Modeling the contributions of phytoplankton and non-algal particles to spectral scattering properties in near-shore and lagoon waters.

Particular attention was focused on modeling the spectral scattering properties of phytoplankton ( b ph ( λ )) and non-algal particles (detrital organic and inorganic sediments b NAP ( λ )) from absorption and attenuation measurements in near-shore and lagoon waters. The absorption line height ( a LH (676)) measured above a linear background between 648 nm and 714 nm in particulate and dissolved organic matter absorption spectra ( a p ( λ )) is a spectral feature that is primarily associated with the chlorophyll with significantly less pigment package effect compared to the blue peak, and hence it is solely attributed to the phytoplankton absorption ( a ph ). The correlation of a ph ( λ ) with b ph ( λ ) in terms of the spectral shape and the relation of a LH (676) with chlorophyll concentration hold the key to derive b ph (648) from the a LH (676) measurements. b NAP (648) values are then determined by subtracting the b ph (648) from b p (648), allowing the power-law model to derive the b NAP ( λ ). In-situ determination of b ph ( λ ) is subsequently achieved by subtracting the featureless b NAP ( λ ) from b p ( λ ) provided by the ac-s sensor. These data form the basis for the development of models for independent estimates of b ph ( λ ) and b NAP ( λ ) based on the measurements of a LH and suspended sediment concentration or turbidity. The validity of this method was demonstrated in a wide variety of samples from coastal and inland environments. Comparison of the modeled and measured spectral variations of b ph ( λ) showed the mean relative percent difference between these two data to be within 20%. b NAP ( λ) predictions also had an error a few percent and the correlation coefficient close to unity. When comparing the modeled b ph ( λ) with laboratory culture data, the results were exceptionally good although discrepancies in size and refractive index of cells of monospecific lab culture samples and natural assemblages due to the simultaneous presence of different species. The proposed approach and models are highly instrumental in investigating the scattering properties of phytoplankton and non-living constituents, and will provide new tools for improving our current understanding of particle dynamics, advancing biogeochemical and ecosystem modeling, and assessing phytoplankton blooms and sediment plumes within inland and coastal environments. [ABSTRACT FROM AUTHOR]