26 / 58
Ref. No. [UMCES] CBL 2015-011
ACT VS15-04
26
Moss Landing Marine Laboratories Field Deployment Site
A month-long moored field test was conducted at the Moss Landing Marine Laboratories
from August 26 to September 22, 2013. The deployment site was located at 36.80°N, 121.79°W,
in the Small Boat Facilities area of Moss Landing Harbor (Photo 2). This secure deployment site
was located in the Harbor on the junction of the northern tributary of the Salinas River and
Elkhorn Slough National Estuarine Reserve on the central coast of California. Instrumentation
was deployed off a floating dock in waters with a tidal range of 2 meters and a maximum depth
below the dock of 4 meters.
Photograph 2.
Aerial view of MLML Harbor (left) and dockside mooring deployment (right).
Time series results of ambient conditions for tidal height, temperature, and salinity are
given in figure 8. Temperature ranged from 14.9 to 18.6 and salinity from 30.7 to 33.7 over the
duration of the field test. The bottom panel displays the maximum difference recorded between
all reference thermistors (RBR Solo and SBE26) mounted at the same depth and different
locations across the mooring rack. The average temperature difference observed was 0.11
o
C
with a maximum of 0.8
o
C. The difference between the test instruments instantaneous
temperature reading and the final reference temperature will contribute to the variability and
offset to the calculated ambient reference pH. It is not possible to quantify the exact difference
between the averaged reference temperature and that measured by the test instrument, but a
difference of 1
o
C would amount to an approximate offset of 0.015 pH units at ambient
conditions. Additional differences resulting from variation in the actual chemistry of the water
across this space may exist but will be minimized because the sampling bottle integrates across
the mooring space.
The Troll 9500 operated over the entire deployment period however an internal
malfunction occurred approximately three hours after logging initiated on August 26
th
at 18:00
hours. No useable data was produced to compare to the reference dye results. Ambient pH as
measured from the dye reference samples ranged from 7.933 to 8.077 over the 28 day test period.
The Troll 9500 measured pH from 7.94 to 7.98 during the first three hours, but then showed an
abrupt increase to nearly 14, indicating some internal malfunction. Complete time series results
are presented just to explain the retrieved data but no comparative statistics are generated for this
deployment test (Figs. 9 and 10).