The spiny water flea (Bythotrephes longimanus) is an invertebrate aquatic invasive species (AIS) in the Great Lakes that competes with native fish species for zooplankton, perhaps contributing to a decline of fish populations or changes in zooplankton communities in Lake Michigan. Bythotrephes produce two types of eggs, immediately hatching versus resting eggs which are tolerant to harsh conditions and allow for rapid dispersal. We determined Bythotrephes population density and population dynamics in Green Bay during the summer months of 2015 and 2016. Population dynamics were similar at both sites in Green Bay in each year, with peak population abundances in September of 2015 and late July in 2016. Resting eggs were produced by July 8 in 2015, and by June 17 in 2016; production continued into at least early October in both years, after which sampling ceased. Production rates for zooplankton and consumption rates for Bythotrephes were estimated in Green Bay and showed that consumption exceeded production at times. Zooplankton composition changed and abundance generally declined with an increase in Bythotrephes abundance. Sampling conducted by the Fox River Navigational System Authority did not observe Bythotrephes in 2015 and only on a single date at one site in 2016 in the Lower Fox River. Due to the negative effects Bythotrephes cause on zooplankton communities in Green Bay, population dynamics in Green Bay should be considered when managing the lock system along the Fox River to prevent further invasion upstream of the Lower Fox River and into Lake Winnebago.
Level of Honors
magna cum laude
Bart De Stasio
Merkle, Casey Ann, "A Spiny Water Flea Invasion and Effects on the Zooplankton Community in Southern Green Bay, Lake Michigan" (2017). Lawrence University Honors Projects. 102.