Following an impassioned speech by Australian deputy PM Barnaby Joyce (right, not exactly as shown) on government plans to deliberately infect invasive carp with herpes, an increasing number of green sea turtles on Australia’s Great Barrier Reef, with pollution being investigated as the prime culprit.

The animals have a turtle-specific herpesvirus that causes fibropapillomatosis – a condition in which disfiguring tumours grow on the eyes, flippers, tail, shell or internal organs.

“The tumours are benign but can grow up to 30 centimetres in size and block the turtles’ vision, says Karina Jones of James Cook University in Townsville, Australia. “This means they can’t find food or see predators or boats.”

Turtles with tumours are also more vulnerable to other infections, she says. “Severely affected turtles are quite skinny and have other pathogens affecting them – that’s why they die.”

The unpublished results of surveys by Jones’s team this year show that herpesvirus is most prevalent within a narrow stretch of Cockle Bay at Magnetic Island, a popular tourist destination in the middle of the reef. Roughly half the turtles in this hotspot have fibropapillomatosis, compared with less than 10 per cent of turtles sampled across the rest of Cockle Bay.

The cause remains unclear, but environmental contaminants are at the top of the suspect list. “We see these tumours in turtles in very localised hotspots around the world where there is heavy human activity,” says Jones.