Coral bleaching

Coral bleaching is an ecological phenomenon in which the pigment expulsion or destruction of algae that live in symbiosis with the coral is observed.

Coral bleaching, as its name implies, is a problem in which the color loss of these organisms is observed. This phenomenon, which is directly related to the increase in water temperature and, consequently, to the global warming process , occurs as a result of the expulsion or loss of pigment from algae that live in association with coral .

→ Coral reef

The coral reefs are rigid structures formed by marine life that have calcareous skeleton, such as coral, which are animals belonging to the phylum Cnidaria. Despite the name, these reefs are not only formed by corals, but also the participation of other living beings, such as coral algae.

Coral reefs are ecosystems rich in biodiversity and serve as a shelter and breeding site for various species. In addition, it is an area rich in food for the animals that live in that environment.

According to the Ministry of the Environment, one in four marine species lives in corals, including 65% of fish species. The reefs are therefore highly diverse ecosystem with a complex food web.

Because of their great biodiversity and beauty, coral reefs are often exploited by man, who removes food from these areas for his family and for trade. In addition, many explore tourism in these spaces, which ends up compromising this ecosystem, since many tourists do not respect the visiting rules, leaving garbage and stepping on the reefs.

We must not forget that coral reefs also contain organisms whose substances can be used in the pharmaceutical industry. This is the case, for example, of some sponges that have compounds used in the manufacture of AZT, a drug used to treat people with AIDS.

→ Coral reefs and zooxanthellae

Some corals have a mutualistic relationship with zooxant

The zooxanthellae live within the coral tissue, being responsible for the typical coloration of the animals and meet their energy needs. For this, they rely on the help of organic compounds produced by them in the photosynthesis process. In addition, algae are related to the increase in the rate of coral calcification.

Algae also benefit from coral , which in addition to protecting them, provides them with carbon dioxide and inorganic nutrients.

→ How does coral bleaching occur?

Coral bleaching is a problem that has been reported in several parts of the planet, including Brazil. It results from the expulsion of zooxanthellae from coral tissues or the destruction of photosynthetic pigments in these algae. Thus, the tissues of the corals become translucent, making it possible to observe the skeleton of this animal. Therefore, the whitish appearance.

hella algae, that is, they present an interaction that benefits both involved This association is important, especially in aquatic environments poor in nutrients (oligotrophic), where coral development would be impaired.

The expulsion of algae or the destruction of their pigments is a phenomenon related to environmental factors, among which are:

  • Temperature
  • Salinity
  • Pollution
  • Light
  • Excessive sedimentation

Among the most relevant factors is the increase in the temperature of the oceans, which may occur as a result of seasonal variations, such as the case of El Nino , or as a result of so-called global warming.

→ How does bleaching affect corals?

The bleaching of corals has the most serious consequence of the death of these animals. This is because, in this phenomenon, zooxanthellae, algae that provide nutrients for some species of corals, are destroyed or have their pigment removed.

Bleached coral becomes more susceptible to disease and has a reduced growth rate, even if it is recolonized by zooxanthella algae. With the coral affected, the entire reef can be harmed, negatively affecting the reef ecosystem.

Coral bleaching and global warming

The global warming is a process where an increase in average temperature of the Earth. This phenomenon is related to the intensification of the greenhouse effect, which occurs mainly due to the increase in greenhouse gas emissions, such as carbon dioxide.

Read also: Greenhouse effect and global warming

The increase in the average global temperature leads to an increase in the temperature of the water in the oceans, presented as the main factor that causes coral bleaching.

It is worth noting that corals are able to survive a bleaching event and, subsequently, be recolonized by new zooxanthellae. However, this recolonization depends on the return of adequate environmental conditions.

→ How to avoid coral bleaching?

Coral bleaching is a phenomenon related to changes in the marine environment, such as increased temperature, changes in salinity and pollution. Thus, to avoid bleaching, we must reduce or end these stressful phenomena. Among the measures that can be adopted, the following stand out:

  • Reduction of polluting gas emissions and, consequently, of global warming;
  • Creation of coral protection areas, preventing the exploitation of these ecosystems;
  • Creation of stricter policies related to the protection of the environment;
  • Individual attitudes to protect the environment, such as not throwing garbage on the street, reducing the use of cars and saving energy.

If each one does his part, we can have a healthier planet for this and for the next generations.

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