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Tuesday, January 30 • 2:00pm - 2:20pm
ASIAN CARP & OTHER AQUATIC INVASIVES: From Water Chemistry to Fish: The Impacts of Zebra Mussels Across Multiple Trophic Levels

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AUTHORS. Casey W. Schoenebeck, Minnesota Department of Natural Resources; Lee Engel, Minnesota Pollution Control Agency; Heidi Rantala, Minnesota Department of Natural Resources; Jodie Hirsch, Minnesota Department of Natural Resources; Gary Montz, Minnesota Department of Natural Resources; Gretchen Hansen, Minnesota Department of Natural Resources; Brian R. Herwig, Minnesota Department of Natural Resources

ABSTRACT. Zebra mussels Dreissena polymorpha are known to disrupt trophic dynamics but long-term monitoring data rarely exist to evaluate changes through multiple trophic levels. We documented changes in water chemistry, phytoplankton and lake productivity, aquatic macrophytes, zooplankton, macroinvertebrates and fish in one of Minnesota’s long-term monitoring lakes, Lake Carlos, where zebra mussels (ZM) were discovered in 2009. Site-specific ZM density ranged from 43/m2 to 33,843/m2 during 2015 with densities less than 10,000/m2 for most of the 117 sites sampled. Additional changes in the benthos included a decline in native fingernail clams. Chlorophyll-a decreased post ZM establishment and total phosphorus also declined. Water transparency doubled resulting in an increased maximum Secchi transparency depth and percent of sites with aquatic macrophytes. Total zooplankton density and biomass decreased post ZM establishment with mean biomass consistently less than 100 ug/L and mean total density less than 20/L. Thus far, few changes have been observed in the littoral or pelagic fish communities with an increased relative abundance of Smallmouth Bass Micropterus dolomieu as the exception. This presentation describes these trophic changes relative to a control lake.

Tuesday January 30, 2018 2:00pm - 2:20pm CST
102D&E