I believe that at one time or another, almost all of us would have visited the beach at the south-east coast of Singapore. The shoreline along what we know as the East Coast Park [!] is different from those at either Labrador Park or the north shore, in the sense that obviously, its recreation potential is much higher. This is because of the quality of the sand present there, by natural means or otherwise.

Not surprisingly, therefore, given the recreational value of this beach, efforts have been made by the government to protect it from erosion. This is despite the fact that the fetch here is shorter than that at Labrador Park. Why then should there be erosion along the East Coast Park?

During November to January, Singapore and Peninsular Malaysia are affected by the north-east monsoon. This is by far the wettest time of the year because the strong monsoon winds pick up moisture from the South China Sea before arriving at Singapore and the east coast of Peninsular Malaysia.

Technically, this still does not explain why wave energy along the East Coast Park is relatively high for two reasons: first, because Johor bears most of the brunt of the north-east monsoon before Singapore. Second, the beach along the East Coast Park does not face the wind direction of the north-east monsoon head on, but is instead more or less parallel to the prevailing wind [?]. So just where does the answer lie?

Although Johor bears the brunt of the storm waves brought by the north-east monsoon, the waves at the southernmost end of Johor are refracted round the southern tip, such that no longer are they approaching land from the north-east (from which Singapore would be quite adequately sheltered by Johor), but instead they are approaching land from the south-east (from which Singapore receives little or no protection).

Refraction takes place because that part of the wave which is nearer land is travelling in shallower water than the rest of the wave. The part of the wave which is travelling in shallower water slows down, as a result of encountering friction from the shallow sea-bed. The rest of the wave, however, still continues at its normal pace, in open water. The wave front thus starts to curve landward, that is, it starts to refract.

Now that we have established that during the north-east monsoon, waves are approaching the East Coast Park from the south-east, what is the next step? How does this relate to a loss of beach material at the park?

During the north-east monsoon, the waves along the East Coast Park approach at an oblique angle to the shore.

When these waves break, the water rushes up the shore diagonally, carrying the sand on the beach along with it in the same (diagonal) direction. However, once the water starts to recede back to the sea, it will respond to gravity and drag the sand straight down the beach perpendicular to the shore.

The water from the next breaker will transport the sand up the beach diagonally again and the cycle continues. The net result of this is that sand is moved along a beach as a result of what is termed longshore drift.

This explains why the beach at the East Coast Park must be protected.

Protection is carried out at the park by the construction of several breakwaters built parallel to the shore. When waves impact on these structures, their energy is dissipated.

By March 1997, two new breakwaters would have been built at Siloso beach, on the southwest shore of Sentosa island. They will serve to protect the beach there, as erosion has been accelerated by the wash from the high-speed ferries plying between the nearby World Trade Centre and the Riau islands of Indonesia.

At almost a kilometre in length, Siloso beach is the longest of three artificial beaches built at a cost of $20 million in 1991. The new breakwaters will cost more than $1 million. They will each be eighty metres long and will be placed about a hundred metres offshore.

Breakwaters are only needed at Siloso Beach and along the East Coast Park because elsewhere in Singapore, longshore drift is negligible. So the next time you find yourself at either beach, be on the lookout for more than just the opposite sex.

In fact, if you know where to look, you can actually discover some quite fascinating aspects of our marine ecosystems [?]. Did you know that there are about a hundred-and-eighty species of hard coral [!] in Singapore's waters, which is more than at Pulau Tioman or Hawaii?

Hard corals form the main components of the reef ecosystem. Reefs are structures made of calcium carbonate, derived from the exoskeletons of animals called polyps. A coral consists of a thin layer of living tissue covering the hard skeleton. Each polyp has a mouth which is surrounded by tentacles which trap food particles.

The reefs in Singapore's waters are mainly fringing reefs, which means that they are connected to the shoreline, as opposed to being separated by a lagoon. These reefs are located around the southern islands such as Pulau Semakau (which also happens to be the site of Singapore's first offshore landfill!). In addition, there are patch reefs, which are not connected to any visible landmass but are exposed at low tide. An example of a patch reef is the Cyrene Reef.

Sadly, the land reclamation [?] programme of the mid-sixties saw about sixty percent of good fringing reefs on the west, southwest and southeast coasts being obliterated. The sandy beaches stretching from Changi [!] to the Kallang Basin have been reclaimed. The reefs of Pulau Sudong, Pulau Hantu, Kusu Island [!] and the Ayer Chawan group of islands have also been affected by reclamation. Visibility underwater is now less than two metres on a clear day, compared to as far as ten metres in the early sixties.

Reclamation is significant because it results in turbid sea water. This in turn reduces light penetration, inhibiting plankton growth. The coral polyps feed on the plankton. Other environmental conditions are more favourable to coral growth. For example, sea surface temperatures around the Southern Islands range between 27 ^oC and 31 ^oC throughout the year, and pH lies between 8.0 and 8.2 (Chou, 1986).

