Research Quantitatively On Relationship Between Benthic Diatoms And Water Environmental Factors In Middle And Upper Of Wujiang River

Diatoms are used for monitoring and evaluating the quality of river water. Some European countries have evaluated the quality of rivers and lakes water by diatoms. But now in China, the biological monitoring system of diatom has not been built. In order to built the system, we should study on the relationship between diatoms and physcicochemical factors. The quantitative investigation of the benthic diatoms in the middle and upper of Wujiang River has not been reported yet, as well as the relationship between diatoms and physcicochemical factors.In the drought and peak periods, Benthic diatoms of the 15 sample points were collected and identified. The aboundance, relative aboundance and dominant sociales of diatom were analyzed quantitativly. WT, ORP, DO, COD, COND, pH, anions, cations and heavy metals were measured. The relationship between the benthic diatoms and the physcicochemical factors were analyzed by Principal Component Analysis, Cluster Analysis and Correlation Analysis. At the last, the diatom-enviromental factors transfer functions were established.The main conclusions were summarized as following:(1) The Tp optima of Navicula. ontana Krasske and other 7 benthic diatoms were above 100ug/L, which may be indicators of the outbreak of eutrophication in the middle and upper of Wujiang River. The Tp optima of Diatoma,Fragilaria,Synedra and Achnanthes were 50mg/L—70mg/L,which may be indicators of rivers of less contain of Tp.(2) HCO₃^-, SO₄^2-, K⁺ were the most prominent factors which affected the distribution of the bnethic diatom in the drought period. HCO₃^- was the first factor. The HCO₃^- optima of Gomphhonema affine Kütz. and other 12 benthic diatoms were 108mg/L—123mg/L, which may be indicators of rivers of more contain of HCO₃^-. (3) TP was the most important factor which affected the distribution of the benthic diatom in the drought period, then TN, COD, COND.(4) TP was the most important factor which affected the abundance of benthic diatom in the drought period(R=0.682,P<0.01). TN,COD,COND,pH,Turb,SiO₂ and DO were also the important factors(R=0.674,R=0.666,R=0.597,R=0.621,R=0.548,R=0.572,R=-0.526).The equation of TP and the abundance of benthic diatom was Y=8926+4291X(P<0.01).(5) In 8 kinds of ions, Ca2+ was the most important factor which affected the abundance of benthic diatom in the drought period (R=0.893,P<0.01), then SO₄^2- and HCO3-(R=0.584,R=0.640,P<0.05). The line regression equation of Ca²⁺ and the benthic abundance of diatom was Y=-242.44+183.81X(P<0.01).(6) V was the first factor which affected the abundance of the benthic diatom in the peak period(R=0.749,P<0.01), COND, COD and TP were also very important factors(R=0.526, R=0.563, R=0.629, P<0.05)。The Logarithmic equation of V and the benthic abundance of diatom was y=9702.75+2793.17ln(t) (P<0.01).(7) In 8 kinds of ions, Hg was the first dominant factor which affected the abundance of the benthic diatom in the peak period(R=0.808,P<0.01), and The Compound equation was y=8836.75×2.58418t(P<0.01).(8) Totally 239 species (including varieties) were identified in the drought and peak period. The multiplicity of benthic diatom in the peak period was less than in the drought period. Navicula was dominant in both the two periods. The dominant sociales of the every sample point in the two periods were different, the common species were similar.The conclusions will support scientific foundation for studying the character of Wujiang River, monitoring and estimating water quality and setting up diatom monitoring system.