I built a device called an anemometer, which used glass tubes to measure the amount of pressure caused by fluid motion. I used it to measure the pressure at several points along my base plate. By knowing how much pressure drops along the base plate, I can directly calculate the amount of shear force that is causing that pressure drop. And thus I know how much I will be blasting the spores in my tests.
I was so wrapped up in the testing, that I didn't take any pictures of the setup! But I do have the first data graph to show you.
This shows how the shear force that I'm generating corresponds to the height of the pipe I use in the flume. The trend is pretty linear, as hoped. If I fill up a pipe twice as high with water, then twice as much pressure is driving water through my flume, and I get twice as high shear forces in my flume.
And I was able to hit 30 Pa, the magic shear stress number. For whatever reason, most studies haven't been able to go much higher than 30 Pa, so as long as I can get to that force, my flume is working as strong as anyone elses.
I did learn a few things from this testing, such as how the position of my clamps can effect the forces I measure by allowing water to leak out the sides of the flume. To compensate for this effect, I had to adjust from a four clamp system to a ten clamp system, meaning I had to go buy a bunch of clamps from the hardware store.
Pressing Highlight: Porphyra sp.
This week's algae is probably the most famous of seaweeds. It comes from the genus Porphyra, and is also know as nori, the stuff you wrap around your sushi. It's a red algae, paper thin and quite delicate. To make nori, Porphyra is ground up, layed flat, and baked into a textured sheet. You can eat Porphyra (as well as many other algae) raw, but I'll confess it's much improved by the nori processing.
You'll notice that I've left the description at sp. (meaning unidentified species) rather than giving a species epithet. I know there a few Porphyra species in Washington, but I'm not that great at telling them apart. From talking with Porphyra experts at Phycology meetings, I've learned that even the experts are still creating and redefining new species constantly. So even if I were to use a guide to find the "name" of this species, there'd be a decent chance that name would be wrong anyways. As a results, I don't bother and just leave most species in this genus as Porphyra sp.
The species I've pressed look a little beat up, almost as if their degrading. But the degrading is perfectly normal for this genus, the red degraded regions are the reproductive parts of the plant. Porphyra gets reproductive on it edges, converting it's tissue entirely to sperm and eggs. Once the reproductive tissue is primed and ready, it simple deattaches from the parent plant, to float in the water and find a mate! The reddish color indicates that this is a female, males have white edges. Some of the red, gooey portions around the plant were egg packets about to be released, and got caught around the edges of the plant in the pressing process. So actually, this individual is quite sexy at the moment, and we quite literally caught it in the act in this pressing!
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