Looking like an alien landscape, egg and sperm bundles rise out of a Starry Cup Coral (Acanthastrea hemprichii).

You know that indescribable buzz you get when you’re anticipating a special event like your first wedding anniversary, your forever 29th birthday or that long-awaited Madonna concert? Well, I get that feeling at the start of each year as the cool Christmas breeze slowly gives way to warmer winds and as the monsoon wanes to welcome clearer skies and warmer waters.

Around February and March each year, I start to monitor the seawater temperatures around Singapore’s coral reefs to determine when the waters jump from a cooler 27°–28° C to a more balmy 28°– 29° C. Around this same time, I also start to check the corals for telltale signs of imminent coral spawning. I would snap off a few selected coral branchlets of some hard coral species to monitor the development of egg-sperm bundles. These bundles, which are visible to the naked eye, signal their maturity by changing colour from white to beige, or pale-yellow to pink.

The pale-pink egg-sperm bundle of an Acropora coral in late March 2014, indicating that there are maturing bundles that will spawn after the full moon in April.

I look forward to the yearly mass coral-spawning event in Singapore like a greedy kid in a candy store since the first time I witnessed it some 12 years ago off the fringing coral reef at Pulau Satumu, where Raffles Lighthouse is located.

Even after all these years, I am still amazed by the event where individuals of many species release thousands of egg-sperm bundles (or eggs and sperm separately) into the water column within minutes of each other, guided by some primordial rhythm that dictates  the synchrony of coral spawning.

Individual eggs and a cloud of sperm burst forth from a Lobed Brain Coral (Lobophyllia hemprichii) like a volcanic eruption.

If I had to introspect and scrutinise why the event stirs such strong emotions in me, I will have to say that more than anything, the event evokes a sense of unbridled hope for the future of Singapore’s coral reefs.

In an ever-changing environment where coral reefs are subjected to a barrage of anthropogenic and natural stressors, the fact that corals are able to reproduce and safeguard their next generation bodes well for the long-term sustainability of Singapore marine biodiversity. Hard corals play a major role in the reef ecosystem as they form the very foundation that supports the survival of other reef species.

A Blue-spotted Stingray (Neotrygon kuhlii) ventures into a cloud of coral sperm.

As a serial coral spawning enthusiast, over the years I have been visiting our reefs for three consecutive nights, from the third to the fifth night after the late March or April full moon. In the process, I have made several observations.

Firstly, the strength and intensity of each yearly spawning event reflects the favourability of the reef environment in the preceding year, so when reefs experience a significant impactful event in a year, the strength and intensity of spawning in the following year may be affected. Secondly, the colour, size, shape and movement of egg-sperm bundles differ between species; and thirdly, it is possible to locate a spawning coral by following the spawn trail in the water column down to the coral.

A section of the coral reef at Pualu Satumu, where Raffles Lighthouse is located. Coral reefs play an important role in the marine ecosystem as they support other species by providing them with shelter and food.

This year, a team of around 10 enthusiasts spent a weekend in mid-April documenting the synchronous mass-spawning event in Singapore. The spawning was generally robust and at least 25 species of hard corals spawned over the three nights.

However, with predictions of a strong El Nino event occurring during the latter half of 2014, which may result in coral bleaching, it is possible that the reproductive potential of corals maybe affected. So while I had looked forward to the 2014 mass coral spawning event with joyful anticipation, I am approaching the 2015 event with some trepidation.

Photos and text by Karenne Tun

Glossary
Anthropogenic stressors: Agents, conditions or stimuli, e.g. pollution, directly caused by or produced by humans, that would stress an organism. Fringing coral reef: It is a coral reef that develops along coastlines.

Sisters’ Islands Marine Park – Singapore’s First Marine Park
The 46-hectare Sisters’ Islands Marine Park is a good place for the public to view corals, sea anemones and other marine life up close. Public guided walks are available from August 2014 onwards. These walks offer visitors a good opportunity to explore the rich marine life around Singapore’s Southern Islands. Singapore’s first marine park includes the Sisters’ Islands and the western reefs of both St John’s Island and Pulau Tekukor, and was established to carry out outreach, education, research and conservation activities related to our native marine biodiversity.
To sign up for the walks or for more information on the Marine Park, visit the website.