Process of Biogeochemical Cycles


Biogeochemical Cycles

A Diagrammatic Representation of Biogeochemical Cycles


What are Biogeochemical cycles?

Biogeochemical cycles mainly refers to the movement of nutrients and other elements between living and non-living beings. Carbon and Nitrogen in the environment just keep moving around living and non-living beings. The matter on Earth is conserved and is either Biotic or Abiotic. The biotic part is called the Biosphere and the nutrients we need for living is –

  • Carbon
  • Hydrogen
  • Nitrogen
  • Oxygen
  • Phosphorus and
  • Sulphur

Abiotic factors consist of

  • Atmosphere
  • Hydrosphere and
  • Lithosphere

The study of Biogeochemical cycles is all about how these nutrients move between the living and non-living. Let’s break the word –

Biogeochemical = Biological Chemical + Geological Process

Types of Biogeochemical Cycles 

Biogeochemical cycles are basically divided into two types:

  • Gaseous cycles  – Includes Carbon, Oxygen, Nitrogen, and the Water cycle.
  • Sedimentary cycles – Includes Sulphur, Phosphorus, Rock cycle, etc.

Thus we can say that with the help of these two processes, the biogeochemical cycles are possible. Some of the major biogeochemical cycles are –

  1. Water cycle
  2. Carbon cycle
  3. Nitrogen cycle
  4. Oxygen cycle
  5. Phosphorus cycle
  6. Sulfur cycle
  7. Rock cycle

The Water Cycle

With the sun’s heat and the process of evaporation, the water from the different water bodies evaporates and form clouds. There’s another process called Evapotranspiration (i.e. vapour produced from leaves) which aids this process. Again due to condensation and precipitation, in the form of rain, the water comes back to the Earth surface and runs off into the ocean.

The Carbon Cycle

All green plants, both land and aquatic plants, get carbon through photosynthesis, whereas the animals get carbon through the diet it eats, that is by eating plants. Hence the carbon goes back to the environment by an animal’s cellular respiration. This produces huge carbon content in the form of carbon dioxide as well. This carbon is again stored in the form of fossil fuel (coal & oil) and can be extracted again for various commercial and non-commercial use.  When factories use this fuel, with the process of combustion, the carbon is again released back in the atmosphere.

The Nitrogen Cycle

Most of the nitrogen in the atmosphere is present in the form of Nitrogen gas (i.e. a Nitrogen molecule). To get it into the living systems, the process of Nitrogen Fixation is required. The bacteria present in the roots of plants convert this Nitrogen gas into a usable compound called Ammonia. Ammonia sometimes is also supplied to plants in the form of fertilizers. Now plants and animals assimilate this ammonia and use it. Once these plants and animals are dead, bacteria and fungi break this Nitrogen into ammonium. There are other sets of bacteria which again breakdowns this Nitrite and Nitrate. These form of Nitrogens leaches into the land and water. Bacteria with the help of Denitrification returns the nitrogen to the environment so that this whole cycle can occur again.

NOTE: Nitrogen is an essential element of life which means life cannot sustain without nitrogen. The nitrogen in water lets algae bloom. But too much of algae growth and a bane for the environment because when these algae die, through the process of Eutrophication, other bacteria have to decompose them which leads to a lot of oxygen consumption, which is ultimately not good for the water biome or the environment.

The Oxygen Cycle

This biogeochemical cycle moves between the atmosphere, the living matter and the biosphere. Oxygen is a very abundant element on our Earth. It is found in the elemental form in the Atmosphere to the extent of 21%. The oxygen in the air is inhaled by the living organisms. When they excrete, it decomposes and breaks down into water and oxygen. Plants again use this water, along with other fresh water as well, to do the process of photosynthesis.

The plants with the help of sunlight, water, and chlorophyll, produce food or energy, which is consumed by the primary and secondary consumers. In this whole procedure of photosynthesis, the plants produce oxygen gas in the atmosphere. In this way, the whole cycle continues.

The Phosphorous Cycle

The rocks where phosphorous being uplifted, with Weathering erosion, the phosphorous is moved into the water supply. With the assimilation, the producers and consumers get it. When they die, by decomposition, excretion, and decay, it returns to the environment or ocean where it eventually settles down in sediments. Which means it never goes into the atmosphere and becomes phosphate rocks which are uplifted again and this cycle takes a long time to.

