Comparisons of fast repetition rate fluorescence estimated primary production and 14C uptake by phytoplankton

Abstract

Comparisons of primary productivity measured by 14 C uptake and fast repetition rate fluorescence (FRRF) for samples taken from Massachusetts Bay and Narragansett Bay demonstrated a linear relationship between the 2 techniques. The slope of the regression for different phytoplank- ton samples ranged between 0.23 and 1.04, with most between 0.4 and 0. The r 2 was usually high and >0.9 in the best cases. The results indicated that the FRRF usually underestimated primary produc- tivity relative to 14 C. The variability in the relationship between 14 C uptake and the FRRF productiv- ity estimates indicates that FRRF field measurements should be calibrated against other productivity measurement techniques such as 14 C uptake or oxygen production if they are to be compared to his- torical productivity estimates. The Kolber & Falkowski (1993; Limnol Oceanogr 38:1646-1665) and the Smyth et al. (2004; J Plankton Res 19:1637-1670) models for estimating productivity by variable fluorescence were compared, and agreed very well with an r 2 of 0.99 for the linear relationship between the 2 techniques.