Dead algae accelerate ocean acidification

As air pollution has increased the amount of atmospheric carbon dioxide, our oceans have absorbed nearly half of it, becoming 30 percent more acidic than they were before the Industrial Revolution. Research has shown that our oceans are acidifying at a faster rate than at any other time in at least the last 300 million years – and, scientists have stumbled upon another source of carbon dioxide: water pollution.

Nutrient-enriched water feeds massive algae blooms that die, sink to the bottom of the ocean and release carbon dioxide as they decompose. Taken individually, these two acidification processes have moderate effects on the biological environment, but together, these mechanisms are expected to feed off one another in a synergistic way. In other words, the acidification resulting from their interaction will be worse than the sum of their parts, and that’s bad news for marine ecosystems. When the ocean becomes too acidic, many marine organisms like oysters, clams, sea urchins, corals, and some forms of plankton can’t find enough calcium carbonate to build their shells and skeletons.

Viewer Tip: Excess nutrients make their ways into our rivers, streams and oceans by seeping into our groundwater or catching a ride whenever it rains. At home, nitrogen and phosphorus are found in our fertilizers, septic tanks, laundry detergents, yard waste and pet waste. You can reduce your impact with these tips.

(Sources: Sunda, William J. and Wei-Jun Cai, 2012, “Eutrophication Induced CO2-Acidification of Subsurface Coastal Waters: Interactive Effects of Temperature, Salinity, and Atmospheric PCO2,” Environmental Science and Technology, 46:19, 10651–10659, DOI: 10.1021/es300626f; Hönisch, Bärbel et al. 2012, “The Geologic Record of Ocean Acidification,” Science, 335:6072, 1058-1063, DOI: 10.1126/science.1208277; PMEL Carbon Program, “What is Ocean Acidification?” NOAA, Accessed Online October 9, 2012,; Ballantyne, A.P. et al. 2012, “Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years,” Nature, 488, 70–72, doi:10.1038/nature11299)

Earth Gauge, October 2012. Article.

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