On the basis of the recently developed typology and classification of Lithuanian water bodies and accepted criteria of reference and good quality conditions of lakes, the ecological status of the Dovinė river basin lakes Amalvas, Dusia, Simnas and Žuvintas was assessed with respect to the phytoplankton quality element values with regard to the implementation of the WFD requirements.

All phytoplankton quality elements as well as water transparency parameters for the deep Lake Dusia showed a good, while for the shallow lakes Amalvas and Simnas a bad status. The shallow Lake Žuvintas makes an exception. In accordance with phytoplankton biomass and chlorophyll a content Lake Žuvintas should be estimated as a good water quality lake. Lake Žuvintas obviously does not meet the Lithuanian shallow lake type proposed by the DANCEE project. This lake, according to phytoplankton biomass, chlorophyll a and especially species composition, should be ranked as a separate lake type.

Keywords: phytoplankton parameters, ecological status, Dovinė river basin lakes, EU Water Framework Directive