Consultant's Report - Minnesota State Legislature

Aquatic invertebrates in upper Pelican Brook - Impacts from copper
sulfate treatment of Muslde Bay, Lake Ossawinnamakee
Gmy Montz, Jodene Hirsch and Richard Rezanka
Division ofEcological Services, Milmesota DNR
November 2004
Introduction
Pelican Brook is a small stream that begins as an outlet from Muskie Bay in Lake
Ossawinnamakee (Crow Wing County), and flows approximately 5.5 miles until it is
tributary to the Pine River. In fall 2003, zebra mussels were confirmed in Lake
Ossawinnamakee in a variety ofsites, attached to docks, vegetation, rocks and wood.
Additional sampling in Pelican Brook itmnediately below the lake outfall discovered
scattered single zebra mussels attached to natural substrate in the stream. The discovery
ofzebra mussels in both the lake and the immediate vicinity ofthe brook raised alarm
that the veliger (larval) stage ofthis exotic could be transported in water ofthe brook to
the Pine River. This could create a reproducing population that could move veligers
downstream in the Pine River, which is tributary to the Mississippi River.
To address the threat ofveliger downstream transport, the Minnesota DNR
contracted with a private aquatic pesticide applicator to apply copper sulfate to
approximately 26 acres ofMuskie Bay weekly from mid-June through September, 2004.
Application dose rates. were 0.6ppm ofCutrine Ultra, with 400 gallons applied per
treatment via subsurface injection.
Methods
Monitoring ofcopper levels was conducted immediately at the outflow location
(Highway 39) in the brook and approximately 2.5 miles downstream (Highway 3) at the
next road crossing. Water samples were collected and monitored at the sites using a
Hach pocket colorimeter II test kit for copper. Monitoring began prior to the start ofthe
first treatment (to establish a baseline) and continued nearly daily through October.
Sampling for zebra mussel veligers was conducted during the summer by vertical
tows with a Wisconsin plankton net at a site in the main lake basin and the treatment area
(Muskie Bay) to determine efficacy and relative veliger densities. Samples were
analyzed by examining collected material with cross-polarized light to separate veligers
from other microinvertebrate fauna.
Samples ofaquatic macroinvertebrates were collected in 2004 from three sites in
Pelican Brook using D-frame kicknets. Sites sampled were at the highway 39 bridge
crossing, the Highway 3 bridge crossing, and approximately 0.5 miles downstream ofthe
highway 3 bridge. At the first two sites (highways 39 and 3), two kicknet samples were
taken in rock/cobble substrate, and one qualitative composite was colleted from woody
debris at each site. At the site downstream ofHwy 3 only a single sample was collected
from roc1dcobble substrate. Samples were collected in spring prior to any treatments (17
May) and in fall after treatments (9 September). Samples were preserved in the field,
transported back to the office, and sorted and identified under a dissecting microscope.
Aquatic insects were identified generally to genus ifpossible, with the exception ofthe
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