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Agrochemical pollution is causing massive tumors in sea turtles

Agrochemical pollution

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(NaturalNews) Runoff from urban and agricultural pollution in Hawaii appears to be causing tumors that are the main cause of death for endangered green sea turtles, according to a study conducted by researchers from Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration (NOAA) and published in the peer-reviewed, open-access journal PeerJ on September 30.

Nitrogen from fertilizer runoff and other pollution sources seems to be changing the nutritional content of the algae that the turtles eat, fueling the growth of 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," researcher Kyle Van Houtan said.

Pollution fuels tumor-causing virus

Fibropapillomatosis (FP), a lethal, tumor-forming disease, first became a global problem for green turtles (Chelonia mydas) in the 1980s. Scientists describe the disease as "panzootic"; in humans, pandemic can be seen as an equivalent term. Yet the cause of the disease has remained difficult to determine. Currently, the foremost hypothesis is that FP is induced by a variety of herpes virus. Yet data show that such herpes viruses have existed for thousands of years and therefore could not solely explain the sudden surge in FP.

But in turtles as well as in humans, herpes viruses are characterized by a pattern in which the virus widely infects a population at a latent or subclinical level and is only triggered into an active form by certain environmental factors.

In a 2010 study, the same researchers showed that FP was more prevalent in areas receiving large volumes of nitrogen-rich runoff. They hypothesized that runoff might be changing the nutrient composition of algae, thus triggering latent herpes infections to produce FP. That study showed that the hypothesis successfully explained 72 percent of the regional variation in FP rates across the Hawaiian islands.

In the new study, the researchers set out to further test the nitrogen-algae hypothesis. They suggested that excess nitrogen may cause algae to accumulate an amino acid named arginine, which is a major food source for herpes viruses.

"If this disease is a car, arginine [is] its fuel," Van Houtan said.

Invasive algae worsening situation

"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."

Consistent with their hypothesis, the researchers found that, in areas highly polluted by nitrogen-rich runoff, both algae and FP tumors were unusually high in arginine, whereas algae in less-polluted regions and non-tumorous turtle tissue had very low levels of the amino acid.

Notably, the study also showed that an invasive species of red algae, Hypnea musciformis, had significantly higher levels of arginine than native algae species. H. musciformis is known to thrive in nitrogen-rich, polluted waters, thereby outcompeting native species. In some areas of Hawaii, it now comprises 90 percent of the green sea turtle diet. Because H. musciformis is much less nutrient-dense than native algae, however, sea turtles need to eat twice as much of it to meet their energy needs.

The researchers calculated that this combination of factors would cause green sea turtles living in more polluted waters to consume 14 times as much arginine as turtles in less polluted seas.

"The energy and arginine content of (the algae) may therefore act as a sort of one-two punch for promoting this disease," the researchers wrote.

The research has implications for other forms of marine life affected by pollution, the scientists said.

"It's not just green turtles, but fish and coral reefs that have similar diseases in these locations," Van Houtan said.





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