Direct Sentences in an article
After the Tsunami, Japan’s Sea Creatures
Crossed an Ocean
TOKYO — The towering tsunami that
devastated Japan six years ago also unleashed a very different sort of threat
onto the distant coastline of North America: a massive invasion of marine life
from across the Pacific Ocean.
Hundreds of species from the coastal
waters of Japan — mostly invertebrates like mussels, sea anemones and crabs —
were carried across the Pacific on huge amounts of floating debris generated by
the disaster, according to a study published Thursday in Science. Less than a
year and a half after the enormous earthquake and tsunami on March 11, 2011,
left more than 18,000 dead or missing in Japan, the first pieces of wreckage
began washing up on the shores of Canada and the United States.
To the surprise of scientists, the
debris was covered with sea creatures that had survived crossings that in some
cases had taken years.
The study’s authors say it is too early
to tell how many of these tiny invaders have gained a foothold in North
American waters, where they could challenge or even displace native species.
While such “rafting” of animals across oceans happened in the past, the authors
say the Japanese tsunami is unprecedented because of the sheer number of
organisms that it sent across the world’s largest ocean.
And this points to one of the main
findings of the study: that this mass migration was the result of not just the
huge natural disaster, but changes in human behavior. Such large numbers of
marine animals were able to cross the Pacific because they rode on debris —
made of materials like plastic and fiberglass — that proved durable enough to
drift thousands of miles.
These synthetics, the use of which has taken off around the world, can
stay afloat for years or even decades. The debris that was dragged out to sea
by the 2011 tsunami formed an unsinkable flotilla capable of transporting a
large population of organisms across the world’s largest ocean.
“We
have created a new ecological process, the process of mega-rafting,” said
Steven L. Chown, a professor of biology at Monash University in Australia, who was not involved in the report,
but wrote a commentary that also appeared in Science. “The development of
materials that can float for ages, and the rising levels of seas due to climate
change, make the possibility of these events larger and larger.”
This flotsam ranged in size from coolers
and motorcycle helmets to entire fishing boats and even larger objects, teeming
with living sea animals that were native to the coastal waters of Japan, but
foreign to North America.
The larger the object,
the more animals it carried. One of the first pieces of tsunami debris that
appeared was a 180-ton floating dock that washed
ashore in Oregon in June 2012. It was carrying a diverse mini-ecosystem of more
than 120 different species.
“This
was our first heads up, that this was the vanguard of what might be coming from
Japan,” said one of the report’s co-authors, James
T. Carlton, a professor emeritus of marine sciences at
Williams College. “After
that, we got a steady stream of reports of boats, buoys and other debris, all
with Japanese markings, and all carrying an amazing cross section of Japanese
sea life.”
Dr. Carlton called it remarkable that
such a wide range of species — which also included barnacles, worms and tiny
filter-feeders called bryozoans — could survive the journey across the northern
Pacific. In many cases, these passages took years, longer than the life spans
of the individual organisms. The authors concluded that not only did these
creatures adapt to an open ocean where food was scarcer than in rich coastal
waters, they were also able to reproduce, in some cases for at least three
generations, before reaching the North American coast.
“We found that hundreds of species could survive for
multiple generations at sea,” said Dr. Carlton, who is a former director of
William’s Maritime Studies Program in Mystic Seaport, Conn. “They could do this so
long as their rafts did not dissolve or sink.”
To
conduct the study, the authors relied on more than 200 volunteers, including
state park rangers and beachcombers, to find and examine some 634 pieces of
debris that washed ashore from 2012 to earlier this year. While there was
concern in the early days that some debris might have been contaminated from
the nuclear accident at Fukushima that was caused by the tsunami, Dr. Carlton
said such worries quickly eased after tests showed no traces of radioactive
contamination.
The
washed up objects were found to carry 289 invasive species from the western
Pacific. While most were invertebrates, a few vertebrates survived the journey,
including a small number of emaciated fish that were trapped inside the
water-filled hulls of half-sunken fishing boats.
All
told, thousands of pieces of debris from Japan washed up on North American
coasts from Sitka, Alaska, to Monterey, Calif., and as far afield as Hawaii.
Since the authors and volunteers were only able to inspect a fraction of these
objects, Dr. Carlton said he believes hundreds more species likely made the
crossing.
It is
unclear how many of these will actually gain a foothold in North America. It
takes years for an invasive species to establish a viable population, and these
may be hard to spot on so long a stretch of coastline. Most of the newcomers
will simply vanish in a Darwinian process of selection that Dr. Carlton likened
to “a game of ecological roulette.”
Species
that do prosper can cause enormous environmental and economic damage,
especially if they supplant native species upon which coastal communities
depend for livelihoods. The study concluded that such disruptions will become
more frequent as the use of plastics and other synthetics proliferates. Nor
does it take an event as rare as a giant tsunami to launch the next invasion fleet.
Dr. Carlton pointed to Hurricane Irma, which blew large amounts of plastic
debris from devastated Caribbean islands onto Florida’s beaches.
“We have loaded the coastal zones of
the world with massive amounts of plastic and materials that are not biodegradable,”
he said. “All it takes is something to
push this into the ocean for the next invasion of species to happen.”
Members of Group :
1. Ai Fitri Yuliani (10614628)
2. Luluk Rahmawati (16614166)
3. Nissa Tumanggor (
4. Wahyu Widya Lestari (1C614162)
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https://www.nytimes.com/2017/09/28/science/tsunami-japan-debris-ocean.html
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