Exploring seawater a drop at a time.

Apr 02, 2017 • 7:22 PM UTC

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Microorganisms

bray1624

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Recently our class did some casual plankton surveying at the Monterey Coast Guard Jetty. We filled several jars from a plankton tow using a 202 micron net, to focus on living zooplankton, which we observed under dissecting scopes back in the lab.
As predicted, evidence of spring was in the water as well as the air, with plenty of barnacle larvae to be found, and even what looks to be a polychaete larvae.

What may be a polychaete larvae (center) with other zooplankton. From our watch glasses, it was easy to select specimens to examine under our new foldscopes. You can stack paper slides to add depth for your little critters to still squirm a bit on their clear tape cover, or use a glass slide. I had installed the new high magnification lens on my foldscope, and was excited to see how much detail I could find. But, used to glass slides with a well in them, I still was smashing larvae to the point of blurriness several tries later. So this time I avoided the charismatic, but large copepods, skimmed off some tar flakes and packed the rest up to practice some more from home.
Clearly nothing but the littlest zooplankton in here…

I tried to go smaller this time, after my initial impression that the scope would do best with the contrast and distinct shapes of some of our barnacle larvae.

So small, I can barely focus. A 2mm shrimp larvae is top right, its eyes are just visible as two dots. My specimen was a 2mm shrimp-like larvae with very little abdominal color, and two visibly black eyes. I scanned my slide, looking for the black beady eyes, only to find perched just below my specimen, a piece of plastic — probably frayed boat line — that I ID’ed from its telltale blue color. Contrary to its name, even blue-green algae isn’t blue. Luckily we’re not looking to drink from the marina any time soon, but microscope plastic is never good. Needless to say, the high power magnification lens may take more practice, but it is high! Has anyone out there used foldscopes to test for microplastics in their water?

An otherwise invisible piece of blue plastic under magnification.

Exploring seawater a drop at a time.

bray1624

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