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Ref. No. [UMCES] CBL 2016-011

ACT VS16-02


salts (Instant Ocean) to Type 1 deionized water. Salinity was verified at the beginning and end of

each test condition by analysis on a calibrated CTD


Dissolved oxygen concentrations were

controlled by use of compressed gases of known oxygen concentration sparging through diffusers

within the tank. Tanks were covered with a layer of floating closed-cell plastic insulation that

continuously sealed the water surface and to minimize atmospheric exchange. If required by the

manufacturer, instruments were only calibrated prior to the start of the first lab test, and then again

prior to the stability test which began one month later. The following series of tests were

conducted in the laboratory trials:

Accuracy at various T/S and DO conditions

A series of measurements were conducted under 36 discrete conditions to target 3

temperatures, 3 salinities, and at least 4 DO concentrations as follows:

Temperature Conditions: 5, 15, 30



3 Salinity Conditions: 0, 10, 34

Dissolved oxygen,(% air saturation): 0% (hypoxic), 20 – 30%, 100% and >120%, (levels were

achieved by mixing pure O


and N


sources with pure N


was used for the 0% O



Tests were run such that all 4-6 DO concentrations were tested for a fixed temperature and

salinity on the same day.

The tests began at ambient, near air saturation, conditions following

overnight equilibration of tank water to the test salinity and temperature. Subsequently DO were

dropped to near 0 mg/L and increased stepwise to the highest concentration

. Instruments were

allowed to equilibrate at the fixed temperature and salinity for 1 h before the start of that day’s

trial. Sparging with each DO gas concentration was conducted for a minimum of 60 minutes prior

to the start of data collection and reference sampling. For each test condition, the test instruments

were programmed to sample at no slower than 1 minute intervals and reference samples were

collected at 6 timepoints spaced 5 minutes apart for each of the fixed conditions. For three of the

timepoints duplicate samples were collected from two different sampling ports mounted at opposite

ends of the tank to access heterogeneity within the tank. Inlets of sampling ports were positioned

at the depth of the sensor heads (ca. -0.5m). All reference samples were collected while the gas

sparging was off and took approximately 1 minute to complete. Reference samples were processed

and analyzed as defined below.

The order of the test conditions were 15 then 5 then 30


C, going

from 0 then 10 then 34 salinity at each temperature.

Precision Test at various DO concentrations

Instrument precision was evaluated under stable conditions generally achieved at the start

of each trial’s day. Instruments were equilibrated to each test condition for a minimum of one hour

prior to testing. The sampling frequency for test instruments was 1 minute with reference samples

matching instrument sampling to monitor for drift in tank DO. At least 6 reference samples were

collected over a 30 minute instrument precision evaluation trial. Reference samples were processed

and analyzed as defined below.

Functional Response Time Test

A response time test was conducted by examining measurements during a rapid exchange

across a large gradient in dissolved oxygen for a fixed temperature (15


C) in deionized water,

following the approach described in Bittig et al. 2014. The reservoirs of the thermostat baths were