Fenshuijiang Reservoir And Xin’anjiang Reservoir Ecological Studies Of Macroinvertebrate

Macroinvertebrate was monthly sampled at7stations of the FenshuijiangReservoir from Nov.2008to Oct.2009. Totally,37taxa were collected,most of which belonged to oligocheata and Chironomidae. Limnodrilushoffmeisteri was dominant in the communities of macrozoobenthos inspring, summer and autumn, and Chironomus gr. plumosus prevailing inwinter. Limnodrilus hoffmeisteri and Branchiura sowerbyi communities inspring, summer and autumn, Chironomus group plumosus communities inwinter.Analysis of functional feeding group showed that collector-gathererswere the predominant group in term of abundance, biomass and speciesnumber. Annual mean density and biomass were (488.0±48.8) ind·m-2and(1.86±0.49) g·m-2. Two-way ANOVA revealed that there were nosignificant differences in density among stations, and in biomass amongstations and between seasons; however, density conspicuously seasonallydiffered with the maximum in spring and the minimum in autumn. Theresults of bioassessment of water quality by Shannon diversity, Pielou evenness, Goodnight-Whitley, Wright, and Carlander’s biomass indexshowed that Goodnight-Whitley and Shannon diversity indices were notsuitable for water quality assessment of Fenshuijiang Reservoir, and theother indices indicated that this reservoir was slightly polluted.A profundal community of macrozoobenthos in Xin’anjiang Reservoir, adeep reservoir in Zhejiang Province, China, was investigated from2007to2009. Totally,24taxa from5classes were recorded. Oligochaetapredominated in the macrozoobenthic community in terms of importantvalue (IV), density, and standing crop, among which Limnodrilushoffmeisteri was prevailing. The annual average density and biomass were793.8±92.1ind. m-2and2.25±0.32g m-2, respectively. There were noclear differences in density and biomass between seasons, but significanthorizontal differences revealed a maximum in the upper reaches andminimum at the lower reaches. Both density and biomass negativelycorrelated with water depth and Secchi depth (SD); density positivelycorrelated with total nitrogen (TN) and total phosphorus (TP) of mixedwater samples from the water column (MWSWC) and with TP of localwater samples at the bottom (LWSB). Biomass positively correlated withTP of MWSWC. Only water depth (from eight physical and chemicalvariables) was selected by a stepwise regression model to explain thevariation in density and biomass of macrozoobenthos in2007to2008. Bathymetrically, both density and biomass increased with water depth,peaked just below the thermocline, and then decreased gradually. Thisnumerical bathymetric change in Xin’anjiang Reservoir conformed to thepatterns of vertical distribution of zoobenthos in oligo-and mesotrophiclakes. The relationship of density and biomass with the main environmentalvariables, the bathymetric distribution pattern of macrozoobenthos, and thetwo biological indices (Wright index and Carlander’s biotic index) alltypified Xin’anjiang Reservoir as oligo-and mesotrophic, with the upperreaches mesotrophic or moderately polluted and the middle and lowerreaches oligotrophic or slightly polluted. Three other biological indices(King, Goodnight–Whitley, and Shannon–Weaver) were unsuitable toassess water quality.