The Dangers of Ocean Acidification

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The Dangers of Ocean Acidification

• Scientific American
• March 2006, pp 58-65
• Scott C. Doney

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Question 1

• Is the rate of CO2 appearing in the atm (Rin)
  equal to the rate of CO2 being removed from the
  atm (Rout) by plant uptake and deposition in the
  ocean?
• The assumption in 1950 was that Rin Rout.
• Scientists set up CO2 monitors in Antarctica and
  Mauna Loa n 1958.
• Result Rin gt Rout. Fig 16.8, 16.9 in text.

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Question 2

• How much of the CO2 from fossil fuel burning has
  been deposited in the oceans?
• 1980-1990 studies mapped carbon concentrations
  worldwide. 2004 analysis of these data
  determined how much of total carbon is from
  fossil fuel burning.
• Result 50 of fossil fuel carbon has been
  deposited in oceans.

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CO2 Chemistry

• Pristine oceans have pH 8-8.3
• CO2 H2O ? H2CO3 carbonic acid (weak acid)
• H2CO3 ? H HCO3-
• HCO3- ? H CO32-
• 2000, pH of oceans was 0.1 pH units lower
• By 2100, it may be 0.3 pH units lower

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More Chemistry

• Shellfish, coral, phytoplankton need calcium
  carbonate for body building.
• There is competition for the carbonate ion
  (CO32-) between Ca2 and H
• Ca2 CO32- ?? CaCO3
• H CO32- ?? HCO3-
• As H increases, the second rxn dominates, thus
  removing too much CO32-.

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Question 3

• What is the effect of CO2 in the oceans?
• Some phytoplankton that live at the water's
  surface are covered with CaCO3 plates.
• If the ocean's pH decreases, less carbonate ion
  will be available for plate building.
• These plankton are a major food source for fish
  and marine mammals.
• They are also important in converting sunlight to
  carbon containing molecules and oxygen.

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Question 3

• Coral are actually algae or sea anemone-related
  species that filter plankton and secrete CaCO3
  for structure. With reduced levels of the
  carbonate ion, less CaCO3 is available and less
  coral is produced.
• Deep sea coral reefs are important habitats for
  fish. In turn, fish are eaten by marine
  creatures higher on the food chain.

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Question 3

• The colors characteristic of shallow water coral
  are due to bacteria. Environmental stress such
  at high T and low pH cause these bacteria to
  leave the coral surface causing coral bleaching.

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Current ResearchThree Approaches

• Study the impact of increased CO2 levels on a
  single species.
• Study an isolated portion of a real ocean
  habitat.
• Study geologic records to determine the impact of
  increased CO2 levels in the ocean
• http//www.royalsoc.ac.uk/displaypagedoc.asp?id13
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