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Corals in the western Indian Ocean are in danger of extinction

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By Grecu Daniel CristianPublished 2 years ago 3 min read
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Rising water temperatures and overfishing threaten coral reefs in the western Indian Ocean, which could become extinct in the next 50 years, according to the first global study of these ecosystems, published on Monday, AFP reports, according to Agerpres.

The findings of the study, published in the journal Nature Sustainability, warn that coral reefs along Africa's east coast face an increased risk of extinction if urgent action is not taken.

For the first time, researchers have been able to assess the vulnerability of several reefs in the western Indian Ocean and identify the main risks to the health of corals in this part of the world.

Researchers estimate that all corals in the region are at risk of "total ecosystem collapse and irreversible damage" in the coming decades. Several coral habitats are already critically endangered.

"It simply came to our notice then. These reefs are in danger of extinction, "David Obura, founder of the CORDIO East Africa Research Institute in Kenya and lead author of the study, told AFP.

"Reefs are not in good condition anywhere in the region. All are affected and this situation will continue ", he explained.

The study, signed by members of the International Union for Conservation of Nature (IUCN), covered nearly 12,000 square kilometers of reefs, about 5 percent of the world's total.

Reefs near islands such as Mauritius, Seychelles, Comoros and Madagascar - popular tourist destinations for their marine ecosystems - are the most threatened, say researchers.

Corali. Foto: Shutterstock

Coral reefs cover only a small part (0.2%) of the ocean floor, but are home to at least a quarter of all marine flora and fauna. They also provide protection against storms and erosion in coastal areas, as well as jobs for millions of people.

For David Obura, the health of the reefs is "very precious", and their loss would be "a double test": "For biodiversity, but also for all kinds of activities in coastal areas that depend on reefs".

Global warming is the biggest threat to corals in the western Indian Ocean, where scientists say water temperatures are rising faster than anywhere else on the planet.

The oceans absorb more than 90% of the excess heat caused by greenhouse gases, which helps cool the land, but generates intense and long heat waves in marine areas.

From Kenya to South Africa, the pressure of overfishing is also identified as another risk factor.

The study emphasizes the need to respond to these two threats, global and local, as soon as possible, says David Obura: “We need to give these corals the best possible chance. To do that, we need to reduce these factors, relax the pressure on corals. ”

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Corals are marine invertebrates that belong to the phylum Cnidaria's class Anthozoa. They usually form dense colonies made up of many similar individual polyps. Coral species, which live in tropical oceans and secrete calcium carbonate to form a strong skeleton, are crucial reef builders.

Red sea fingers (Alcyonium glomeratum), a soft coral

Grooved brain coral (Diploria labyrinthiformis), a hard coral

A "group" of coral polyps is a colony of genetically identical polyps. Each polyp is a sac-like animal with a diameter of a few millimeters and a height of a few centimeters.

A central mouth opening is surrounded by tentacles. Near the base, each polyp excretes an exoskeleton.

The colony builds a skeleton distinctive to the species over many generations, which can be many meters in length. Polyps reproduce asexually, which allows individual colonies to flourish.

Corals can also reproduce sexually by spawning, in which polyps of the same species release gametes at the same time, usually around a full moon. Planulae, a mobile early form of the coral polyp that settles to create a new colony, are formed from fertilized eggs.

A coral outcrop on the Great Barrier Reef, Australia

Although some corals use stinging cells on their tentacles to gather plankton and tiny fish, most corals get their energy and nutrition from photosynthetic unicellular dinoflagellates of the genus Symbiodinium that dwell within their tissues.

The coral hue comes from zooxanthellae, which are widely known as zooxanthellae. These corals require sunshine and thrive in clean, shallow water, usually less than 60 meters deep.

Corals play an important role in the physical construction of coral reefs that form in tropical and subtropical waters, such as the Great Barrier Reef off Australia's coast.

Bleaching episodes, in which polyps expel zooxanthellae in response to stress such as high water temperature or toxins, are becoming more common in these corals.

Other corals, such as the cold-water genus Lophelia, which can survive as deep as 3,300 meters, do not rely on zooxanthellae and may thrive globally in much deeper water (10,800 feet; 1,800 fathoms).

Some have been discovered as far north as the Darwin Mounds, northwest of Cape Wrath, Scotland, and others have been discovered off the coasts of Washington and the Aleutian Islands.

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Grecu Daniel Cristian

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