| The construction of dam could cause some changes in the aquatic ecosystem,such as water depth,velocity,sediment deposition,river bed character and other characteristics of aquatic ecosystems,and these changes will lead some serious influences to the river aquatic ecosystems.Benthic macroinvertebrates,one of important biological groups in the river aquatic organisms,are an important part of the river aquatic ecosystem.The Three Gorges Reservoir has been running about ten years,however,there are no systematic reports about the benthic macroinvertebrates resources in the tributaries of the reservoir area at present.In order to explore the present situation of benthic macroinvertebrates resources in the reservoir area tributaries and make it clear how the impact of the Three Gorges Reservoir on benthic macroinvertebrates in tributaries,we investigated the benthic macroinvertebrates in 20 tributaries of the Yangtze River in the Three Gorges Reservoir Area in July 2015,January 2016 and April 2016.The main findings are as following:(1)A total of 11,812 benthic macroinvertebrates individuals were collected in the20 tributaries in rainy season,dry season and normal season,they are belonging to 246species(genus).The number of insect species is largest and follow is Molluscs,Crustaceans and Oligochaeta ranked third and fourth respectively,other species are mainly composed by Nematomorpha,Hirudinea and Turbellaria,with the least number of species.In rainy season(July 2015 when Three Gorges Reservoir operated at the altitude 145 meters water level),dry season(January 2016 when Three Gorges Reservoir operated at the altitude 175 meters water level)and normal season(April2016)are the same results with the annual results respectively.(2)The average density and average biomass of benthic macroinvertebrates in our collected seasons were 78.50ind/m~2 and 17.1528g/m~2 respectively.In the rainy season,the average density(82.57 ind/m~2)and average biomass(28.5491 g/m~2)of benthic macroinvertebrates were highest.In the dry season,the average density(74.84 ind/m~2)and average biomass(6.9559 g/m~2)of benthic macroinvertebrates were lowest.The average density and average biomass were 78.10 ind/m~2 and 16.0268 g/m~2 in the normal season,which is medium in the three seasons.(3)There were 116 benthic macroinvertebrates species(genera)in the tributaries totally which were from Jiangjin to Fulin segment.In the rainy season,there were 43species(genus);in the dry season,there were 72 species(genus);and in the normal season,there were 58 species(genus).198 species(genera)were collected in the tributaries which located from Fulin to the Dam segment.In sampling three season,there were 103 species(genus),106 species(genus)and 125 species(genus)respectively.The number of benthic macroinvertebrates species in Fulin-Dam segment tributaries was significantly higher than that in Jiangjin-Fulin segment tributaries,the significant value were P=0.007 in rainy season,P=0.049 in dry season and P=0.021 in the normal season.(4)There was no significant difference in the average density of benthic macroinvertebrates in Jiangjin to Fulin segment tributaries and Fulin to Dam segment tributaries in three sampling seasons(rainy season P=0.966,dry season P=0.700,normal season P=0.790);However,the average biomass of benthic macroinvertebrates in Jiangjin to Fulin segment tributaries were significantly higher than that in Fulin to Dam segment tributaries in the rain season and normal season(rainy season P=0.041,normal season P=0.031),in the dry season,there were no significantly differences in the average biomass of benthic macroinvertebrates between Jiangjin to Fulin segment tributaries and Fulin to Dam segment tributaries(P=0.356).(5)The Shannon-Wiener index and Margalef index of benthic macroinvertebrates in Jiangjin to Fulin segment tributaries were significantly lower than those in Fulin-Dam segment tributaries in the three seasons(P<0.05).(6)In tributaries from Jiangjin to Fulin,the average number of benthic macroinvertebrates species in the reservoir river reaches were significantly lower than that in the natural river reaches(P=0.033)in rainy season,but there were no significant differences in dry season and normal season.(7)The density,biomass and every diversity indexes of benthic macroinvertebrates were no significantly difference between reservoir river reaches and natural river reaches in Jiangjin to Fulin segment tributaries in the three seasons.(8)In Fulin to Dam segment tributaries,the average number of benthic macroinvertebrates species in the reservoir river reaches was significantly lower than that in the natural river reaches(P<0.001)in the three seasons.(9)In Fulin to Dam segment tributaries,the average density of benthic macroinvertebrates in the reservoir river reaches was significantly lower than that in the natural river reaches in the three sampling seasons(P<0.001);The average biomass of benthic macroinvertebrates in the reservoir river reaches were extremely significantly lower than that in the natural river reaches in rainy season(P=0.003),however,there were no significantly difference in dry season and normal season.(10)In Fulin to Dam segment tributaries,the Shannon-Wiener index,Margalef richness index and Simpson dominance index of benthic macroinvertebrates in the reservoir river reaches were all significantly lower than those in the natural river reaches(P<0.01)in the three sampling seasons;The Pielou evenness index of benthic macroinvertebrates were no significant difference between the reservoir river reaches and the natural river reaches in the three seasons.In summary,the construction of Three Gorges Reservoir had caused influences on benthic macroinvertebrates in the reservoir river reaches,while,the benthic macroinvertebrates in Jiangjin to Fulin segment tributaries were less affected by the impoundment of Three Gorges Reservoir.The benthic macroinvertebrates in the tributaries from Fulin to Dam segment were greatly affected by the impoundment of Three Gorges Reservoir. |
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