The reefs of Palmyra Atoll, a small peripheral atoll of the equatorial Pacific Ocean, have evolved from hard corals to systems dominated by corallimorphs, marine invertebrates that share characteristics with anemones and hard corals. A published study in Coral reefs led by the University of Hawaii In MÄnoa, marine biology researchers found that although the invading corallimorph is the same species that has been around for decades, its appearance has recently changed and it has become much more insidious.
Phase shifts like this are seen in many marine environments globally, whether due to local pollution, global climate change, or natural environmental variations. Researchers from EUH by Manoa School of Earth and Ocean Science and Technology (SOEST) wanted to determine if a new species of corallimorph was responsible for the takeover in Palmyra.
“These phase shifts are negative for our global biodiversity,” said Kaitlyn jacobs, lead author of the study and graduate student at the Hawaii Institute of Marine Biology in SOEST. âOver the past decade, the coastal reefs of Palmyra have been overrun by colonies of corallimorphs that can quickly monopolize the seabed and achieve 100% coverage in some areas. “
Compete with surrounding corals
Jacobs and his team used DNA data to compare the mitochondrial genomes of four corallimorphic individuals collected from Palmyra Atoll. They discovered that the corallimorph that supplanted surrounding corals is not a new species but rather is closely related to a species from Okinawa, Japan.
The Palmyra Atoll National Wildlife Refuge was established in 2001 and has been protected ever since. The atoll has been characterized as an almost pristine coral reef ecosystem, supporting a highly productive ecosystem and high levels of coral cover.
Due to their adaptability, corallimorphs are excellent competitors. As well as being able to directly kill corals, they can quickly move around disturbed areas and outsmart surrounding organisms, creating a kind of cover over the reef.
“Scientists and conservationists fear that the phase shift of rocky coral dominated habitats may be irreversible due to a negative feedback loop of coral decline and the subsequent dominance of algae, sponges or corallimorphs,” Jacobs said.
This effort is an example of EUH MÄnoa’s goal of Research Excellence: Advancing the Business of Research and Creative Work (PDF), one of the four objectives identified in the Strategic plan 2015â25 (PDF), updated in December 2020.