Spatial and temporal variability of flux of photosynthetically active solar radiation in a shallow lake during open water period

Based on measurement data 2013-2014 analysis, spatial-temporal variability of the flux of photosynthetically active solar radiation (PAR) in a water column of a small shallow Karelian lake in early summer is estimated. The peculiarities of distribution of temperature in a water column of the lake during open-water period and the formation of the seasonal thermocline are considered. The distribution of extinction coefficient characterized the maxima values in the surface layer and substantially constant values deeper 1-1.5 m. The maximal value of the PAR attenuation coefficient kw was observed in the surface layer in May (1.9-2.1 m-1) and June (1.5-1.75 m-1) 2013, when the transparency of the water was minimal. Coefficient values ranged from 0.9 to 1.25 m-1 at depths over 1.5 m.