Wherever they may be found, Singapore's fringing and patch reefs share certain similar characteristics. The intertidal reef flat, regardless of its width, has a gentle gradient of around 1:600. It is exposed to varying amounts during low tide. About five to ten metres before the sudden plunge of the reef slope is the reef crest, where coral cover is very dense. It is in this area, together with the upper five metres or so of the reef slope, where vigorous growth and a healthy species diversity are still maintained.

The reef slope itself can be almost vertical and levels off to a sandy bottom at a depth of between fourteen to thirty metres, where sunlight can no longer penetrate because of the turbid water. In fact, according to Chuang (1977), at a depth of fourteen metres, ninety-nine percent of surface light is blocked off, resulting in a light intensity there of only two hundred lux. It is here that the leathery, white, soft corals are found.

The reef flat is a relatively hostile environment for several reasons. First, it is exposed twice a day, during low tide, for up to three hours each time. The flat can dry out during this period, as it is exposed to intense solar radiation and ultraviolet light. Second, the flat is also subject to wave abrasion more than the slope.

Third, coral larvae can be smothered by the sand stirred up by the waves which settles on the gently sloping flat, as compared to the steep reef slope. Fourth, if it rains heavily while the flat is exposed during low tide, salinity can decrease suddenly. For example, Lim (1984) showed that surface salinity can fall to as low as twenty-two parts per thousand during heavy rainfall, compared to an average of about thirty parts per thousand.

Fifth, exposure to wind can mean high rates of evaporation of the surface lining of moisture around the organisms, which both increases dehydration as well as salinity of this film. Sixth, the organisms are vulnerable to casual collecting by curious man. Currently, there are no laws against this. Similarly, although the reefs at St John's Island and Pulaus Hantu, Semakau and Sudong are earmarked for conservation, there is still no administrative structure present to protect the sites. Seventh, large algae - such as Sargassum (easily recognised by their round air bladders) - compete with the coral for living space on the flat. All this means that only hardy, boulder-shaped species can survive there.

More recently, the reef community as a whole faces a threat of oil pollution from both shorebased as well as shipboard sources. As if this were not enough, there is also the threat of indiscriminate dumping of soil from excavation and dredging, as well as illegal poaching.

For example, although the Port of Singapore Authority [!] has set aside a dumping site east of Pulau Semakau, some barge drivers do not follow the rules and dump the soil even as the barge is moving, spreading it around like fertilizer. To combat this, every craft transporting earth spoils is now required to be fitted with a device which records the vessel's draught while it is en route to the dumping ground. Between 1991 and 1996, more than six million cubic metres of spoil have been dumped there.

Given all of the above, it is not surprising that an ongoing study by the National University of Singapore [!] has discovered that even where coral cover is highest, at Raffles Lighthouse, it has declined from seventy-six percent in 1987 to sixty-nine percent in 1993. Coral cover is the amount of living coral covering a given area of seabed. However, the same study has recommended that the variety of coral life left is still worth conserving.

Between 1993 and 1995, 876 coral colonies from the Pulau Ayer Chawan reef were moved to a five-hundred square-metre new site off Sentosa [!] because of land reclamation. A year later, studies showed that despite the fact that 377 showed signs of dying and 190 had died (because waves from ferries were not only sweeping them away, but also choking them with sediment), some corals had also started to grow on their own there.

In May 1995, the Ministry of the Environment [!] started work on a seven-kilometre-long perimeter bund and wharf at Pulau Semakau. To be completed by 1999, this will create a landfill area of about 350 hectares which should contain about sixty-three million cubic metres of refuse. The light at the end of the tunnel is that three steps have been taken to minimize the impact on the ecosystem.

First, even before construction work started, a survey was carried out to establish whether there were live corals within the proposed landfill site. Second, during construction, silt barricades (large underwater screens) were erected to keep the sediment within the working area. Third, water quality is being monitored regularly.

In 1996, the Sisters' Islands, St John's Island, Lazarus Island, Kusu Island and Pulau Seringat were designated a Marine Nature Area by the URA [!]. All development proposals for these five Southern Islands will now have to be assessed by the National Parks Board [!] (NParks). Elsewhere, nine mooring buoys have been laid near Pulau Hantu so that the anchors of dive boats will not damage the reef. Two hundred more such buoys will be installed by 2002.

What then, is the moral of the coral? In a nutshell, it is that while the urban growth and industrial development which has indirectly precipitated the turbidity of Singapore's waters has more or less been inevitable and necessary, nature is certainly more resilient than many of us believe her to be.

We do not need however, to load the dice even less in her favour by our thoughtless collection of hard coral whenever we visit our reefs. Hard coral take many years to grow to a moderate size, and if they are removed faster than they can reproduce, our reefs will surely die - not because of some faceless national policy of development, but because of our own selfishness.