Biggest coral reseeding project launches on Great Barrier Reef

Environment and Ecology Concept of Ecology

Scientists have launched the largest-ever attempt to regenerate coral on the endangered Great Barrier Reef by harvesting millions of the creatures’ eggs and sperm during their annual spawning.
It is to grow coral larvae from the harvested eggs and return these to areas of the reef which have been badly damaged by climate-related coral bleaching.
This is the first time that the entire process of large scale larval rearing and settlement will be undertaken directly on reefs on the Great Barrier Reef.

What is coral bleaching?

Many types of coral have a special symbiotic relationship with a tiny marine algae (zooxanthellae) that live inside corals' tissue and are very efficient food producers that provide up to 90 per cent of the energy corals require to grow and reproduce.
Coral bleaching occurs when the relationship between the coral host and zooxanthellae, which give coral much of their colour, breaks down. Without the zooxanthellae, the tissue of the coral animal appears transparent and the coral's bright white skeleton is revealed.
Corals begin to starve once they bleach. While some corals are able to feed themselves, most corals struggle to survive without their zooxanthellae.
If conditions return to normal, corals can regain their zooxanthellae, return to their normal colour and survive. However, this stress is likely to cause decreased coral growth and reproduction, and increased susceptibility to disease.
Bleached corals often die if the stress persists. Coral reefs that have high rates of coral death following bleaching can take many years or decades to recover.

Coral bleaching and the Great Barrier Reef

The Great Barrier Reef has experienced mass coral bleaching events in the past.
In 1998, there was a global mass bleaching event where 50 per cent of the reefs on the Great Barrier Reef suffered bleaching. During this time, sea temperatures on the Great Barrier Reef were the highest ever recorded.
Mass bleaching also occurred in 2002, with 60 per cent of reefs were affected. This was the largest coral bleaching event on record. Two periods of hot weather resulted in sea surface temperatures a few degrees centigrade higher than long-term summer maxima.In both events, about five per cent of the Great Barrier Reef's coral reefs were severely damaged