A biogeochemical cycle is defined as the movement or circulation of elements through organisms and the environment. The term consist of two parts — bio, meaning biological organisms like bacteria, plants, animals and geochemical involves geological and chemical processes such as the formation of molecule.
Elements within biogeochemical cycles flows in various forms from the non living (Abiotic) components of the biosphere to the living (biotic) component and back.
In order to survive, all the chemicals elements need to be recycled continuously to maintain the survival of living components of ecosystem. The term was given by Russian geographer named B. B polynov in 1937 . It is also referred as the study of exchange of materials between living and non living components of the Biosphere. The rapid exchange of elements occurs between the biotic and abiotic components of an ecosystem.
The biogeochemical cycles are of two types : gaseous and sedimentary.
The classification has been given on the basis of primary source of nutrients input into the ecosystem.
- Gaseous - in these cycles the gaseous phase is dominant. The main pool of nutrients is atmosphere and oceans. Cycling of carbon, nitrogen occurs as gaseous cycles. Gaseous cycles tend to move more rapidly than do sedimentary ones and adjust to changes in the biosphere because of the large atmospheric reservoir.
- Sedimentary - in these cycles, the circulation of various elements such as carbon, nitrogen, phosphorous, sulphur occurs. The nutrients are released from lithosphere (main reservoir) via weathering of rocks. The main pool of elements is rocks, soil and minerals. Sedimentary cycles get disrupted by local disturbances as the materials remains Immobilized in the earth’s crust.
- Water also circulates within the different components of the ecosystem. Water from the water bodies gets heated up due to sun’s rays and evaporates to reach the atmosphere as vapour (gaseous form) . It gets condensed to form which again send the water back to earth in the form of rain.
Sedimentary cycles vary from one element to another . Each cycle consist of a solution phase ( water related) and a rock phase (sediment) . In the solution phase, wethering releases minerals from Earth’s crust in the form of of salts. The minerals dissolve in water, pass through a series of organisms and ultimately reach the deep seas, where they get stored as reserve and moves out of circulation. In the rock phase, salts deposit as sediment eventually that get weathered and recycled.
Reservoirs or pools of nutrients include atmosphere or rocks. These are generally large in size. The nutrients moves to different areas/compartments during cycling. The effect of human activities on nutrients cycles needs to be assessed. Disturbances such as global warming, wildfires and storms seriously affect the capacity for self adjustment. Accumulation of gases such as carbon dioxide (CO2) are dissipated by winds or taken up by plants
biogeochemical cycles are said to be perfect or imperfect. In perfect cycles, nutrients get replaced with the same pace as they are used up. Most of the gaseous cycles are considered to be perfect in contrasts, sedimentary cycles are considered to be imperfect because some of the nutrients are lost into soil and sediments as reserves and is not available for Recycling. Some parts of nutrient stagnation occurs in lakes and oceans .
Both the nutrient cycles involves the biological, non biological processes and are driven by flow of energy through ecosystem. Water as the medium helps in the movement of elements and other material through the ecosystem.
plants and some animals obtain nutrients present in various components of the environment. Animals get the nutrients through the plants and animals. After the death of an organisms, the elements fixed in its body are returned to the environment through the action of decomposers (decay organisms such as bacteria, insects and fungi) and become available to other living organisms.
Nutrient cycles
These cycles consist of two parts — the environmental phase and the organisms phase in the environmental phase, cycling of nutrients by different components of environment such as air, water, soil occurs where in organisms phase transfer of nutrients to plants, animals and microorganisms occurs. Many nutrient cycles operate simultaneously in biosphere to ensure the availability/supply of chemical nutrients to all living organisms.
There are different types of cycle
- Carbon cycle
- Nitrogen cycle
- phosphorus cycle