Shipwreck fuels invasion of unwanted species

By Nora Schultz Aggressive invaders are spreading through a coral reef in Hawaii thanks to a shipwreck that ran aground in the remote Palmyra Atoll in 1991. Researchers believe that iron leaching from the ship is fuelling the invasion. And now they are calling for shipwrecks to be removed from sensitive ecosystems elsewhere. The invader, Rhodactis howesii, is a corallimorph, a yellow-brownish animal related to corals and anenomes. With its tentacles full of stinging cells, the corallimorph wipes out any organisms that get in its way. “Think of it like using a flame thrower to get real estate,” says Thierry Work at the US Geological Survey National Wildlife Health Center’s Honolulu Field Station and lead author of the study. Work and his colleagues measured the spread of R. howesii through Palmyra Atoll and found that their coverage doubled between 2006 and 2007. This means the invaders have claimed several hundred metres of reef in all directions. Where diverse corals were thriving until recently, there are now two square kilometres of corallimorph monoculture. Work believes the organism may be native to the area but is now running amok thanks to iron leaching from the wreck. He thinks that R. howesii may be best equipped to take advantage of the possible sudden iron bounty, not only because of their powerful tentacles but also because of their impressive reproductive capabilities. As a result, the researchers worry that even if the US Fish and Wildlife Service successfully manages to get the ship out of the water, the corallimorph crusade may continue owing to sheer power of numbers. If this happens, chemical sterilisation of the area may be the only option to rescue the reef, says Work. Jason Hall-Spencer at the University of Plymouth, UK, says that while the correlation between the shipwreck and the spread of the corallimorphs is convincing, this may have nothing to do with iron leaching from the ship. The wreck might have killed off competitors of this species when it hit the reef, and allowing the corallimorphs to spread, he says. But Hall-Spencer agrees that conservationists should look out for the effects of shipwrecks elsewhere: “If something like this wrecks the balance of an ecosystem once, it’s likely to happen again.” Journal reference: PLoS ONE (DOI:
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