A Study On The Anthropogenic Influence On Xitiao Stream Ecosystem In Anji County, Zhejiang Province, China

Human beings activity is the major disturbance on stream ecosystem. The influence of five kinds of anthropogenic disturbance on stream ecosystem were study, reference (no or very few anthropological disturbance), hydropower (n=1), agricultural activity (n=7), town (n=3) and urban(n=1) in the upper Xitiao Stream, Anji county, Zhejiang Province, China. Water quality, and physical habitats were mothly collected from the total of 15 sampling sites from April 2006 to March 2007, while benthic macro-invertebrate were seasonal collected. The aim of our study was to uncover the mechanism of stream ecosystem degradation under the disturbance of agricultural activity and urban development in upper Xitiao stream.1. T-Test of DO, NH₃-N ,TN, TP, COD_Mn, conductivity and pH from reference and disturbed streams show that the Cond,TN,TP,COD,NH₃-N in urban polluted stream were significantly higher than those in hydropower polluted stream, agricultural source , town sewage polluted streams and reference streams (p<0.05) . However, pH and DO were significantly lower than those polluted streams and reference streams (p<0.05) .Only conductivity varied rather significantly between reference streams and hydropower polluted streams (p<0.05),and the other Physical and Chemical parameters had no significant differences (p>0.05) . TP and conductivity were statistically significant between reference streams and agricultural polluted streams(p<0.05) ; Also the varables of NH3-N, TP, COD and Conductivity were remarkably different between reference streams and town sewage streams (p<0.05) .The results show that :the human activities caused more pollutions in the streams water , resulted in significant increase in contents of TN,TP,COD, NH₃-N and Conductivity, and the water quality discreased. In city polluted stream, the water quality degraded badly.2. The total taxa richness, EPT tax richness, Shannon-wiener index ,Simpson index , Evenness index and B-IBI had no siginificant difference between reference streams and hydropower disturbed stream (p>0.05). Agricultural polluted streams and town sewage polluted streams (p>0.05) . Whereas these community parameters varied significantly between reference streams,hydropower disturbed stream,agricultural polluted streams,town sewage and city sewage polluted streams (p<0.05) .The total taxa richness, EPT-richness, Shannon-wiener index ,Evennes sindex ,B-IBI in reference streams were significantly higher than those in agricultural source and town sewage polluted streams, whilethe city sewage polluted streams had lowest benthic macroinvertebrate diversity.3. The analysis on the stream physical habitats(substrate, velocity and flow volum) of five groups showed that under pollution disturbance from agricultural activity, town and urban development, the substrate's diversity was degraded and the ratio of the big size of substrate (Dm>256) was decreased . The pollution disturbance would widen the variation's range of the stream water's velocity and flow volum; and their varieties along an altitude gradient .the upper stream, the smaller metrics, also the ratio of depth/width .these variation was manifested the concept of RCC.4. The results of Pearson's correlation and Canonical Correspondence Analysis (CCA) between benthic macroinvertebrate community and environmental factors showed the total taxa richness, B-IBI hace significant negative relationship with TN, TP and COD and it indicated that as the increasement of TN, TP and COD in stream water body, the diversity of benthic macroinvertebrate decrease. Meanwhile, the diversity of benthic macroinvertebrate also decreased as the increasement of velocity. The significant positive relationship between velocity, flow volum and crop land% and the significant negative relationship between total taxa richness and B-IBI suggested that higher velocity resulted from the increasement of crop land% in a watershed might be the mechanism of degradation of benthic macroinvertebrate in stream.