Fewer creatures found on affected beaches one year after incident: Study
Grace Chua Straits Times 30 Apr 11;
NEARLY a year after an oil spill off Singapore's east coast, the seashore life there is still showing lingering effects.
Starfish flipped onto their backs took longer to right themselves than their counterparts from an unaffected shore, and the affected beaches had fewer young seashore creatures.
The findings were made by National University of Singapore (NUS) final-year students last year and this year over the course of their biology honours projects.
They were studying the results of the oil spill last May, when an oil tanker collided with a bulk carrier off Changi East. About 2,500 tonnes of light crude oil leaked along a 7km stretch, including Tanah Merah, East Coast Park, Changi Beach and the Chek Jawa intertidal shore on Pulau Ubin.
The spill was cleaned up rapidly with chemical dispersants, but scientists noted it could have longer-term effects depending on how much shore life there was at each site.
Miss Goh Kai Ying, 23, spent her final-year project flipping common sea stars over.
The slender-armed starfish from Tanah Merah took up to two minutes to right themselves, while those from Pulau Hantu, which was not affected by the spill, took 30 to 50 seconds.
Such flipping ability is an indicator of sea stars' health, explained the students' supervisor, biology professor Chou Loke Ming.
Those that are unhealthy may not be able to escape from predators or compete for food, he added.
Miss Goh also noticed there were fewer juvenile sea stars in Tanah Merah than on Pulau Hantu's shores, suggesting the oil spill had somehow affected the creatures' reproduction as it took place in the middle of the April-to-June mating season, or that younger sea stars were somehow more susceptible to the oil.
Likewise, fellow biology student Wong Hiu Fung, 23, found fewer young dog whelks, a kind of sea snail, in Tanah Merah than on Pulau Hantu.
But they said more work is needed to properly explore the findings.
Meanwhile, their classmate Jeremy Tan, 24, lab-tested mixtures of oil and dispersants on green mussels from a local farm.
Dispersant chemicals are typically used to break apart large swathes of oil so they degrade faster in the environment, but they can be toxic to some marine life.
He found that green mussels, which feed by sweeping food in with their gill filaments, could not feed when exposed to commercial dispersants, and suggested the chemicals somehow damaged the mussels' gills.
In another study last year, Prof Chou worked with the National Parks Board (NParks) and National Environment Agency (NEA) to assess the immediate impact of the spill on seashore habitats.
They found that the short-term impact of the spill and clean-up on the overall ecosystem was not severe.
Besides the NUS projects, NParks and NEA are also hiring a consultant to monitor the affected sites over the long term.
An NParks spokesman said the composition of biodiversity in the areas will be surveyed to study if there are any longer-term effects of the oil spill.
The result of this second survey will also provide valuable updated baseline data on the biodiversity of these sites, she said.
Prof Chou added: 'Impacts (of a spill and clean-up) are always there, it is a matter of how we react and respond to them to try and decrease the full extent.'
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Singapore Changi East Oil Spill (25 May 2011) facebook page
