Oceans Becoming More Acidic

ocean5.jpgBy now you’ve probably heard most of the doomsday scenarios regarding global warming. Temperatures and sea levels are rising, glaciers and ice caps are melting, and shifting weather patterns are wreaking havoc with ways of life that have otherwise changed little for centuries. Climate change has been connected with everything from water-rights squabbles to failing crops to an increasing prevalence of malaria and dengue fever. Some scientists have speculated that these scenarios may be avoided by sequestering greenhouse gases in large bodies of water, but this short-sighted approach begs the question: what exactly are these emissions doing to our oceans?

“Ocean acidification” was a hot topic at the recent meeting of the American Association for the Advancement of Science (AAAS). According to researchers, our oceans have lower pH levels now than at any point in the last 40 million years, and at the present rate these levels will drop by another .3 units by the end of the century. This is due to the chemical reactions that result when carbon dioxide is dissolved in water, forming carbonic acid. Over the long term, this process could affect the food chain in significant ways. First, many organisms will not grow as large or will produce fewer offspring, as increased levels of CO2 render respiration and other physiological processes less efficient. Also, the absorption of greenhouse gases is likely to create dead-zones at some depths where the CO2-oxygen ratios are too low to support life. This is apparently already happening and is somewhat similar to the poisonous volcanic crater lakes that exist in central Africa, where high levels of CO2 and other gases are kept at the lake bottom due to water pressure — until something stirs up the water, leading to the release of noxious plumes that can have lethal, large-scale consequences, such as the 1700 people killed in Cameroon in 1986.

It is unlikely that the presence of such dead-zones in the oceans will present any significant danger to human populations, except in that such zones will lower the productivity of the ecosystem, affecting subsistence fishermen and others who rely on the sea for their sustenance and livelihood. But there is one more way in which ocean acidification could have serious consequences. Shellfish, coral and echinoderms may not be able to form their exoskeletons, as the calcium carbonate on which they depend dissolves during carbonic acid formation. One researcher referred to the massive volcanic explosions at the end of the Permian period 250 million years ago which caused oceanic pH levels to change suddenly, leading to the extinction of 90% of oceanic species, particularly those that make shells from calcium carbonate. Another researcher, looking into the combined effects of acidification and temperature increase, conducted experiments on purple sea urchins that replicated the ecological conditions that will exist in 2100 if emissions levels continue unabated. Her results indicated that the urchins had to work up to three times harder to create their shells, and that these shells were often deformed.

All this goes to show that you can’t simply shrug off greenhouse gases by pumping them underwater.


Posted on Wednesday, March 19th, 2008 at 11:40 am | Tagged in Art, Global Warming, Technology, Waste, Water | posted by Bill

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