Performance Demonstration Statement Sunburst Sensors SAMI-CO2.

• Main Authors: Schar, D., Atkinson, M., Johengen, T., Pinchuk, A., Purcell, H., Robertson, C., Smith, G.J., Tamburri, M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Alliance for Coastal Technologies (ACT) 2009
• Subjects: Biogeochemistry; sami
• Online Access: https://dx.doi.org/10.25607/obp-344; https://www.oceanbestpractices.net/handle/11329/787

Alliance for Coastal Technology (ACT) demonstration projects are designed to characterize performance of relatively new and promising instruments for applications in coastal science, coastal resource management and ocean observing. ACT has evaluated four commercial pCO2 instruments that are capable of being moored for weeks to months. This document is termed a “Demonstration Statement” and provides a summary of the results for the Sunburst SAMI-CO2. Briefly, test instruments were mounted on surface moorings in a temperate stratified estuary (Twanoh Buoy, Hood Canal Washington; August-September 2009; http://orca.ocean.washington.edu/mooringDesign.html;) and a coral reef (Kaneohe Bay Hawaii; October-November 2009; http://www.pmel.noaa.gov/co2/coastal/HI/). The sites were chosen based on existing moorings and the expected rapid changes in seawater temperature and pCO2. Water samples were collected to determine pH and Total Alkalinity (TA) for calculation of pCO2 (CO2Sys; Pierrot et.al. 2006) and direct measurements of pCO2 using a flow-through pCO2 analyzer (Oregon State University; gas equilibration and infrared gas detection). In situ pCO2 measurements are compared to both of these references and estimates of analytical and environmental variability are reported. Quality Assurance (QA) and oversight of the demonstration process was accomplished by the ACT QA specialists, who conducted technical, protocol and data quality audits. At Twanoh buoy, Hood Canal, temperature varied from 11.09 to 19.62 oC and salinity varied from 24.3 to 29.1. Measured pCO2 values of reference samples varied from 334 to 488 µatm, while the 30 minute measurements by the SAMI-CO2 varied from about 340 to 900 µatm, demonstrating a more complete assessment of the variability in the ecosystem. The mean and standard deviation of the difference for individual SAMI-CO2 determinations and the Flow Analyzer reference measurements were +23 ± 13 µatm (n=31; SAMI-CO2 - Flow Analyzer). The mean and standard deviation of the difference for individual SAMI-CO2 determinations and the pCO2Sys reference measurements were +18 ± 40 µatm (n=42; SAMI-CO2 - pCO2Sys). At NOAA Crimp 2 buoy, Kaneohe Bay, temperature varied from 23.24 to 28.27 oC and salinity varied from 34.1 – 35.2 over the deployment. Measured pCO2 values of reference samples varied from 314 to 608 µatm, while the 30 minute measurements by the SAMI-CO2 varied from about 320 to 900 µatm, again capturing more of the full variability in the ecosystem. The mean and standard deviation of the difference for individual SAMI-CO2 determinations and the Flow Analyzer measurements were +28 ± 9 µatm (n=13; SAMI-CO2 - Flow Analyzer). The mean and standard deviation of the difference for individual SAMI-CO2 determinations and the pCO2Sys reference measurements were +40 ± 13 µatm (n=45; SAMI-CO2 - pCO2Sys). The instrument on both test moorings functioned throughout the month-long deployment, and 100 percent of expected data were retrieved. The continuous, 30 minute time-series data (plotted hourly; n=535 and n=618 for WA and HI, respectively) provided by the instruments revealed diel patterns in pCO2 and captured a significantly greater dynamic range and temporal resolution than could be obtained from discrete reference samples. There were no changes in the differences between instrument and reference measurements during either test, indicating that biofouling and instrument drift did not affect measurement performance over the duration of the test.