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December 2008

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Green Island: The Vitality and Crisis of the Tiny Heaven

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Montipora of Green Island, covered with black spongesMontipora covered by black sponges
Blackened Corals, Paled Beauty
In December, 2005, Prof. Chang-fong Dai of NTU was appalled to discover all the black sponges that
tightly encrust the bright corals around “Big Mushroom”. And the originally bright and lively coral reef is now like some deadly ruins.

Different from the coral bleaching in Kenting, what threatens the coral ecology in Green Island is some ghostly “black plague”. The Marine National Parks thus commissioned of Dr. Chen’s research team to investigate the cause of the plague. The team coordinated the investigative efforts of scholars with different specialties. The team finds that the plague has spread throughout the whole island; among the infected areas, the coral reefs in Gongguan have the highest infection percentage, reaching 10.91% of the total coral surface area. And the most seriously infected is the reef-flat corals.

What on earth is the black monster that has been attacking our corals? “Looking across the world, we can find only three related research. And the reference is the black plague in Guam of USA and Ryukyu Islands of Japan dated back in 70’s and 80’s.”

After sampling and analysis, the culprit can almost be confirmed to be Terpios hoshinota, a sponge infected with blue-green algae. “The coral reefs infected with the black disease
are taken up by one species of blue-green algae, which could be a new type of bacteria, different from that previously reported in Japan,” Dr. Chen cited the result of Dr. Sen-lin Tang’s research.

More and more coral reefs in Green Island have been infected with the plague. “It is spreading fast, with the rate of a yearly 4 to 8 cm growth. We can then infer the breakout of this plague in the island has begun about two years ago.”

Chen pointed out that after cross validation, researchers found corals in the eastern and northern marine areas have a higher incidence of the plague, because of a higher population density here. The water quality analysis also shows there is a higher level of ammonia and nitrogen in the water waste of these areas. The landfills of Youzihu and the Sleeping Beauty also result in an excess of the nutrient in the water. What worsens the condition is that during the summer, the sea water velocity is too slow to wash the pollutants away. On the other hand, the highly populated Nanliao area does not suffer as much from the black plague, possibly due to the strong ocean current in this area. These data indicate that the occurrence of the black plague requires many complex conditions to form simultaneously. For all that, Dr. Chen suggests work on the origin of the pollution, building a simple sewerage system to stop the water waste discharge into the ocean.
Dr. Chen and his assistant spotting groups of Platygyra spp. with obvious infection of the black plagueHealthy coral colonies of Green Island.
  • upper left: Montipora of Green Island, covered with black sponges / provided by Allen Chen
  • upper rught: Montipora covered by black sponges / provided by Allen Chen
  • lower left: Dr. Chen and his assistant spotting groups of Platygyra spp. with obvious infection of the black plague / provided by Allen Chen
  • lower right: Healthy coral colonies of Green Island. / provided by Allen Chen
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