Coral reef coverage off the main Samoan island of Upolu sank to less than 10 per cent due to global warming and other local factors in the area, according to findings by researchers published in the scientific journal Marine Pollution Bulletin in April.
Scientists participating in the two and a half year Tara Pacific expedition — aimed at observing and sampling isolated coral reefs in the Pacific Ocean — said they did not expect to find the reef in such poor health when they began in November 2016.
After observing the damaged reef, the team decided to extend their study from three sites to 124 around Upolu, which covers over 80 kilometres of coastline.
“Throughout the sites there was less than one per cent of living coral. There are only two zones with 40 and 60 per cent of living coral and those two zones are in fact reserves put in place specially, protected areas,” said Valerie Barbe, a researcher at the French Alternative Energies and Atomic Energy Commission (CEA) who spent a month onboard the expedition.
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Despite the distance of Upolu from large urban centres, scientists discovered that coral coverage was extremely low: less than one per cent on approximately half of the sites and less than 10 percent on 78 per cent of the 124 sites they studied.
Climate change combined with local factors such as pollution and overfishing are mainly responsible for the coral‘s death, said Jean-Francois Ghiglione, research director in oceanographic microbiology at France’s National Centre for Scientific Research (CNRS).
Coral die-off is also considerably due to bleaching, which occurs when the water is too warm, forcing coral to expel living algae and causing it to calcify and turn white. Mildly bleached coralcan recover if the temperature drops, otherwise it may die.
Although the impact has been exacerbated by one of the strongest El Nino weather systems in nearly 20 years, scientists believe climate change is the underlying cause.
The French scientific research sailing boat Tara is now in Japan.
Having collected more than 25,000 samples to study the health of coral reefs and the impact of climate change, the boat should complete its voyage in October and return to its home port in Lorient, France.
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