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Ref. No. [UMCES] CBL 2016-011
ACT VS16-02
40
Moored Deployment off Coconut Island in Kaneohe Bay, Hawaii
An 18 week long moored field test was conducted in Kaneohe Bay from September 22,
2015 to January 20, 2016. The deployment site was located at 21.43° N x 157.79° W, on the
fringing reef flat surrounding Coconut Island (HIMB) in a depth of 3 meters (Photo 5). Kaneohe
Bay, located on the eastern side of Oahu, Hawaii, is a complex estuarine system with a large
barrier coral reef, numerous patch reefs, fringing reefs, and several riverine inputs. Tides in
Kaneohe Bay are semi-diurnal with mean tidal amplitude of approximately 68 cm day.
Photo 5.
Aerial view of HIMB deployment site (left) and instrument rack in-situ (right).
Time series results of ambient conditions for tidal height, temperature, and salinity are
given in figure 7. Temperature at the sensor level ranged from 23.1 to 29.1 °C and salinity from
27.3 to 34.7 over the duration of the field test. The bottom panel displays the maximum difference
recorded between all reference thermistors mounted at the same depth but located across the
mooring rack. The average temperature difference observed across the space of the mooring rack
was 0.15 ±0.17
o
C, with a maximum of 1.23
o
C. Differences between instrument and reference
readings resulting from this variability should be minimized as the sampling bottle integrates
across the mooring space.
The PME miniDOT reported data throughout the entire deployment and generated 16,957
observations based on its 10 minute sampling interval over the 17 week deployment. Only two
instrument value fell outside of an acceptable data ranged based on ± 2mg/L from any min-max
reference sample of other independent sonde data. The data completion result for the deployment
was essentially 100%. Time series results of the miniDOT and corresponding reference DO results
are given in figure 8. Ambient DO measured by the PME miniDOT ranged from 1.98 to 10.83
mg/L while the range captured by reference samples was 3.630 to 9.851 mg/L. The average and
standard deviation of the differences between instrument and reference readings (limited to ± 2.0
mg/L DO; n=128 of 129 potential observations) were 0.201 ± .426 mg/L, with a total range in the
differences of -1.7021 to 1.441 mg/L.
There was a small, but statistically significant, drift in
instrument offset (slope = 0.003 mg/L/d; r
2
= 0.05; p=0.009) throughout the deployment period.