SPATIAL DISTRIBUTION OF BENTHIC ALGAE IN THE ERHAI BASIN OF SOUTHWESTERN CHINA

The Erhai is a highland basin situated in the Yunnan province of southwestern of China. In this area benthic algae and environmental variables of 44 sites were sampled twice, in February and in March 2009. In our study, 182 benthic algae taxa of 60 genera were observed. Bacil-lariophyta with high relative abundance was the dominant group in all samples. Achnanthidium minutissima, Achnanthidium rivulare and Achnanthidium deflexum dominated the monoraphids as they commonly occurred in most rivers. There was heterogeneity in benthic algae distribution. NMDS analysis divided sampling sites into five groups (B, CU, CD, M, X) and MRPP showed significant differences among these five groups (p<0.0001). CCA results showed that the spatial distribution of benthic algae in the Erhai basin is linked to the gradients of NO3-N, CODmn and Ca2+. Species richness and Ch1 a concentration correlated positively with NO3-N. Our study suggests that nutrient supply is the limiting factor for benthic algae richness and biomass. NO3-Nis also an important variable influencing benthic algae distribution, diversity and biomass in the Erhai basin.