Biological Carbon Sequestration on Land and in Oceans Revision Notes for Edexcel A-Level Geography

Biological Carbon Sequestration on Land and in Oceans

Carbon Cycle Pumps

🔗 The processes operating in oceans to circulate and store carbon. There are three sorts:
• Biological • Carbonate • Physical.

Carbon Cycle Pumps

Biological Pump	The organic sequestration of CO2 to oceans by phytoplankton → Microscopic, usually single-celled, marine plants float near the surface (allows them to access sunlight for photosynthesis) • known as the base of the marine food web ● Phytoplankton have rapid growth rates (NPP) • especially in shallow water of continental shelves where rivers carry nutrients far out to sea ● C then passed up the food chain by consumer fish and zooplankton, which release CO2 back into the water and atmosphere ● Most is recycled in surface waters ↳ Only 0.1% reaches the sea floor after the dead phytoplankton sink, where they decompose or are turned into sediment
Carbonate Pump	Relies on inorganic carbon sedimentation ● Marine organisms utilise CaCO3 to make hard outer shells and inner skeletons ● When organisms die and sink, majority of shells dissolve before reaching the sea floor sediments ● The C becomes part of the deep ocean currents ● Shells that do not dissolve build up slowly on the seafloor, forming limestone sediments
Physical Pump	Based on the oceanic circulation of water including upwelling, downwelling and the thermohaline current → The global system of surface and deep water ocean currents is driven by temp and salinity differences between areas of oceans ● CO2 in oceans mixed up more slowly than in the atmosphere ∴ there are large spatial differences in CO2 conc ○ Colder the water, the more potential for CO2 to be absorbed ↳ Warm tropical waters release CO2 to the atmosphere but colder high lat oceans take in CO2 from the atmosphere

Biological Pump

The organic sequestration of CO2 to oceans by phytoplankton → Microscopic, usually single-celled, marine plants float near the surface (allows them to access sunlight for photosynthesis) • known as the base of the marine food web
● Phytoplankton have rapid growth rates (NPP) • especially in shallow water of continental shelves where rivers carry nutrients far out to sea
● C then passed up the food chain by consumer fish and zooplankton, which release CO2 back into the water and atmosphere
● Most is recycled in surface waters
↳ Only 0.1% reaches the sea floor after the dead phytoplankton sink, where they decompose or are turned into sediment

Carbonate Pump

Relies on inorganic carbon sedimentation
● Marine organisms utilise CaCO3 to make hard outer shells and inner skeletons
● When organisms die and sink, majority of shells dissolve before reaching the sea floor sediments
● The C becomes part of the deep ocean currents
● Shells that do not dissolve build up slowly on the seafloor, forming limestone sediments

Physical Pump

Based on the oceanic circulation of water including upwelling, downwelling and the thermohaline current → The global system of surface and deep water ocean currents is driven by temp and salinity differences between areas of oceans
● CO2 in oceans mixed up more slowly than in the atmosphere ∴ there are large spatial differences in CO2 conc
○ Colder the water, the more potential for CO2 to be absorbed
↳ Warm tropical waters release CO2 to the atmosphere but colder high lat oceans take in CO2 from the atmosphere

Terrestrial Sequestration

Plants take C out of the atmosphere through photosynthesis and release CO back into the atmosphere through respiration
When consumers animals eat plants, carbon from the plant becomes part of the consumer's fats and proteins
Microorganisms and detritus feed on waste material from animals, this becomes part of the microorganisms
After plants/animals die, tissues such as leaves decay faster than more resistant structures such as wood ↳ Faster process in warmer environments

Terrestrial Sequestration