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Ref. No. [UMCES] CBL 2016-015
ACT VS16-06
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qualitative estimate of biofouling during the field tests. In the final step before deployment,
instruments were placed in a well aerated fresh water bath, with a known temperature, for 45
minutes and allowed to record three data points as a baseline reference. Reference samples were
drawn at the corresponding sampling times and analyzed for dissolved oxygen using Winkler
titration method described below.
All instrument packages were deployed on a single box shaped rack that allowed all sensor
heads to be at the same depth, with instruments side by side and all sensor heads deployed at the
closest proximity feasible. The rack was deployed so that all sensor heads remained at a fixed
depth of 1 m below the water surface, except as noted above. A standard and calibrated CTD
package was deployed at each test site and programmed to provide an independent record of
conductivity and temperature at the sensor rack during each instrument sampling event. At least
four additional RBR temperature loggers were placed on the rack to capture any spatial variation in
the temperature across the rack.
A standard 4 L Van Dorn bottle was used at each test site to collect water samples for
Winkler titrations. The bottles were lowered into the center of the sensor rack, at the same depth
and as close as physically and safely possible to the sensor heads. The bottle was triggered to close
at the same time as the instruments were measuring to ensure that the same water mass was
compared for DO content. Three replicate 125 ml BOD bottles were filled from each reference
sample and immediately fixed in the field for subsequent Winkler titration analysis as described
below. The order of each sub-sample was recorded and tracked to examine any variation that arose
from sample handling. Approximately 10 - 12 independent sampling events were conducted each
week. At least once per week an intensive sampling event was conducted to capture the maximum
diurnal range of dissolved oxygen concentrations. Once per week field duplicates were collected
to examine fine-scale variability around the mooring site. Approximately 120 comparative
reference samples were collected over the 3 - 4 month-long deployments.
In conjunction with each water sample collection, each deployment site also recorded site-
specific conditions. The following information, logged on standardized datasheets were
transmitted electronically on a weekly basis to the ACT Chief Scientist, for data archiving and site
performance review:
•
Date, time (local) of water sample collection.
•
Barometric pressure from nearest weather station at time of water sample collection.
•
Weather conditions (e.g., haze, % cloud cover, rain, wind speed/direction) and air
temperature at time of water sample collection.
•
Recent large weather event or other potential natural or anthropogenic disturbances.
•
Tidal state and distance from bottom of sensor rack at time of water sample collection.
•
Any obvious problems or failures with instruments.
ACT was responsible for accurately characterizing temperature and salinity surrounding the
mooring with the goal of characterizing micro-stratification or heterogeneity surrounding the
mooring. Four RBR Solo temperature loggers and two SeaBird CTDs were deployed at each
mooring site. Sensors were mounted both at the instrument sampling depth and approximately 0.5
m above the sampling depth