Watch: Unbelievable Swarm of Spiny Water Fleas Invade Hasler Lab

Last Friday, my phone started “blowing up” with text messages about some sort of invasion at Hasler Lab and where, exactly, our new Go Pro camera could be found. Perhaps because I’ve recently binged-watched both seasons of Stranger Things, I pictured CFL staff and students jumping on their bikes and racing to the lab with walkie talkies and flashlights to document whatever weird thing had showed up in our boat slip. Considering the creature in question eats enough to devour the entire city of Madison, I wasn’t too far off.
The photo above shows the culprit – the prolific spiny water flea, an aquatic invasive species found in an abundance in Lake Mendota that far surpasses its numbers anywhere else in the world. Why, exactly, these tiny zooplankton do so well in Madison’s iconic lake is still somewhat of a mystery. But, whatever the reason, three straight days of wind blowing right at Hasler Lab had sent waves crashing against the door to our boat slip and shoved the lake’s surface water our way. Floating along for the ride were millions upon millions of these alien-looking invaders. Our post doctoral researcher, Jake Walsh, put together some helpful GIFS to chronicle the situation:

That’s right, not only did spiny water fleas show up on our doorstep in alarming abundance, they’re producing eggs at a rapid rate – eggs that can spend a winter (or two or three) in the lake sediment just waiting for conditions to get nice again, leading to another population boom. That’s a big problem for our native zooplankton, especially daphnia pulicaria, a big, slow-moving zooplankton that eats algae and keeps our water clear. You see, “big and slow moving” is music to a spiny water flea’s ears and they love chowing down on daphnia. (Okay, they don’t have ears but you get the point.)
While it appears one of our newest invaders isn’t exactly going away any time soon, it’s still possible to be amazed by an invasion in action. Take this eerie video Vince Butitta and Martin Perales got of the spiny water fleas following their flashlight beam in the boat slip.

They then dipped a fish tank into the water and caught a bunch of spiny water fleas to get a closer look. Even with that casual sampling method, they caught so many spinies that the little animals were making their own current just from so many moving parts swimming in a small area. Watch as a drop of red dye heads quickly for the bottom of the tank and then (faintly) upwells back to the surface.

All in all, it was a unique natural phenomenon we were able to document. Of course we’d much rather see a swarm of daphnia in Lake Mendota’s troubled waters!

You can learn more about the spiny water flea from some of our previous posts.