Extraction of photosynthesis-irradiance parameters from phytoplankton production data: demonstration in various aquatic systems

A method is presented for extraction of the photosynthesis-response parameters from profiles of phytoplankton production. The procedure, previously proposed but not tested, is implemented here in various types of aquatic system and a protocol is established for its use. Values of daily primary production integrated over the photic zone were estimated from in situ or simulated in situ incubations in four coastal and open-ocean marine systems, and from photosynthesis-irradiance (P‐E) curves in the afore-mentioned marine systems, as well as in two freshwater systems. The slope of the measured daily water-column production (normalised to water-column chlorophyll a biomass) plotted against the daily incident irradiance was variable from system to system (0.09 to 0.60), showing a broader range than previously reported values. Using an iterative procedure, we estimated the photosynthetic parameters from this linear relationship. Generally, estimated values lie within the 95% confidence interval of the photosynthetic parameters obtained from the P‐E curves, showing that the estimates agree well with measurements. The new method, based on the photophysiological response of the phytoplankton community, provides a way to enhance our ability to compute primary production from remote sensing of ocean colour.