Underwater compressed air effectively removes invasive coral species in Brazil
Invasive corals are blown out of the water – with underwater air cannons.
As corals around the world die in large numbers due to ocean acidification, climate change, overfishing and disease, their invasive counterparts such as sun corals are taking over biodiversity hotspots. Compressed air jets can likely rid ecosystems of these fast-spreading intruders and prevent them from recovering, researchers report April 4 in Ecological solutions and evidence.
Solar corals (Tubastrée) are “very aggressive,” says Guilherme Pereira-Filho, a biologist at the Federal University of São Paulo. They first arrived in Brazil in the 1980s, although their origin is not clearly established. Anytime you come to an attractive new home, “it can spread very quickly,” Pereira-Filho says. A tiny fragment can reproduce in a new colony, driving out native corals and changing the ecosystem so that other squatters move in.
The most common removal method is air hammering, says Pereira-Filho. Unfortunately, this often releases exactly the tiny fragments that colonize again. And this technique, which requires a lot of time and work, does not always make it possible to reach the underwater nooks and crannies where these corals grow.
Inspired by the practice of using compressed air in the laboratory to separate the soft tissues of corals from their stony skeletonsPereira-Filho and his colleagues created an underwater facsimile by connecting an air gun to a scuba regulator, the mechanism that controls a diver’s breathing air. In Brazil’s Alcatrazes Archipelago Wildlife Reserve, they donned scuba gear – along with an extra tank for the air gun – and destroyed 48 colonies alongside 14 colonies left intact for comparison. They observed each colony immediately after blasting, 30 days later and 180 days later. The solar corals they destroyed had been largely obliterated.
Since previous research has shown that some tissues can regenerate without any skeleton, the team wanted to know if air blasting solves this problem. During the removal process, they collected samples with the goal of bringing them back to the lab’s aquariums. None of the samples regenerated.
“The experimental procedures are very well thought out,” says Joel Creed, a marine ecologist from Rio de Janeiro State University. Creed initially feared that the result would be “a soup of tissue that could spread out and settle”, instead of inert fragments falling to the ocean floor.
Pereira-Filho was delighted that the team’s relatively inexpensive idea worked. “It’s a fairly simple method that can provide many benefits for managing this invasive species,” he says.
Next, researchers think big. They have done this work on a small scale at a popular dive site on the refuge and want to try blasting on a much larger scale, such as on an entire island. They would also like to develop robust equipment that can remove corals from artificial structures such as ship hulls, a major source of invasive corals.
And another technique for combating invasive corals is welcome, Creed says. “Remember that the status quo would be to let the coral happily produce hundreds of larvae per year,” he explains. “This method is a step forward.”
