What is a coral reef

Coral reefs are one of the most diverse ecosystems on the planet, hosting up to 25% of the total marine biodiversity that exists in the oceans. In addition, they are one of the natural carbon deposits most necessary to achieve adaptation and mitigation of climate change. But what exactly is on a coral reef? How are they formed and what aquatic animals and plants constitute their wealth of biodiversity?

What is a coral reef and how is it formed?

Coral reefs are one of the most biodiverse marine ecosystems on the planet. Constituted as complex structures of calcium carbonate, coral reefs are home to an immense variety and quantity of aquatic animals and plants.

But what are corals and how exactly are reefs formed? The main organisms that make up reefs are stony corals , characterized by a hard calcareous skeleton. This skeleton is formed from the continuous secretions of coral polyps , small invertebrate animals that tend to anchor themselves to the rocks of the seabed, where they find food and the ideal environmental conditions to reproduce, giving rise to thousands of clones of polyps. . These end up constituting an extensive calcareous structure that connects them together, giving rise to an extensive colony in continuous growth and evolution, which tends to group with other colonies to form complex reefs.

The growth of polyps with the consequent formation of marine coral colonies can take place for thousands of years, so that, today, we can find amazing reefs that began to form more than 50 million years ago.

Types of coral reefs

In nature, it is possible to distinguish three main types of coral reefs, according to their shape and location:

  • Coastal reef: also called coastal reef, since it is directly connected to the shore of the coastal area, sometimes being somewhat separated from it by some type of channel or even by shallow lagoons.
  • Barrier reef: the structure of these reefs appears separated from the coast, be it continental or insular, by sediments as a barrier or deep lagoons and channels.
  • Atoll or platform reef: this last type of reef has a more or less circular shape, extending around a central lagoon.

Where are the coral reefs

The Australian Great Barrier Reef is the largest coral reef in the world, stretching for more than 2,000 kilometers off the northwestern coast of Australia. The position of this gigantic reef is not accidental, since the tropical climate of its waters, together with the shallow depth at which it is found and the absence of cold ocean currents, are the factors that make it possible for it to be located in that strategic position.

Thus, complying with these same factors, it is possible to find a large number of coral reefs in the coastal areas of the Indian and Pacific oceans , such as Southeast Asia, the Yucatan Peninsula, Honduras, the Maldives and the Bahamas.

Coral reefs, despite being complex ecosystems, function as a single individual organism , in which there is a great variety of interspecific relationships , such as the outstanding symbiosis between the polyps and the algae that make up the corals of the reef.

The immense Biodiversity in coral reefs can host hundreds of different types of corals, thousands of varieties of mollusks and millions of colorful coral reef fish of different species, which find in these rich aquatic ecosystems the food and shelter they need to survive.

In addition, among the main characteristics of the coral reef that make it the ideal ecosystem for numerous animals and plants, we can highlight:

  • Warm water temperature, around 26-27 ºC.
  • Protection against larger predators and shelter close to the coast.
  • Shallow depth, allowing the arrival of sunlight necessary for photosynthesis of aquatic plants.
  • Nutrients required for filter feeding of numerous mollusks and other reef-dwelling invertebrates that feed on phytoplankton and zooplankton .

Importance of the coral reef

Among the main functions of the coral reef we can highlight:

  • Their role in natural adaptation to climate change, since they are natural carbon deposits, that is, they are capable of absorbing atmospheric CO2, thus reducing the climatic risks associated with Greenhouse Gases.
  • The great richness of its biodiversity makes it one of the essential aquatic ecosystems for the survival and protection of millions of species of animals and plants.
  • Coral reefs also play an important role within the social and economic aspects of the regions in which they exist, since billions of people in the tropics depend on them for their subsistence, thanks to the food they provide and the promotion of the development of activities. sustainable tourism.

Coral reefs in danger of extinction

There are more and more threats to corals and the need to implement strict measures for the management of these natural spaces. From the UN Intergovernmental Panel on Climate Change (IPCC), they warned of the possible loss of up to 90% of current coral reefs if it is not possible to stop the increase in the global temperature of the planet to +1, 5 ° C.

The increasingly rapid bleaching of corals causes their slow death , due to the stress they suffer from the continuous increase in water temperature, the acidification of the oceans and the extreme changes in the amount of light and nutrients that reach them. . The small coral polyps progressively lose their color, with the consequent decrease in coral growth and, in the extreme, the death and extinction of entire reefs .

Furthermore, beyond the effects of climate change, reefs are rapidly degrading as a result of various human factors such as:

  • The oil fields.
  • Fishing overexploitation coupled with aggressive fishing techniques.
  • Pollution from spills, accumulation of plastics, sewage and excessive sedimentation.
  • Deterioration due to excessive marine tourism.

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