The Trials and Tribulations of Attempting an Experiment


Mussel with extended mantle. Photo credit: Chanelle Samuel

The last month of my experimental invertebrate biology class at UBC was devoted to each student devising and implementing their own experiments. We had 2-3 weeks to run trials for our experiment, and then we had to present our results to the class. For my experiment, I decided to determine how temperature affects mussel filtration rate. Originally, I had wanted to use multiple temperatures, but that idea was quickly discarded as keeping an intermediate temperature stable for one hour was going to be very tricky. So I settled on using two temperatures, one equivalent to our sea table ~13°C and one around room temperature ~20°C.

Initially, the plan to measure mussel filtration rate involved adding algal cells into a tank with some mussels, and then using a fluorometer to measure the fluorescence of the chlorophyll located in the algal cells. Then I would take samples at 15 minute intervals to hopefully track a decrease over time as the mussels filter the algal cells out. But, before the experiment even started I had to create a standard curve of what the fluorescence would look like with known concentrations of algal cells, so I could compare them with my unknown results. Now, it had been awhile since I had done dilutions and apparently I was a little rusty…..After my third try I was ready to start running my dilutions through the fluorometer. There was one small problem with this; I kept getting very similar results from the machine even though the concentrations were completely different. After despairing with 2 other classmates over our inability to figure this out, we enlisted the help of Katie who was more familiar with the machine. She fiddled with our dilutions and concluded that the fluorometer was not sensitive enough to detect the differences between the concentrations we were using. So we scrapped the fluorometer and moved on to our next option, the Coulter Counter!


Coulter Counter. Photo Credit: Chanelle Samuel

So the Coulter Counter is a machine that is probably more than twice my age. As its name suggests, it counts cells. It uses an elective current that it passes through your water sample as it is being sucked up a small tube, when a cell passes through it acts as a resistor to the current and is registered as a blip by the machine. The Coulter Counter then counts all the blips in order to give you a cell count in cells/L. This was a brilliant solution to our problem, and did work quite well in the end, except for a few glitches it had. If there is any sort of electric background current the machine is interfered with and registers an outrageously high number. And when the water is being sucked up through the aperture, the opening is so small that it often gets clogged and therefore the count is off until you clear the debris from the opening. But after some time and some practice, we got the hang of it!

All in all, it took a LOT of time and effort, and a lot of reworking, and redesigning, but I learned a lot. I discovered that mussels are way more active than I originally thought, and they can move around quite a bit. Also, that temperature does effect mussel filtration and depressed the amount filtered at high temperatures. And that whatever you write down on paper, or how you expect something to go, it most likely will not occur as you thought it would!


Mussel with extended foot. Photo credit: Chanelle Samuel

Check out this cool video on mussel movement!


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