Which statement best describes carbon sinks?

• A. They store carbon in biomass, sediments, and oceans
• B. They release carbon into the atmosphere during respiration
• C. They are only located in the oceans
• D. They have no relation to carbon storage

Answer: (A)

Carbon sinks are natural reservoirs that remove carbon dioxide from the atmosphere and store it for varying lengths of time. They help regulate climate by taking in more carbon than they release over time. Carbon ends up stored in biomass (like trees and other vegetation), in soils, and in the oceans as dissolved carbon and in sediments. This storage can last from years to centuries, and much longer when carbon becomes part of sediments and rocks. That is why storing carbon in biomass, sediments, and oceans is the best description of what carbon sinks do. In contrast, respiration releases carbon back into the air, which is a carbon source, not a sink. And carbon storage isn’t limited to the oceans—the terrestrial environment also acts as a significant sink—so saying sinks are only in oceans isn’t correct.