Hawaii’s golf courses and pineapple farms are causing tumors in imperiled green sea turtles, a study published Tuesday finds.
The link is an amino acid called arginine, which trickles down from the island’s nutrient-rich urban runoff into the turtle’s food source, riddling their bodies with white tumors.
“We’re drawing direct lines from human nutrient inputs to the reef ecosystem and how it affects wildlife,” said Kyle Van Houtan, lead researcher on the study, in a statement.
Scientists at Duke University, the University of Hawaii, and the National Oceanic and Atmospheric Administration teamed up to study fibropapillomatosis—a tumor-forming disease that is the leading cause of death in green turtles.
“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,” said Van Houtan.
Nitrogen gets into waterways through polluted runoff from farmland and cities. Typically used in fertilizers—but also found in detergents and sewage—nitrates not taken up by crops wash into the ocean, where they can spawn algal blooms.
Those algal blooms are the problem.
Hawaii’s native green algae—a major food source for sea turtles—is being replaced by an invasive red algae that is thriving owing to the excess nitrogen from urban runoff.
Turtles munch on the arginine-laced red algae, which also contains fewer calories than the green algae, leaving the turtles to ingest even higher amounts of the tumor-fueling algae per meal.
The result can mean 14 times more arginine in a turtle’s system than if it was eating natural algae.
“If this disease is a car, arginine is its fuel,” said Van Houtan. While the study linked arginine to both the sea turtle’s food supply and the tumors, it remains unclear why the fibropapilloma virus leads to the formation of tumors.
Turtles stricken with fibropapillomatosis grow cauliflower-like tumors that often form around their shoulders and eyes. That can impede a turtle’s movement and often leave it blind, according to the Turtle Hospital in Marathon, Fla.—one of the few locations worldwide that treats turtles for the disease. The first case was reported in a green turtle in the New York Aquarium in 1938 and has spread to turtles worldwide.
“The most common surgery performed is the removal of debilitating viral tumors that affect over 50 percent of the sea turtles in the keys and around the world,” the Turtle Hospital states on its website.