Acidic oceans may be a boon for some marine dwellers

Researchers fret that many species of invertebrates will disappear as the oceans acidify due to increased levels of atmospheric carbon dioxide (CO₂). But a new study concludes that some of these species may benefit from ocean acidification, growing bigger shells or skeletons that provide more protection. The work suggests that the effects of increased CO₂ on marine environments will be more complex than previously thought.

Bottom-dwelling marine critters such as lobsters and corals encase themselves in shells or exoskeletons made from calcium carbonate. Previous studies predict that rising ocean acidity will result in the loss or weakening of these exoskeletons or shells and increase their owner’s vulnerability to disease, predators, and environmental stress. But marine scientist Justin Ries of the University of North Carolina, Chapel Hill, hypothesized that not all ocean organisms would respond the same way to acidity because they use different forms of calcium carbonate for their shells.

Ries and two colleagues from the Woods Hole Oceanographic Institution in Massachusetts exposed 18 species of marine organisms to seawater with four levels of acidity. The first environment matched today’s atmospheric CO₂ levels, and two others were set at double and triple the pre-Industrial CO₂ levels, mimicking conditions predicted to occur over the next century. The fourth CO₂ level was 10 times pre-Industrial levels. Although CO₂ levels won’t rise that high in our lifetime, Ries says they could within 500 to 700 years. The atmosphere did contain that much CO₂ during the Cretaceous period about 100 million years ago, Ries says. “This is an interval in which many of these organisms lived and apparently did okay, despite the extremely elevated levels of atmospheric CO₂ that existed at that time.”

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DeLene Beeland, ScienceNOW Daily News, 1 December 2009. Full article.