Reef bleach

Great Barrier Reef bleaching

Coral reefs can take thousands of years to build but are surprisingly susceptible to climatic events. Coral bleaching is the primary cause of reef destruction. El Niño combined with rising sea temperatures have meant for the loss of up to 25 per cent of the Great Barrier Reef since 2014.
Past events have shown reefs recover from mass bleaching including the Great Barrier Reef – record sea temperatures in 1998 and 2002 saw more than 50 per cent bleaching but 95 per cent reef recovery once the temperatures normalized. However, given the sheer scope and rate of recent bleaching events, scientists fear the reef’s inability to recover and it has prompted them to take action.

Symbiodinium are single-celled, photosynthetic microbes that live within coral. The coral animal itself requires food from the photo synthesizing Symbiodinium to live. Hence, a unique symbiotic relationship exists between them. However, rising sea temperatures inhibit Symbiodinium photosynthesis thus effecting the coral’s food uptake. A downward spiral occurs as the coral rejects the Symbionts turning white and brittle leaving it vulnerable to disease.
But this symbiotic relationship is actually a unique evolutionary strategy for coral to adapt to changing climatic conditions. With less severe temperature changes it is normal for the coral to reject Symbiodinium that fail to generate enough food and to take up different, heat tolerant Symbiodinium.
In their quest for coral eco-diversity, scientists discovered examples of high tolerant, heat-resistant species in other Australian waters. In super heated tidal pools created by tropical tides off north -west Australia in the Kimberley region. Different corals have adapted to extreme temperature changes and thrived in these conditions. Dr Verena Schoepf from University of Western Australia and co-author of a peer-reviewed study on heat resistant coral has discovered unique examples of species subject to extreme and daily temperature fluctuations. It is hoped they may provide answers for less tolerant species.
The idea of Super-Symbionts as proposed by Rachel Levin in the journal Frontiers in Microbiology concerns genetically engineering Symbiodinium for high temperature tolerance and to eventually re-populate bleached coral. Formally a cancer pharmacologist, she has applied her knowledge in micro biology to coral ecosystems. She has likened her research into reef depletion as important as the study of human disease and cancers. The survival of coral ecosystems is paramount and they may be assisted through the genome mapping of aquatic microbes and the developing of a high temperature tolerance Super-Symbiont.
With limited time and added pressures on coral ecosystems all research and specialist knowledge will need to come into play given the unknowns in these bio diverse systems. Thomas Mock, a pioneer in the genetic modification of phytoplankton from the University of East Anglia admits this area of biology is still a mystery but believes it is necessary to “get started somewhere and (to) see what we can achieve”.
The CSIRO of Australia recently announced research funding for genetically modified coral symbionts.

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