Biomass, species composition and diversity of epipelic algae in mire pools

The biomass, species composition and diversity of epipelic algae in two sma ll pools of contrasting physicochemical characteristics in Miyatoko Mire we re studied in 1992 (pool 3 =site B4 and pool 50 =site D2). A total of 93 sp ecies and 67 species of epipelic algae occurred at sites B4 and D2, respect ively. Considerable differences were observed between the two sites in the seasonal fluctuations of species number, biomass and dominant species. At s ite B4, little changed with species number during April-August and markedly increased in October, while biomass was largest in April and gradually dec reased during June-October. Diatoms and desmids occupied 33-82% and 15-63% of total algal biomass, respectively. At site D2, species number and biomas s were small in April just after the snow-thaw, and increased in June and d ecreased in August and October. Diatoms occupied 90-98% of total algal biom ass. The species diversity was always higher at site D2 than B4. As a resul t of analyses of water chemistry in the two pools, pool B4 can be recognize d as a habitat experiencing high disturbance frequency. It is predicted tha t pools experiencing frequent disturbance will have less epipelic algal bio mass and diversity.