A herpesvirus outbreak among sea turtles on the Great Barrier Reef is leaving the animals riddled with tumors, and humans may be to blame.
By Kate Wheeling
(Photo: Mark Kolbe/Getty Images)
A growing number of green sea turtles on Australia’s Great Barrier Reef are turning up with unwieldy tumors on their faces and flippers. The condition is known as fibropapillomatosis, and the tumors, which Douglas Mader, a veterinarian at the Marathon Sea Turtle Hospital in Florida, has described as “cauliflower-like growths,” can reach the size of small dinner plates. As you might imagine, a face full of tumors, while themselves benign, can still cause harm by interfering with the reptiles’ vision, and thus their ability to both find prey and avoid predators.
Fibropapillomatosis is caused by a herpesvirus, but turtles can usually carry the virus without becoming afflicted with disfiguring tumors. So what is triggering the uptick in tumor growth in these sea turtles? Human-induced environmental contamination, probably.
Reporting on unpublished data from a team of researchers from Australia’s James Cook University, Alice Klein wrote in New Scientist that the outbreak is largely localized to regions with heavy human activity:
The unpublished results of surveys by [the research] team this year show that herpesvirus is most prevalent within a narrow stretch of Cockle Bay at Magnetic Island, a popular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.
But the turtles living along the Great Barrier Reef are not the only sea turtle populations to come ashore with fibropapillomatosis. The first case of the condition was observed in 1938 in a green sea turtle captured off the coast of Key West, Florida. By the late 1950s, fibropapillomatosis began appearing in green turtles off of Hawaii’s coasts, and experts have since noted an uptick in the condition among turtles in these regions.
By 1994 researchers were noting a possible, if anecdotal, link between human industry and turtle tumors, according to a paper in the journal Annual Review of Fish Diseases from the same year. A 2014 study from Duke University hints at one potential mechanism by which man-made pollution in the form of nitrogen run-off can lead to turtle tumors. Rachel Nuwer reported on the research for Smithsonian:
In 2010, researchers found that turtles living in parts of the ocean with higher concentrations of nitrogen also suffered a higher instance of the disease. To better establish that link, the researchers studied how algae — which turtles eat — stores nitrogen. As Duke describes, algae converts excess nitrogen into arginine, an amino acid. Turtles that suffered from fibropapillomatosis, the team reports in the journal PeerJ, had higher levels of arginine than those that were healthy. Algae in the water where they lived also contained elevated levels of the compound. Arginine, in turn, supports the growth of the virus that causes fibropapollomatosis.
It’s not yet known if similar fertilizers might be at play off the coast of Australia, but researchers at James Cook suspect that the blame lies with an environmental contaminant, Klein reports. Now it’s just a matter of figuring out which one.