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Post-Calibration of Fluorescence Data from Continuous Monitors (To adjust or not to adjust, and if so, how?) A Gang of N Production Elgin Perry - Statistics Consultant Marcia Olson - NOAA/CBP Beth Ebersole - MD DNR Bill Romano - MD DNR Presented to the Tidal Monitoring and Analysis Workgroup on 3 December 2003

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(Kim Mikitas data)

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Tidal cycle Diel cycle

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log(x/y)=log x - log y LNRAT = LNCHL_F – LNCHL_A

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Model Evaluated Season Sonde deployed Light Turbidity Log ratio as a function of:

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Station Signed-rank Test SeasonSondeLightTurbidity Turville CreekP<0.0001NS BishopvilleNS Shelltown0.0042NS CHWSNS Rehobeth0.0008NS ChicamacomicoNS NS Ben OaksNS NS Sherwood NS0.0276NS WhitehurstNS StoningtonNS Model Results

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At higher light levels, extractive samples exceed fluorescence data?

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Fluorescence exceeds extractive at all light levels, so no light effect.

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Fluorescence exceeds extractive under all light levels, so no light effect.

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Similar pattern to Turville Creek and Shelltown.

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Chlorophyll Adjustment Methods Regression method – CF (adj) = ß 0 + ß 1 CF (Model CS = CF) Multiple regression – CF (adj) = ß 0 + ß 1 CF + ß 2 Turb (Model CS = CF, Turbidity) Ratio method – CF (adj) = CF x (CS/CF) Subtract background fluorescence

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Linear Regression Assumptions Y is linearly related to X Expected value of the error term is zero Constant variance in the error terms, which are uncorrelated Independent variable(s) is measured without error Independent variables are not linearly related

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Correction Using Ratio of Extractive to In Vivo

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Conclusions Stop collecting data Full speed ahead (one size fits all) Test various models and select one that minimizes root mean square error on a per station basis Hire an expert to assess covariate measurement error problem Log transform for correction and then back transform

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