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SCIENCE Friday 10 July 2020
Aggressive seaweed smothers one of world's most remote reefs

HONOLULU (AP) — Re- The first order of business,
searchers say a recently officials say, is to ensure
discovered species of sea- anyone studying the sea-
weed is killing large patch- weed doesn't inadvertently
es of coral on once-pristine spread it.
reefs and is rapidly spread- "All of our dive gear, all of
ing across one of the most our boats, everything got
remote and protected saturated with bleach,"
ocean environments on said Randall Kosaki, NOAA
earth. research coordinator at
A study from the University the marine monument and
of Hawaii and others says expedition lead for the ear-
the seaweed is spreading lier surveys.
more rapidly than anything "If something like this got
they've seen in the North- back to Waikiki or any-
western Hawaiian Islands, a where in the main Hawai-
nature reserve that stretch- ian Islands it would be an
es more than 1,300 miles ecological disaster, but
north of the main Hawaiian also an economic disaster,"
Islands. Kosaki said. "q
The study was published in
the journal PLOS ONE on
Tuesday.
The algae easily breaks off
and rolls across the ocean
floor like tumbleweed, sci-
entists say, covering near- In this July 31, 2019 photo provided by researcher Heather Spalding, a thick mat of a new spe-
cies of seaweed is held by a diver at Pearl and Hermes Atoll in the remote Northwestern Hawaiian
by reefs in thick vegetation Islands.
that out-competes coral Associated Press
for space, sunlight and nu-
trients. Scientists say the actual Manoa Interim Associate Great Barrier Reef Founda-
"This is a highly destructive coverage area is likely Dean and Professor Alison tion. "But it is a matter of
seaweed with the potential much larger than docu- Sherwood, chief scientist concern whenever you see
to overgrow entire reefs," mented because they on the study. an ecosystem start to dis-
said biologist Heather couldn't survey many sites Researchers studied the play symptoms ... like this."
Spalding, a study co-author during their brief visit. seaweed's DNA to try to de- Mumby, who was not in-
and longtime Hawaii algae Close to Midway Atoll, site termine its origin but con- volved with the Hawaii re-
researcher. "We need to of a pivotal World War II air cluded it's a new species search, said more needs
figure out where it's cur- and sea battle, Pearl and of red algae they named to be done to understand
rently found, and what we Hermes Atoll is mid-Pacific Chondria tumulosa. what is driving the sea-
can do to manage it." about 2,000 miles (3,200 The algae can spread in weed growth.
In 2016, government re- kilometers) from Asia and various ways, Sherwood But he noted that in other
searchers were on a routine North America. said. It produces tumble- parts of the world algae
survey of Pearl and Hermes The uninhabited atoll is in weed-like clumps that blooms often occur be-
Atoll when they found small the 600,000-square-mile move around the immedi- cause fish that eat the
clumps of seaweed they'd (1.6 million-square-kilome- ate area, but it also gener- plants have been harvest-
never seen before. ter) Papahanaumokuakea ates spores that could be ed or forced to relocate by
Last summer, they returned Marine National Monu- traveling much greater dis- environmental changes.
to find algae had taken ment, one of the world's tances. The new seaweed could
over huge areas of the largest protected marine Among the unknowns are have been introduced by
reef — in some areas cov- environments. why the algae is growing a boat or marine debris. But
ering "everything, as far as Noting that individual mats so fast and how it reached there is no fishing allowed at
the eye could see" — with of seaweed were as big such a remote place. Pearl and Hermes, and any
seaweed nearly 8 inches as several soccer fields, Scientists say seaweed ship that enters the region
(20 centimeters) thick, said researchers say the algae blooms happen worldwide is required to have been in-
Spalding, who was among could dramatically alter and can be seasonal, but spected and cleaned. The
the divers there. Pearl and Herme's reef this does not appear to species could also be na-
"Everything underneath of and threaten the entire be the case. The National tive, having lived in small,
it was dead," she said. Hawaiian archipelago if it Oceanic and Atmospheric unseen nooks and cran-
The area was mostly devoid spreads. Administration has been nies before a change in lo-
of large schools of tropi- Hawaii's main islands have monitoring the site for over cal conditions caused it to
cal fish and other marine several established invasive 20 years. bloom, researchers said.
life that usually cruise the seaweeds, but cases in the "When you see something The NOAA research crews
vibrant reef, and fish that remote northwest are rare. unusual in the last few years, will soon return to study the
typically eat algae were "We have, not until now, you can be pretty sure that outbreak and find out if
not grazing on the new seen a major issue like this this is something that's a bit currents have spread it to
seaweed, researchers said. where we have a nuisance special as opposed to just nearby Midway, home to
Dives along the outer reef species that's come in things that change from the Battle of Midway Na-
of the 15-mile (24-kilome- and made such profound year to year," said Universi- tional Memorial, a U.S. Fish
ter) atoll revealed the sea- changes over a short pe- ty of Queensland Professor and Wildlife Service base
weed in varying densities riod of time to the reefs," Peter Mumby, who is also and the region's only air-
and depths. said University of Hawaii at chief scientist for Australia's strip.