A team of divers removing marine debris from Papahanaumokuakea Marine National Monument last month found an invasive alga at Midway Atoll National Wildlife Refuge, according to the U.S. Fish and Wildlife Service.

It was suspected – and confirmed to be — Chondria tumulosa, a nuisance algae that can grow quickly and smother coral reefs. Scientists confirmed via DNA sequencing that it was indeed Chondria.

The National Oceanic and Atmospheric Administration had first discovered Chondria at Pearl and Hermes Atoll, or Manawai, during a cruise in 2019. On that expedition, researchers from the College of Charleston diving at Manawai saw mats of red algae that stretched for the length of football fields, smothering native corals.

This invasive-like algae was identified as a new species to science in 2020, and was named Chondria tumulosa.

NOAA scientists that went on a two-part research expedition to Papahanaumokuakea in July and August were initially hopeful that Chondria had not spread to other atolls in the monument. What they found was that the amount of algae since 2019 had not diminished, and may have actually increased. At the time, satellite images and randomly selected sites did not exhibit signs of Chondria elsewhere in the monument.

To date, Chondria has not been confirmed to occur at any other location in the world.

Although it displays invasive characteristics, researchers are not labeling the alga as invasive because it is not yet clear whether it is native to Hawaii or introduced. It is for now considered a “nuisance” species.

Researchers are investigating the ecology and physiology of Chondria to better understand what might be fueling its rapid growth, with the goal of developing management practices to reduce its spread.