An inversion model based on salinity and remote sensing reflectance for estimating the phytoplankton absorption coefficient in the Saint Lawrence Estuary

Abstract

The inversion of individual inherent optical properties (IOPs) is very challenging in optically complex waters and within the violet spectral range (i.e., 380–450 nm) due to the strong light attenuation caused by chromophoric dissolved organic matter, nonalgal particulates, and phytoplankton. Here we present a technique to better discriminate light absorption contributions due to phytoplankton based on a hybrid model (QAA‐hybrid) that combines regional Saint Lawrence System estimates of IOPs derived from a quasi‐analytical algorithm (hereafter QAA‐SLE) and empirical relationships between salinity and IOPs. Preliminary results in the Saint Lawrence System during May 2000 and April 2001 showed that QAA‐hybrid estimates of phytoplankton absorption coefficient at 443 nm have a smaller bias with respect to in situ measurements (root‐mean‐square deviation, RMSD = 0.156) than those derived from QAA‐SLE (RMSD = 0.341). These results were valid for surface waters (i.e., 0–5 m depth) of the lower estuary with a salinity and chlorophyll‐a concentration range of 22–28 psu and 2.1–13.8 mg m−3, respectively.