Pollution Causing Tumors in Endangered Sea Turtles

Pollution from urban and farm runoff in Hawaii is causing tumors in endangered sea turtles, a new study found.

The study, published Tuesday in the journal PeerJ, shows that nitrogen in the runoff ends up in algae that the turtles eat, causing the animals to sprout tumors on their eyes, flippers and internal organs.

"We're drawing direct lines from human nutrient inputs to the reef ecosystem, and how it affects wildlife," Kyle Van Houtan of Duke University said in a statement.

The disease behind the turtle tumors is called Fibropapillomatosis, and is thought to be prevalent in areas with high levels of nitrogen runoff. Now, researchers want to test the theory that algae can store excess nitrogen that finds its way into Hawaiian waters, and thereby turtles' stomachs.

"In this paper we drill down on whether excess nitrogen inputs are causing a nutrient cascade in the system that's ending up in these tumors in green turtles," explained Van Houtan.

Researchers found during their study that algae can store nitrogen in the form of the amino acid arginine, which was found in unusually high levels both in the algae in highly polluted waters and in the tumors of diseased turtles. One non-native red algae species in particular, Hypnea musciformis, had especially high levels of arginine compared to other species sampled. And since this invasive species grows more successfully than native algae, it can make up as much as 90 percent of the turtles' diet.

Do to these combined factors, the turtles have approximately 14 times more arginine in their systems than they would if they were eating native algae species in less-polluted waters. What's more, these algae-eating herbivores have to eat twice as much of the invasive algae to get the same amount of calories that they would if they were consuming native species of algae, acting as a sort of "one-two punch for promoting this disease," the study noted.

How the virus causes the disease is still unclear, but researchers nonetheless hope their findings help scientists better understand how to protect not only sea turtles, but also other marine plants and animals that face similar threats from pollution.