Carbon Cycle: Definition, Process, Diagram, Steps, Importance

What Is A Carbon Cycle?

The carbon cycle is an integral process that governs the cycling of carbon through the biosphere, atmosphere, hydrosphere, and lithosphere. It elaborates on the cycle through which carbon constantly undergoes change and circulates within the atmosphere, water bodies, the ground and all the life forms. It is a process that all ecology and climate students know well and it relates to the movement of CO2 in and around the Earth and influences the balance of the greenhouse gases.

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This knowledge is critical for unravelling recent and future changes in global carbon loading, the productivity of the earth’s ecosystems, and the effects of fossil fuel burning and deforestation on climate and atmospheric carbon burden. Terms like, carbon capture and storage, carbon reservoirs and carbon budgets are important in understanding complex relationships between ecosystems and the atmosphere, and how these systems support life on the earth.

Components Of The Carbon Cycle

The carbon cycle involves several key reservoirs where carbon is stored and exchanged:

Carbon Reservoirs

Atmosphere:

Carbon is mostly in the form of carbon dioxides, a greenhouse gas crucial to planetary photosynthesis by plants and algae. Major activities that enhance CO2 in the atmosphere include the burning of fossils, and the felling of trees and other vegetation for various uses, all of which cause adverse changes in the world climate.

Biosphere:

The biosphere contains the carbon in living organisms in forms like plants, animals and microorganisms. In photosynthesis, plants take carbon dioxide from the atmosphere, converting it to a component of their structure. Plants thereafter, through photosynthesis fix carbon dioxide from the atmosphere and release it through respiration once feeding animals consume the plants (or other animals).

Hydrosphere:

Oceans and other water bodies, also contain dissolved carbon mainly in the forms of bicarbonate and carbonate ions and carbon in the form of organic matter from marine organisms. The ocean takes up CO2 from the atmosphere, in this way acting as a major controlling variable of atmospheric CO2. although this process enhances the absorption of CO2 it has negative effects such as the acidification of the oceans destructing the marine life.

Lithosphere:

Carbonate minerals that include limestone and dolomite are the lithosphere carbon storage systems involving rocks and sediments. Weathering and volcanic activities in the atmospheric system recycle carbon dioxide at relatively slow rates and determine the carbon cycle.

Diagram: Distribution of Carbon in Different Reservoirs

Processes In The Carbon Cycle

Oceanic Absorption And Release

One of the critical processes in the carbon cycle involves the oceans, where carbon dioxide (CO2) is absorbed and released through various mechanisms:

Oceanic Absorption:

The upper layer of oceans also continues to sequester large amounts of GHG, and CO2 from the atmosphere in the form of carbon through physical and biological mechanisms. Carbon dioxide that is dissolved in seawater then forms carbonic acid, bicarbonate ions, and carbonate ions. It also assists in maintaining the steadiness of the atmospheric CO2 amount and moderates the consequences of human emissions.

Biological Pump:

Marine life especially phytoplankton is involved in the process of photosynthesis and thus offers strategic importance in the cycles of carbon in the sea. CO2 that dissolves in water from the atmosphere is taken up by phytoplankton which then incorporate this carbon into organic carbon molecules. When phytoplankton decompose or are eaten by zooplankton and other consumers the carbon contained in their cells is transported to deeper ocean water layers for long-term storage.

Carbonate Compensation Depth (CCD):

At a certain point beneath the oceans referred to as the CCD, carbonate minerals go into a solution with thickness, profundity, and intricacy to deliver CO2 once more into the water basin. They include temperature, salinity and the carbon saturation state of seawater whereby the process is slowed down by an increase in any of the mentioned factors.

Oceanic Release:

CO2 can also be returned to the atmosphere by oceanic fancies, like upwelling, in which nutrient-rich and hence carbon-rich water rises to the surface and exchanges gases with the atmosphere. Furthermore, the effect of climate change contributes to the increase in ocean temperature and as a result, the capacity of seawater to dissolve CO2 may decrease with an implication of increasing emissions from oceans.

Diagram: Carbon Cycle Processes

Detailed Steps Of The Carbon Cycle

The steps are listed below-

Carbon In The Atmosphere

Sources of atmospheric carbon

Natural Sources:

• Respiration: Plants and animals give off CO2 in the process of cellular respiration and this increases AFM.

