Brazilian Volunteer Divers Are Killing a Beautiful Coral to Protect the Cagarras Islands Off Rio
Off Ipanema, ICMBio and volunteer divers pull invasive sun coral by hand. A project that has removed 230,000 corals says repeated removal can drive it to zero.
Sunday, November 8, 2026/3 min read
Off Rio de Janeiro, five kilometres from the crowds on Ipanema Beach, a team of volunteer divers is doing something that sounds perverse. They are working through a protected marine area and killing coral, one colony at a time, to save the coral that belongs there.
The invader is sun coral, and the team's work was documented this week in a Mongabay video report published on 7 November. It is a small, unglamorous front in one of Brazil's longest-running marine invasions.
What is sun coral and why is it a problem in Brazil?
Two species, Tubastraea coccinea and Tubastraea tagusensis, are native to the Indo-Pacific. According to Mongabay, they were first seen in Brazil in the 1980s on an offshore oil platform in Rio de Janeiro state. From there they spread: the outlet reports they travel about 2 kilometres a year and now occupy roughly 3,500 kilometres of the Brazilian coast.
The harm is to the neighbours. Mongabay says sun coral damages native Brazilian brain and star corals with chemicals and outcompetes them for space on rocky reefs. It cites research suggesting an ecosystem may be profoundly altered once sun coral covers about 45 per cent of a rocky reef. A project summary from Brazil's Sun-Coral Project, published on the TAC Frade site, found a roughly 50 per cent shift in the composition and abundance of seabed life where the coral is established, and in the Ilha Grande bay it is replacing the Perna perna mussel, with consequences for fishing and tourism.
How are volunteer divers removing it?
The Cagarras Islands are a protected area about five kilometres off Ipanema, designated a Hope Spot, Mongabay reports. The divers work with Adriana Gomes, a marine biologist at the Chico Mendes Institute for Biodiversity Conservation, known as ICMBio, the federal conservation agency. They remove colonies by hand, one by one, rather than with chemicals or machinery.
Brazil has a national plan to address the invasion, created in 2018. The Sun-Coral Project, which began in 2006, says on the TAC Frade page that more than 160 management actions along the coast have removed over 230,000 corals, about 8.3 tonnes. Experiments at three sites, including Ilha Comprida in the Cagarras archipelago, compared strategies. Repeated removal brought the invader's population to zero at every site studied, the project reports, and was recommended where the coral is abundant, while a single removal sufficed where it is scarce. The project also found that removal did not stimulate the release of larvae, a worry that is often raised about disturbing colonies.
Does hand removal work in the long run?
The results are encouraging, but the scale is the problem. Hand removal is slow and local, and the coral is spreading along thousands of kilometres of coast, while the project's own list of challenges includes the reach of the invasion, the cost to fishing and tourism, and the need for coordinated work between agencies. The islands near the city are a good place to keep a protected reef clean. They are not a template for every reef.
Diving of this kind is also work done to a protocol. The Sun-Coral Project says removal is done by trained divers following its procedures, which is a reminder that conservation diving is a skill set, not a casual weekend task. This is journalism, not instruction, and anyone interested in volunteering should train with a certified instructor and an accredited agency, and join an organised programme.
The test for the Cagarras effort is whether the reef stays clear when the volunteers stop for a season. Repeated removal is what worked in the experiments, so the answer will depend on whether the dive teams can keep showing up.
Published in The Outspoken Digest
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