(N/A) Carbon constitutes $49\%$ of the dry weight of organisms and is second only to water in abundance.
If we look at the total quantity of global carbon,we find that $71\%$ of carbon is found dissolved in the oceans.
This oceanic reservoir regulates the amount of carbon dioxide in the atmosphere. The atmosphere contains only about $1\%$ of the total global carbon.
Fossil fuels also represent a significant reservoir of carbon.
- Carbon cycling occurs through the atmosphere,oceans,and through living and dead organisms.
According to one estimate,$4 \times 10^{13} \text{ kg}$ of carbon is fixed in the biosphere through photosynthesis annually.
$A$ considerable amount of carbon returns to the atmosphere as $CO_{2}$ through the respiratory activities of producers and consumers.
Decomposers also contribute substantially to the $CO_{2}$ pool by processing waste materials and dead organic matter from land or oceans.
Some amount of the fixed carbon is lost to sediments and removed from circulation.
Burning of wood,forest fires,combustion of organic matter,fossil fuels,and volcanic activity are additional sources for releasing $CO_{2}$ into the atmosphere.