Ocean Acidification and Phytoplankton

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Ocean Acidification and Phytoplankton

• By, Chelsea Sheffield

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Questions

• What biogeochemical process leads to
  acidification?
• Ocean acidification causes decreased saturation
  of what minerals?
• What do the most current studies indicate about
  calcification of coccolithophores?

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Anthropogenic CO2

• Burning of fossil fuels
• 40 of CO2 or 127 billion metric tons absorbed by
  ocean over past 200 years
• pH has dropped about 0.1
• Atmospheric CO2 increased from 280ppm to 380ppm

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Biogeochemical Process

• CO2 H2O ? H2CO3
• H2CO3 ionizes HCO3- ? CO32-
• Lower pH more HCO3- and less CO32-
• Could decrease as much as 50
• CO32- Ca2?CaCO3

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Decreased Mineral saturation

• Decrease aragonite and calcite saturation with
  increasing CO2 concentration

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Skeletons

• CaCO3 necessary for marine calcifying organisms
  to make shells and skeletons
• Calcification could decrease by 60 by the end of
  the century
• Phytoplankton responsible for 45 of the earths
  primary photosynthetic production
• Coccolithophores
• Coccoliths
• HCO3-

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Decreased Calcification

• Degree of supersaturation decreased then
  calcification will decrease
• Decreased calcification and damaged coccoliths
  under high CO2 concentrations for Emiliania
  huxleyi and Gephyrocapsa oceanica

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Diverse Effects

• Outdoor mesocosms in a fjord south of Bergen,
  Norway
• Natural phytoplankton
• CO2 bubbled in
• Under high CO2 concentrations E. huxleyi most
  abundant
• Coccolithophores benefited

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Diverse Effects

• E. huxleyi increased production rates and
  decreased growth rates, but increased volume of
  coccoliths, and no malformations

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Conclusions

• Need more studies for more conclusive results
• Laboratory and field experiments
• Standards on how pH is controlled in experiments
• More organisms studied

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References

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