcium carbonate, because they have different sorts of calcificated structure. Even though they are tiny species, they are the very basis of the food chain and the web of ocean life. These problems trickle up to affect the large fish that depend on smaller organisms for food.
Acidification also causes some coral species to grow more slowly or disappear. Since coral reefs support 25 percent of the ocean’s species of fish, this spells widespread trouble. Marine ecosystems are so interconnected, in fact, that scientists cannot predict the full effects of acidification. They only know that changes in the availability of food and in community structure can scale up quickly.
NO DEBATE: INCREASED ACIDITY IS MANMADE
We spend a lot of time worrying about carbon dioxide in the atmosphere, as a form of pollution and also as a key greenhouse gas that traps solar heat. But we pay less attention to the effects emissions have in the ocean. There is no debate that rapidly increasing seawater acidity is the result of man-made carbon emissions.
“The chemistry of the uptake of carbon dioxide and its changing pH of seawater is very, very clear,” explains Feely.
The new study concurs: “Marine ecosystems and biodiversity are likely to change as a result of ocean acidification, with far-reaching consequences for society,” according to the summary led by the International Geosphere-Biosphere Programme.
“Economic losses from declines in shellfish aquaculture and the degradation of tropical coral reefs may be substantial owing to the sensitivity of molluscs and corals to ocean acidification,” the study said.
And some studies have found that young clown fish, made famous by the movie “Finding Nemo”, behaved as if drunk in more acidic waters, their brains apparently disoriented.
Another study found that rockfish can become more anxious.
“A normal fish will swim equally in light and dark areas in a tank … an anxious one on high carbon dioxide spends more time in the darker side, the more protected side,” said Lauren Linsmayer of the University of California, San Diego.
“If society continues on the current high emissions trajectory, cold water coral reefs, located in the deep sea, may be unsustainable and tropical coral reef erosion is likely to outpace reef building this century,” the report said.
Deep cuts in emissions of greenhouse gases, from power plants, factories and cars, would limit acidification.
The Warsaw talks are working on plans for a global deal, due to be agreed in 2015, to limit climate change.
Source: Planet Ark, by Alister Doyle
Image: Great Barrier Reef Foundation