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Ref. No. [UMCES] CBL 2015-010
ACT VS15-03
Great Lakes Field Test Site
A month-long moored field test was conducted in Lake Michigan from June 21 to July
19, 2014. The Great Lakes deployment site was located at 43.23°N, 86.34°W on a fixed pier at
the Lake Michigan Field Station of the NOAA Great Lakes Environmental Research Laboratory,
in Muskegon, Michigan. The site is located at the outfall of Lake Muskegon into Lake Michigan
with a depth of approximately 3 meters. The temperature range during deployment was 11.6°C
through 24.9°C and salinity averaged 0.031.
Photo 7.
Aerial view of Muskegon Lake (left) and rack deployment at GL Site
Time series results of ambient conditions for water depth, temperature, and salinity are
given in figure 15. Temperature ranged from 11.6 to 24.9 and salinity from 0.024 to .035 over
the duration of the field test. While there are no tidal cycles at this site there was significant
exchange between the open lake and the protected basin within the break wall as evidenced by
changes in salinity and water depth. The bottom panel displays the maximum difference recorded
between all reference thermistors mounted at the same depth across the mooring rack. The
average temperature difference observed across the space of the mooring rack was 0.08 ±0.18
o
C
with a maximum of 2.53
o
C. As noted above, it is not possible to quantify the exact difference
between the averaged reference temperature and that measured by the test instrument, but
differences resulting from this variation and variation in the chemistry of the water across will be
minimized because the sampling bottle integrates across the mooring space.
The Idronaut 305 Plus operated continuously over the 29 days of the deployment and
generated 2671 observations at 15 minute intervals. The range in ambient pH measured by the
305 Plus was 7.523 to 8.462 compared to 8.013 to 8.526 for the reference pH measurements
(Fig. 16). The bottom panel presents the time series of the difference between the instrument and
reference pH for each matched pair (n=98 observations). The average and standard deviation of
the difference for the entire deployment was -0.184 ± 0.081 with a total range of -0.465 to -
0.019.
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