Thursday, November 13, 2008

Water Quality Monitoring in Bukit Timah Area: Binjai Stream (18 Sep 2008)

I had the honour of being attached to the Marine Biology Lab in NUS for a week. During this period, I learned more about the use of macroinvertebrates in water quality monitoring. The attachment was made more interesting with a field trip to one of my favourite haunts for recreation and water quality monitoring.

Binjai Stream is located in the Binjai area of Bukit Timah. Casual trekkers are not likely to stumber upon the entrance to this stream as it involves wading through a long, dark tunnel under an expressway. The occasional inhabitants of the tunnels, swifts of some kind, fiercely demonstrated their displeasure at our intrusion by playing touch-and-go near our faces.

This can qualify as one of the cleanest streams we have monitored. Forests surround the stream and the clear waters are occupied by numerous pond skaters. Unfortunately, the area further upstream is subject to land slides, especially after heavy rains. This really messes up the water quality as the stream water quickly becomes "kopi susu" with high levels of suspended sediments.

Yet despite the clear and clean (indicated by water quality tests) water, the benthic macroinvertebrate population was surprisingly disappointing. Kick sampling with a net yielded little macroinverts. Most were surface insects such as pond skaters.

Is this a normal trend in our waters? Or could this imply something unpleasant festering in the background? We do not have the answer at this point.

Figures (L - R): A freshwater crab deftly scoped up; numerous pond skaters; Esther working on the net to score some macroinverts; typical habitat of Binjai Stream

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