Mystery Algae of No Known Origin Discovered on Hawaii Coral Reef

A new species of algae, the origin of which is unknown, has been discovered in Hawaii, smothering coral reefs and posing a threat to ocean ecosystems in the region, scientists have warned.

The algae, which has been named Chondria tumulosa, was identified by researchers led by Alison Sherwood, from the School of Life Sciences at the University of Hawaii. It was found during surveys of the Papahānaumokuākea Marine National Monument (PMNM), with samples taken in 2016 and 2019.

During the first survey, researchers with the National Oceanic and Atmospheric Administration (NOAA) noticed a "red alga" that formed "mat-like growths" extending over several square meters. They said detached pieces appeared "tumbleweed-like" and the subsequent survey showed how it had spread around the northern, eastern and western sides of the Pearl and Hermes Atoll. The researchers said the alga had reached "alarming levels" of coverage over the period between the two surveys, with extensive growth documented.

Findings were published in the journal PLOS One.

The PMNM sits off the northwest of the Hawaiian Islands. It is a World Heritage site covering 583,000 square miles of ocean waters. The Pearl and Hermes Atoll, which is part of the PMNM, is a group of small islands and atolls, with the surrounding reef covering 450 square miles. It is home to many species of sponge and coral. In the latest survey, researchers found the new algae species was smothering entire sections of the reef.

new algae species hawaii
The newly discovered species of algae on a coral reef in the Pearl and Hermes Atoll. NOAA/National Marine Sanctuaries

"This is a highly destructive seaweed with the potential to overgrow entire reefs," study co-author Heather Spalding, from the College of Charleston, said in a statement. "We need to figure out where it's currently found, and what we can do to manage it. This type of research needs trained divers in the water as quickly as possible. The sooner we can get back to [PMNM], the better."

Analysis of the samples showed it belonged to the genus Chondria, but there was no match to a known species. DNA analysis also showed the alga was unique.

Where this new species came from is unknown. Its sudden appearance in the region and its rapid increase is "of particular concern" because the PMNM is a remote and pristine environment, the team says. Because it is unclear where the species came from, it cannot be classified as invasive. Instead, the team has called it a "nuisance" species. They also say the species is "clearly having a harmful effect on the environment."

"Until the origin of Chondria tumulosa is clarified, we qualify this species as exhibiting invasive characteristics, given its sudden appearance, rapid overgrowth and ecological harm to the coral reef ecosystem," they wrote. "Given the protected nature of the PMNM it will be difficult-to-impossible to confirm the mode of introduction, especially while the biogeographic origin of the seaweed remains a mystery."

They said changing environmental conditions in the region associated with climate change may have made it possible for this new type of algae to become established on the reefs of the Pearl and Hermes Atoll.

"I think this is a warning of the kinds of changes that are to come for the northwestern Hawaiian Islands," Alison Sherwood said in a statement. "We have, not until now, seen a major issue like this where we have a nuisance species that's come in and made such profound changes over a short period of time to the reefs."

Pearl and Hermes Atoll
The Pearl and Hermes Atoll. NOAA/National Marine Sanctuaries