Time Series of Autonomous Carbonate System Parameter Measurements from Crocker Reef, Florida, USA

OCSv1 Description: The OCSv1 consists of 5 sensors, 1 pump, 1 submersible data logger, a submersible battery pack, and a seafloor mounting system. The equipment models are: Pro-Oceanus CO2-Pro for measurement of carbon dioxide concentration; Sea-Bird SeaFET sensor for measurement of pH on the total scale; Sea-Bird 16 Plus CTD Recorder for measurement of conductivity, salinity, temperature and depth; Sea-Bird/WET Labs ECO-PAR for measurement of photosynthetically active radiation (PAR); Aanderaa oxygen optode for measurement of dissolved oxygen; Sea-Bird STOR-X data logger; and a Sea-Bird SBE-5P submersible pump. Sensor resolution is as follows: Pro-Oceanus CO2-Pro 0.01 ppm; 1 mbar for PRESS(IRGA); SeaFET 0.004 pH; Sea-Bird 16 Plus Recorder 0.0001 °C for temperature; 0.00005 siemens for conductivity (used by the instrument to calculate salinity) and 0.002% of full scale range for pressure; Aanderra optode 0.003 mg/L for dissolved oxygen (based on resolution of 0.1 micromoles per liter); and ECO-PAR 14-bit digital output resolution.
The sensors were packaged as a single unit in a custom-designed platform that was mounted on the seafloor. The Sea-Bird SBE-5P submersible pump pulled water through a stainless or copper mesh strainer and pumped the water to the CO2-Pro CV for pCO2 measurement. Water flow from the CO2-Pro was then pumped through the flow through cap of the SeaFET. The sensors not requiring flow were located in close proximity to the pump intake and measured ambient water. The STOR-X and sensors were powered by a 240 amp-hour submersible battery system.
The STOR-X distributed power to the attached sensors according to a custom schedule. The OCSv1 operated 24 hours per day, with a sampling acquisition period once every hour at the half-hour mark prefaced by a 20-minute warm up period for the CO2-Pro CV. The sampling acquisition period ran for approximately 00:01:10. The CO2 sensor re-zeroed every 8 hours and collected approximately 22 CO2 and PRESS(IRGA) measurements during each sampling period. The ECO-PAR sensor collected approximately 7 PAR measurements per sample period. The SeaFET collected approximately 10 pH measurements per sample period. The 16 Plus CTD collected 1 conductivity, temperature, and pressure measurement per sampling period. The Aanderaa optode collected approximately 7 oxygen measurements per sample period.
Data Storage and Preprocessing: Data were managed and stored by the STOR-X data logger. Acquired data were saved into sensor-specific .raw files that contained the information for each Julian day. Downloading this data from the site occurred at regular intervals to ensure the sensor's operational status. Downloading these .raw files from the STOR-X required the use of STORXCom software to communicate between the STOR-X and a computer. Once the data were downloaded, SatCon version 1.5 data conversion program converted the .raw files into .dat files and applied any processing required. Individual sensor Julian day .dat files were then combined into one large multi-day dataset per sensor. These files were opened in Microsoft (MS) Excel and saved in .xlsx format. The combined multi-day files contained headers for each individual day file that were strung together; these headers were manually removed in MS Excel leaving only the top header line. Multi-day files were then processed through a custom averaging code written in Pearl, designed by David Zawada (USGS). This code averaged the multiple measurements from each sensor per sampling period to generate a single averaged value for each sensor per sampling period, reported at the start time of the sampling period and day. In addition to averaging parameter values, the code also provided the mean, standard deviation, minimum and maximum for each sampling period. Averaged data for each sensor parameter were then manually merged into a single .xlsx file for further processing. Data files were deleted from the STOR-X after confirmation of successful download and storage of parameter data.
Advanced Data Processing: Preliminary QA/QC of sensor data was performed after averaged data were compiled into .xlsx files and after advanced data processing was performed. The SeaFET pH data were corrected for salinity and temperature, using Sea-Bird 16 Plus CTD recorder data through a MS Excel macro provided by Satlantic. The Satlantic macro was also used to perform a single point calibration of the SeaFET pH data using discrete pH measurements determined in-situ and concurrently with OCS sample acquisition. Discrete pH measurements were performed using spectrophotometric pH methods. Once corrections were completed, parameter data were plotted to examine sensor performance and identify non-trending outliers. Cross validation of sensor parameters was performed to further analyze outliers and identify questionable or bad data points. Further validation of pH and CO2 sensor data was performed by comparing sensor values to values measured in discrete water samples. CO2 was calculated from discrete measurements of pH and dissolved inorganic carbon (performed using carbon coulometry methods). Measurement of sensor data was periodically validated with discrete data.

Added keywords section with USGS persistent identifier as theme keyword.