Vertical distribution of planktonic ciliates in strongly stratified temperate lakes

The vertical distribution of planktonic ciliates in eight strongly stratifi ed temperate lakes was studied in summer 1998. Ciliate abundance and biomas s were highest (mean 39.9 cells ml(-1) and 181.9 mug C l(-1)) in the epi-, and lowest (mean 8.2 cells ml(-1) and 97.6 mug C l(-1)) in the hypolimnion. The community of ciliates was dominated by five orders: Oligotrichida, Hap torida, Prostomatida, Scuticociliatida and Peritrichida. The community comp osition varied greatly with depth. In the epilimnion, the ciliate numbers w ere dominated by oligotrichs but small algivorous prostomatids, peritrichs and haptorids were also numerous. In the metalimnion, these groups were rep laced by scuticociliates and mixotrophic prostomatids. In the hypolimnion s pecies known as benthic migrants appeared. We found a positive significant correlation (p < 0.05) between ciliate numbers and Chl a and bacterial dens ities. Only in the hypolimnion, the correlation between ciliates numbers an d Chl a was not significant.