Due to high insularity and a high rate of endemism, freshwater ecosystems are particularly vulnerable to the impacts of non-native species colonization. Lake Mendota has experienced invasions of Dreissena polymorpha (zebra mussel) and Bythotrephes longimanus (spiny water flea). Lake Mendota had been predicted as a prime candidate for the invasion of Dreissena polymorpha, yet Lake Mendota remained uncolonized by Dreissena polymorpha until their discovery in 2015. In 2009, Bythotrephes longimanus invaded Lake Mendota and fed on native zooplankton, including Daphnia pulicaria. With the predation of Daphnia pulicaria by Bythotrephes longimanus, the biomass of Daphnia pulicaria decreased by an order of magnitude while the population of Dreissena polymorpha exploded in 2016. This suggests that the population of Dreissena polymorpha was controlled by top down predation by Daphnia pulicaria prior to the 2016 outbreak. In this study, the hypothesis of veliger predation by Daphnia pulicaria was tested in a sequence of two similarly controlled laboratory experiments, which involved two species; Daphnia pulicaria and Dreissena polymorpha veligers. Daphnia pulicaria in both feeding experiments exhibited predation on 7-day old Dreissena polymorpha veligers. Results showed significant differences in reduction of the mean veliger counts among treatments. This study showed that Daphnia pulicaria have the ability to prey on the invasive Dreissena polymorpha veligers. This lends support to the hypothesis that Daphnia pulicaria contributed to the delayed invasion of Dreissena polymorpha in Lake Mendota in 1989 to 2009, prior to the invasion of Bythotrephes longimanus. As Daphnia pulicaria are native to many north temperate lakes, further modelling of their feeding will aid in determining the vulnerability of these lakes to the invasion of Dreissena polymorpha.
Hayranto, Daniel, "Changes in the Lake Mendota food web composition: Predation of invasive zebra mussel (Dreissena polymorpha) veligers by native water fleas (Daphnia pulicaria)" (2018). Internship Reports (Restricted). 326.
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