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Scientists Directly Link Agricultural/Urban Runoff to Fibropapillomatosis in Sea Turtles

Scientists have for the first time found a direct cause of tumors found on the internal organs, face, body, and flippers of green sea turtles (Cheloni

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Scientists have for the first time found a direct cause of tumors found on the internal organs, face, body, and flippers of green sea turtles (Chelonia mydas) living in Hawaiian waters. According to a study published in the journal PeerJ, nitrogen found in urban and agricultural runoff off Hawaii’s main islands finds its way into the algae that turtles eat, which causes fibropapillomatosis in the turtles. Fibropapillomatosis is the leading cause of death of the green sea turtle (Honu in Hawaiian) in Hawaiian waters. 

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“We’re drawing direct lines from human nutrient inputs to the reef ecosystem, and how it affects wildlife,” Kyle Van Houtan, who is also a scientist in NOAA’s Turtle Research Program said in a statement put out by Duke University. 

The study, which involved scientists from Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration expanded on a 2010 study that determined that the disease was prevalent in areas with high levels of nitrogen runoff. 

“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,” said Van Houtan.



According to the paper, the sea turtles store excess nitrogen in arginine, an amino acid. High levels of arginine was found in the algae where the waters were highly polluted as well as in the tumors of the sea turtles. 

A non-native red algae species, Hypnea musciformis was found to have high concentrations of the arginine, and does very well in nitrogen rich Hawaiian waters that are caused by agricultural and urban runoff. Since this non-native algae is in high abundance, the sea turtles made it as much as 90 percent of their diet. According to the study, the sea turtles have 14 times the amount of the arginine in their system due to eating the red algae. Couple this with the fact that the turtles have to eat twice as much of the non-native, arginine-heavy red algae to retain the same amount of calories causes what Van Houtan says is a one-two punch for promoting the disease.  

In addition to the arginine, the scientists also recorded high levels of amino acids such as proline and glycene, that are commonly found in human cancer tumors. Van Houtan noted that it is not just the sea turtles that are affected in the area studied, but the fish and coral reefs also have similar diseases caused by the urban and agricultural runoff. 


In addition to Van Houtan, the co-authors of the study are Celia M. Smith, Meghan L. Dailer and Migiwa Kawachi of the University of Hawaii at Manoa.

The complete report can be read on the PeerJ website.

John B. Virata keeps a ball python, two corn snakes, a king snake, and two leopard geckos. His first snake, a California kingsnake, was purchased at the Pet Place in Westminster, CA for $5. Follow him on Twitter @johnvirata