Biologist Thayana Giao holds a Green Sea turtle during an intentional capture to monitor turtles’ health, weight and pollution level, by Universidade Federal Fluminense (UFF), in the Guanabara Bay in Rio de Janeiro, Brazil August 29, 2024.
| Photo Credit: Reuters

Sea turtles in the Guanabara Bay of Rio de Janeiro are getting healthier after struggling for years with a tumour disease that hampers their movement, sight and feeding, and ultimately leads to their death.

Scientists said it came after authorities made an effort to clean up the water of the natural harbor that shapes the identity of the region.

Research has linked fibropapillomatosis, a benign tumour in sea turtles, to both a virus and environmental factors.

Kassia Coelho, a professor of veterinary pathological anatomy at the Federal Fluminense University, said samples taken from the animals and the water pointed to a much healthier environment.

“It’s about analysing health by collecting blood and tumours from these turtles, and also biometrics of the animals, seeing their growth over the years and monitoring these animals from one year to the next,” she said.

“Many of these turtles are recaptured and we can assess whether they’ve grown, whether they’re heavier, whether they’ve lost weight, whether they have more tumours or fewer tumours.”

Surrounded by a dense urban population, Guanabara Bay was once a nursery for marine life but has over the years suffered from sewage and other garbage being dumped there.

In 2022, scientists found that three quarters of sea turtles there were carrying the tumours.

While research is still ongoing, Gustavo Baila, an oceanographer and professor at the Federal University of Rio Grande, said sea turtles have been healthier since 2023.

“These are very important species for marine conservation,” he said. “We had observed a high incidence of sea turtles with tumours, with deformities that ended up being very serious for the development of these animals.”

Brazil is home to five of the seven species of sea turtles that exist worldwide. However, their natural habitat is sometimes severely impacted by humans. Conservationists have called for stricter measures to protect these animals.

Alexandre Bianchini, a vice president at Brazilian water and sewage treatment company Aegea, said some 2 billion reais ($356.42 million) had been invested into cleaning up the water in the area. “Now, nature responds,” he said.