The dive takes place on what appears to be a healthy and pristine coral reef surrounding Lady Elliot Island, at the southern end of the Great Barrier Reef off Queensland.
There are no visible signs of bleaching that has afflicted other parts of the reef in recent years, but the government agency responsible for the reef, the Great Barrier Reef Marine Park Authority, has confirmed that the natural site has suffered a third massive bleaching of corals episode in five years, describing the damage as “widespread”. The mass laundering events in 2016 and 2017 affected large areas of the reef.
As the speed at which bleaching events hit the world’s largest reef system increases, scientists, farmers and volunteers in Queensland are trying to do their part to lessen the impact.
Gary Spotswood is a third generation farmer at Mt Alma Organics, an organic farm a few hours’ drive from Townsville, a town on the northeast coast of Queensland. Spotswood installed pumps to accumulate runoff on its 430 acres, which then filter through the aquatic plants growing in the adjacent wetlands. The project is partially funded by a grant from the Great Barrier Reef Foundation, which has received a controversial grant of 444 million Australian dollars (217 million pounds) from the Australian government to sponsor projects on the reef.
“I try to keep as much water on the land as possible,” says Spotswood, who runs land use courses for other farmers and grazers. “Changes take time. But in five years people have changed their patterns of land use, “he said.
At the Townsville Tropical Marine Research Center, scientists from the Australian Institute of Marine Sciences (Aims) are studying how the so-called super corals (corals that can withstand rising water temperatures) could be used to save reefs. About 25 coral strains are crossed with identical or different species. The research is carried out in the National Sea Simulator, the world’s most advanced research aquarium, and intends to show that young descendants of corals – produced by mixing corals from various parts of the reef – can survive in warmer sea temperatures.
“It’s like crossing corn. We do the same thing with corals, so they can withstand higher temperatures, “said Kate Quigley, a reef restoration researcher at Aims.
The method is called “assisted gene flow” and, although at an early stage, it gives encouraging results in the marine simulator, as well as on the reef – where cross fertilized corals have been transplanted. The hybrids have a parent from the north and a parent from the central reefs, and the results show that corals with at least one parent from the most heat-resistant northern reefs survive when placed in cooler environments. Research has also confirmed that offspring inherit heat tolerance from their northern parents, and these genes can ultimately be passed on to make reefs more heat resistant.
Aims is also carrying out research on how to reduce the number of thorny crown starfish (camp beds) that eat corals. There are currently more than five million beds on the reefs between Cairns and Cooktown, and the invasion is spreading south as the highly thorny species (which normally range from 25 to 35 cm in diameter and can be up to 23 arms) devour the corals and leave nothing but traces of fine calcium carbonate.
Females can produce up to 50 million eggs per year and each ingests 10 square meters of coral each year. Rising sea temperatures and increased availability of nutrients due to runoff from farming practices are believed to be responsible for the increase in the number of camp beds. So far, divers have slaughtered around half a million by injecting starfish with white vinegar.
Amers scientists are trying to wield another – a more natural weapon – to fight the mass epidemic. They breed the rare giant newt, a large sea snail that feeds on cradles. Scientists aim to reintroduce snails to reefs – from where they disappeared.
The climate crisis and evidence of another mass laundering, however, continue to obscure any signs of progress.
Quigley says hundreds of studies point in the same direction. “They show that climate change is the biggest threat to the reef,” she said. “We don’t know what future reefs will look like. But we need to mitigate the effects of climate change on the corals. “