Carbon cycle

What is carbon cycle?

The carbon cycle is the exchange of carbon atoms between the Earth’s atmosphere, oceans, land, and living organisms.

Carbon dioxide is the most common type of carbon in the atmosphere (CO2). Physical, chemical, and biological activities such as photosynthesis, cellular respiration, and the breakdown of dead organic matter drive the carbon cycle.

The ocean is important in the carbon cycle because it absorbs roughly one-third of the carbon dioxide produced into the atmosphere by human activity.

Biogeochemical cycles

What are biogeochemical cycles?

The Biogeochemical cycle refers to the cyclic movement of important chemical components through the biosphere’s atmosphere, hydrosphere, and lithosphere.

In the biosphere, water, carbon, nitrogen, oxygen, and phosphorus circulate cyclically. These biogeochemical cycles keep the natural environmental balance.

Steps of the carbon cycle

The carbon cycle describes the movement of carbon between different reservoirs on Earth, including the atmosphere, oceans, soil, and living organisms.

Carbon fixation:

The process by which atmospheric carbon dioxide (CO2) is converted into organic carbon by photosynthetic organisms such as plants, algae, and some bacteria. This is the primary way that carbon enters the biological part of the carbon cycle.


When living organisms use organic carbon as fuel, they combine it with oxygen to release energy and produce carbon dioxide as a waste product. This returns carbon to the atmosphere.


When dead organisms and organic matter are broken down by bacteria and fungi, carbon is released into the soil as carbon dioxide and other organic compounds.


When fossil fuels such as coal, oil, and gas are burned, carbon is released into the atmosphere as carbon dioxide. This is a major contributor to the increase in atmospheric carbon dioxide concentrations in recent years.


Carbon dioxide moves between the atmosphere and the oceans through diffusion, which is the natural movement of particles from an area of high concentration to an area of low concentration.

Ocean uptake:

The oceans are a large carbon sink, and can absorb carbon dioxide from the atmosphere through a process called dissolution. However, this can also lead to ocean acidification, which can have harmful effects on marine life.

Geological processes:

Carbon can also be stored in rocks and fossil fuels for millions of years, through processes like sedimentation, burial, and compression.

Carbon cycle diagram

Ocean plays a significant role in the carbon cycle

By absorbing, storing, and cycling vast amounts of carbon, the ocean plays an important role in the carbon cycle. The ocean is a large carbon sink, meaning it absorbs and stores carbon from the atmosphere over extended periods of time. The ocean has absorbed around one-third of the carbon dioxide emissions caused by human activities such as fossil fuel combustion, deforestation, and land-use changes.

Ways that the ocean is involved in the carbon cycle:

Carbon dioxide absorption:

The ocean absorbs carbon dioxide from the atmosphere through a process called diffusion. The concentration of carbon dioxide in the atmosphere is higher than the concentration in the ocean, so carbon dioxide moves from the atmosphere to the ocean. This process aids in climate regulation by lowering the quantity of carbon dioxide in the atmosphere, which lessens the greenhouse effect and moderates the Earth’s temperature.

Carbon storage:

The ocean stores large amounts of carbon in the form of dissolved inorganic carbon, such as carbon dioxide, bicarbonate, and carbonate ions. These carbon compounds can remain in the ocean for centuries, millennia, or even longer.

Biological pump:

The ocean also has a biological pump that cycles carbon from the surface waters to the deep ocean. Phytoplankton, tiny photosynthetic organisms that live near the ocean surface, take up carbon dioxide from the atmosphere and use it to grow. When phytoplankton die, they sink to the deep ocean, taking carbon with them. This process helps to remove carbon from the surface waters and sequester it in the deep ocean.

Ocean acidification:

When carbon dioxide is absorbed by the ocean, it reacts with seawater to form carbonic acid. This can lower the pH of seawater and make it more acidic, a process known as ocean acidification. Ocean acidification can have harmful effects on marine life, such as reduced growth and survival of shell-forming organisms.

Role played by cellular respiration the carbon cycle

Cellular respiration is an important part of the carbon cycle because it is the process by which living organisms release carbon dioxide back into the atmosphere. During cellular respiration, organic molecules like glucose are broken down by living cells to produce energy, and carbon dioxide is released as a waste product. This process involves the oxidation of organic compounds, which transfers electrons from the organic molecule to an electron acceptor, such as oxygen or other oxidized organic compounds. This transfer of electrons generates energy that the cell can use for various metabolic processes.

