Remote Sensing of Cyanobacteria in the Baltic Sea

Kurzfassung

Effective control methods are of high importance to establish and maintain certain water qual-ity standards. Eutrophication and annual phytoplankton blooms play an important role in the Baltic Sea. The cyanobacteria dominated summer bloom causes special problems in that eco-system, not only because of the ability to fixate atmospheric nitrogen, but also for the capabil-ity of producing cyanotoxins, harming other life forms. An impact on human life is given di-rectly by blooms being washed ashore, as well as indirectly through the food chain. In Situ measurements in wide aquatic areas are time-consuming and expensive, yet only give spatial-ly and temporally limited information. A special algorithm addressing the specific optical properties of cyanobacteria in the Baltic Sea is developed at the Marine Remote Sensing group of the German Aerospace Centre. Based on inherent optical properties of cyanobacteri-al pigments and other water constituents, a four component model with parameters for Chlo-rophyll-a, Phycocyanin, Suspended matter and CDOM was developed for the optically com-plex Baltic Sea. Using the simulated dataset, a neural network was trained for the task of in-verting atmospherically corrected MERIS reflectances. This algorithm extends the set of standard water quality products (C,S,Y) by a qualitative new parameter for the pigment Phy-cocyanin and accounts for the specific optical properties of the Baltic Sea. The results coin-cide well with corresponding Algaline ship of opportunity data. The algorithm was imple-mented as a plugin for the BEAM VISAT toolbox.