Biogeochemical cycles

Biogeochemical cycles are pathways through which elements and compounds essential for life are cycled and recycled in ecosystems. These cycles involve the movement of elements and compounds between biotic (living) and abiotic (non-living) components of the Earth’s systems, including the atmosphere, hydrosphere (water bodies), lithosphere (Earth’s crust), and biosphere (living organisms).

Essential Elements Involved in Biogeochemical cycle

The six most common elements associated with organic molecules—carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur—take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath Earth’s surface.

Geologic processes, such as weathering, erosion, water drainage, and the subduction of the continental plates, all play a role in the cycling of elements on Earth. 

The six aforementioned Hydrogen and oxygen are found in water and organic molecules, both of which are essential to life. Carbon is found in all organic molecules, whereas nitrogen is an i elements are used by organisms in a variety of ways.mportant component of nucleic acids and proteins. Phosphorus is used to make nucleic acids and the phospholipids that comprise biological membranes. Lastly, sulfur is critical to the three-dimensional shape of proteins.

The cycling of these elements is interconnected. For example, the movement of water is critical for the leaching of sulfur and phosphorus into rivers, lakes, and oceans. Minerals cycle through the biosphere between the biotic and abiotic components and from one organism to another.

Biogeochemical cycles can be broadly classified into two, namely

Endogenic cycles – This cycle involve movement of materials (mostly minerals) predominantly found within the subsurface rocks of various kinds such as Phosphorus and Sulphur cycle do not have a gaseous component.

Exogenic cycles

This cycle involves circulation of material which occur largely on Earth’s surface and usually have an atmospheric component. Many are exogenic cycles in which the element in question spends part of the cycle in the atmosphere include   the nitrogen cycle, carbon cycle, oxygen cycle etc.

1. Carbon Cycle: The carbon cycle is the process by which carbon is exchanged between the atmosphere, plants, animals, and the ocean. It involves various processes such as photosynthesis, respiration, decomposition, combustion, and carbon sequestration. Carbon dioxide (CO2) is taken up by plants during photosynthesis and converted into organic compounds, which are then consumed by animals. Through respiration and decomposition, carbon is returned to the atmosphere or the soil. Human activities, such as burning fossil fuels and deforestation, have significantly impacted the carbon cycle by releasing additional CO2 into the atmosphere.

2. Nitrogen Cycle: The nitrogen cycle involves the conversion of nitrogen gas (N2) from the atmosphere into forms that can be utilized by living organisms. Nitrogen fixation is the process by which certain bacteria and cyanobacteria convert atmospheric nitrogen into ammonia (NH3) or nitrate (NO3-), which can be taken up by plants. Animals obtain nitrogen by consuming plants or other animals. Decomposers break down organic matter and release nitrogen back into the soil or atmosphere through processes like denitrification. Human activities, such as the use of synthetic fertilizers and combustion of fossil fuels, have altered the nitrogen cycle, leading to increased nitrogen pollution and environmental problems.

3. Phosphorus Cycle: The phosphorus cycle involves the movement of phosphorus, an essential nutrient, through the environment. Phosphorus exists in rocks, soils, and sediments and is released into the environment through weathering. Plants take up phosphorus from the soil, and it moves through the food chain as animals consume plants or other animals. Phosphorus returns to the soil or water bodies through excretion and decomposition. Unlike the carbon and nitrogen cycles, there is no significant atmospheric component in the phosphorus cycle. Human activities, such as the excessive use of phosphorus-containing fertilizers and runoff from agricultural practices, can lead to eutrophication in water bodies.

4. Water Cycle: The water cycle, also known as the hydrological cycle, involves the continuous movement of water between the atmosphere, land, and oceans. It includes processes such as evaporation, condensation, precipitation, runoff, and transpiration. Water evaporates from water bodies and land surfaces, forms clouds, and then falls back to the Earth as precipitation (rain, snow, etc.). It flows through rivers, lakes, and groundwater, and is taken up by plants through their roots, eventually returning to the atmosphere through transpiration. Human activities can impact the water cycle through activities like dam construction, water extraction, and deforestation, affecting the distribution and availability of water resources.

These biogeochemical cycles are interconnected and influence one another. They are essential for maintaining the balance of elements and compounds necessary for life on Earth. Disruptions or alterations in these cycles, often caused by human activities, can have significant environmental impacts and disrupt the functioning of ecosystems. Therefore, understanding and managing these cycles is crucial for sustainable resource use and environmental conservation.