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. âThink of it like using a flame thrower to get real estate,â says Thierry Work at the US Geological Survey National Wildlife Health Centerâs Honolulu Field Station and lead author of the study.