title: Review of fluorescent standards for calibration of in situ fluorometers: recommendations applied in coastal and ocean observing programs.
abstract: Fluorometers are widely used in ecosystem observing to monitor fluorescence signals from organic compounds, as well as to infer geophysical parameters such as chlorophyll or CDOM concentration, but measurements are susceptible to variation caused by biofouling, instrument design, sensor drift, operating environment, and calibration rigor. To collect high quality data, such sensors need frequent checking and regular calibration. In this study, a wide variety of both liquid and solid fluorescent materials were trialed to assess their suitability as reference standards for performance assessment of in situ fluorometers. Criteria used to evaluate the standards included the spectral excitation/emission responses of the materials relative to fluorescence sensors and to targeted ocean properties, the linearity of the fluorometer's optical response with increasing concentration, stability and consistency, availability and ease of use, as well as cost. Findings are summarized as a series of recommended reference standards for sensors deployed on stationary and mobile platforms, to suit a variety of in situ coastal to ocean sensor configurations. Repeated determinations of chlorophyll scale factor using the recommended liquid standard, Fluorescein, achieved an accuracy of 2.5%. Repeated measurements with the recommended solid standard, Plexiglas Satinice® plum 4H01 DC (polymethylmethacrylate), over an 18 day period varied from the mean value by 1.0% for chlorophyll sensors and 3.3% for CDOM sensors.
authors.affiliation: Plant Functional Biology and Climate Change Cluster, University of Technology, Sydney, NSW, Australia.
authors.forename: Alan
authors.initials: A
authors.lastname: Earp
authors.forename: Christine E
authors.initials: CE
authors.lastname: Hanson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Ralph
authors.forename: Vittorio E
authors.initials: VE
authors.lastname: Brando
authors.forename: Simon
authors.initials: S
authors.lastname: Allen
authors.forename: Mark
authors.initials: M
authors.lastname: Baird
authors.forename: Lesley
authors.initials: L
authors.lastname: Clementson
authors.forename: Paul
authors.initials: P
authors.lastname: Daniel
authors.forename: Arnold G
authors.initials: AG
authors.lastname: Dekker
authors.forename: Peter R C S
authors.initials: PR
authors.lastname: Fearns
authors.forename: John
authors.initials: J
authors.lastname: Parslow
authors.forename: Peter G
authors.initials: PG
authors.lastname: Strutton
authors.forename: Peter A
authors.initials: PA
authors.lastname: Thompson
authors.forename: Mark
authors.initials: M
authors.lastname: Underwood
authors.forename: Scarla
authors.initials: S
authors.lastname: Weeks
authors.forename: Martina A
authors.initials: MA
authors.lastname: Doblin
mesh_terms: D002138:Calibration; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000592:standards*; D019544:Equipment Failure Analysis / Q000592:standards; D009792:Oceans and Seas; D012015:Reference Standards; D013050:Spectrometry, Fluorescence / Q000295:instrumentation* / Q000592:standards*; D014481:United States