Yesterday I made the rookie mistake of leaving my dorm for class without an umbrella. What started as a slight drizzle when I left quickly turned into a full-on downpour, leaving campus (and me!) wet and cold. The weather today has been more hospitable, but the ground everywhere is still wet. I took a quick walk around the sports field in the afternoon, and seeing all the murky puddles along the side of the path made me curious: what exactly is in the water? What microorganisms might it have compiled from the nearby soil and passing shoes? I decided to take a look at some water samples under a Foldscope and find out. I conducted this project as part of Professor Pringle’s EEB321 class at Princeton University.

The first thing I learned was that taking samples of water on a coverslip is a challenge in and of itself. In most of my wells the water droplets remained intact, making it difficult to see anything inside. However, the droplets were pretty fun to look at as well. I showed this picture to a friend and she commented that they looked like clear planets!


In this picture the dirt particles tracked in with the water are more visible. At higher magnifications, I wonder if you would be able to see bacteria in the dirt.


Here is a particularly large droplet that took up almost the entire well. The surface of the droplet appears creviced instead of smooth -- I'm not sure if that's accurate or if it has something to do with the setup of the slide.


While I didn't see any life in those images of water droplets, I did have one well properly filled with water that was more promising. Lots of grains of dirt are visible, and in this video clip you can see something that could be a microorganism moving from left to right near the center of the well. The magnification isn't strong enough to identify what it might be, but it's moving fairly quickly and smoothly in a zig-zag pattern.

I wonder how the makeup of puddle water might differ across campus. There's been a lot of construction going on recently, and so I wonder: if I had gotten water samples from around those sites instead of by the sports field, would I have seen different things? Plenty of questions to be answered!