Sea Turtle Herpes Tumors

Around the Hawaiian islands, several seaweed species were either accidentally introduced or deliberately harvested for food crops and later "escaped" cultivation and spread into the wild.

Hookweed—native to the Mediterranean, the Caribbean, the Indian Ocean, and the Philippines—was introduced to Hawaii in 1974. Gorillo ogo and spiny seaweed came from the Pacific and Indian Oceans and Guam, respectively.

The seaweed absorbs the extra nitrogen and converts it into an amino acid—the building block of protein—called arginine. When turtles eat the seaweed, arginine awakens dormant herpes viruses in the turtles' bodies that generate the tumors.

It's possible that nonnative seaweed in Hawaii is better than native seaweed species at converting nitrogen to arginine, Van Houtan noted.

And because Hawaiian green sea turtles now rely on the invasive seaweed for food, Van Houtan suspects the animals get dosed with tumor-triggering amino acids at every meal.

Alonso Aguirre, a wildlife epidemiologist with the environmental nonprofit EcoHealth Alliance in New York, praised the study for confirming the link between pollution and sea turtle tumors. But he also said that the tumors' cause may be more complicated.

The pollution-virus link is "a very simplistic pathway to explain the whole disease," Aguirre said, adding he suspects other factors, such as water temperature, and possibly additional viruses, are at play.