Dynamics of the diatom algae part in total Lake Baikal phytoplankton mass for the period 1951–1999 was
analyzed. For 1973–1999 in the upper layer 0–50 m average share of diatoms in total plankton phytomass varied
from 23 % (1978) to 78 % (1976) with long-term average 48 % and median 44 %. There is no linear trend for diatom
algae share dynamics, but there is U-shaped well expressed parabolic trend with R2 = 0,48. Minimal share of
diatoms was observed 1984–1987 (from 25 % in 1986 to 32 % in 1987) with average 28 %. Starting from 1997
yearly average share of diatoms increases, reaching 72 % in 1999.