Wednesday, May 11, 2011

Ocean Acidification

Extracting, transporting, and burning fossil fuels have resulted in numerous environmental and public health problems and the present-day global Fossil Fuel Crisis.  Fossil fuels (oil, gasoline, natural gas, and coal) pollute our water, food, and air.  Carbon dioxide, which is released to air when these fuels are burned, contributes to climate change and the warming of the global ocean.  People are also becoming increasingly aware of the other “evil twin” of climate change: ocean acidification

Ocean acidification is the chemical process in which the pH (a measure of acidity) of seawater is lowered (meaning it becomes more acidic).  

Ocean waters draw down carbon dioxide from the air, and since the beginning of the last century have drawn down around 50% of the carbon dioxide humans have emitted into the atmosphere.   This “sink” of carbon dioxide unbalances the chemical equilibrium in the ocean which causes a chemical reaction cascade and a decrease in the pH level.  So far, the pH of the ocean has dropped from 8.2 to 8.1; because of the pH scale is logarithmic, this 0.1 pH decrease actually means that the oceans have become 30% more acidic!

If current trends in emitting carbon dioxide to the atmosphere continue, predictions show a drop in pH to 7.8 by 2100.    

The pH of the ocean affects marine organisms in many ways: 

A recent report by Oceana summarizes some of these effects, detailing how acidity impacts organisms like corals, shellfish, and plankton at the base of the marine food web – primarily, these are the animals and plants which build their shells and skeletons out of calcium carbonate. Calcium carbonate, a chemical used by these base-of-the-food-web animals for shells (and also used by many fish species during their larval stages), is significantly impacted by both increased levels of carbon dioxide as well as lower pH levels.  With too much carbon dioxide, calcium carbonate isn’t readily available in for animals to use, and at low pH levels, calcium carbonate dissolves

Ocean pH also affects physiology (basic life processes: breathing, breakdown of food for energy, etc) of marine life.  Fish species have a harder time reproducing, shellfish have a harder time growing and attaching to rocks, and marine mammals are deafened by ocean noises (today’s ocean, because of the increased acidity, transmits sound waves 70% farther than 50 years ago). 

Within decades, the changing pH of the ocean could have severe effects on ocean food webs, biodiversity, and fisheries.   The April, 2011 issue of National Geographic includes an article on ocean acidification that examines the sea near an island off Italy to gain insight into the effects of high carbon dioxide levels on the marine environment.

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