MEPS 322:51-59 (2006)  -  doi:10.3354/meps322051

Quantifying uncertainties associated with the measurement of primary production

Katharine L. Pemberton, K. Robert Clarke, Ian Joint*

Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK
*Corresponding author. Email:

ABSTRACT: Depth-integrated primary production was estimated in the Celtic Sea (European Shelf) by 2 independent methods. Daily production rates were derived from photosynthetic parameters determined by photosynthesis/irradiance (P/E) experiments on samples incubated with 14C-bicarbonate (14C method) and from in situ profiles with the fast repetitive rate fluorometer (FRRF) method. Production was estimated to be between 332 and 910 mg C m–2 d–1 by the 14C method and from 351 to 1278 mg C m–2 d–1 by the FRRF method. The uncertainty, or error, of these estimates was determined by calculating 95% confidence intervals using Taylor series and Monte Carlo modelling approaches. Both approaches revealed significant uncertainty in estimates. The Taylor series analysis of the 14C method indicated that 95% confidence interval widths were between 4 and 20% of the estimated production. The smallest error in this study, calculated using a Taylor series analysis, gave a 95% confidence interval of (578, 622) mg C m–2 d–1 for an estimated production rate of 600 mg C m–2 d–1. The largest error was calculated using a Monte Carlo analysis and found that a production rate of 377 mg C m–2 d–1 had 95% confidence limits of (300, 453) mg C m–2 d–1. Larger uncertainties were associated with the FRRF method, but reflect only the increased complexity of equations used to derive photosynthetic parameters and not a known greater degree of error in the approach. The precision of primary production measurements is a neglected but important factor that should be considered in primary production experiments and in testing satellite remote sensing algorithms.

KEY WORDS: Primary production uncertainty · Remote sensing error · Taylor Series · Monte Carlo modelling · 14C P/E curves · Fast repetitive rate fluorometer

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