The Effect of the Optical Properties of Two Cyanobacteria Species on the Remote Sensing Reflectance - a Modeling Study
Wojtasiewicz, Bożena; Krężel, Adam
University of Gdansk, POLAND
Blooms of cyanobacteria, mostly formed by Aphanizomenon sp. and Nodularia sp., occur in the Baltic Sea almost every summer. Considering the usual sizes of areas covered by blooms formed by potential toxic species, remote sensing methods seem to be very useful to monitor this phenomenon. The development of satellite ocean colour sensors provides a great opportunity to study phytoplankton blooms from space. The aim of this project was to investigate the variability in the shape of the remote sensing reflectance spectra resulting from the difference in the composition of the bloom-forming community. The reflectance spectra were obtained on the basis of measured spectra of chlorophyll-specific absorption and scattering coefficient spectra of Aphanizomenon flos-aquae and Nodularia spumigena with the use of Hydrolight software. The analysis of the results were mainly focused on the data for the wavebands that are used by MODIS and OLCI sensors. The reflectance spectra calculated for the case of no additional sources of yellow substance and mineral suspensions were sufficiently different to evaluate the taxonomic composition of the bloom, especially within the short-wave part of the spectrum. In the case of coastal areas with large loads of additional dissolved and particulate matter it was much harder to distinguish between different bloom-forming species, mainly due to CDOM absorption. However, it seems that the analysis of the ocean colour data may be also efficient in such cases, but it requires to be verified mostly with the use of field data.