Which of the Following Reservoirs Holds the Most Carbon

Question

Which of the following reservoirs holds the most carbon?  
A) Marine sediments
B) Ocean water
C) Plant biomass
D) The atmosphere
E) Fossil fuel

Accepted Answer

Marine sediments hold the most carbon, estimated at around 40,000 gigatons. This is because carbon has been accumulating in marine sediments for millions of years through processes such as the burial of organic matter and the weathering of rocks. The other options, while important reservoirs, do not hold as much carbon as marine sediments.

B) Ocean water holds around 36,000 gigatons of carbon in the form of dissolved CO2 and other compounds.
C) Plant biomass holds around 600 gigatons of carbon, mainly in the form of cellulose and other complex carbohydrates.
D) The atmosphere holds around 830 gigatons of carbon in the form of CO2 and other gases.
E) Fossil fuel reserves hold around 5,000 gigatons of carbon, but most of this is not currently in the carbon cycle and is not accounted for in estimates of carbon reservoirs.