The Biological Carbon Pump
– One part of the carbon cycle moves faster – biological carbon pump – at the surface of the ocean, there’s always an exchange of carbon.
– The ocean’s surface layer contains tiny phytoplankton, which have shells and sequester carbon dioxide through photosynthesis – creating calcium carbonate as their shells develop.
– When they die, these organisms sink to the ocean floor and accumulate as sediment, this process is known as the carbon pump.
– This is important as it pumps CO2 out of the atmosphere and into the oceans, preventing an imbalance of carbon within the atmosphere.
– Maintained by thermohaline circulation.
Terrestrial stores
– Terrestrial primary producers sequester carbon through the process of photosynthesis.
– Carbon is found in plants, animals, soils and micro-organisms.
– Leaves, roots, dead material and decaying litter in soil all contain carbon.
– Exchange of carbon between plants and the atmosphere is rapid.
– CO2 absorbed and converted into new plant growth during photosynthesis and as plants grow they release CO2 into the atmosphere through respiration.
– Organisms such as insects, worms and bacteria feed on dead plants, animals and waste are known as biological decomposers.
The Role of Trees
– 95% of a tree’s biomass is made up from the CO2 that it sequesters and converts into cellulose.
– Carbon fixation turns gaseous carbon – CO2 into living organic compounds that grow.
– Amount of carbon stored within a tree depends on balance between photosynthesis and respiration.
Mangroves and the Role of Soil
– Biological carbon can be stored in soils in the form of dead organic matter, or returned back to the atmosphere as a result of decomposition.
– Depending on the nature of the soils, this process can be relatively quick or, as in tundra soils, very slow.
– Deforestation and land use change can release carbon stores very rapidly.
– Mangrove forests are vital processors, sequestering almost 1.5 metric tonnes of carbon per hectare every year.
– Their soils are anaerobic so little carbon is respired back to the atmosphere.
Tundra Soils
– Much of the soil is permanently frozen and contains ancient carbon.
– Usually roots and dead and decayed organic matter are frozen, locking carbon into an icy store
Tropical Forests as Carbon Stores
– Huge carbon sinks, with carbon mainly being stored in trees, plant litter and dead wood.
– When litter and dead wood decay, they are recycled quickly so a soil stores does not develop.
– Tropical rainforests absorb more CO2 than any other terrestrial biome.