In this paper we present the evaluation of trophic state of lagoon aquatic ecosystems connected to the Adriatic Sea. Vilun lagoon is one of these lagoons in Albania. It is one of the most important ecosystems in the country. For trophic state evaluation, spectrophotometry methods of absorption, as well as turbidimetry ones are applied. This ecosystem is monitored for a year from April to October. The evaluation of trophic state is based on these four indicators: the containment of chlorophyll a in phytoplankton; the distribution of photosynthetic pigments; water turbidity and phosphorus containment in water. The monitoring process is performed in different areas of the lagoon, in order to be able to make a more characteristic evaluation of trophic state. All selected areas of Vilun lagoon show a reasonable level of trophic state, which is characterized such as being mezotrophic. Changes related to trophic level are observed during the monitoring period, in each and all the selected areas. Furthermore, changes in the distribu-tion of chlorophylls and their relative content between selected areas are observed.