An invasive algae has wrecked huge sections of reef in Papahānaumokuākea Marine National Monument. Scientists are racing to find out what it is, where it came from and whether anything can stop it.
Papahānaumokuākea — Manawai, also known as Pearl and Hermes Atoll, is where scientists found an invasive seaweed in 2019 smothering reefs. It’s deep in the Northwestern Hawaiian Islands, protected as part of the nearly 600,000-square-mile Papahānaumokuākea Marine National Monument. Map: April Estrellon/Civil Beat/2024
It began more as a curiosity than a concern.
Scientists spotted a seaweed they didn’t recognize as they dove around an atoll in the Northwestern Hawaiian Islands. In 2016, it looked like brownish-red threads stitched into a few pockets of branching coral.
They returned three years later to the remote waters of Manawai, also known as Pearl and Hermes, to find the seaweed had formed mats several inches thick. Blankets of it — some bigger than football fields — were smothering the atoll’s outer reef system.
Peering through holes in the seaweed, divers could see the white skeletal remains of coral that had been the backbone of a thriving ecosystem. Huge schools of reef fish, some found nowhere else in the world, were mysteriously absent. The green water was murky and menacing.
The reef was clearly under siege despite being 1,200 miles from urban Honolulu and its polluted runoff. This intruder was operating deep within the boundaries of Papahānaumokuākea Marine National Monument, the country’s largest protected place.
Scientists with the National Oceanic and Atmospheric Administration immediately feared the consequences of the seaweed spreading to nearby atolls, or worse. If it reached the Main Hawaiian Islands, it could deliver a disaster as much economic as environmental.
The state depends on a healthy ocean for the panoply of activities that attract tourists and make local residents want to stay. Reefs also function as natural seawalls that diffuse the destructive power of storms and provide habitat for the fish people rely on for food, culture and recreation.
“It is the scariest thing I’ve seen in 40 years of diving,” said Randy Kosaki, a research ecologist who serves as NOAA’s deputy superintendent of Papahānaumokuākea.
And he knows scary, or at least what most might consider scary. He talks of being “tornadoed” by dozens of sharks on dives in the most isolated parts of the Hawaiian archipelago. But as Kosaki says, he and his colleagues are “the type of people who jump into the water when someone yells shark.”
Among hundreds of dives during his post-graduate work at the University of Hawai‘i in the 1980s, one took him into the water around an active lava flow off of Big Island. It was to research how the marine environment changes during volcanic events. He and his buddy Rich Pyle, now an acclaimed scientist at Bishop Museum, joined scientist Gordon Tribble to check out the action below the surface.
With the underwater visibility at almost zero, Kosaki prodded actively forming pillow lava with a crowbar. One of Pyle’s fins began to melt, eventually getting stuck in the lava. An explosion caused by hot lava hitting the cold water cracked the dome lens casing on Tribble’s underwater film camera.
“I’m really more of an explorer, a discoverer,” Kosaki said. “If I lived on the mainland, I’d be a paleontologist.”
After decades of discovering new species of fish and algae, he did not expect to be confounded by a seaweed taking over one of the largest reefs in the Hawaiian archipelago.
First he needed to figure out what it was. A new species of native algae? An invasive that drifted in? If so, from where? And, most importantly, could it be stopped?
Kosaki found himself anxious during the 2019 trip to get samples collected in Manawai back to the lab on O‘ahu. He had alerted state and federal colleagues in Honolulu the same day they found it. That threw a wrench in his plans: Some state officials were so alarmed they […]
Full article: www.civilbeat.org