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

Abstract

Comparisons of primary productivity measured by 14C 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 phytoplankton samples ranged between 0.23 and 1.04, with most between 0.4 and 0. The r2 was usually high and >0.9 in the best cases. The results indicated that the FRRF usually underestimated primary productivity relative to 14C. The variability in the relationship between 14C uptake and the FRRF productivity estimates indicates that FRRF field measurements should be calibrated against other productivity measurement techniques such as 14C uptake or oxygen production if they are to be compared to historical 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 r2 of 0.99 for the linear relationship between the 2 techniques. © Inter-Research 2006.