The chlorophyll-a concentration was measured using the standard method of in vitro fluorescence according to the monitoring programme of HELCOM (Helsinki Commission). The suspended matter concentration (SPM) was determined according to the ESA validation protocols (Doerffer 2002). Before filtration, the Whatman GFF filters were washed, glowed and weighted. The water samples were filtrated using the pre-treated filters. After filtration, the filters were washed with Milli-Q water, dried at a temperature of 70°C and weighted. The yellow substance absorption (ay(440 nm)) was determined according to Højerslev, (1980). The water samples were filtrated using Whatman GFF filters. The absorbance of the filtered water was measured with Perkin-Elmer Lambda-2 spectrophotometer. The ay(440nm) value was calculated using the equation ay(440 nm)= 2.303A(440 nm)/l where A is the absorbance and l is the length of the quartz cell in meters.