Study finds ways to fight invasive anemone

Corallimorphs are a type of invasive anemone that typically thrives in coral reefs that have been degraded by environmental or man-made disturbances. The arrows in this image point to mouths of individual corallimorphs. Each corallimorph mouth is surrounded by a corona of tentacles. USGS / Thierry Work photo

The Maui News

A new U.S. Geological Survey study has found that control efforts, such as the removal of shipwrecks and application of chlorine, may help mitigate the damaging effects of corallimorph, a type of invasive anemone, on coral reefs in the Central Pacific.

“Coral reefs are home to a significant diversity of marine life, provide valuable economic and environmental services to millions of people, buffer shorelines from erosion and waves and can serve as a resource for the development of new medicines,” said Thierry Work, a USGS scientist and the lead study author.

Corallimorphs can spread rapidly in coral reefs that have been degraded by environmental or man-made disturbances. At the Palmyra Atoll National Wildlife Refuge in the Central Pacific, researchers found the anemone expanding and smothering otherwise pristine coral reefs in an area near a shipwreck.

Starting in 2007, USGS scientists and partners surveyed the corallimorph-infested coral reef before and after removal of the shipwreck. They found that wreckage removal helped reduce the proportion of highly infested areas from 21 to 14 percent.

That was the first time that shipwreck removal was shown to have beneficial effects for reef recovery from the invasive species.

The scientists then devised additional methods to control corallimorph on a small scale. By exposing it to chlorine, they found that they could nearly eradicate the organism from small plots of about 100 square feet after several days. These plots remained mostly free of the anemone for at least 15 months, allowing native organisms such as coralline algae and small corals to regrow.

“Scaling up the control methods tested in our study might provide hope that the Palmyra corallimorph could be contained or possibly eradicated,” Work said. “Coupling these methods with shipwreck removal could potentially help control infestations at other sites.”

Coral reefs can experience phase shifts where they quickly transition from coral-dominated to a uniformity of other organisms, typically algae. Palmyra is a less common case where the transition was from corals to corallimorphs. USGS scientists discovered the infestation at the Palmyra shipwreck in 2007. The affected area had more than tripled by 2011, prompting the U.S. Fish and Wildlife Service to remove the wreckage in 2013.

“Ships are often sunk deliberately to promote diving or recruitment sites for reef organisms, but our study provides a cautionary note for such practices in tropical marine systems,” Work said.

The USGS partnered with the University of Hawaii, Bigelow Laboratory for Ocean Sciences, the U.S. Fish and Wildlife Service and The Nature Conservancy on the new study.