Beyond the pale
Warmer seas hurting corals; experts suggest moving them to deeper waters or into controlled environments
Audrey Tan Straits Times 24 Jun 16;
Just as flowers wilt in strong sunlight, soft corals are bleached and appear shrivelled when the water gets too warm.
All is not well in the sea, where temperatures have risen and caused coral bleaching in Singapore and around the world.
Water temperatures have dipped slightly since early this month, and scientists are hopeful that partially bleached corals can recover if the water does not get any hotter.
Bleaching occurs when abnormally high sea temperatures cause corals and related organisms - such as sea anemones - to expel the symbiotic micro-algae living in them.
Corals depend on the symbiotic algae, called zooxanthellae, for food.
"The algae exit the coral, leaving the coral without the zoo- xanthellae's colour and exposing the limestone skeleton which is white, hence 'bleaching'," explained Assistant Professor Huang Danwei, a marine biologist from the National University of Singapore's (NUS) biological sciences department.
Without the algae, the corals derive nutrition by trapping plankton. "But this is not sufficient over the long term, and will result in the weakening of the coral and increase its susceptibility to stress," said coral expert Chou Loke Ming.
A conservative estimate of the temperature threshold at which corals bleach is 31.15 deg C, +/-0.20 deg C, according to the National Parks Board (NParks).
"From end April, temperatures began exceeding the bleaching threshold, reaching up to 0.8 degrees above the threshold some time in May," said Dr Karenne Tun, director of the coastal and marine division at NParks' National Biodiversity Centre.
Temperatures have dipped to just below the bleaching threshold from early this month, and scientists are monitoring the reefs here.
Professor Chou, an adjunct research professor at NUS' Tropical Marine Science Institute, said researchers are not sure yet if the current bleaching episode has peaked.
"But this is certainly a major bleaching event, like in 1998 and 2010. Water temperature is still above normal," he added. The average sea temperature here is 28 deg C, he Chou said.
This year, as in 1998 and 2010, is an El Nino year. This refers to the phenomenon linked to prolonged warmer weather.
Dr Tun said NParks' management strategies include safeguarding local rare species by moving them to deeper water with stronger currents or into controlled environments.
Prof Chou said these measures could help, although the responses are limited in scale. Transplantation is a stressful process for corals and the number of colonies that can be moved is also limited, he said.
Also, when temperatures go back to normal, corals moved to deeper water may suffer from the lack of sunlight at those depths.
Added the marine conservation veteran of 30 years: "A more effective approach is not to wait until warming occurs before responding.
"We should start translocating coral colonies to different and more challenging sites, and give them sufficient time to adapt so that they can tolerate the impact of warming when it next comes."
Keppel Land building homes for man and marine life
Keppel Land condo project includes effort to house corals
Audrey Tan Straits Times 24 Jun 16;
Marinas, docks and harbours may not sound like the ideal homes for marine creatures, but property developer Keppel Land has taken up the challenge: It wants to build homes not only for people but also for marine life.
To do this, it has embarked on a project to enhance the existing marine habitat in the waters around King's Dock, next to its upcoming waterfront condominium Corals at Keppel Bay.
Naturally-occurring hard corals that are unattached or overturned due to natural processes are first picked up from around Keppel Island and grown in a nursery. They are then transplanted onto artificial reefs at the new site in the Keppel Bay waterfront precinct.
In April, 10 underwater "condominiums" were completed. These are artificial reef structures made of fibreglass, which provide a substrate where transplanted corals are attached.
Marine biologist Brian Cabrera from consultancy DHI Water and Environment, which was appointed by Keppel Land for the project, said marine organisms can naturally be found in the area.
"But by providing more substrates, it adds complexity to the reef and encourages more marine habitat formation. These reef enhancement structures also serve as fish-aggregating devices and should improve natural coral recruitment," he said.
Mr Cabrera and his colleagues will be doing their first monitoring dive next month to document the health and growth of the transplanted corals and provide the necessary maintenance, such as cleaning sediment.
When The Straits Times joined the marine biologists for a dive on Monday, fish such as the monocle bream, orange-spotted rabbitfish, pipefish and copperband butterfly fish were seen flitting around the arms of the transplanted branching coral. Butterfly fish, in particular, are a good sign as they are usually found in healthy reef environments, said Mr Cabrera.
Mr Tan Swee Yiow, president of Keppel Land, Singapore, said: "True to its name, Corals at Keppel Bay, apart from featuring world- class waterfront homes, also provides an underwater sanctuary for marine life to thrive."
Work on the project started as early as 2014 when Keppel Land appointed DHI to helm it.
Marine biologists first collected fragments of coral measuring roughly 10cm from the waters around Keppel Island. They were then nurtured in a coral nursery for about 16 months. During this period, they grew to about five times their original size. Biologists then attached them to the fibreglass structures using marine epoxy cement.
The coral project is Keppel Land's latest initiative to protect the marine life around Keppel Island Bay.
The Marina Industries Association had last September touted the developer's Marina at Keppel Bay as Asia's first fish-friendly marina, in recognition of marina operators who work to improve fish habitats.
Among other things, boat owners are encouraged to use biodegradable washing liquids and detergents when cleaning their vessels. Fishing is also not allowed. The measures are part of Keppel's City Reef project, which aims to nurture a kaleidoscope of marine life under its pontoons. As a result, marine creatures such as jellyfish and harlequin sweetlips are thriving there.
Coral expert Chou Loke Ming, an adjunct research professor at the National University of Singapore's (NUS) Tropical Marine Science Institute, said there are benefits to nurturing a healthy marine ecosystem, whether man-made or natural.
"It will help to make the water clearer by filtering pollutants from the water, and also attract more marine life and become biologically productive. People can look and enjoy the splendour of life thriving in sea."
Assistant Professor Huang Danwei from the NUS Reef Ecology Lab added: "Many marine organisms are effective indicators of water quality. A thriving marine ecosystem in a marina, for example, indicates an environment that is probably safe for recreation."
Beyond the pale