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Ref. No. [UMCES] CBL 2016-010
ACT VS16-01
8
Lab-based Stability Test
A laboratory stability test was conducted to examine potential instrument drift in a non-biofouling
environment. These results are contrasted to the stability of measurement accuracy observed in the
long-term field mooring deployments. The test occurred over 56 days, with daily temperature
fluctuations of approximately 10
o
C, achieved by alternating the set point of the recirculation chiller.
Reference samples were collected at minimum and maximum temperatures at least 3 times per week.
The test was conducted in deionized water at saturated air conditions. Tanks were well circulated and
open to the atmosphere. Water in the test tank was exchanged as needed if there was any indication of
biological growth. Instruments stayed continuously submerged and were not exposed to air during any
water exchange. The goal of
comparisons of accuracy over time between the field and a sensor
deployed similarly in the laboratory is intended to provide insight into drift and reliability intrinsic to
the instrument relative to changes that may result from biofouling.
Moored Field Tests
Field Deployment Sites and Conditions
A four month moored deployment was conducted at Michigan Technological University’s
Great Lakes Research Center dock in Houghton, MI. Instruments were deployed in January and kept
under ice cover until April. Instruments were programmed to sample at a minimum frequency of once
per hour. ACT collected reference samples twice per day for 4 days per week during the entire
deployment. Instruments were moored at approximately 4m depth and surface access through the ice
was maintained by gentle circulation with a propeller to allow deployment of the Van Dorn sampling
bottle. The goal of this test application was to demonstrate instrument performance (reliability,
accuracy, and stability) in winter-time environmental conditions and to demonstrate the ability to
operate continuous observations under ice.
A three month moored deployment was conducted at the Chesapeake Biological Lab Pier,
Solomons, MD. Instruments were deployed between May and August during a period of warming
temperatures and high biological production. Instruments were moored at fixed depth of 1m on a
floating dock. Instruments were programmed to sample at a minimum frequency of once per hour.
ACT collected reference samples twice per day for 3 days per week and collected six samples on one
day per week during the entire deployment. The intensive sampling was spaced to capture the
maximum range of expected diurnal variation in dissolved oxygen concentrations. The goal of this test
application was to demonstrate instrument performance (reliability, accuracy, and stability) under high
biofouling conditions and over a range of salinity and temperature conditions in a coastal estuarine
environment.
A four month moored deployment was conducted in a shore patch reef at the Hawaii Institute
of Marine Biology (HIMB), Coconut Island, Kaneohe, HI. Instruments were deployed between
September and January. Instruments were moored at approximately 1m depth on a bottom mounted
PVC rack and were programmed to sample at a minimum frequency of once per hour. Some
manufacturers chose to sample more frequently to demonstrate that capability. ACT collected
reference samples twice per day for 3 days per week and collected six samples on one day per week
during the entire deployment. The intensive sampling was spaced to capture the maximum range of
expected diurnal variation in dissolved oxygen concentrations. The goal of this test application was to