A team of scientists from Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration (NOAA) discovered that pollution around the Hawaiian islands is causing lethal tumors in the endangered sea turtle population. The report, which was published in the peer-reviewed open-access journal PeerJ, states that high levels of nitrogen from urban and farm runoff have poisoned the algae that sea turtles eat, causing deadly tumors to grow on the poor turtles’ flippers, eyes and internal organs.
The tumor-forming disease Fibropapillomatosis is the leading known cause of death in green turtles, according to Kyle Van Houtan, adjunct associate professor at Duke’s Nicholas School of the Environment. The team’s research found that the tumors were more prevalent in areas with high levels of nitrogen runoff, lending credence to the theory that it is nitrogen-rich algae causing the illness.
The team looked at how algae stored excess nitrogen within itself via an amino acid called arginine. They found that unusually high levels of arginine appeared in both highly polluted algae and in the tumors of diseased turtles. Arginine levels in algae in less polluted waters and in tumor-free tissues were comparatively low. One non-native red algae species in particular, Hypnea musciformis, had especially high levels of arginine compared to other species sampled. Hypnea is invasive and thrives in the nitrogen-rich waters caused by nutrient pollution.
As a result, the team found that the turtles had approximately 14 times more arginine in their systems than they would if they were eating native algae species in less-polluted waters. Even worse, the turtles were eating twice as much of the invasive algae species to get the same amount of calories they would gain from eating native algae.
“The energy and arginine content of (the algae) may therefore act as a sort of one-two punch for promoting this disease,” the study noted. “And it’s not just green turtles, but fish and coral reefs that have similar diseases in these locations.”