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Ref. No. [UMCES] CBL 2016-011

ACT VS16-02


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

At the end of each mooring deployment a pre- and post-cleaned comparison of sensor response

to a 100 % saturated water bath was conducted. Upon retrieval the sensor was wrapped in a damp

towel and returned to the lab as quickly as possible. Prior to any cleaning, the sensor was

submerged in a 100 % DO water bath (via bubbling with air) and DO recorded for a minimum of

three readings after an initial 30 minute equilibration period. Then the sensor was removed from

the bath and cleaned of any visible biofouling according to recommended manufacturer

procedures. Following cleaning the sensor was submerged in a second 100% DO water bath to

avoid any biofouling debris carryover and DO recorded for a minimum of three readings after an

initial 30 minute equilibration period. Temperature of the both water baths was monitored

continuously and maintained at a constant condition within 0.5


C. DO concentration was

maintained at a constant saturated level with bubbling and confirmed by Winkler titration at the

beginning and final instrument reading timepoints.

Water-Column Profiling Test Procedures

Instruments were tested in a profiling application on a CTD rosette aboard the R/V Laurentian

in the Great Lakes. Profiling tests were conducted during strong thermal stratification (late

August, thermal gradient of >15 °C) and in two different regions including a normoxic and

hypoxic hypolimnion. The normoxic hypolimnion site was in Lake Michigan within a 100m deep

water column approximately 15 km offshore of Muskegon, MI. The hypoxic site profiling was

conducted in Muskegon Lake, a drowned river mouth lake adjacent to Lake Michigan.

Two full water-column CTD casts were conducted at each test site. The first trial involved