Dependence of mean spectral extinction coefficient of phytoplankton on depth, water color, and species

From published absorption spectra of algae (green, blue‐green, and diatoms) and from published data describing spectral irradiance as a function of depth in blue, green, and blue‐green waters, values of the mean spectral extinction coefficient k̅ c (m 2 ·mg −1 Chl a ) of the algae were calculated. For all three algal types, k̅ c has nearly the same value (0.014±0.002) at the surface. For all three types, k̅ c increases with depth in blue water, decreases with depth in green water, and changes relatively little in blue‐green water. The largest variation occurs with the green alga, k̅ c ranging from 0.005 at depth in green water to 0.021 or more at depth in blue water.