CARBON - Biological processes sequestering carbon

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  • Biological processes sequestering carbon
    • Oceanic sequestering
      • oceanic store is 50x larger than the atmosphere. Carbon stored in algae, plants and coral (rest is dissolved).
      • Three oceanic carbon pumps:
        • PHYSICAL - Water in oceans. Upwelling of rich-nutriented, cooler water occurs due to winds blowing parallel to coast. The oceanic circulation of water.
          • slower mixing of CO2 in water than in atmosphere. 10% more CO2 is absorbed in deep, cold water. warm water releases  CO2, cold water absorbs.
          • CO2 gets into ocean by diffusing into water surface and dissolving. variables of rate include wind, temp of water and CO2 conc.
        • BIOLOGICAL - Phytoplanktontransforms old C compounds to new ones. They photo-synthesise on ocean surface at the PHOTIC ZONE. C then passed up the food chain by fish, releasing CO2 into the atmosphere.
          • 0.1% of C reaches the ocean floor as dead sediment. Sequester over 2 billion tonnes of CO2 annually to ocean.
        • CARBONATE - shells form form sediments of dead organisms on the ocean floor. (hard outer shells and skeletons of crustaceans, fish, coral, plankton).
          • The White Cliffs of Dover - CaCO3.
    • Happens in a few hours to centuries.
    • Terrestrial sequestering
      • Plants sequester carbon out of the atmosphere during photo-synthesis. carbon enters the food chain and nutrient cycles of ecosystems. (when animals eat plants, carbon becomes part of their fat).
        • respiration returns some of the carbon back into the atmosphere, and waste can be eaten by micro-organisms (bacteria) and detritus feeders (beetles). When these die, carbon is built into the soil.
      • Vary's on timescales:
        • Diurnally - during the day, fluxes are positive (from atmosphere to ecosystem) and at night, the opposite.
        • seasonally - seasonal. More CO2 is present in the atmosphere in winter because of low levels of plant growth. in spring, the conc's decrease as plants grow.


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