SIAU MING EN Today Online 17 Jun 16;
SINGAPORE — Swathes of coral reefs along the fringes of the Southern Islands and in the north-east of Singapore are bleaching — a phenomenon caused by stress from higher-than-usual sea temperatures in recent months due to the El Nino effect.
Along the Cyrene Reef, about 80 to 90 per cent of the hard and soft corals are bleaching, while 60 to 70 per cent of the hard and soft corals at Terumbu Hantu are also facing a similar situation, wrote Ms Ria Tan, who runs the Wild Shores of Singapore blog.
The situation is not as dire in Pulau Jong, with about 30 to 40 per cent of the hard and soft corals bleaching — including those in the deeper waters, she added.
In response to TODAY’s queries, Dr Lena Chan, the National Parks Board’s (NParks) group director of the National Biodiversity Centre, confirmed that “from the start of June, various stages of bleaching were reported at reefs within our southern waters”.
She added: “This includes some that are completely bleached, while the majority are partially bleached or not bleached at all. We are hopeful that those that are partially bleached will recover completely if temperatures do not increase further.”
Coral bleaching occurs when the water is too warm, forcing corals to expel the algae called zooxanthellae living in their tissues, exposing the limestone skeleton.
The zooxanthellae will tap on sunlight to make food in the form of sugars, while the corals provide shelter and raw materials.
Mildly bleached coral can recover if the temperature drops, otherwise it may die.
El Nino is the abnormal warming of the tropical Pacific Ocean which, in the case of South-east Asia, leads to prolonged drier and warmer weather.
Marine biology expert Huang Danwei noted that the widespread bleaching event is “definitely a cause for concern” as it might have an adverse impact on the long-term health of the coral reef ecosystems.
Although temperatures appear to have somewhat stablised in the last two to three weeks, Assistant Professor Huang noted that the bleaching continues to worsen mainly because the high temperatures have been sustained over such a long time.
Without the nutritional support from the algae, corals have to expend more energy capturing plankton for food. This affects their growth and immunity levels, which can cause corals to die, he said.
“The loss of living corals is detrimental to the health and function of the coral reef. These reefs have been built naturally over hundreds of years, and have provided ecosystem services such as coastline protection, food, medicines and recreation. Coral bleaching at the scale we are witnessing will impact these services,” he added.
Since the onset of the El Nino phenomenon last year, Dr Chan said NParks has been monitoring global and local temperature trends. Since the start of the year, NParks has also initiated bleaching monitoring, which entails monitoring sea surface temperatures and photosynthetic responses of corals.
To “augment the genetic diversity of each species” and strengthen their survival capability during extreme conditions, NParks is moving locally-rare species into deeper waters with stronger currents or into controlled environments and at the same time, making efforts to increase the number of individuals of each species through programmes like Plant a Coral.
NParks is in also in discussion with researchers on ways and means to propagate bleaching-resistant species, added Dr Chan.
Asst Prof Huang said there are about 200 species of hard corals in Singapore waters, while Dr Chan puts the number at more than 250 species. Singapore’s total reef area is about 13.25sqkm.
The last mass coral bleaching in Singapore occurred in 2010 when Singapore also experienced moderate to strong El Nino effect and before that in 1998, when Singapore experienced a similar situation.
Both events were more serious than the present situation, although Asst Prof Huang noted that it is difficult to predict the relative severity of the current situation given that bleaching in the last two weeks has worsened.