Cellular respiration contributes significantly to the atmospheric carbon dioxide pool by emitting massive volumes of carbon dioxide into the atmosphere. The carbon dioxide produced by respiration, on the other hand, is utilized by photosynthetic organisms, which take up the carbon dioxide and use it to form organic molecules via carbon fixation. This balances the carbon released by respiration with the carbon fixed by photosynthesis, which is a crucial part of the carbon cycle.

detritus feeders and the carbon cycle

Detritus feeders, also known as decomposers, are organisms that feed on dead organic matter, such as fallen leaves, dead animals, and fecal matter. They are an important part of the carbon cycle because they break down complex organic compounds into simpler compounds, such as carbon dioxide, water, and nutrients. By doing so, they release carbon back into the environment, making it available for use by other organisms.

Detritus feeders carry out the process of decomposition, which is a crucial step in the carbon cycle. During decomposition, detritus feeders break down complex organic molecules into simpler compounds, such as carbon dioxide and water. These releases carbon back into the atmosphere, and also makes nutrients available for use by other organisms, such as plants.

Detritus feeders help to cycle carbon via soil ecosystems in addition to their role in decomposition. When they devour organic materials, they release nutrients into the soil, which plants can subsequently absorb. This process aids in the preservation of the carbon-nutrient balance in soil ecosystems.

Why is the carbon cycle important

Climate regulation:

By balancing the quantity of carbon in the atmosphere, the carbon cycle helps to keep the Earth’s climate. Carbon dioxide is a greenhouse gas that stores sun’s radiation and heats the Earth. The carbon cycle contributes to the maintenance of a carbon balance in the atmosphere, which in turn regulates the Earth’s temperature and climate.

Life support:

Carbon is a building block of life and is essential for the growth and survival of all living organisms. The carbon cycle helps to cycle carbon through living organisms, the atmosphere, and the environment, making it available for use by plants, animals, and other organisms.

Soil health:

The carbon cycle helps to maintain healthy soils by cycling nutrients and organic matter. When carbon is cycled through soils, it helps to maintain soil structure and fertility, which is important for supporting plant growth.

Ocean health:

The carbon cycle also plays an important role in ocean health. The oceans absorb carbon dioxide from the atmosphere, which can help to regulate the Earth’s climate. However, excess carbon dioxide can also lead to ocean acidification, which can have harmful effects on marine life.

Fossil fuel production:

The carbon cycle is also important for the production of fossil fuels, such as coal, oil, and natural gas. Fossil fuels are made from the remains of ancient plants and animals, which were preserved in the Earth’s crust over millions of years.

How do humans affect the carbon cycle

The use of fossil fuels, deforestation, and changes in land use have resulted in a considerable rise in the amount of CO2 in the atmosphere, leading to global warming and climate change. Carbon dioxide levels in the atmosphere are rising, causing ocean acidification, which is harming marine life and ecosystems.

To reduce the effects of climate change, it is essential to reduce carbon dioxide emissions into the atmosphere while increasing carbon storage in terrestrial and oceanic ecosystems.

This can be accomplished through reducing greenhouse gas emissions, planting trees, and protecting and restoring ecosystems, all of which play an important role in carbon sequestration.

How does deforestation affect the carbon cycle

Deforestation has a significant impact on the carbon cycle because it removes large amounts of carbon stored in forests and disrupts the natural balance of carbon cycling. Trees absorb carbon dioxide from the atmosphere through the process of photosynthesis, and store the carbon in their leaves, branches, and trunks. When forests are cleared or burned, the stored carbon is released back into the atmosphere in the form of carbon dioxide, a greenhouse gas that contributes to climate change.

Deforestation affects the carbon cycle in several ways:

Loss of carbon sinks:

Forests are significant carbon sinks, meaning they absorb more CO2 than they emit. Deforestation reduces the quantity of carbon dioxide absorbed by trees, resulting in an increase in atmospheric carbon dioxide levels.

Carbon emissions:

Deforestation releases large amounts of carbon dioxide and other greenhouse gases into the atmosphere. This occurs when trees are burned, or when the organic matter in the soil is exposed to the air and decomposes, releasing carbon dioxide into the atmosphere.

Reduction in photosynthesis:

The loss of trees and plants reduces the amount of photosynthesis occurring in the area, which means less carbon dioxide is being absorbed from the atmosphere.

The impact of deforestation on the carbon cycle is significant and can contribute to climate change, which has far-reaching consequences on the environment and human health. It is important to preserve and protect forests to maintain the natural balance of the carbon cycle and reduce the amount of carbon dioxide in the atmosphere.

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