EX­TREME CORALS

Asian Diver (English) - - Science - Text by Emma Camp Im­ages by Burt Jones and Mau­rine Shim­lock

Hard-core corals liv­ing in ex­treme en­vi­ron­ments may be the key to the sur­vival of our reefs, but sci­en­tists need your help!

OUR OCEANS ARE

chang­ing at an alarm­ing rate – along­side lo­calised pol­lu­tion, reefs world­wide are be­com­ing warmer and more acidic – which to­gether threaten the sur­vival of coral reefs. 2016 has seen the world’s third mass coral bleach­ing event. (Not sure what “coral bleach­ing” is? See the box op­po­site.) We have all seen im­ages and videos from around the world show­ing fields of white coral skele­tons, where only weeks be­fore ex­isted colour­ful, healthy coral reefs.

THE WA­TER’S HOTTING UP

Warmer sea­wa­ter is of­ten the cause of coral bleach­ing; this year alone, it is es­ti­mated that over a third of Aus­tralia’s North­ern Great Bar­rier Reef has been killed due to coral bleach­ing from the warmer-than-nor­mal wa­ter as­so­ci­ated with an El Niño event.

• Above av­er­age sea­wa­ter tem­per­a­ture is the main cul­prit caus­ing coral bleach­ing but it can also oc­cur from other stres­sors such as dis­ease, high light, pol­lu­tion and changes in salin­ity.

• Corals can only re­cover from bleach­ing if “host tis­sue” re­mains in­tact on the bleached skele­ton to reac­quire zoox­an­thel­lae and re­build en­ergy re­serves. This is only pos­si­ble given enough time be­tween re­peat El Niño (or stress) events.

Corals that lose their host tis­sue are dead, and col­lapse of the reef frame­work fol­lows. Corals can only re­pop­u­late im­pacted ar­eas from neigh­bour­ing reefs that are unim­pacted or through “reef restora­tion” prac­tices.

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