The Effect Of Mining On Periphyton Assemblages And Thresholds For Periphyton Protection In Taizi River Basin

Taizi river basin is located in the middle of Liaoning province,is China's im-portant industrial and agricultural production base.The ecological environment prob-lem is prominent in Taizi River basin.This paper analyzes temporal variation charac-teristics of water body physical and chemical indicators and periphyton assemblages of Taizi River in 2009-2014,and assess stream health conditions and changing trend of Taizi River in 2009-2014.the paper mainly studies the impact of Talc Ore Mining on Periphyton Community Structure and Water environment in Taizi River,and and ecological threshold of primary water environmental factors were also explored for the periphyton community protection.The main results are as follows,?1?In order to understand temporal variation characteristics of water environ-mental factors and periphyton assemblages of Taizi River in 2009-2014,water envi-ronmental factors and periphyton assemblages are analyzed f in 2009-2014.The re-sults showed that periphyton assemblages structure of gradually changed,species rise to 238 by 175,periphyton assemblages species richness,Shannon diversity index in-creased significantly.Relative abundance of Chlorophyta,Cymbella,Oscillatoriales,diatoms with handle significant increased,and relative abundance of Nitzschia significant decreased in periphyton assemblages composition.Total phos-phorus,nitrate nitrogen,total nitrogen,total dissolve suspended particles and suspend-ed particles concentration decreased significantly,the dissolved oxygen concentration significantly increased.Canonical Correspondence Analysis showed that,in 2009,total nitrogen?TN?and ammonia nitrogen?NH₃-N?were the primary environmental factors affecting periphyton assemblage structure,whereas in 2014,electric conduc-tivity?EC?,TN and NH₃-N predominated?P<0.05?.?2?To understand the change trend of water ecological condition in Taizi River basin,using periphyton biological integrity index?P-IBI?to asess stream health con-ditions,the results show that ecological health condition in Taizi River existed spatial heterogeneity.Health condition from upstream to downstream tend to degenerate,the upstream and middle reaches of the water ecological health significantly better than that of the downstream river.Average score of P-IBI in Taizi River basin was47.01±2.28 in 2009,while P-IBI scored an average of 47.64±2.42 in 2014.Generally,the average score of P-IBI reached"Good"grade in 2009 and 2014.The basin water ecological health status of the overall increase slightly,but Tang River and Lan River,important tributaries of Taizi River which located in mining area,were not improved.In 2016,sampling and evaluate water ecosystem health condition of Tang River and Lan River,the results show that average score of P-IBI in Tang River was 26.66±0.02,belong to"general"rank.?3?In order to explore the impact of Talc ore mining on aquatic ecological en-vironment,the periphyton communities and water environment factors at 6 sites?Co-trol portion:TH01-TH02,Impacted portion:TH03-TH04,Recovering portion:TH05-TH06?,sampling from Tang River?important tributary of Tazi River?upstream respectively in November 2015,April 2016,July 2016,were investigated and analyzed.Mann-Whitney U test were used to compare differences of water environmental fac-tors and periphyton community structures in three portion.Using Spearman correla-tion analysis,canonical correspondence analysis and t value biplot analysis the rela-tionship of water environment factors and periphyton community structures.the re-sults showed that,Compared with environmental variables in control portion and re-covering portion,mass concentrations of magnesium?Mg?,selenium?Se?,arsenic?As?,iron?Fe?,molybdenum?Mo?,electric conductivity?EC?,bicarbonate ion?HCO₃^-?,ni-trate ion?NO₃^-?and power of hydrogen?pH?were the highest,and mass concentra-tions of Potassium?K?,sodium?Na?,strontium?Sr?,barium?Ba?,silicon dioxide?SiO₂?and dissolved oxygen?DO?were the lowest in impacted portion.For mass concentra-tions of Mg,Mo,As,EC and HCO₃^-,there were significant differences?P<0.05?among control portion,impacted portion and recovering portion.Compared with those in control portion and recovering portion,periphyton density,species richness,diatom siltation index and relative abundance of Achnanthes sp.was the highest,while percentage of handle diatom,relative abundance of Surirella sp.and relative abundance of Navicula sp.was lowest in impacted portion.Species richness of pe-riphyton were significant differences?P<0.05?among control portion,impacted por-tion and recovering portion.Mg,EC and HCO₃^-from Talc Ore Mining had significant affectes on periphyton assemblage structure.?4?Using Locally weighted scatterplot smoothing?LOWESS?and threshold Indicator Taxa Analysis?TITAN?to deduce ecological threshold of EC,TN and NH₃-N for the periphyton community protection.the results showed that when the concentration of EC control in 375-382.5?s/cm,86.67%of sensitive species can be protected.Indicator species for the concentration range had Cocconeis placentula,Nitzschia sinuata,Achnanthes hauckiana and Gomphonema intricatum;when the concentration of NH₃-N control in 0.22-0.31 mg/L,92.31%of sensitive species can be protected.Indicator species for the concentration range had Synedra rumpens,Cymbella ehrenbergii and Cosmarium obtusatum;when the concentration of TN con-trol in 0.94-1.00 mg/L,94.12%of sensitive species can be protected.Indicator spe-cies for the concentration range had Cocconeis placentula,Cymbella sinnata,Achnanthes hauckiana and Anomoeoneis sphaerophora.