Tuesday, April 06, 2010

The forgotten mangroves at Sungei Pandan

Talk about mangroves in Singapore and you will hear about places like Sungei Buloh, Pasir Ris, Pulau Ubin and from the savvy ones, Sungei Sembawang, Sungei Punggol, Pulau Tekong. Only from the most experienced naturalists will you pick up whispers of Sungei Pandan. If you look up "Longman atlas: Singapore and the world", you won't even find mangroves there.

There is a very good reason too - Singapore's northern coast is well suited for mangrove building with gentle currents for sediment deposition. Yes, you need to have accumulation of the "yucky muck" for a good substrate. Sungei Pandan mangroves thus appears to be an odd orphan located near the southern coast. Could the conditions at Sg Pandan be similar to those of our northern coast?

I simply can't resist taking my advanced elective module (AEM) class to this interesting habitat for a water quality monitoring (WQM) field trip.

Figure: A massive dam lying right across Sg Pandan. Such dams are common on rivers and canals leading to the sea (Marina Barrage is the big brother among them). They control the loss of fresh water into the sea so that the reservoir (Pandan Reservoir in this case) can be pumped up. Another important function of a dam is to prevent the flow of seawater (read salty water) into the reservoir. Treatment of salty water is expensive since you need reverse osmosis or distillation to do the job. Conventional water treatment does not cut it.

But... (there is always a "but") these dams also disrupts the continuity of the flow, separating the stream into 2 parts with distinct characteristics, one of which being salinity. (1st hint: take note of the vegetation on the bank in the above figure.)

Bad for the aquatic life but great for an outdoor lesson. Here is a Google Earth file compiling the data collected by the participants.

Aside to FMSS students in selected groups: Please use this file to prepare for your case study presentation.

2nd, a dam may prevent precious sediment from reaching downstream. To you, sediment may be muck; to the creatures downstream, it is food, nutrients, home and more. Just as sediment is blocked, the migration of animals for spawning, feeding etc. across the great divide in both directions is also hindered. I am sure environmentalists all over the world have more to say about these dam problems (1, 2; Mekong - 3, 4).
Figure: Steady rain for the whole field trip but what the heck, we are living in the tropics - rain is a standard feature. As long as safety is not compromised (e.g. lightning), some work in the rain is good for the spirit.

Figure: A denizen of the mangroves cleverly avoided the rain by following the guy with the umbrella

Figure: Downstream of the dam. Spot the different root systems of mangrove plants. The exciting mangroves in this figure is a vivid contrast to the boring grasses (no offence to the grass people) upstream.

Figure: Mudskippers surfacing to enjoy the cool rain which keeps their bodies comfortably moist.

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