Scientists have built a thriving new coral reef the size of a tennis court from rubble and rock - growing up to 80 per cent coral cover in just six years - in a reef restoration trial at Green Island off Cairns.
The trial's success has been hailed as a boost for efforts to rehabilitate damaged high-value sites and to support the growth of naturally heat-tolerant coral species on the Great Barrier Reef.
The hand-restored coral reef is now a popular snorkelling and diving site for some of the 350,000 tourists who visit Green Island every year.
Reef Authority project lead Neil Mattocks said preliminary estimates found up to 80 percent healthy coral cover at the site.
- "It is clearly supporting good and diverse coral cover," Mr Mattocks said.
"It is also attracting noticeably more reef fish, including damselfishes and other species commonly associated with healthy coral habitat,'' he said.
"This trial has shown we can successfully use this technique to restore small areas of reef."
Green Island is considered a high-value tourism site and a source reef, meaning it can help supply coral larvae to nearby reefs.
Queensland Parks and Wildlife Service marine biologist Michelle Janssen said improving coral cover at Green Island could have benefits beyond the project site.
- "It is also a source reef, so a reef that spawns and provides coral babies to other reefs nearby," Ms Janssen said.
"When you've got a really high-value reef like that, it's great to see so much coral growth."
The six-year trial began in November 2020 after the site was identified as having low coral cover, unstable coral rubble and bare limestone rock.
The Green Island Reef Rehabilitation Project used 165 MARRS reef stars, 200 Coralclip® devices and about 2,675 coral fragments at a depth of 4-6m across about 200 sqm of reef.
The Reef Star or Mars Assisted Reef Restoration System (MARRS) is a sand-coated metal frame, shaped like an interlocking hexagon, that is placed on unstable rubble to create a stable base for coral fragments to grow.
Mars Sustainable Solutions Australian Marine Program manager Freda Nicholson said the restored area resembled a natural reef.
- "It is starting to look and behave like a natural healthy coral reef," Ms Nicholson said.
"New corals have come into the site that we didn't even plant there; they've come in and started colonising, and it is starting to look really good.
"Anywhere on the Great Barrier Reef where there is rubble because of physical disturbances, like a cyclone, is a place where this restoration technique could potentially be useful."
GBR Biology and Reef Unlimited marine biologist Dr Eric Fisher said the trial showed Reef Stars could speed up recovery on rubble-damaged sites.
"Normally, a rubble site would normally take 30 to 40 years to recover on its own," Dr Fisher said.
"Here we've seen incredible growth in six years, where we can't even see Reef Stars."
The project used loose coral fragments found on the seabed, which were unlikely to survive without being reattached to a stable surface.
The project was a joint initiative between the Reef Authority, Queensland Parks and Wildlife Service, Mars Incorporated, Quicksilver Cruises, Big Cat Green Island Cruises, the Coral Nurture Program and Gunggandji Traditional Owners.
