Hyperspectral analysis of algal biomass in northern lakes, Churchill, MB, Canada

Abstract

A hyperspectral approach to quantify algal biomass was studied across 30 shallow ponds in the Hudson Bay Lowlands near Churchill, MB. Normalized difference algal indices (NDAI) were calculated based on hyperspectral measurements of the reflectance collected on shore with a hand-held spectrometer in parallel to estimations of biomass with an in vivo fluorometer designed for benthic algae. Algal biomass and coarse assemblages were differentiated through their spectral reflectance as a demonstration of concept for future upscaling that would be necessary for regional monitoring using remote sensing technology. Results indicated strong agreements between the calculated NDAI for measured reflectance from each pond and that of the isolated benthic zone. Cyanobacteria were the dominant component of the algal community for most ponds. As such, measures of reflectance and use of simple NDAIs may be able to characterize the total biomass of northern ponds. However, the distinction between algal groups may require independent validation of algal assemblages for estimations beyond total biomass. Nonetheless, hyperspectral analysis could provide a strong potential for monitoring northern freshwater systems at a regional scale.