The under-ice and bottom periods in the life cycle of Aulacoseira baicalensis (K. Meyer) Simonsen, a principal Lake Baikal alga

The under-ice development of the meroplanktonic diatom Aulacoseira baicalensis was studied, using underwater video recording. This is an ice alga, which not only succeeds in vegetating under the ice, but also reproduces intensively in interstitial water-filled spaces inside the ice. This report yields first results of the underwater filming done during the under-ice period of 2000. Our studies have shown that the A. baicalensis aggregations on the ice bottom can be easily destroyed by water currents and drift away as large flakes up to tens of centimetres in size. These macro-aggregations are capable of free-floating in the water-column for some time, gradually sinking to the bottom. Cells in the aggregations continue to divide, and they cover objects on the bottom with peculiar mucous coats. These coats act as a major food resource for bottom invertebrates.