Spectral absorption coefficient of phytoplankton and its relation to chlorophyll a and remote sensing reflectance in coastal waters of southern China

Abstract

The spectral absorption coefficient of phytoplankton in coastal waters of southern China is investigated. Large variations in the absorption coefficient of phytoplankton are found. The absorption coefficient of phytoplankton at 443 nm ranged from 0.006 m−1 to 0.484 with an average value of 0.067 m−1 The chlorophyll-specific absorption coefficient of phytoplankton is also a bio-optical variable, with a spectrally averaged value of 0.025 m2˙mg−1. The variations of chlorophyll-specific absorption coefficient are mainly attributed to pigment composition of phytoplankton and package effect. The chlorophyll-specific absorption coefficient of phytoplankton decreases with the increasing of chlorophyll a concentration. This relationship can be described by a power law function, with the parameters and the coefficient of determination r2 as functions of wavelength, but the parameters describing the relationships in present study differed from that in Case 1 waters, thus the regional adjustment of model parameters was of particular significance for improving the accuracy of bio-optical algorithms for estimation of Chl-a concentration and primary production from remotely sensed data. Regression analysis of reflectance (Rrs) ratio and absorption coefficient of phytoplankton (aph) indicates a close correlation between them, which means that it is possible to sretrieve absorption coefficient of phytoplankton using ocean color remote sensing data in optically complex coastal waters.