FAU Harbor Branch's LOBO Network

Quality Assurance/Quality Control (QA/QC) refers to: the process or set of processes used to measure and assure the quality of a product (QA) and the process of meeting products and services to consumer expectations (QC). This is an overview of the QA/QC actively used for FAU Harbor Branch's Land/Ocean Biogeochemical Observatory (LOBO) units.

Calibration and Verification of the Instrumentation

All instruments are factory calibrated by the manufacturers every 12 months. In addition, the instruments are retrieved by FAU Harbor Branch scientists for verification of sensor performance every six months. The purpose of the verification is to confirm that the individual sensors in the LOBO unit are performing within factory specifications. Corrective actions are taken whenever needed.

The water quality monitor (WQMX) integrates conductivity, temperature, depth (pressure) and dissolved oxygen sensors (CTD-DO) from Sea-Bird Electronics with a chlorophyll fluorescence, CDOM, and turbidity sensor (ECO-BBFL2) from WET Labs, Inc. to make highly accurate measurements in estuarine applications. The WQMX is factory calibrated after every twelve months of in-water use. In addition, further characterization is performed by FAU Harbor Branch scientists on a semi-annual basis to ensure sensors are performing within specifications.

• Verification for the CTD-DO sensors includes taking measurements in air to ensure values are within expected ranges as well as comparison to factory calibration values.
• Performance for the ECO-BBFL2 sensor is verified by measuring and updating offsets as necessary and confirming sensor saturation for each parameter. Further, turbidity standards including an ultrapure water blank, 2.5, 5.0, 10.0 and 20.0 NTU are evaluated (three runs) to determine calibration and evaluation of the sensor over a range of values common in the Indian River Lagoon (IRL).
• Characterization of the chlorophyll sensor includes comparison of the measured value of an IRL grab sample to the extracted value from standard spectrophotometric analysis (Method #10200H, APHA, Standard Methods for the Examination of Water and Wastewater, 19th edition).

The Cycle-PO₄ (WETLabs, Inc.) is an in situ instrument that uses wet chemistry to measure phosphate (PO₄) colorimetrically with methods modified from Murphy and Riley (1962) and EPA method 365.5 (1997). The Cycle-PO₄ is fully calibrated at WETLabs on an annual basis with documentation of optical, electronic and fluidic parameter values. Further, the Cycle-PO₄ is then subjected to environmental stress and leak tests. On a semi-annual basis, FAU Harbor Branch runs a standard curve to determine calibration and verify the instrument is operating within specifications. Standards include ultrapure DI water blank, 0.5, 2.6 and 5.3 µM (three runs).

The submersible ultraviolet nitrate analyzer (SUNA; Satlantic, Inc.) is an optical sensor for high resolution ultraviolet spectrophotometry of nitrate in coastal waters. The SUNA is fully characterized at Satlantic on an annual basis. In addition, instrument performance is checked semi-annually by FAU Harbor Branch to ensure optimized accuracy of data. The concentration of nitrate in ultrapure DI water is measured before and after cleaning the optical window. If the nitrate concentration does not read 0.00 ± 2 µM instrument's calibration will be updated following protocols established by Satlantic. Next, nitrate standards, including an ultrapure water blank, 0.71, 1.71, 3.57, 7.14 and 14.28 µMare evaluated (three runs) to determine calibration and evaluation of the sensor over a range of values common in the IRL.

Validation

FAU Harbor Branch researchers visit the LOBOs every four to six weeks (depending on season/biofouling) to collect discrete samples to be used to QA/QC sensor data and document drift. Discrete samples are collected with a five-liter Niskin bottle lowered separately and concurrently with a Seabird CTD to the depth of the LOBO. Once the CTD and Niskin bottle are at the same depth, the CTD is run for 60 seconds to equilibrate the sensors. The messenger on the Niskin line is released at 90 seconds and CTD sampling continues through 120 seconds. The Niskin is brought on board the vessel and samples for dissolved oxygen are taken, followed by samples collected for analysis of nutrients, turbidity, and chlorophyll concentrations. The CTD data are downloaded in the laboratory upon return and used to QA/QC the real-time sensor readings.

Water samples for oxygen will be collected directly in pre-cleaned containers and fixed according to Labasque et al. (2004). Oxygen samples are shaken twice with an intermediate settling, and then maintained in the dark with deionized water filling the bottle top. Pre-cleaned syringes used for sample collection will be rinsed with ambient water three times before filtering and repeated for each LOBO. Nutrient samples will be collected in 500-mL pre-cleaned high-density polyethylene (HDPE) bottles, filtered (25 mm Whatman GF/F filters) into pre-cleaned 125-mL HDPE bottles, and frozen until analyzed. Water samples for chlorophyll and turbidity will be collected into two pre-cleaned HDPE 1-L bottles. Chlorophyll, turbidity, and nutrient samples are immediately placed on ice and kept in the dark. Samples are stored according to established protocols (see Table 1). All samples are transported back to FAU Harbor Branch the same day as collection for analysis.

Table 1. FAU Harbor Branch laboratory measurement procedures

Data Use and Metadata

The data made available on this website should be considered provisional for any use. Each year metadata files will be made available to all interested parties. The term metadata refers to "data about data". Metadata are helpful to interpret ecological and environmental data. Annual metadata reports will be drafted at the end of each calendar year to document research objectives and methods, site location information, the data collection period, the QA/QC process, sensor resolution and accuracy, and anomalous data. To receive metadata reports or request any other information, please contact FAU Harbor at: HBOI_IRLO@fau.edu.

References

APHA. 1995. Standard Methods for the Examination of Water and Wastewater. 19^th ed. Washington, DC: American Public Health Association.

EPA. 1997. Method 365.5 determination of orthophosphate in estuarine and coastal waters by automated colorimetric analysis. Cincinnati: National Exposure Research Laboratory Office of Research and Development U.S. Environmental Protection Agency.

Labasque, T., C. Chaumery, A. Aminot, and G. Keroat. 2004. Spectrophotometric Winkler determination of dissolved oxygen: re-examination of critical factors and reliability. Mar. Chem. 88:53-60.

Murphy, J. and J.R. Riley. 1962. A modified single solution method for the determination of phosphate in natural waters. Anal. Chem. 27:31-36.