Boat Bottoms, Barnacles and Modern Medicine:

Dan Rittschof Hopes the Drug Store Will Offer a Safe Substance to Keep Barnacles Off Boats p.4

Jonathan R. Matias, who knows Rittschof and his antibiofouling work well, also thinks the Duke researcher is on the right track. Matias’ New York City-based company, Poseidon Ocean Sciences, has been using Rittschof’s testing system for years. He has identified a natural antifouling agent and plans to register it with the EPA this year.

“The approach that Dan is doing is reasonable and hopefully he will find some products that are low enough in cost and approved by the EPA at the same time,” Matias said.

Earlier this year, Rittschof spent four weeks setting up an antifouling lab at a brand new, palatial marine laboratory nestled among the coconut trees of Singapore’s St. John’s Island. For the next few years, Rittschof will shuttle between North Carolina and Singapore to serve as adviser and collaborator.

The team set out to pinpoint metabolic pathways mutual to both humans and barnacles. Then they targeted those that, in the shellfish, serve as a key link in the biochemical events that lead to its metamorphosis from swimming larvae to stubborn barnacle. They were looking for drugs that, for example, interact with the human opioid-2 pathway in both creatures. They tried a range of common prescription and over-the-counter products and found a few.

So, it was back to the barnacle larvae, known as nauplii. After they shed their outer shells several times, the larvae turn into “cyprids,” creatures that live on their own fat. However, if cyprids don’t anchor themselves to a hard surface within two weeks they die. Drawn by pheromones, they seek out surfaces already colonized by other barnacles, where they attach themselves and transform again, this time into filter feeders.

Rittschof’s team was trying to find a way to spare the nauplii, which are an important part of the maritime food chain, but kill the cyprids before they could settle. So they conducted a toxicity test by bathing the nauplii in drugs. Since the larvae need to move at that stage in order to find a place to settle, the researchers measure how much of the drug they could handle without dying. If they stopped swimming, it was too much. They then expose cyprids—settlement stage larvae—to different concentrations of drugs to see if they have any effect on its ability to settle. By combining data from the two tests, they were able to come up with a therapeutic ratio—in other words, enough to kill the cyprids without killing the nauplii.

So the same dose that is safe for nauplii will kill a barnacle. But, what else will it kill? Rittschof said that drugs have the potential to be just as harmful to the marine environment as metals. But because drug effects and fates are so well studied in humans, they should have predictable lifetimes in the environment.

“In a drug, you know the most likely place on a molecule for a compound to break down,” he said. “You know how it interacts with other compounds and you know what’s been done to keep that from happening. There is just so much more of a knowledge base because billions of dollars have been spent on building drugs.”

This summer, Rittschof presented a paper on his work at the 11th International Congress on Marine Corrosion and Fouling, an international scientific conference on the chemical and biological deterioration of materials in the sea. Now, the team Rittschof advises is ready to start engineering the technology. To do that, they will be looking at the drug’s chemistry to see if it can be made compatible with existing antifouling coatings.

Informed by the lessons of the past, Rittschof is hoping that he’ll have a head start this time.

“The next round we’ll become much more specific in the way we work with things,” he said. “If we really understand our chemistry, we shouldn’t have to go back to the drawing board.”

Tinker Ready is a health and science writer based in Cambridge, Mass. She writes regularly for Nature Medicine, the Utne Reader and the Los Angeles Times.

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