Out of Sight, But Not Out of Mind: How Will Zooplankton Fare in Warmer Lakes?

by Cassie Gauthier —  When I walked out of my cabin, it was pouring. It was my first week on station and had been raining almost every day. I went to the station and layered on waders and my raincoat. To me, it seemed like a less than ideal day to go out sampling. But, for Ella Schmidt, the Ph. D student I was tagging along with, today’s weather was perfect compared to all of the days in April and May when she was on the lake while it was snowing. So I, too, decided to be thankful for warmer weather.

Ella takes a Secchi disk reading in a snowstorm on Escanaba Lake. Photo: E. Schmidt

Once we got to Escanaba Lake, we bailed out the boat, loaded it with equipment and set out to our first sample site. Every ride out to a sampling spot I try to observe and ponder as much of the environment around me as I can. On this ride I couldn’t help but realize how big the trees, water snakes, bluegill and even tadpoles I saw were compared to what I was going to help sample for: zooplankton.

Zooplankton are microscopic animals in the water. Ella has been collecting samples of the zooplankton in Escanaba Lake every other day since the ice melted off of the lake’s surface in early April. This year was the 3rd earliest ice off ever recorded on northern Wisconsin lakes and she hopes to find out how this earlier than expected ice off on Escanaba Lake affected its zooplankton populations.

Even though we can’t see the zooplankton swimming around in the water, they have a big role in helping lakes stay healthy. “The zooplankton communities affect everything people like about lakes such as the water quality and wildlife,” Ella told me. “Zooplankton are at the bottom of the food web and feed on a lot of the algae in the water which keeps the water looking clear and also are food for a lot of the fish in the lakes.”

As climate change pushes the ice off lakes earlier and earlier each year, it leads to warmer water temperatures. Ella and her larger research team at Trout Lake Station and the Center for Limnology are concerned that the warming temperatures will no longer be tolerable for some of the zooplankton species that like colder water. This is Ella’s first year as a Ph. D student, and while she doesn’t yet know how zooplankton are affected, she’s thrilled to learn more. She says she loves how much she is learning right now because this project is covering many parts about limnology she has never studied.

Ella enjoying sampling in the sun on Escanaba Lake. Photo: C. Gauthier

Last Friday was one of Ella’s final days sampling the lakes this season. This time it wasn’t raining but the temperature hovered over 90 degrees. Still, she didn’t complain. She loves what she’s doing and said she was very happy to be on the lake collecting samples – which must mean she picked the right career path considering she has sampled in many drastic weather conditions!

Ever since Ella was a little girl, she has loved visiting lakes in northern Wisconsin and recalls how she never considered that there were smaller animals in a lake than a minnow. Now that she is studying zooplankton, she hopes she can help other people have a better understanding of how important animals at the base of the food web are for their ecosystem and that even though zooplankton may be out of sight, they will not always be out of mind.