Phytoplankton “Missing” Absorption in Marine Waters: A Novel Pigment
Compensation Model for the Packaging Effect
Abstract
The packaging effect of phytoplankton pigments is sometimes capable of
accounting for over half of the variability in the phytoplankton
absorption coefficient (aph) in oceanic waters. Given the significance
of aph in many marine biogeochemical and environmental processes,
exploring the packaging effect on absorption properties thus becomes a
crucial task. In the present study, two pigment compensation models for
quantifying the packaging effect are developed for Case I and Case II
waters, respectively, based on high-performance liquid chromatography
(HPLC)-derived pigments and aph data from the NOMAD and the marginal
seas of China. As a critical quantity in developing our models,
phytoplankton “missing” absorption is derived by subtracting the
reconstructed aph without the packaging effect from the measured aph.
Our proposed models use the established relationships between
“missing” absorption and specific absorption coefficients of pigment
groups without the packaging effect to quantify pigment group
concentrations. Validation using independent in situ data sets
demonstrates that great improvements are achieved for the quantification
of the packaging effect, especially for waters under abnormal packaging
effect conditions. Applying the proposed models to satellite data
displays the spatial distributions of the packaging effect in the
Atlantic Ocean and the marginal seas of China, as delegates of Case I
and II waters, respectively. The generated spatial distribution
demonstrates a rule that the packaging effect intensity positively
covaries with chlorophyll-a distribution. The findings of this study
exhibit a capability of mapping a spatial distribution of the packaging
effect from satellite observations for the first time.