Studies On The Community Characteristics Of The Phytoplankton And The Relationship With Environment Factors In Heihe River Basin

Water samplings were collected at76sites across Heihe River basin during the comprehensive investigation in the fall of2009and summer and fall of2010.242species, which belong to8divisions,11classes,25orders,45families and94genera, were identified from these water samplings. Bacillariophyta which makes up of38.43%of the total number of the species is the dominant group, followed by Chlorophyta and Cyanophyta. Synedra ulna, Dactylococcopsis irregularis and Synedra acus are dominant species, whose ecological dominance are0.060,0.031and0.021.And frequencies of their occurrence are43.42%,43.42%and46.05%respectively. The analysis of biodiversity indicates that the complex and stability of phytoplankton community in middle and downstreams are both higher than those of upstream. The water quality of upstream is of no-pollution or slightly polluted, but slightly or moderately polluted in the middle and downstreams. The correlation analysis between basin-wide total phytoplankton density and environment factors of water shows that the phytoplankton density is positively corrleated with water hardness in the upstream while the midstream phytoplankton density is not significantly related with any factors. In the downstream, the phytoplankton density is negatively correlated with water hardness but positively correlated to nutrient index of the total nitrogen multiply by the total phosphorus (TN×TP). In the whole basin, phytoplankton density is positively correlated with Total Dissolved Solids (TDS), pH and water hardness. The spatial distribution of phytoplankton in Heihe River Basin shows obvious vertical zonality and horizontal zonality corresponding to differentiation characteristics of river hydrological zonation. These results showed the spatial correlationship between phytoplankton communities and their natural environment backgrounds. We hope this research could be favor to make policies to improve the management and sustainable utilization of the aquatic biological resources, to protect the water ecological environment in Heihe River basin and even other continental river basins.