MEPS 448:67-78 (2012)  -  DOI: https://doi.org/10.3354/meps09544

ABSTRACT: The fluorescence signal emitted from phytoplankton exposed to natural sunlight has been considered a potentially useful tool to examine phytoplankton physiology from in situ radiometers and satellites, but variability in the fluorescence signal is confounded by nonphotochemical quenching (NPQ). This pathway dissipates excitation energy as heat rather than fluorescence. It is necessary to first correct for this NPQ signal in order to extract physiological information, such as rates or nutrient stresses. Here we examine the fluorescence−irradiance response and NPQ in a marine diatom grown under simulated vertical mixing. Contrary to previous studies, we find that low-light-acclimated cultures express greater NPQ than high-lightacclimated cultures. Our results differ from previous studies because we employ realistic vertical mixing, rather than constant light conditions. We also find that fluorescence yields do not saturate at high-light levels. This observation impacts how we might apply NPQ corrections to radiometer and satellite data.

KEY WORDS: Fluorescence · Non-photochemical quenching · Fluctuating light · Diatom