Phycocyanin concentration retrieval in inland waters: A comparative review of the remote sensing techniques and algorithms

Phycocyanin (PC), as a characteristic pigment, is more suitable for monitoring cyanobacterial blooms and toxic cyanobacteria than chlorophyll-a (Chl-a). Because the absorption peak of PC is about ~620 nm, the application of remote sensing using a wavelength range of 615-630 nm becomes very attractive for the implementation of PC-targeted inversion algorithms. Numerous researchers have applied empirical and semi-analytical algorithms to derive PC concentration as proxies for cyanobacterial blooms. However, in contrast to Chl-a, the remote sensing estimation of PC concentration at the larger scale is still limited by the scarcity of data with sufficient spatial and spectral resolution. Therefore, this review attempts to provide a comprehensive overview of remote sensing techniques and retrieval algorithms as applied to the PC monitoring. The main emphasis is on the PC inversion algorithms and their realization via the available and perspective remote sensors. Based on the above analysis of state-of-the-art techniques and algorithms, the overall challenges and potentials of remote sensing-based cyanobacterial PC pigment retrieval are discussed in detail.