Abstract. The fluorescence and absorption measurements of the samples collected from a surface microlayer (SML) and a subsurface layer (SS), a depth of 1 m were studied during three research cruises in the Baltic Sea along with hydrophysical studies and meteorological observations. Several absorption (E2 : E3, S, SR) and fluorescence (fluorescence intensities at peaks: A, C, M, T, the ratio (M + T) / (A + C), HIX) indices of colored and fluorescent organic matter (CDOM and FDOM) helped to describe the changes in molecular size and weight as well as in composition of organic matter. The investigation allow to assess a decrease in the contribution of two terrestrial components (A and C) with increasing salinity (~ 1.64 % and ~ 1.89 % in SML and ~ 0.78 % and ~ 0.71 % in SS, respectively) and an increase of in-situ produced components (M and T) with salinity (~ 0.52 % and ~ 2.83 % in SML and ~ 0.98 % and ~ 1.87 % in SS, respectively). Hence, a component T reveals the biggest relative changes along the transect from the Vistula River outlet to Gdansk Deep, both in SML and SS, however an increase was higher in SML than in SS (~ 18.5 % and ~ 12.3 %, respectively). The ratio E2 : E3