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CRITTER: Possible cause of tumors killing our honu

Divers and snorkelers come from around the world to visit our green sea turtles. They bring in millions of dollars from tourists, and the honu don’t seem to mind having lots of people in the water with them.

I have dove all around the plant and the largest concentration of green sea turtles I have found is right here in Hawai‘i. The honu are part of Hawaiian culture and a precious gift to the sea who help people connect with nature. No matter how bad your day may have been, getting in the water and swimming with a sea turtle melts away your problems as they are calm, peaceful creatures.

All is not well with our honu population because in some parts of Hawai‘i, like Kane‘ohe Bay in O‘ahu, the sea turtles are dying from terrible tumors that are growing all over their heads and flippers. More than 60 percent of the green sea turtles in the bay are infected with these ugly tumors that are almost always fatal, killing the turtle slowly.

The tumors grow over their eyes until they cannot see to feed; the tumors also grow in their throat. The honu basically starves to death over several years; the tumors seem to be very painful.

On the southside of Maui and along Po‘ipu Beach in Kaua‘i, the honu also have a high tumor infection rate and it is so sad to see one of these creatures slowly swim by just covered in huge white fleshy tumors. Studies have shown that the tumors are a herpes virus, but for many years we had no idea what caused the tumors to grow.

What has been interesting to me as a marine biologist is the locations where the turtles have the tumors because on the North Shore of Kaua‘i and O‘ahu, I have only seen one honu with tumors out of more than 500 turtles I have pictures of.

It was obvious that the cause of the tumors simply does not occur on the North Shore, where there is constant surf and almost all of the infected honu live on the southside of each island and usually near larger coastal cities.

Recent research has shed some light on the possible cause of the tumors and it has to do with the type of limu (seaweed) they eat.

Our native limu grows on the reef and in cracks, and can grow quite well in the surf zone. There are several invasive seaweed species that grow in Hawai‘i, but they do not do well in the surf as they just get ripped off of the reef.

The invasive species grow best in calm water, like in Kane‘ohe Bay and along the Kihei coast in Maui. We mapped out where the invasive limu species grow best and that is the same location where the turtles have more tumors, so we have known for quite a while that the tumors must be stimulated in some way by the non native seaweed that the turtles feed on.

Chemical studies have found an amino acid called arginine that is present in high concentrations in the turtle tumors; this same amino acid has also been found in the invasive limu. It was also discovered that in polluted areas that have high nitrates from sewage runoff and farm chemicals, the invasive limu has a higher concentration of this amino acid. Arginine stimulates the growth of the herpes virus in the tumors.

It is highly likely the turtle tumors are caused by arginine that grows in the non-native limu and is stimulated by pollution, but more studies need to be done to confirm this hypothesis. We know how bad leaking cesspools are here in Hawai‘i on the environment and the dying honu may just be another good reason to get rid of them and stop treating our ocean as a toilet bowl.

I have a wonderful hourlong documentary movie about our sea turtles here in Hawai‘i; I just released it for free on YouTube at Underwater2web, where you can see the turtles with the tumors. The movie is for the whole family to watch; it is also a good educational movie.

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Terry Lilley is a marine biologist living in Hanalei Kaua‘i and co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawai‘i go to www.reefguardianshawaii.org.
Source: The Garden Island

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