Using mesocosms and long-term data to explore the impacts of zebra mussels on the microbial food web of a eutrophic lake

Invasive species pose a global challenge for aquatic ecosystem function and resilience. Understanding how they alter long-term food web structure and ecosystem function is crucial for effectively managing aquatic ecosystems in our current era of global change. Forecasting the impacts of invasive species is notoriously difficult, especially at lower trophic levels where impacts can cascade up and down trophic levels. Lake Mendota, WI experienced two successive invasions over the past 25 years: spiny water flea (2009; Bythotrephes longimanus) and zebra mussels (2015; Dreissena polymorpha). Despite the well-known impacts of zebra mussels on aquatic ecosystems, their impacts on the entire lower food web—zooplankton, phytoplankton, protists, and microbes—are less understood, particularly within cyanobacteria-dominated eutrophic lakes. We designed a mesocosm experiment to quantify zebra mussel impacts on phytoplankton, protists, and microbes in Lake Mendota and compared our results to a 20-year record of zooplankton, phytoplankton, protist and microbial dynamics. We show how zebra mussels have lower ecological impact under cyanobacteria-dominant conditions and compare the effects within zooplankton-dominated and protist-dominated mesocosms. We then place our mesocosm findings within the context of long-term trends and successive species invasions within the lower food web of Lake Mendota. Understanding these complex interactions is crucial for taking the pulse of our aquatic ecosystems and developing effective management paradigms for the future.

Presentation Preference: Oral

Primary Presenter: Tyler Butts, University of Wisconsin-Madison (tyler.james.butts@gmail.com)

Authors:

Tyler Butts, University of Wisconsin-Madison  (tyler.james.butts@gmail.com)

Jackie Lemaire, University of Wisconsin-Madison  (jlemaire@wisc.edu)

Katherine McMahon, University of Wisconsin-Madison  (trina.mcmahon@wisc.edu)

M. Jake Vander Zanden, University of Wisconsin-Madison  (mjvanderzand@wisc.edu)