Artifacts in measurements of chlorophyll fluorescence transients, with specific application to fast repetition rate fluorometry

Abstract

A theoretical framework was developed to describe how instrument and sample artifacts affect measurements of variable fluorescence transients in phytoplankton. This framework identified the proper procedure for correcting for common artifacts in the transients measured with a widely used instrument, the Fasttracka fast repetition rate fluorometer. The impulse response of this fluorometer can be substantial, requiring correction for a dynamic instrument artifact in addition to the static artifacts that can be assessed using traditional “blanks.” In a low‐biomass region of the North Pacific, approximately one‐third of the fluorescence transient measured with this instrument represented such artifacts. Correcting for these using filtered seawater blanks only, and not accounting for the instrument's own response, failed to remove errors as high as 22% in estimates in the photochemical yield and as much as −16% to +22% in estimates of the functional cross section of Photosystem II. This analytical framework and the corrective procedure are generalized and can be used to determine how a wide range of artifacts affect measured variable fluorescence transients, including those characteristic of fluorometers other than the Fasttracka or those more relevant in meso‐ or eutrophic regions of the ocean.