Study On Macroinvertebrate Community Structure In Linan Section Upstream Of Tiaoxi River

The macroinvertebrate community structure in Linan section upstream of Tiaoxiriver was studied in April, July, October2010and January2011. Biodiversity indexand biotic index were used to evaluate the water quality there. SPSS18.0and CCAwere used to analyse the influence of environment factors on macroinvertebrate anddominant species respectively. Comparative study between quantitative (Surber netsample) and semiquantitative (D shaped net sample) sampling method was alsoconducted, the main results were as follows:1. A total of202species belonging to4phyla,60families and141genuses wereidentified in Linan section upstream of Tiaoxi river. Of which1family1genus and1species were Platyhelminthes;3families4genuses and6species were Annelida;3families6genuses and6species were Oligochaeta;8families9genuses and12species were Mollusca;44families120genuses and173species were Arthropod;1families1genus and4species were Shrimp. At family level, Trichoptera possessedthe highest taxa richness with11families, accounting for18%of total families; Atgenera level, Diptera were the most with45genuses, accounting for32%of totalgenuses; At species level, Diptera were the highest with80species, accounting for40%of total species.2. There were obviously horizontal and seasonal changes in the taxa richness anddensity of macroinvertebrate in Linan section upstream of Tiaoxi river. The orderfrom high to low of species level taxa richness of each sample site were as follows:Up Lifan reservoir (101)> Xiashu Bridge(64)> Xu Wu(60)> Tai huyuan Bridge(54)>Linglong industry district(49)>Under Lifan reservior(39＞San yan Bridge(37)=LanjinBridge(37)> Hu Kou(29). The annual mean macroinvertebrate density were1.46×104ind./m2and624.9ind./m2in Jinxi river and Tiaoxi river respectively. In Jinxi river,the highest density occurred in summer(3.6×104ind./m2) and followed by spring(1.25×104ind./m2) and winter(5.88×103ind./m2). the lowest was in autumn(4.06×103ind./m2). The same trends were showed in Tiaoxi river, the density in four seasonsaccordingly were1.07×103ind./m2,522ind./m2,453.6ind./m2and451ind./m2 respectively. The horizontal change of density in Jinxi river and Tiaoxi river were asfollows: In spring, Jinxi river showed: Lan Jin bridge>Xia yu bridge>San yanbridge>Xu Wu>Hu Kou>Lin long industry districy, while Tiaoxi river showed: up Liban reservior>under Li ban reservior>Tai Hu yuan bridge; In summer, Jinxi rivershowed: Lan Jin bridge>Xia yu bridge>Lin Long industry district>San yanbridge>Xu Wu, while Tiaoxi river showed: ai Hu yuan bridge>up Li ban reservior>under Li ban reservior; In autumn, Jinxi river showed: Lan Jin bridge＞Lin longindustry districy＞Hu Kou＞Xia yu bridge＞San yan bridge＞Xu Wu, while Tiaoxiriver showed: up Li ban reservior＞Tai Hu yuan bridge＞under Li ban reservoir; Inwinter, Jinxi river showed: Lan Jin bridge＞Hu Kou＞Lin long industry districy＞Xiayu bridge＞San yan bridge＞Xu Wu, while Tiaoxi river showed: up Li ban reservior＞Tai Hu yuan bridge＞under Li ban reservoir. The macroinertebrate density in Jinxiriver was mainly contributed by Oligochaeta and Diptera while Diptera and Ephemerawere the main contributor in Tiaoxi river.3. In order to discuss the scientificalness and practical applicability ofsemi-quantitative sampling method, the difference between quantitative andsemi-quantitative sampling method was analysed in terms of taxa richness, abundance,taxa similarity and otherness between biotic index. The result showed that: The taxarichness was higher in semi-quantitative sample than the quantitative sample. Therewas no significant difference between them. The density in semi-quantitative samplewas less than the quantitative sample. And showed significant difference(p<0.05)between them. From the taxa similarity, taxa smililarity were highest in autumn withan average of0.64. Then followed by winter with an average of0.63. The taxasmililarity in spring and summer were0.60and0.62respectively. The biotic indexbetween the two sampling methods showed no significant differences I n the same sitewhich indicated that assessed water quality using semi-quantitative sampling methodwas completely feasible.4. Water quality was analyed through several biotic index combined by the studyon population and species ecology and environmental factor data tested. The resultshowed that: The best water quality was in summer and followed by autumn andspring, the poorest was in winter. Up Lifan reservoir showed best water quality,followed by Xuwu and the poorest were Lanjin Bridge and Hukou. The water qualityin different sample site was as follows: Tiaoxi river: St1＞St2＞St3; Jinxi river: St9＞St5＞St8＞St7＞St4＞St6. The best water quality was in Up Lifan reservoir, and followed by Xuwu, Down Lifan reservoir, Xiayu Bridge, Taihuyuan Bridge, Linglongindustry district and Sanyan Bridge. The water quality in Lanjin and Hukou were thepoorest. The water quality in Linan section upstream of Tiaoxi river was in clean toheavily polluted condition.5. Environmental factors such as pH, DO, COD, and NH4+-N showed directlyinfluence on the macoinvertebrate community structure in Linan section upstream ofTiaoxi river. Other factors showed indirectly influence. The density of Oligochaetashowed significantly negative correlation with DO, significantly positive correlationwith COD and very significantly positive correlation with NH4+-N; The density ofDiptera showed significantly negative correlation with NH4+-N; The density ofShrimp showed significantly negative correlation with pH; The density of Molluscashowed significantly negative correlation with pH.6. Through the analysis of CCA, the result showed that Limnodrilus hoffmeisteri,ranchiura sowerbyi, Rhyacodrilus sinicus, Conchapelopia sp., Barbronia weberiwhich were all tolerant species were positively correlated with TN,TP,COD andNH4+-N, and negatively correlated with pH and tempreture. Radix swinhoei, Caenissinensis, Dicrotendipes nigrocephalicus were negative correlated with TN,TP,CODand NH4+-N, and positively correlated with temperature and pH.