Examining temporal variations of phytoplankton photoacclimation using a novel fluorescence based approach

Abstract

Models of primary production require parameters to describe photosynthesis as a function of irradiance, such as the saturation irradiance (Ek, ?mol photons m-2 s-1). However, this parameter varies in both time and space, is expensive to measure, and its variability in the oceans is not well described. A novel fluorescence-based approach is presented to determine an empirical parameter (EFT, ?mol photons m-2 s-1), which is strongly correlated with Ek. This correlation provides evidence to use EFT as a proxy for Ek. Using an autonomous profiling instrument package (SeaHorseTM, located on the Scotian Shelf) and an autonomous oceanographic observational buoy (Land/Ocean Biogeochemical Observatory, located in the Northwest Arm, N.S., Canada), the variability of EFT was examined on three time scales: hours, days, and seasons. Studying variations of EFT with these autonomous instruments provided insights to its variability on time scales relevant to models of primary production.