The Sulphur Cycle

This cycle moves from the oceans. The sulphur is converted by bacteria into Dimethyl Sulphide which eventually becomes Sulphur Oxide or Sulphur Dioxide. Volcanoes also release a Hydrogen Sulphide in an enormous amount which becomes Sulphur Dioxide. Factories and industries also contribute to the atmosphere by producing sulphur gases.

These gases, in the form of Sulphuric Acid and Sulphate, further is returned back in the environment through rainfall. Living organisms assimilate this sulphuric rainwater and assimilate it. The organisms die, their body gets decomposed and again are mixed into the land or water.

The Rock Cycle

Rocks are the most common material on Earth. Some rocks are made up of only one mineral where some are made up of two or more types of minerals. Rocks are constantly being formed, worn down and formed again. This is known as the Rock Cycle. Though this cycle takes thousands and millions of years. Rocks can be primarily of three types, depending on the origin of the formation. They are –

  • Igneous Rock
  • Sedimentary Rocks
  • Metamorphic Rocks

Igneous Rock

The word Igneous means ‘born out of the fire’. It is formed when the molten magma from deep within the Earth cools and eventually turns into solid rock. When the magma cools and hardens slowly, below the Earth’s surface, they form Intrusive Igneous Rocks. For example – diorite, gabbro, granite, pegmatite, and peridotite. These rocks have larger crystals.

When the magma goes out of the surface and flows out as lava during a volcanic eruption, it cools down and hardens quickly to form Extrusive Igneous Rocks. For example – Lava rock or Pumice Stone, andesite, basalt, obsidian, pumice, rhyolite, scoria, and tuff. These rocks have smaller crystals as compared to intrusive igneous rocks.

Forces of nature like wind, heat, rain, snow and ice together form the effect on the exposed rocks on the Earth’s surface to gradually erode and transport the broken bits. All the mountains are especially subjected to slow gradual erosion.

Sedimentary Rocks

Broken bits are carried down by rivers and streams as sediments. When the water slows down enough, the sediments settle down at the bottom of lakes and oceans. Over many years, layers of these sediments pile up on each other to be cemented together and harden to form Sedimentary Rocks. Most rocks found on the Earth’s surface are sedimentary rocks. For example – breccia, conglomerate, sandstone, siltstone, shale, rock salt, iron ore, chert, flint, coal, some Dolomites, some limestones, and some limestones.

Sedimentary rocks often contain fossils in them. With layers of sediments piling up on top, dead animals and plants settle at the bottom, they get compressed to eventually turn into fossil fuels.

Metamorphic Rocks

Metamorphic rocks are those who change form due to the application of tremendous heat and pressure. When the Earth’s crust moves, it causes rocks to get squeezed so hard that the heat causes the rock to change. Also, the extreme pressure under many thousands of feet of bedrock can crush the rock to form a metamorphic rock.

Metamorphic rocks are originally igneous or sedimentary rocks, which have transformed due to great heat or pressure. For example, the sedimentary rock -Limestone undergoes the process of metamorphosis to form Marble and rock igneous rock Granite changes into Gneiss.

Each of the rock types, that is igneous, sedimentary and metamorphic can be recycled into the other two. These dynamic transitions occur through geologic time. Igneous, sedimentary and metamorphic rock can be eroded and weathered into smaller fragments and carried away as dissolved material. Over time the fragmented materials accumulate, get buried by additional material and are cemented into sedimentary rocks.

Igneous, sedimentary or metamorphic rocks, when exposed to high temperatures or pressures, can be changed physically or chemically to form a different rock called Metamorphic Rock. When these rocks are pushed deep under the Earth’s Surface, they may melt into magma. This magma, when cooled, solidifies into Igneous rock.

Erosion plays a vital role in the rock cycle. Erosion happened mainly as a result of weathering which is the effect of water, temperature, and wind on the landscape. Water causes most of the erosion. Acid rain, chemicals in the air, combined with precipitation, dissolves certain rock, that is sensitive to acid. There is some kind of rocks that are soluble in water, easily gets dissolved when they come in contact with groundwater. Heavy rains, floods and fast-moving rivers, and waves break away and carry rocks. Similarly, continuous waves can crash and crumble rocks. Glaciers pick up large rocks and scrape bedrock while moving down its course. The freezing and melting of ice can cause the crack on the rocky mountains as well.

Stay tuned with BYJU’S to learn more about the Biogeochemical cycle and other related topics @ BYJU’S Biology

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