BIODIVERSITY OF CRUSTACEAN ZOOPLANKTON IN THE ST. LOUIS RIVER ESTUARY OF WESTERN LAKE SUPERIOR

Zooplankton communities are indicators of environmental stressors such as climate, invasive species introduction, and other anthropogenic influences on water quality. The St. Louis River estuary on the Western tip of Lake Superior is important ecologically as the largest US tributary into Lake Superior. Industrially, it is also the location of the most active Great Lakes cargo shipping port and is the largest receiver of inter-lake ballast water, the vector by which numerous aquatic invasive species (AIS) have become established in the region. In 2008, ballast water exchange was fully implemented for vessels travelling internationally into the Great Lakes as a means of reducing movement of AIS from other locations. We sampled in 2007/2008 to establish a baseline of zooplankton biodiversity in the estuary and resampled the same locations in 2024/2025 to assess differences before and after ballast water policy changes. In both pairs of years, we conducted semi-weekly sampling comprising vertical zooplankton net tows (100-µm mesh) and a suite of water quality parameters from roughly April to September. We visited nine locations through varying habitats and levels of industrialization and shipping activity. Spatial and temporal variability in zooplankton communities will be assessed as a function of habitat development with a focus on biodiversity and abundance.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Michael Nagel, University of Minnesota Duluth (nage0138@d.umn.edu)

Authors:

Michael Nagel, University of Minnesota Duluth  (nage0138@d.umn.edu)

Donn Branstrator, University of Minnesota Duluth  (dbranstr@d.umn.edu)

Matthew TenEyck, University of Wisconsin Superior  (MTenEyck@uwsuper.edu)