Carbon Dioxide Buoy

Carbon Dioxide Buoy

Water Conditions




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Station Details

  • Station Description

    The Bay Ocean Buoy (BOB) is moored in the SF Estuary 300 feet North East of the Estuary & Ocean Science Center in Tiburon, CA. BOB is comprised of a MApCO2 system (designed by NOAA's Pacific Marine Environmental Lab using Battelle hardware) which collects CO2 data from surface seawater and estuarine boundary air every hour. Daily summary files of the measurements are transmitted back to PMEL and SF State’s servers where the data are examined and plots of the results are posted to the web in near-real time.

  • Location




  • Sensor Information

    The heart of the system is a LiCor LI-820 CO2 gas analyzer contained in the Electronics Assembly. The LI-820 measures CO2 concentration as a function of the absorption of infrared (IR) energy as it travels through the optical path. Concentration measurements are based on the difference ratio in the IR absorption between a reference and a sample signal. The instrument uses digital signal processing to determine the temperature and pressure corrected CO2 concentration using a ratio technique. The instrument is calibrated in-situ using a zero reference (ambient air that has passed through a soda lime canister to remove all CO2) and a span reference (stored air with a precisely known concentration of CO2, provided from a pressure cylinder). The sub-surface section of the buoy contains a Seabird 16+V2 sonde (that measures water temp, O2, chlorophyll, turbidity, and salinity) and a SeaFET (that measures pH).


  • Available Parameters


    Sensor Depth
    Distance the sensors are below the water's surface. The sensors are in a fixed position attached to a pier, so depth also measures tidal range. (units = meters or feet)
    Water Temperature
    Water temperature at sensor depth. (units = °C or °F)
    Salt content of the water at sensor depth. (units = Practical Salinity Scale 1978)
    Phytoplankton pigment concentration at sensor depth estimated from fluorescence measurements. (units = µg chlorophyll L-1)
    The clarity of the water at sensor depth. (units = nephelometric turbidity units, NTU)
    Dissolved O2
    The amount of oxygen dissolved in water. (units = mg L-1 or % of saturation)
    Acidity or alkalinity of the water at sensor depth. (units = -log[H+])

Data Access

Data is available through our ERDDAP data server in a variety of formats including .csv, .xls, .mat and more.

Available Parameters: Water CO2, Air CO2, salinity, water temperature, turbidity, chlorophyll, and pH data are available at a sampling frequency of 1-hour.

Dates Available: May 2018 to present

Access Links

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