Researchers say a recently discovered species of seaweed is killing large patches of coral on once-pristine reefs and is rapidly spreading across one of the most remote and protected ocean environments on earth. A study from the University of Hawaii and others says the seaweed is spreading more rapidly than anything they've seen in the Northwestern Hawaiian Islands, a nature reserve that stretches more than 1,300 miles north of the main Hawaiian Islands. The algae easily breaks off and rolls across the ocean floor like tumbleweed, scientists say, covering nearby reefs in thick vegetation that out-competes coral for space, sunlight, and nutrients. The study was published in the journal PLOS ONE on Tuesday.
"This is a highly destructive seaweed with the potential to overgrow entire reefs,” says biologist Heather Spalding, a study co-author and longtime Hawaii algae researcher, per the AP. “We need to figure out where it’s currently found, and what we can do to manage it.” In 2016, government researchers were on a routine survey of Pearl and Hermes Atoll when they found small clumps of seaweed they'd never seen before. Last summer, they returned to find algae had taken over huge areas of the reef—in some areas covering “everything, as far as the eye could see”—with seaweed nearly 8 inches thick, says Spalding, who was among the divers there. "Everything underneath of it was dead,” she says. Researchers studied the seaweed's DNA to try to determine its origin but concluded it’s a new species of red algae they named Chondria tumulosa.