Latest

This data is provisional*
Middle Tampa Bay
2018-05-23 16:30:00 EST
CO2 500.90 ppm
pHT 7.8677  
Dissolved O2 6.62 mg/l
PAR 266.361 µM/m^2/sec
Pressure 2.582 dBar
Salinity 31.80 PSU
Temperature 26.56 °C
Click a value for 72 hour graph.

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* All data are preliminary or provisional and are subject to revision. The data have not received final approval by the USGS and are provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the data.

QA/QC

Calibration and Verification of the Instrumentation

All instruments are factory calibrated by the manufacturers every 12 months. In addition, instrument performance is verified by USGS scientists prior to field deployment through short-term deployment and testing in the USGS Carbon Laboratory test tank. Use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US government.

The Pro Oceanus CO2-Pro CV is tested by comparing CO2 measurements acquired from the instrument at approximately 15-minute time intervals with CO2 measurements calculated from discrete dissolved inorganic carbon (DIC) and pHT samples collected during the same time intervals. DIC and pH were measured and CO2 calculated using methods described in Yates et al. (2017). The instrument is verified when CO2 measurements from the instrument are within plus or minus 3% of the value calculated from discrete water samples.

The pH sensor of the Sea-Bird SeapHOx instrument is tested by comparing pHT measurements acquired from the SeapHOx at approximately 5 to 20-minute intervals with measurements of pHT from discrete water samples using spectrophotometric pHT analysis as described in Yates et al. (2017). The instrument is verified when pHT measurements from the instrument are within plus or minus 0.05 pH unit as determined by the manufacturer reported accuracy of the SeapHOx pH sensor.

The Sea-Bird SBE 37-SMP-ODO MicroCAT CTD and ECO-PAR sensors are tested by cross validation with concurrent measurements of salinity, temperature, dissolved oxygen and PAR collected using either a calibrated YSI Professional Plus multi-meter and/or a co-deployed Sea-Bird SBE 16plus SeaCAT CTD and second ECO-PAR sensor.

Validation

USGS scientists service the OCS system and perform discrete validation sampling every 2 to 3 weeks to evaluate sensor performance and document drift. During each service the OCS is cleaned to remove biofouling. Sensor performance is evaluated using internal controls (known voltage tolerances for drift and parameter cross-correlations). Duplicate or triplicate water samples are collected for total alkalinity, dissolved inorganic carbon and pHT analysis using water sampling tubes installed within 0.5 m of OCS sensors. Seawater is pressure filtered through a 0.45 micron cellulose nitrate filter in a filter housing mounted in line with a peristaltic pump to insure exclusion of particulates from samples. Samples for TA and DIC are collected in 300 mL borosilicate glass bottles, preserved by adding 100 µL saturated HgCl2 solution. Bottles are positive-pressure sealed with ground glass stoppers coated with Apiezon grease and transported to the USGS Carbon Analytical Laboratory for analysis (https://coastal.er.usgs.gov/carbonlab/). Seawater samples for pHT are collected from the same peristaltic pump, filtered into 30mL glass optical cells, and are analyzed within 1 hour of collection. Samples are analyzed for TA using spectrophotometric methods of Yao and Byrne (1998), for DIC using a UIC carbon coulometer model CM5014 and CM5130 acidification module and methods of Dickson et al. (2007), and for pHT (±0.005) via spectrophotometric methods of Zhang and Byrne (1996). CO2 is calculated from paired TA and pHT, TA and DIC, and/or DIC and pHT using the carbonate speciation program CO2sys (Pierrot et al., 2006). Approximately quarterly, QA/QCed and validated data are synthesized and published online as USGS Data Releases ( https://doi.org/10.5066/P9BAFC7L ).

Data Use

The data provided on this website are considered provisional. The data have not received final approval by the USGS and are provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the data. Real-time data may be changed after review for the following reasons:

  • In situ calibration of sensors
  • Fouling of sensors
  • Algal and aquatic growth on instrumentation
  • Malfunction of sensors Malfunction of recording equipment

Validated and QA/QCed OCS data are synthesized and published online as USGS Data Releases approximately quarterly (web link coming soon).

References

Dickson, A.G., Sabine, C.L., and Christian, J.R. (Eds.). 2007. Guide to best practices for ocean acidification CO2 measurements. PICES Special Publication 3, 191pp

Pierrot, D. E., Lewis, E., and Wallace, D. W. R.: Ms Excel program developed for CO2 system calculations, ORNL/CDIAC-105a, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, Tennessee, 2006.

Yao, W. and Byrne, R.H. 1998. Simplified seawater alkalinity analysis: use of linear array spectrometers. Deep-Sea Research Part 1 45:1383-1392.

Yates, K.K., Moyer, R.P., Tomasko, D., Smiley, N., Torres-Garcia, L., Powell, C.E., Chappel, A.R., and Bociu, I. 2017. Ocean acidification buffering effects of seagrass in Tampa Bay. In, Burke, M. (ed.), Proceedings: The Sixth Tampa Bay Area Scientific Information Symposium, BASIS 6, pp. 273-284. www.tbeptech.org/data/tbep-basis/213-6th-bay-area-scientific-information-symposium-proceedings.

Zhang, H. and Byrne, R.H. 1996. Spectrophotometric pH measurements of surface seawater at in-situ conditions: absorbance and protonation behavior of thymol blue. Marine Chemistry 52:17-25.