A myth busted... and a new believer is born (10 Mar 09)

How often do you hold onto a belief for years and see it busted to shreds within minutes? Not often, I hope unless you have been living in a cave.

It started as another lesson for a secondary school. These students were brought out of the classroom to yet another field trip to a nearby pond. They were given big, robust nets and told to dig into the bottom mud and be aggressive about it. No big deal for kids 50 years ago but for them, it was a novelty... a thrilling experience no classroom lesson could have prepared them for. Yes, you have be there to get your hands dirty to find out.

You are probably wondering what they were supposed to do with the mud. In short, check out the bugs in the mud. Anything without backbone, isolate and identify them. These include insects, worms, snails and....

Bingo! The students scooped up half a dozen or so leeches! These are not your 1-inch wriggling critters commonly found in Malaysian forests. Imagine these half-foot whoppers* clinging everywhere on your body including those parts of your body not exposed to the sun, furiously competing against one another to feed on your blood.... blood chilling. And I have always believed that there are no carnivorous leeches in Singapore. There goes that belief. Never will I nonchalantly wade into an unknown pool/pond/reservoir here.


Is anyone screaming yet? Oh yes, the students were indeed screaming, not in terror but in excitement. I guess there is a big difference between seeing leeches in a sample bowl and having them stuck on your own body.

On the technical side, the presence of this significant number of leeches indicate a bad water quality with a low oxygen content. This was confirmed by our oxygen tests.

In case you conclude that I hate leeches, on the contrary, they are one of my favourite animals. Not the kind that you keep at home but the kind that you admire. Their tenacity and survivalability rank tops among animals. This is in addition to their arsenal of biochemicals that allow them to do what they do best - all these packed into a compact but ferocious package.

* These half-foot critters are fish fry compared to the half-METRE Amazonian leech.

Figures (L-R, T-B): Classroom lesson of looking at dead (and boring) specimens under the microscope; trying to score some live specimens in the field; mud and bugs are part of the job; searching intently for the tiniest bugs; cute aquatic leeches - are they carnivorous buffalo leeches?; check out my article on the chemical secrets of the leech in Singapore Scientist no. 111 (2008)

How mercury flows downstream

A comprehensive piece of research by USGS on the biogeochemistry of mercury in 8 different streams in US. Several interesting observations were made in the study but I will just highlight 2 points why mercury is an insidious pollutant posing a high degree of hazard.

1. The source of mercury in the study does not go directly into the water. Instead, mercury is carried by air or rain into streams and their watersheds. In other words, the watershed may not have any industry (e.g. mining, smelting, power generation) releasing mercury but mercury can still be transported from other areas by the atmosphere

2. Mercury can definitely move up the trophic levels to reach the top predator, usually fishes, if not man. It does not just remain in the abiotic environment, it can easily enter the food web right at the lowest level (e.g. algae) to affect the entire ecology.

How mercury flows downstream

via ES&T Online News on 3/11/09

A comprehensive study shows the correlations among landscape, mercury, and the life in streams and rivers.

Field work at "Ngee Ann Stream" (16 Mar 09)

A field trip can probably be the most challenging part of any course. Besides the immense amount of preparation, the execution can be fun and intense at the same time.

One big challenge is communication. We are no longer in a classroom where all the participants are nicely seated in neat rows with the projector and computer pointing to them where their attention should lie. No doubt, some teachers may beg to differ about gaining attention in the classroom but wait till you head out to the field where participants are all over the place doing things that may or may not be what you instructed. That is when all the "fun" begins. Of course, this is also when teaching is at its best if well executed.

How about this? You perform your recce with utmost care and plan to the tiniest detail... (as usual, there is a "but") but Murphy still insists on working his Law. Grasses have grown so much taller, making the trail seemingly disappear. Or some agency has decided to do some land clearing and coupled with the unpredictable weather (nothing new here) made the entire site into a mud playground. Suddenly, you have people playing "slip and slide" everywhere... you get the idea.

Nevertheless, this is also a mimicry of life itself when many things are unpredictable. Yet with a cool head and the right experience and knowledge, one can always get through with full marks (or perhaps a scratch or two).

Figures (L-R, T-B): Working by the "open-country urban" stream; moving along the same stream; moving along an "open-country rural" stream; taking a break after some grass and mud bashing; back in the "safe" confines of the lab to run a microbiological test on the water sample collected from the streams

Advanced Elective Module (AEM): Water Quality and Pollution

Apologies for the long overdue post. For the past month, in addition to other work related matters, I am heavily occupied with developing and fine-tuning teaching materials for my AEM. Being a forty-hour module, it involves:

1. classroom lessons
2. classroom activities
3. field work
4. laboratory work
5. assessment

Moreover, field trips must be backed up by good old reconnaisance which also eats into the preparation time.
All these development work can be quite intense as most materials are designed from scratch, blending a good mix of theory and practical. Field work and non-conventional classroom lessons are the corner stones of this module. After all, it does not make sense to immerse the students in more of the same old classroom lessons in an enrichment module.
Nevertheless, the development work was fun and enriching. One of the great things of being a teacher/instructor/lecturer is you get to learn many things because you have to be so much more knowledgeable than your students.