Multi-Spectral Remote Sensing of Phytoplankton Pigment Absorption Properties in Cyanobacteria Bloom Waters: A Regional Example in the Western Basin of Lake Erie

Guoqing Wang,Colleen Mouw,Zhongping Lee

doi:10.3390/rs9121309

Abstract

Phytoplankton pigments absorb sunlight for photosynthesis, protect the chloroplast from damage caused by excess light energy, and influence the color of the water. Some pigments act as bio-markers and are important for separation of phytoplankton functional types. Among many efforts that have been made to obtain information on phytoplankton pigments from bio-optical properties, Gaussian curves decomposed from phytoplankton absorption spectrum have been used to represent the light absorption of different pigments. We incorporated the Gaussian scheme into a semi-analytical model and obtained the Gaussian curves from remote sensing reflectance. In this study, a series of sensitivity tests were conducted to explore the potential of obtaining the Gaussian curves from multi-spectral satellite remote sensing. Results showed that the Gaussian curves can be retrieved with 35% or less mean unbiased absolute percentage differences from MEdium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS)-like sensors. Further, using Lake Erie as an example, the spatial distribution of chlorophyll a and phycocyanin concentrations were obtained from the Gaussian curves and used as metrics for the spatial extent of an intense cyanobacterial bloom occurred in Lake Erie in 2014. The seasonal variations of Gaussian absorption properties in 2011 were further obtained from MERIS imagery. This study shows that it is feasible to obtain Gaussian curves from multi-spectral satellite remote sensing data, and the obtained chlorophyll a and phycocyanin concentrations from these Gaussian peak heights demonstrated potential application to monitor harmful algal blooms (HABs) and identification of phytoplankton groups from satellite ocean color remote sensing semi-analytically.

Highlights

Spectral light absorption and backscattering are the two inherent optical properties directly controlling the light field in water and further influencing water color
We further explored the aGau(λ) distribution obtained from Hyperspectral Imager for the Coastal Ocean (HICO) and Moderate Resolution Imaging Spectroradiometer (MODIS) of the western basin of Lake Erie
The MuPI model was validated for obtaining the peak heights of Gaussian curves (aGau(λ)) from multi-spectral satellite remote sensing data

Summary

Introduction

Spectral light absorption and backscattering are the two inherent optical properties directly controlling the light field in water and further influencing water color. The absorption coefficients of the pigments inside them, play a key role in determining both the penetration of radiant energy in water and the use of this radiant energy for photosynthesis These pigment absorption coefficients and their concentrations are important for understanding photosynthetic rate [1,2], identifying and quantifying phytoplankton functional groups [3] and determining size class distributions ([4,5] and references therein). These properties of phytoplankton and their associated backscattering, along with colored dissolved organic matter absorption and non-algal particle absorption and scattering directly control the light field of water. This Gaussian decomposition scheme sheds light on the potential of obtaining information for multiple phytoplankton pigments beyond chlorophyll a semi-analytically using bio-optical techniques

Methods

Findings

Discussion

Conclusion