This article contains results of measuring light attenuation coefficient values at different water depths in lakes of various kinds located in Altai Krai with regard to seasonal changes during 2011-2013. Seasonal dynamics of the lakes water transparency research data show that maximum values of the attenuation coefficient across almost the whole spectral range are observed at the end of summer season while minimum values - in winter before ice break-up. The reasons are mass propagation of algae, higher concentration, and bigger sizes of phytoplankton particles (cells). The authors have carried out analysis of the obtained experimental data taking into account the particle size (cell size) of phytoplankton.

Key words: lakes, light attenuation coefficient, water spectral transparency, chlorophyll.