Evaluation of the stability of hyperspectral signatures in Microcystis aeruginosa and Dolichospermum sp. under nutrient stress

The early detection of cyanobacteria harmful algal blooms (cyanoHABs) is important to deploy effective rapid response and mitigation strategies. However, monitoring cyanoHAB-prone water bodies remains a challenge, in part due to the limitation of spatial, temporal, and spectral resolutions of current image-based remote sensing technologies. Remote sensing platforms and sensors are rapidly evolving. Before these technologies can be transitioned to operational programs for early warning and routine monitoring, they need to be evaluated and validated in controlled environments. Therefore, in this study, the stability of hyperspectral signatures from two cyanobacteria: Microcystis aeruginosa and Dolichospermum sp. were evaluated under nutrient stress. Cultures were exposed to various nitrate (0.15-1.5 g•L^-1) and phosphate (0.01-0.1 g•L^-1) concentrations and ratios. Assessments were made on overall growth via in vivo phycocyanin fluorescence, toxin production via ELISA, and changes in hyperspectral signatures using a Resonon hyperspectral camera (400-1000nm). Laboratory experiments showed a change in spectral signatures under all of the nutrient stressors examined. This largely coincided with culture senescence, which also corresponded with higher cyanotoxin levels. Currently, this information is being compiled into a database for the identification of cyanobacteria that will be used to validate this technology as it transitions to field-based platforms.