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Ref. No. [UMCES] CBL 2016-010
ACT VS16-01
10
•
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 both water baths was monitored continuously and maintained at a constant condition
within 0.5
o
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
equilibrating test instruments at the surface (3m) for ten minutes and then collecting three Niskin bottle
samples at one minute intervals. Following the third sample, the rosette was quickly profiled into the
hypolimnion where samples were collected immediately upon arrival and then each minute for the next
6 minutes. The second trial was performed in the reverse direction where instruments were
equilibrated for 10 minutes within the hypolimnion, three samples collected, and then profiled into the
surface and sampled at one minute intervals over the next 7 minutes
.
The CTD was then immediately
returned to the ship for sample processing. Triplicate BOD bottles were filled from each Niskin and
immediately fixed for Winkler titrations.
Reference Sample Analysis
The Winkler titration for quantifying dissolved oxygen was used as the standard for comparison.
The specific method is described in detail below and is based on the procedures described in,
Measurement of primary production and community respiration in oligotrophic lakes using the