Biogeochemical Cycle

What a fascinating word! It’s got biology, geology and chemistry in it! When you look at everything on earth on a deeper plane, everything is interconnected and interrelated. And one way to learn about this interesting relationship between the biotic and abiotic components in an ecosystem is through the biogeochemical cycle.

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What is a Biogeochemical Cycle?

You live in a biological ecosystem that shows a constant flow of energy between various organisms. There is an exchange of nutrients, which basically translates to exchange of energy.

Biogeochemical Cycle

Nutrients ultimately are chemical compounds. So, there is this natural pathway where the living matter is constantly circulated. Nutrients are never lost from an ecosystem. Recycling of these nutrients happens at every stage. This recycling of the nutrients through different components in an ecosystem is called the nutrient cycle or biogeochemical cycle.

Here, the chemical elements are always recycled, whereas heat is dissipated. Energy flows but the matter is always recycled. To get a better idea, see the movement of water, which is a chemical compound (H2O). It moves between different living and non-living forms in various places in the biosphere.

Download Ecosystem Cheat Sheet PDF

Ecosystem Cheatsheet

Types of Biogeochemical cycles

Broadly, the biogeochemical cycles can be divided into two types, the gaseous biogeochemical cycle and sedimentary biogeochemical cycle based on the reservoir. Each reservoir in a nutrient cycle consists of an abiotic portion and an exchange pool, where there is a rapid exchange that occurs between the biotic and abiotic aspects.

The gaseous cycles exist in the atmosphere (air) or Oceans through evaporation. The different gaseous cycles are the nitrogen cycle, carbon cycle, oxygen cycle, and the water cycle.

The sedimentary cycles have the earth’s crust as the reservoir pool. These cycles include the chemical components that are more earthbound, such as iron, calcium, sulphur etc. The gaseous cycles move more rapidly when compared to the sedimentary cycles. One of the primary reasons for this could be the large atmospheric reservoir.

Let us understand the basics of a few important nutrient cycles.

Biogeochemical Cycle

Carbon Cycle

Any matter is called organic if it has carbon in it. Carbon is essential and is required to produce the molecules of nutrients such as carbohydrates, proteins, and fats. Plants use carbon dioxide and prepare food. Animals, in turn, consume plants. When plants and animals decompose, they release carbon dioxide.

Animals also release carbon dioxide during their respiration process. Carbon is also released when organic matter in burnt. In this way, carbon dioxide finds its way back to the atmosphere. This is again taken up by plants and the biogeochemical cycle continues.

Water Cycle

Water is absorbed from the soil by plants. When transpiration occurs in plants, they release water. In animals, most of the body is made up of water. Animals also drink water. Also when they perspire, water is released and gets evaporated into the atmosphere.

When animals are eaten by other animals, the water goes from one organism to the other. When animals and plants decompose, they release water, due to the chemical processes that occur. In this way, there is a continuous recycling of water through the various components of the ecosystem.

Nitrogen Cycle

Nitrogen is a very important element that is present in the genetic material – DNA and RNA. The nitrogen cycle is considered as the most complex of all biogeochemical cycles and it exists in nature in many forms. Nitrification, Denitrification, Nitrogen fixation etc. are all processes that are associated with the nitrogen cycle.

In conclusion, all these different biogeochemical cycles do not occur in isolation. The most important connecting link is the movement of water through the water cycle. The movement of water is very important for the discharge of phosphate and nitrogen into the various water bodies, including the oceans. The ocean is a major reservoir that holds carbon, another important element in the biogeochemical cycles.

Solved Questions For You

Q: Give examples of nitrogen-fixing.

Ans. Cyanobacteria, Rhizobium and Azotobacter are some examples. Cyanobacteria play a role in nitrogen fixation in aquatic ecosystems. The other two fix nitrogen in a terrestrial ecosystem.

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