Phycobilins are photosynthetic pigments unique to cyanobacteria (also referred to as blue green algae) and rhodophyta, or red algae. A class of phycobilin pigments known as phycocyanin is unique to cyanobacteria. Measurement of phycocyanin concentrations thus is a reliable way to measure the biomass of cyanobacteria in freshwaters. As is the case for chlorophyll a, phycocyanin may be measured by a variety of techniques, including physical-chemical methods similar to chlorophyll a determination, e.g., solvent extraction and chromatographic analysis.
Remote sensing measurement of phycocyanin is much less common than that for chlorophyll a. Sentinel-3 is the only one of the current constellation of satellites for mapping water quality of inland waters with a sensor band in the range of 600-630 nm, where phycocyanin has a characteristic absorption peak. Algorithms have been published (Randolph et al. 2008; Schalles and Yacobi 2000) that use this spectral band to retrieve phycocyanin data by remote sensing, and the main limitation at present to applying satellite imagery to measuring cyanobacterial distributions in Minnesota lakes seems to be the lack of ground-based calibration data on phycocyanin concentrations in lakes. The spatial resolution of the Sentinel-3 sensor (300 m) limits its use to relatively large lakes (> ~ 400 acres). This includes only about 8% of Minnesota’s lakes, but 900 of the state’s most recreationally important lakes are large enough to be measured by this satellite. Advances in ground-based data collection and remote sensing technology are likely to open up more opportunities to use RS to distinguish blooms of cyanobacteria from other algae in freshwaters.
Randolph, K. L., J. Wilson, L. Tedesco, L. Li, L. Pascual, E. Soyeux. 2008. Hyperspectral remote sensing of cyanobacteria in turbid productive water using optically active pigments, chlorophyll a and phycocyanin. Remote Sens. Environ. 112: 4009-4019.
Schalles, J., and Y. Yacobi. 2000. Remote detection and seasonal patterns of phycocyanin, carotenoid and chlorophyll pigments in eutrophic waters. Archiv. Hydrobiol., Spec. Issues, Adv. in Limnol. 55: 153-168.