Thu, Jul 01, 2021 page2

• Starfish outbreak killing coral reefs near Itu Aba

  OUTBREAK: A proliferation of crown-of-thorns starfish appeared to have killed more than 90% of the corals in waters more than 2m deep, a marine biologist said

  • By Lin Chia-nan / Staff reporter
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  An underwater survey near Itu Aba Island (Taiping Island, 太平島) found an outbreak of crown-of-thorns starfish that has killed almost all the coral reefs there, Academia Sinica marine biologist Jeng Ming-shiou (鄭明修) said yesterday.

  Jeng, who is also the chairman of Society for Wildlife and Nature, in April led a research team on a diving trip to survey coral reefs in the area, a project commissioned by the Ocean Affairs Council’s National Academy of Marine Research.

  To the team’s surprise, more than 90 percent of the corals in waters more than 2m deep were dead, Jeng said, adding that the corals were mostly healthy during their survey in September 2019.

  

  A diver uses tongs and a syringe to remove a crown-of-thorns starfish from coral near Itu Aba Island (Taiping Island) in an undated photograph.

  Photo courtesy of the Society for Wildlife and Nature

  The team found an unusual outbreak of crown-of-thorns starfish, which prey on corals.

  Normally, a 10,000m2 area underwater that is half covered in coral can sustain 20 to 30 crown-of-thorns starfish, he said.

  Anything more could kill the corals, he added.

  In the April survey, the team documented 532 crown-of-thorns starfish along 14 research routes near Itu Aba, with each route measuring about 500m2, he said.

  That translates into 760 starfish per 10,000m2 of water, exceeding the alert level, he said.

  Large coral deaths caused by the propagation of crown-of-thorns starfish had also been reported in waters near Australia, Japan, Indonesia and Guam, he said.

  To restrict the starfish’s growth, people can protect their natural enemies, such as giant triton snails, and control marine pollution to reduce algae that proliferate over nutrients and become food for starfish, he said.

  Removing starfish manually is another option, but the sea creature’s sting is poisonous and can result in painful wounds, he said.

  More than a decade ago, a proliferation of crown-of-thorns starfish was also reported in waters near Penghu County, Jeng said.

  In 2010, he initiated an action to catch 96 starfish in waters southeast of Penghu’s Siji Islet (西吉嶼), while the Penghu Marine Biology Research Center also led another team to catch 139 starfish in waters around the county, he said.

  Another common method is to inject 20cc of diluted acetic acid into starfish, which would die on the seabed, he said, adding that their locations can be identified with the help of image recognition systems.

  However, there is no cure-all to curb the growth of crown-of-thorns starfish, so it is vital to continue monitoring coral reefs on a long-term basis and taking swift action against starfish, Jeng said.

  More research is needed to determine if the starfish’s proliferation is a general phenomenon or an isolated case near Itu Aba Island, the Ocean Conservation Administration said in a news release later yesterday.

  The agency this year started a project to survey the conditions of snails and shellfish crucial to sustaining coral ecosystems, and is working with the National Academy of Marine Research to protect corals.
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