The physically based Modular Inversion & Processing System (MIP) is used in an automized processing chain for inland water constituent retrieval from MERIS level 1B data. Preprocessing routines are used to automatically convert the ESA generic data products into MIP input data format. Water/land masking, atmospheric correction and water constituent retrieval are accomplished by simple batch executables from MIP. The accuracy of the constituent retrieval mainly depends on the spectral fit between the image input data and the radiative transfer model results extracted from a database. Therefore, thresholds and initial values for model fitting have to account for all occurring lake specific temporal variations and need careful adjustment.