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Tags Current Affairs

Corals grow neon colours to survive

Date: 25 May 2020 Tags: Climate Change

Issue

A new study suggests that corals have an unusual survival method of taking on a vibrant neon colour when they face exceptional stress on their existence.

 

Background

When bleaching events occur, extended heat spikes cause corals to turn a ghostly white, often leading to their death. But “colourful bleaching” has the opposite effect: the dying corals gain more pigment, and glow in shades of bright pink, purple and orange. 

 

Details

  • Scientists first spotted the mysterious neon coral a decade ago, but they had been unable to figure out why it occurred. The study suggests the corals change colour as a last-ditch effort to survive.

  • Coral animals symbiotically coexist with tiny algae, providing them with shelter, nutrients and carbon dioxide in exchange for their photosynthetic powers.

  • Even slight increases in annual ocean temperatures can wreak havoc on this relationship, expelling the algae from the coral’s tissue and exposing its white skeleton.

  • After the coral is exposed, it often breaks down and dies, altering the ecosystem for the diverse array of life that relies on it.

  • Researchers recreated the stressful ocean temperatures in a lab. They found that colourful bleaching events occur when corals produce what is effectively a sunscreen layer on their surface to protect against harmful rays and create a glowing display that researchers believe encourages algae to return.

  • Research shows colourful bleaching involves a self-regulating mechanism, a so-called optical feedback loop, which involves both partners of the symbiosis.

  • The resulting sunscreen layer will subsequently promote the return of the symbionts. As the recovering algal population starts taking up the light for their photosynthesis again, the light levels inside the coral will drop and the coral cells will lower the production of the colourful pigments to their normal level.

  • It’s not just warming oceans that cause colourful bleaching. Changes in nutrient levels within coral reefs due to fertilizer run-off from farms also lead to bleaching events. 

  • Experts believe only coral that has faced mild or brief disturbances, rather than extreme mass bleaching events, can attempt to save itself using this process.

  • These corals can still undergo some of their normal functions for a short period of time as they hope their algae come back, whereas drastic changes in ocean temperature almost always lead to coral death.

  • Scientists emphasized that while colourful bleaching is a good sign, only a significant reduction of greenhouse gases globally, in addition to improvement in local water quality, can save coral reefs beyond this century.

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