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Ref. No. [UMCES] CBL 2016-010
ACT VS16-01
4
For the lab-based functional response time assessment, the calculated τ
90
for the AroUSB was
11.8 s during high to low transitions and 7.1 s for low to high transitions covering a DO range of
approximately 8 mg/L at a constant 15
o
C. However, as noted in the report we incorrectly
programmed the sampling rate to 10 seconds which would have a direct impact on the calculated
response rate. For the AroW-USB the calculated τ
90
was 209 s during high to low transitions and 284 s
for low to high transitions for the same conditions.
At Houghton, MI the field test was conducted under the ice over 104 days with a mean
temperature and salinity of 0.7
o
C and 0.01. The measured DO range from our 118 discrete reference
samples was 10.25 – 14.01 mg/L compared to a range of 8.669 – 15.076 mg/L reported by the AroW-
USB over its 9859 observations conducted continuously at 15 minute intervals. The useable data
return for the deployment was 100%. The average and standard deviation of the measurement
difference between the AroW-USB and reference samples over the total deployment was 0.170 ±0.057
mg/L with a total range of 0.055 to 0.309 mg/L. A drift rate in instrument response, estimated by linear
regression (r
2
=0.325, p<0.001) of the difference across time, was -0.001 mg/L/d but directionally
getting closer to the Winkler reference values.
At the Chesapeake Biological Lab, the field test was conducted over 78 days with a mean
temperature and salinity of 25.6
o
C and 10.9. The measured DO range from our 142 discrete reference
samples was 4.370 – 10.858mg/L compared to a range of 2.610 – 14.510 mg/L reported by the AroW-
USB over its 7270 continuous observations conducted at 15 minute intervals. The data completion rate
for this deployment was 100%. The average and standard deviation of the measurement difference
between the AroW-USB and reference samples over the total deployment was -0.056 ±0.131 mg/L
with a total range of -0.375 to 0.392 mg/L. There was minor trend in response accuracy over the
deployment (slope = -0.002 mg/L/d; r
2
= 0.16) but with a low predictive fit.
At Kaneohe Bay, HI the field test was conducted over 121 days with a mean temperature and
salinity of 25.8 °C
and 33.4. The measured DO range from our 129 discrete reference samples was
3.63 – 9.85 mg/L compared to a range of 2.329 – 10.996 mg/L reported by the AroW-USB. Fourteen
percent (785 of 5653) of the continuous 30 minute observations fell more than 2 mg/L outside of a
natural ambient range as determined by the pattern of Winkler reference samples and were excluded
from statistical comparisons. For the accepted data (n=75 of a potential 129 comparisons), the average
and standard deviation of the measurement difference between the AroW-USB and reference samples
over the total deployment was 0.367 ±0.637 mg/L with a total range of -0.720 to 1.991 mg/L. The drift
rate in the instrument offset based on linear regression (r
2
= 0.74) was 0.165 mg/L/d throughout the
deployment period.
Overall, the response of the AroW-USB during field testing showed good linearity across all
three salinity ranges including freshwater, brackish water, and oceanic water. The accuracy of the
response curve was quite consistent across the concentration ranges observed within each test site and
relatively consistent over the wide range of DO conditions (4 - 14 mg/L) across sites.
The Aro-USB was evaluated in a profiling field test in the Great Lakes at two separate
locations in order to experience transitions from surface waters into both normoxic and hypoxic
hypolimnion. In Muskegon Lake, the temperature ranged from 21.0
o
C at the surface to 13.5
o
C in the
hypolimnion, with corresponding DO concentrations of 7.8 and 2.8 mg/L, respectively. In Lake
Michigan, the temperature ranged from 21.0
o
C at the surface to 4.1
o
C in the hypolimnion, with
corresponding DO concentrations of 8.6 and 12.6 mg/L, respectively. Two profiling trials were
conducted at each location. The first trial involved equilibrating test instruments at the surface (3m)
for ten minutes and then collecting three Niskin bottle samples at one minute intervals. Following the