Characterization of Hyperspectral Inherent and Apparent Optical Properties of Harmful Algal Blooms in Lake Erie
Hyperspectral observation is well suited to monitoring CHABs in freshwaters, as there is more information available to differentiate phytoplankton groups and even large species assemblages based on unique spectral features. This is particularly true for freshwater cyanobacteria, which have distinctive optical properties that impact different parts of the spectrum, and have a capability to alter their vertical position through buoyancy control, which strongly impacts the observed remote sensing reflectance.
The purpose of this study is to characterize the natural inter- and intra-annual variability of the inherent and apparent optical properties (IOP/AOP) over the HAB growth cycle in Lake Erie to support the development of hyperspectral bio-optical retrieval algorithms. Weekly IOP/AOP measurements were made at standardized locations in Lake Erie from May-October for the 2015-2019 period. Additionally, high temporal frequency (1-5 minute sampling interval) remote sensing reflectance measurements were made from a fixed location hyperspectral radiometer system from July-October in 2018 and 2019. Results suggest algal assemblages differ significantly within and between years indicating the need for dynamic hyperspectral bio-optical algorithm parametrization.