In sad news for sea turtles, scientists have found that runoff from cities and farms in Hawaii is causing debilitating and deadly tumors, which are believed to be the leading known cause of death for endangered green sea turtles.
Scientists from Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration (NOAA) teamed up to study what’s causing the tumor-forming disease Fibropapillomatosis, which is clearly a major problem for sea turtles.
The study, published this week in the journal PeerJ, found that nitrogen runoff is ending up in algae that sea turtles eat, which is causing the tumors to grow both internally and externally on their eyes and flippers. According to NOAA, these tumors can interfere with their ability to eat and other essential behaviors, while tumors on their eyes can cause permanent blindness. While it’s a major problem for green turtles in Hawaii, it’s also been found in other places and in other species of sea turtles, including loggerhead, olive ridley and flatback turtles.
“We’re drawing direct lines from human nutrient inputs to the reef ecosystem, and how it affects wildlife,” said Kyle Van Houtan, the study’s lead author, who is also a scientist in NOAA’s Turtle Research Program.
Building on previous research that found the disease was more common in areas with high levels of runoff, researchers tested the hypothesis that the disease might be linked to how algae that the turtles eat stores extra nitrogen.
Algae can store excess nitrogen in arginine, an amino acid, and as they explain in a statement, they found unusually high levels of arginine both in the algae in highly polluted waters and in the tumors of diseased turtles, while levels in cleaner water and tumor-free turtles were comparatively low. Researchers believe arginine is responsible for promoting a virus that causes the tumor-forming disease, although it’s still unclear exactly how it causes the tumors.
Adding to the problem is a non-native red algae that is thriving with the excess nitrogen and taking over native algae that turtles need. The red algae has been found to hold especially high levels of arginine, which researchers believe can make up 90 percent of the turtles’ diet. According to Van Houtan, as a result turtles have approximately 14 times more arginine in their systems than they would if they were eating native algae species in less-polluted waters.
More worrisome is that green turtles, who are uniquely herbivorous sea turtles and only eat plants, have to eat twice as much of the invasive algae to get the same benefit they would from native algae, which is compounding the problem.
Researchers hope this work will help lead to a better understanding of how to protect sea turtles, and other marine plants and animals, that are threatened by pollution.
“It’s not just green turtles, but fish and coral reefs that have similar diseases in these locations,” said Van Houtan, who added that he hopes future research delving into this problem can help impact how we manage reef systems. “If research continues to support this hypothesis, we probably need to reconsider our current ways of managing coastal nutrients,” he said.
View original article at: Endangered Sea Turtles Are Getting Nasty, Deadly Tumors, and We’re to Blame