Seasonal Dynamics of Common Phytoplankton in Lake Baikal

Changes in the seasonal dynamics of phytoplankton are potentially important, because they can generate a mismatch between the timing of peak productivity and that of consumers, thereby interrupting energy flow between trophic levels. Here, we use a long term data set for the phytoplankton community in the southern basin of Lake Baikal, Siberia to analyse for changes in the seasonal timing of peak abundance of the 4 most common genera during the period 1951-1999. Despite the development of warmer air temperatures and an earlier date of ice-off in the southern basin during the last century, the timing of peak abundance of Aulacoseira, Cyclotella, Synedra, and Ankistrodesmus(=Monoraphidium) did not change. These phytoplankton, especially the diatoms, may rely on light rather than temperature as a seasonal cue for initiating rapid population growth. During the 48-year period of analysis, mean annual abundance of Aulacoseira declined significantly, but the abundance of the other genera remained unchanged. The decline in Aulacoseira may be related to changes in winter precipitation and ice characteristics, but this remains to be examined.