• Volcanic Activity: Carbon dioxide and other gases interact with volcanoes during their eruptions.

• Decomposition: Consumers feed on dead plants and animals and help decompose them to release CO2.

• Wildfires: Natural fires burn the stored carbon in the form of CO2 emitted into the atmosphere.

Anthropogenic Sources:

• Fossil Fuel Combustion: The burning of fossil fuels releases carbon dioxide that has been stored in the ground for millions of years.

• Deforestation: Trees, particularly in forests, sequester CO2 but when forests are cleared, the measure of CO2 in the atmosphere increases.

Impact on climate

Greenhouse Effect: It is one of the greenhouse gasses, which are gases that tend to trap heat within the atmosphere and hence assist in heat building meaning global warming.

Ocean Acidification: The increased amount of CO2 dissolves in water producing carbonic acid and reducing the pH level that is damaging to the ocean species.

Climate Feedback: They result in feedback such as the thawing of permafrost which results in the release of more CO2 into the air hence worsening climate change.

Carbon In Plants And Animals

Role of photosynthesis in carbon fixation

Photosynthesis: It is a process in which most plants, green algae, cyanobacteria as well as some bacteria utilize sunlight, water, and CO2 to produce glucose and oxygen. It therefore transmutes the atmospheric carbon into organic forms and most are carbohydrates and glucose.

Respiration in plants and animals

Respiration: The two groups of organisms, plants and animals, use respiration to metabolize organic molecules such as glucose to obtain energy for cellular processes.

Diagram: Photosynthesis and Respiration Cycle

Carbon In Oceans

Carbon dioxide absorption

Absorption Process: Oceans also play an important role in physical and chemical CO2 sink through which it takes large quantities of CO2 from the atmosphere. Carbon dioxide reacts with water to form a weak carbonic acid and subsequently dissociates into bicarbonate and hydrogen ions.

Carbonate and bicarbonate formation

Chemical Equilibrium: Namely, in seawater CO2 dissolves and reacts with water forming carbonic acid (H2CO3). It then undergoes dissociation yielding bicarbonate ions (HCO3-) and hydrogen ions (H+). The bicarbonates can also break into carbonate ions, though not all the bicarbonate ions in the water solution extensively do it.

Role Of marine organisms

Biological Pump: This paper focuses on the carbon cycle in the marine environment especially among the phytoplankton organisms. The latter dissolves in water and phytoplankton take up dissolved CO2 as they fix carbon during photosynthesis. Phytoplankton when they die or get consumed by zooplankton and another marine form of plants, the dead matter contains lots of carbon which then sinks to the deeper part of the ocean which may take hundreds of years before it is released back into the atmosphere.

Carbon In Soil

Decomposition of organic matter

Therefore, the deadline plant and animal particles in the soil are broken down by microorganisms which are bacteria and fungi. When the organic compounds decompose it gets catabolized into small molecules and in this process, carbon dioxide (CO2) is emitted into the atmosphere.

Soil respiration

Soil microbes and roots of plants require oxygen in this process and as a result, get to release CO2, in a process otherwise known as cellular respiration. It goes on uninterruptedly as the ground is one of the chief substrates and likely the single most important suppliers of nutrients and energy for the metabolic functions of most of its dwellers.

Impact of agriculture

Several mechanisms that have been identified to enhance the rates of soil carbon loss include; tilling, monoculture and overuse of synthetic fertilizers. These practices interfere with soil structure, promote faster decomposition, and decrease the rates of accumulation of organic matter in soil. Also, deforestation resulting from the expansion of agricultural land relieves the stored carbon into the atmosphere.

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Importance Of The Carbon Cycle

The importance is listed below-

Ecological Balance

Role in maintaining life on Earth

The management of carbon as a life-supporting cycle is deemed central to existence on planet Earth. Carbon is one of the vital structural elements of carbohydrates, proteins, lipids, and nucleic acids, which are the macromolecules in all living organisms.

Interdependence of carbon reservoirs

Carbon pools include the Atmosphere, Biosphere, Hydrosphere, and Lithosphere and the movement of carbon from one reservoir to the other forms the carbon cycle. Certain activities such as photosynthesis, respiration, decay and carbon storage control the transport of carbon between these stores to ensure that an equilibrium that is essential for sustaining an ecosystem is achieved.

Diagram: Balanced Carbon Cycle