Current velocity and the establishment of stream algal periphyton communities

Colonization of periphytic algae on glass slides was studied during a 5-week exposure period at four current regimes, comprising a static pool and three current velocities. After the 4th week, substrata were transferred from each current regime to the others to gain some insight into the regulatory influence of water current on the structure of the periphytic community. An inverse relationship between periphytic accumulation and current velocity was observed. Unlike earlier reports showing greater biomass accumulation at higher current velocities due to stimulatory effect of water current, no such effect was noticed in the present study. This points towards a preference of the majority of species for the pool. Thirty-four species of diatoms constituted the periphytic community, and three species of green algae occurred sporadically. Preferences of some common species for current regimes were determined: pool for Gomphonema parvulum and Gomphonema lanceolatum; 10-14 cm s(-1) for Navicula cryptocephala; and 18-21 cm s(-1) for Gomphonema olivaceum, Caloneis bacillum and Pinnularia gibba. After colonization in the pool, the total biovolume of Surirella ovata increased significantly at intermediate current velocities which suggested there was a stimulatory effect of water current. (C) 1998 Elsevier Science B.V.