The spiny water flea, an invasive species of the Great Lakes and surrounding inland lakes, was discovered in Lake Mendota in September of 2009. Since it’s invasion into the Madison lakes, the spiny water flea population has reached some of the highest densities recorded in any of its known invaded or native ranges. The preferred meal of the spiny water flea is a small aquatic crustacean, Daphnia. The Daphnia of Lake Mendota are essential in maintaining clear, algae free water through grazing (like miniature lake cattle). Through predation, the spiny water flea may decrease the Lake Mendota Daphnia population abundance, which in turn may allow algae to grow unchecked. My goal is to figure out if this is happening in Lake Mendota while also looking at the broader impact of the spiny water flea on other zooplankton (small aquatic crustaceans like Daphnia) and fish communities.