This document summarizes a study assessing beneficial use impairments for benthos and plankton in Wisconsin's Lake Michigan areas of concern (AOCs). Samples of benthos and plankton were taken from 4 AOCs and 6 non-AOCs over 3 sampling periods in 2012. The study aims to determine current community states, compare communities between AOCs and non-AOCs, and identify appropriate metrics for determining impairment. Data analysis will include community analyses, comparisons between sites using metrics like IBI scores, and multivariate statistics to identify differences between AOC and non-AOC groups. The results may help determine if communities differ significantly between each AOC and non-AOCs.
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Assessment of Benthos and Plankton in Wisconsin's Lake Michigan AOCs
1. Assessment of Beneficial Use
Impairments for
Benthos and Plankton in
Wisconsin’s Lake Michigan AOCs
Amanda Bell
US Geological Survey, Middleton, WI
In cooperation with the
Wisconsin Department of Natural Resources
US Geological Survey Menomonee River 1
2. Background
• All of the AOCs along Wisconsin’s Lake
Michigan shoreline have degraded benthos and
three (not Menominee) have degraded plankton
• Consistent/comparable legacy community data for
these sites doesn’t exist
• Stage 2 RAPs were due and TACs needed to
identify projects that would address targets
• Wisconsin DNR and USGS designed a
comparative study to assess plankton and benthos
communities in AOCs and non-AOCS
US Geological Survey Fox River 2
3. Questions
• What is the current state of benthic invertebrate
and plankton communities in Wisconsin's Lake
Michigan AOCs?
• How do the benthos and plankton communities in
these AOCs differ from rivers that are not
considered AOCs?
• What community measures (i.e.
IBI, richness, abundance, diversity) can be used
as guides for determining benthos and plankton
impairment in the AOCs?
US Geological Survey Milwaukee Harbor 3
4. Sampling Design
• 10 Sites/3 times in 2012
– 4 Wisconsin Lake Michigan AOCs
• Menominee River
• Fox River/Green Bay (two river sites)
• Sheboygan River (Replicate)
• Milwaukee Estuary (two river sites, one harbor site)
– 6 Lake Michigan non-AOCs
• Escanaba River
• Oconto River
• Anapee River (Algoma)
• Kewaunee River
• Manitowoc River (Replicate)
• Root River (Racine)
US Geological Survey Sheboygan River 4
6. Sampling Scheme
• Plankton
– Water Depth Profile
– 63 µm Plankton Tow
• Benthos
– Hester-Dendy Sampler
– Ponar Dredge
US Geological Survey Oconto River 6
7. Water Depth Profile Sample
• Water sample (about 1 liter) from each meter
of water depth down to 5 meters
• 3 times during growing season
– June, July/August, September
• Identification/Enumeration at WSLH (soft
algae) and by Paul Garrison, WDNR (diatoms)
• Chlorophyll a and Biomass analyzed at WSHL
US Geological Survey Menominee River 7
8. Plankton Tow Samples
• Vertical tow with 63-µm plankton net
• 1-5 tows to obtain total of 5 meters of depth
• Identification/Enumeration by Paul
Garrison, WDNR
US Geological Survey Milwaukee River 8
9. Hester Dendy Samples
• 3 per sampling location (15 total)
• Deployed end of April
– Retrieved June, redeployed
– Retrieved July/August, redeployed
– Retrieved September
• Identification/Enumeration at UW Superior
US Geological Survey Menominee River
9
10. Ponar Dredge Samples
• 3-5 dredges composited per sampling location
(depending on substrate) near Hester Dendys
• 3 times during growing season
– June, July/August, September
• Identification/Enumeration at UW Superior
• Sediment size analysis at WSLH
• Volatile on Ignition analysis by USGS
US Geological Survey Kewaunee River 10
11. Data Analysis
• Once data come back from lab (fall/winter
2012)
– Macroinvertebrate Community assemblage
analysis
• IBI Scores
• Determine species composition differences between
sites
• Multivariate statistics
US Geological Survey Anapee River 11
12. Data Analysis
• Site to site comparison
– Benthos using WI Larger River IBI
– Plankton using Shannon Diversity Index
– For each season, if the AOC is less than 10% OR
one stand deviation (of all non-AOC sites) of
selected comparison sites, then the seasonal
sampled will be deemed degraded.
– If it is degraded two or more seasons, the benthos
or plankton for the site is deemed degraded.
US Geological Survey Milwaukee River 12
13. Data Analysis
• Overall comparison
– Multivariate analyses designed for multiple sites with
similar multiple samples (seasons)
• Tests if there is difference between groups (AOC vs. non-
AOC sites)
• Tests if there is difference between multiple groups (sites or
seasons)
– Determine what species/metrics differ between AOC
and non-AOC
– Deemed significantly different with a 90% confidence
cut-off (p-value <10%)
US Geological Survey Escanaba River 13
14. Future Questions
• Is there a significant difference in the plankton
(and benthos) communities between each AOC
and the non-AOCs?
• Which species, whether their present or
absent, are indicative of systems that are NOT
considered “degraded”?
US Geological Survey Kewaunee River 14