biogeochemical cycles



We explain what are the biogeochemical cycles or cycles of matter and what types exist. The carbon, phosphorus and nitrogen cycle.

Biogeochemical cycles are the displacement circuits of matter.

What are biogeochemical cycles?

It is known as biogeochemical cycles or cycles of matter to the exchange circuits of chemical elements between living beings and the environment that surrounds them, through a series of transport, production and decomposition processes. Its name comes from the prefixes greek bio, "life and geo, "Earth".

In biogeochemical cycles, the different forms of life (vegetable, animal, microscopic, etc.), as inorganic natural elements and compounds (rains, winds, etc.). It is a perpetual displacement of matter from one place to another, which allows the recycling of nutrients available in the biosphere.

By "nutrients" we mean all those elements or molecules whose presence in the organism of a Living being is essential for the continuity of your existence and the reproduction from his species. Nutrients are usually composed of approximately 31 and 40 different chemical elements and, depending on the species, both the nutrients and the elements that compose them are needed in different proportions. These nutrients can be of different types:

  • Macronutrients. Its presence in the body in its different compounds constitutes around 95% of the mass of all living organisms. They are made up of carbon, oxygen, hydrogen, nitrogen, sulfur, calcium, sodium, chloride, potassium, and phosphorus. They are the nutrients that in greater quantity are in the organism of any living being.
  • Micronutrients. Its presence in the body of living beings is essential, but a minority. They are composed of iron, copper, zinc, iodine and vitamin A.
  • Energetic. They are those that the organism of living beings uses to obtain the Energy necessary to carry out vital functions. For example, amino acids and fats.
  • Structural. They are those that form the structure of the organism of living beings and allow their growth. For example, protein, phosphorus, calcium and some lipids.
  • Regulators They control the evolution of many reactions that occur in the body. The main ones are vitamins, sodium and potassium.
  • Not essential. They can be synthesized by the organism of living beings. They are not totally vital to the functioning of the body.
  • Essential They cannot be synthesized by the organism of living beings, so they inevitably have to be extracted from the environment. For example, essential amino acids and fatty acids.

Biogeochemical cycles vary according to the properties of the element involved and therefore involve different forms of life as well.

Types of biogeochemical cycles

There are several types of biogeochemical cycles:

  • Hydrological. Those in which the water cycle or hydrological cycle, which serves as a transport agent for the elements from one place to another. The water cycle itself can be included in this category.
  • Gaseous. Those in which the atmosphere for the transport of the chemical elements of the cycle, such as the nitrogen, oxygen and carbon cycle.
  • Sedimentary. Those in which the transport of the chemical element occurs by sedimentation, that is, by its slow accumulation and exchange in the Earth crust, like the phosphorus cycle.

Importance of biogeochemical cycles

Biogeochemical cycles are responsible for the vital chemical elements being recycled, otherwise they would be depleted due to which life on the planet would be impossible.

In this sense, biogeochemical cycles are the different mechanisms by which the nature it has to circulate matter from some living beings to others, thus allowing a certain margin to be always available.

None of the nutrients that a living being requires will be inside it forever. All must be returned to the environment so that they can be reused by others.

Cycle of nitrogen

The nitrogen cycle is central because it forms many biomolecules.

The nitrogen cycle is one of the main biogeochemical cycles, in which microorganisms prokaryotes (bacteria) and the plants They fix nitrogen, one of the main gases in the atmosphere, in their bodies. It is essential for various compounds in the body of animals, including the human being.

The cycle can be summarized as follows:

  • Certain bacteria fix gaseous nitrogen (N2) from the atmosphere in their bodies, forming with it organic molecules that can be used by plants, such as ammonia (NH3).
  • Plants take advantage of these nitrogenous molecules and transmit them through their tissues to the herbivorous animals and these through their tissues to the carnivorous animals and these to their predators, throughout the food chain.
  • Eventually, living things return nitrogen to the soil, either through urine (rich in ammonia), or when they die and are decomposed by bacteria, which fix the nitrogen-rich molecules, releasing the nitrogen back into the atmosphere in gaseous state.

Carbon cycle

The carbon cycle is the most important because all organisms contain carbon.

The carbon cycle is the most important and complex of the biogeochemical cycles, since all known life is composed without exception of compounds derived from this element. In addition, this cycle involves the main processes metabolic of plants and animals: the photosynthesis and the breathing.

The cycle can be summarized like this:

  • The atmosphere is made up of a significant volume of carbon dioxide (CO2). Plants and algae capture it and convert it into sugars (glucose) through photosynthesis, using for this the solar energy. This way they get energy and can grow. In return they release oxygen (O2) into the atmosphere.
  • In addition to obtaining oxygen during their respiration processes, animals access carbon from plant tissues, in order to in turn be able to grow and reproduce. Both animals and plants, when dying, provide the I usually the carbon in their bodies that, through sedimentary processes (especially on the ocean floor, where carbon is also dissolved in water), is converted into various fossils and minerals.
  • Carbon in its fossil or mineral state can last for millions of years under the earth's crust, undergoing transformations that throw off matter as different as mineral coal, Petroleum or diamonds. This matter will resurface thanks to the erosion, the eruptions and, especially, human labor: the exploitation of fossil fuels, the extraction of cement and other industries that release tons of CO2 into the atmosphere both at ocean as well as to the earth, in addition to other liquid and solid wastes rich in carbon.
  • On the other hand, animals are constantly releasing CO2 when they breathe. Other energy processes such as fermentation or the decomposition of the organic material they generate CO2 or generate other carbon-rich gases, such as methane (CH4) that also go into the atmosphere.

Phosphorus cycle

The phosphorus cycle is essential for the formation of DNA and RNA.

The phosphorus cycle It is the last and most complex of the main biogeochemical cycles, since phosphorus is an abundant element in the earth's crust, in mineral form, but that living beings essentially require, although in moderate quantities. Phosphorus is part of such vital compounds as DNA and the RNA, and its cycle can be summarized like this:

  • Phosphorus comes from terrestrial minerals, which by action of the erosion (solar, wind, water) are released and transported to various ecosystems. Human mining action can contribute to this stage as well, although not necessarily in a positive environmental way.
  • Rocks rich in phosphorus provide nutrients to plants, which fix phosphorus in their tissues and, again, transmit it to other forms of animal life through the food chain. In turn, the animals return the excess phosphorus to the soil through defecation and the decomposition of their carcasses, keeping the phosphorus in a cycle within the cycle between living beings.
  • However, phosphorus also reaches the sea, where it is fixed by algae and transmitted to animals. In this case, the element is slowly deposited on the seabed, where various sedimentary processes will make it return to the rocks that, later, in a very slow and very long geological process, will be exposed and will again provide phosphorus to the biosphere.
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