BCO-DMO BlogInstrument: Submersible Autonomous Moored Instrument
The Submersible Autonomous Moored Instrument (SAMI) measures and logs levels of dissolved chemicals in sea and fresh water. It is a plastic cylinder about 6 inches wide and 2 feet long that is self-powered and capable of hourly measurements for up to one year. All data collected are logged to an internal memory chip to be downloaded later. SAMI sensors usually are placed a few feet underwater on permanent moorings, while others on floating drifters sample the water wherever the wind and currents carry them. The instruments have been used by researchers around the globe in a variety of studies since 1999. Dr. Mike DeGrandpre, University of Montana, developed the SAMI between 1990 and 1993 during his postdoctoral work at the Woods Hole Oceanographic Institution (Woods Hole, MA, USA). For additional information, see URL: http://www.sunburstsensors.com/ from the manufacturer, Sunburst Sensors, LLC, 1226 West Broadway, Missoula, MT 59802.
Sampling and Analytical Methodology:
Data were collected by SAMI-CO2 sensors equipped with Aanderaa model 4175 oxygen
optodes mounted at 5, 19, 34.5, 50, 75, 105 m depth. All sensors were calibrated
in the lab prior to deployment. Blank solutions, used to detect drift in the CO2
measurements, were run every 3.5 days. The SAMI-CO2 sensor has an accuracy 1 ±1 µatm,
the optodes have an accuracy of 5% (15 µmol kg-1 at an in situ O2 concentration of
300 µmol kg-1).
CO2 and O2 data were collected every half hour, and CO2 data were found to have good
agreement with shipboard data after a 4 µatm was applied, and O2 data agreed well with
discrete Winkler titrations (typically within 1 µmol kg-1). pH data was collected
every hour, and interpolated to half hour intervals. The SAMI-pH sensor has an accuracy
of 0.001 ± 0.0007 pH units.
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