Abstract: Photoautotrophic biofilms were cultured and collected in different water layers of the Donghu Lake of Wuhan City from October to November 2005 in an experiment to study characteristics of their growth and activity.Several parameters including biomass,extracelluar polysaccharides,COD and dehydrogenase,were determined.Results show that the photoautotrophic biofilms in different depths experienced four growth periods like "latent adaptation period,growing period,abscising period,and regrowing period".The photoautotrophic biofilm growing in the water 20 cm in depth was higher than those in the water 100 cm in depth in growth rate,biomass and activity.The findings indicate that the physiological characteristics of the photoautotrophic biofilm in hypereutrophic water are quite similar to those in the clean natural water and eutrophication doesn′t have significant effect on the growth of biofilm.

Key words: Donghu Lake, eutrophication, photoautotrophic biofilm