Which of these is the largest carbon reserve on Earth?

The largest carbon reservoir of the Earth is the deep ocean. Around 36,000 billion tons of carbon are estimated to be stored by the deep ocean. The amount of carbon in the atmosphere is rather small, with carbon dioxide only being around 410 parts per million. Unlike Mars and Venus, which have more carbon dioxide in the air, Earth's carbon is locked up in the form of carbonates, coal and other organic sediments.

It is of vital importance to study the carbon in the deep oceans, as it is intimately connected to the atmosphere and could directly impact the level of carbon dioxide in the air. Carbon dioxide has been directly implicated in global warming, so understanding and eventually manipulating these enormous heat sinks, the oceans, may be the key to our survival.