Hi! My name is Sarah Horn and I’m an undergraduate Biology student at University Wisconsin-Milwaukee. I’m working with Professor Rudi Strickler at the Global Water Center. I was given the opportunity to work with DROPPS through the UW-Milwaukee’s Undergraduate Research Opportunity Program. I began working in the spring semester of 2014. 

Me feeding Daphnia an algae mixture.

I’m working on a project to observe how the freshwater zooplankton Daphnia pulex will react to oil droplets. Oil droplets of a set size are generated to simulate dispersed oil. Daphnia are placed in a Kreisel tank filled with oil droplets and algae. Water is pumped into the Kreisel tank creating a current along the edges of the tank, which keeps the Daphnia from getting too close to the edge. Daphnia behavior when surrounded by oil droplets is documented by taking a high speed video using laser holography. Using holography means that the Daphnia can be out of focus while it is being filmed, and reconstructed with imaging software later. This is necessary because of the Daphnia’s constant movement. After the video is taken, the size of oil droplets is measured to see if the Daphnia have attempted to eat the dispersed oil. Additionally, the behavior of Daphnia when surrounded by oil droplets is observed.

A Kreisel tank

Freshwater zooplankton are used because they are easy for us to access. We get our zooplankton from the Menomonee River, Milwaukee River, Kinnickinnic River and Lake Michigan, all which are located less than a mile away from the lab. Once we obtain adequate results using the freshwater zooplankton, a species of saltwater zooplankton will be used.