class at the University of Wisconsin–Madison, making it the third known inland lake to harbor this species in Wisconsin. Scientists from the Long Term Ecological Research Network had initially believed that Lake Mendota was an unsuitable habitat for the spiny water flea, which prefers cold lakes, as limnologists from the North Temperate Lakes site of the LTER had conducted over three decades of sampling trips into the lake and had never found a single spiny water flea. However, after extracting sediment cores from Lake Mendota and analyzing them at the UW–Madison Zoological Museum, researchers found evidence that spiny water fleas had been present in low concentrations in the lake for at least a decade before their sudden population increase in 2009. This conforms with recent research proposing that invasive species can spend years or decades as "sleeper populations," remaining at low population densities until environmental conditions become favorable for explosive population growth, at which point they are detected by researchers. In 2015, a reproducing population of invasive zebra mussels was found in Lake Mendota, which generated concern among ecologists because the mussels have been linked to increases in the frequency of cyanobacteria blooms and beach closures. Biodiversity Lake Mendota, like the other lakes in the Yahara River chain, contains many native aquatic plant species, which are the primary producers of the lake and serve as the foundation for aquatic food webs as well as shelter for northern pike and yellow perch, both of which are native fish species. A 2017 ecological survey of the Yahara lakes conducted by the Dane County Land & Water Resources Department found 24 aquatic plant species, including the coontail, muskgrass, common waterweed, small duckweed, American lotus, variable pondweed, wild celery, and common bladderwort. These native plant species play a role in partially mitigating the increasing eutrophication of Lake Mendota, as they absorb phosphorus and produce dissolved oxygen, and they aid in preserving the physical structure of the lake via their root systems, which stabilize sediment and limit shoreline erosion. The draining and damming of the wetlands that once surrounded Lake Mendota caused extensive losses of fish spawning areas, though about 34 fish species are still common in the lake, including the northern pike, white bass, walleye, largemouth bass, smallmouth bass, and musky. Starting in 2006, the University of Wisconsin-Madison Lakeshore Nature Preserve began to catalogue the bird species found in and around Lake Mendota, and,