Giant coral reef discovered off Tahiti: What is a coral reef and what it means for the environment

The reef is thought to be one of the largest found at such depths and seems untouched by climate change or human activities. AP

In  a rare find, marine scientists have discovered one of the largest coral reefs in “pristine” condition off the coast of Tahiti.

The rose-shaped corals, which have been found deep under water, are apparently unharmed by humans and climate change, UNESCO announced on Thursday.

Let’s take a brief look at what coral reefs are, why they are one of nature’s most diverse ecosystems and why they are vital for the environment:

What are coral reefs?

Sometimes termed “rainforests of the sea”, coral reefs form some of the earth’s most diverse ecosystems. Coral reefs are generally formed by colonies of stony corals, a type of marine invertebrates that secretes calcium carbonate to form a hard skeleton.

While occupying less than 0.1 per cent of the ocean area, it is believed that they provide home for at least 25 per cent of all marine species including fish, mollusks, crustaceans and sponges.

While coral reefs are most commonly found at shallow depths in tropical waters, deep and cold water coral reefs have also been found, although at a smaller scale.

The Indo-Pacific region accounts for 91.9 per cent of the total reef area including 32.3 per cent in southeast Asia, 40.8 per cent in the Pacific and Atlantic and Caribbean coral reefs account for 7.6 per cent of it.

Are they in danger?

Yes. According to a September 2021 report by The Guardian, coral reefs have declined by 50 per cent since 1950.

It has been found in different studies that they are under threat from excess nutrients of nitrogen and phosphorus, rising temperatures, overfishing, and even sunscreen use.

According to the Status of Coral Reefs of the World 2020 report by the Global Coral Reef Monitoring Network, mass coral bleaching events due to rising temperatures has remained the greatest threat to coral reefs.

It found that the planet lost about 14 per cent of its coral reefs, which amounts to about 11654 square kilometres of reef.

Why the discovery is important

Since most reefs grow in warm, shallow, clear, sunny and agitated water, UNESCO said it was “highly unusual” to find the area of healthy coral in cooler waters between 30 and 65 metres (98 to 213 feet) deep.

This discovery could also suggest there are more reefs in the ocean depth that may be safer from the impacts of warming waters.

“The discovery of this reef in such a pristine condition is good news and can inspire future conservation,” said Laetitia Hedouin, a marine biologist at French research agency (CNRS), as reported by Agence French-Presse (AFP).

“We think that deeper reefs may be better protected from global warming.”

The reef is approximately three kilometres (two miles) in length and up to 65 metres wide in places, which UNESCO said “makes it one of the most extensive healthy coral reefs on record”.

According to the BBC, the reef was found in November during a diving expedition to a depth known as the ocean’s “twilight zone” – part of a global seabed-mapping mission called the Seabed2030 Project.

Professor Murray Roberts, a leading marine scientist from the University of Edinburgh told the BBC that the discovery suggests we may find such deeper reef systems are refuges for corals in the future.

“As shallow waters warm faster than the deeper waters we may find these deeper reef systems are refuges for corals in the future. We need to get out there to map these special places, understand their ecological role and make sure we protect them for the future,” Roberts said.

With inputs from agencies

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