Adaptation and Validation of a Sentinel-Based Chlorophyll- a Retrieval Software for the Central European Freshwater Lake, Balaton

The importance of lakes and reservoirs leads to the high need for monitoring lake water quality both at local and global scales. Remote sensing is a rapidly evolving, versatile technology that can be successfully applied in several economic and scientific fields. Numerous studies demonstrate the applicability of satellites in algae detection and monitoring. Algae play an essential role in aquatic ecosystems, although their overgrowth poses a serious risk. Overgrowth of algae, also known as algal bloom, has serious ecological, social, economic and health effects. The research area of our study was Lake Balaton, the largest lake in Central Europe. The aim was to find the most appropriate algorithm(s) for the inland lake to define the chlorophyll- a amount. In addition, two new algorithms were developed based on the reflectance values of the satellite image. The results show that the two highest correlations were performed by the newly validated, blue/green ratio-based algorithm, Chl-a B/G ( r = 0.93) and the chl_re_oc2 algorithm ( r = 0.86) of the Acolite software. Although the Acolite software was not developed for lakes but for marine waters, it is also applicable to inland waters.