Macrozoobenthos Community Structure And Water Quality Bioassessment In Miyun Reservoir And Its Upperstream Chaohe River And Baihe River,Beijing

In order to reveal the community structure of macrozoobenthos in Beijing Miyun Reservoir and its upperstream Chaohe River and Baihe River,we conducted an investigation on the community structure and water quality bioassessment in April,August,October,2015.The main results obtained were as follows:1.The macrozoobenthos community structure and water quality bioassessment in Miyun ReservoirA total of 15 species belonging to 10 genera,two families,two classes and two phyla were collected at eight stations,including 4 Tubificidae species and 11 Chironomidae larvae,of which Tubifex tubifex and Propsilocerus akamusi were the dominant species.The species number at various sites ranged from 2 to 11,the annual mean density was 1864±1996 ind./m2 and the annual mean biomass was 3.10±2.85g/m2,indicating that Miyun Reservoir was subordinated to mesotrophic type.The annual mean density in the Baihe reservoir area was higher than that in the Chaohe reservoir area,followed by the center area of Miyun reservoir.The annual mean biomass in the Baihe reservoir area was obviously higher than that in the Chaohe reservoir area and the reservoir center area.The density and biomass of tubificids were higher than those of chironomid larvae in deepwater area such as sites Kuxi and Baihe Dianzhan,whereas the density and biomass of chironomid larvae were higher than those of tubificids in shallow-water area.In different seasons,the sum density of macrozoobenthos in summer was higher than that in spring,followed by autumn,whereas the sum biomass in spring was higher than that in summer and in autumn.The density and biomass of tubificids showed significant positive linear correlation or power function correlation with water depth,and total organic carbon(TOC)percent and total nitrogen(TN)content in sediments,respectively,but they had no significant correlation with total phosphorus(TP)content in sediments.On the other hand,there were no significant correlations between the density and biomass of chironomid larvae and the above four environmental variables.The Shannon-Wiener index,Margalef index,Goodnight index and Pielou index of macrozoobenthos had highervalues in shallow-water area than in deepwater area.The Pielou index and Wright index showed that the water may be lightly polluted in Miyun Reservoir,which was relatively consistent with the result of hydrochemical evaluation,indicating that these two indexes may be used as an important inference for water quality bioassessment.2.The macrozoobenthos community structure and water quality bioassessment in the upperstream Chaohe River and Baihe RiverWe identified 56 macrozoobenthos species belonging to three families,five classes at eight sites in these two upstream rivers of Miyun Reservoir,Beijing.A total of 33 macrozoobenthos species were collected at four sites in the Chaohe River.The average annual density and biomass of macrozoobenthoswere 358 ind./m2 and 21.59 g/m2.In general,the macrozoobenthic density and biomass of the midstream sampling sites were higher than those of the downstream sites,followed by the upstream sites.The density of macrozoobenthos was highest in August(553ind./m2),followed by April(303 ind./m2)and October(218 ind./m2),while the biomass of macrozoobenthos was highest in August(31.29 g/m2),followed by October(21.56 g/m2)and April(11.92 g/m2).A total of 42 macrozoobenthos species were collected at four sites in the Baihe River.The average annual density and biomass of macrozoobenthos were 269 ind./m2 and 9.61 g/m2,their density and biomasss of the upstream sites were higher than those of the midstream sites,followed by the downstream sites.The density of macrozoobenthos was highest in August(446 ind./m2),followed by April(228ind./m2)and October(122 ind./m2),while the biomass of macrozoobenthos was highest in August(17.34 g/m2),followed by April(5.51 g/m2)and October(4.97g/m2).The macrozoobenthos species in the Chaohe River and Baihe River were primarily composed of aquatic insects,of which an indicator species of clean water(Ephemera sp.)was dominant and widely distributed.The values of Shannon-Wiener index,Margalef index and Pielou index between these two rivers were close,and theyindicated that the water quality of the Chaohe River and Baihe River were both in slight-moderate pollution(?-?).