Analysis Of Plankton Community Structure In The Cascade Hydropower Stations On The Hongshui River

Hongshui River,an important tributary of Xijiang River of Pearl River system,originated from Machon Hill which is located in Zhanyi Country of Yunnan Province.Traversing Guangxi Province from west to east,it's of great significance in economic and social development of Guangxi.For a comprehensive understanding of aquatic organism status after the cascade hydropower stations having been developed,structure communities of plankton of seven reservoirs(upstream to downstream),which were Tianshengqiao-I,Pingban,Longtan,Yantan,Dahua,Letan,Qiaogong,were surveyed from June 1,2013 to August 6,2013.1.Structure of the phytoplankton communities(1)The phytoplankton of seven reservoirs in Hongshui River were detected into 164 species altogether,belonging to 7 phylums and 81 genuses,among which there were 4 Xanthophyta species,5 Cryptophyta species,6 Xanthophyta species,7 Euglenophyta species,41 Cyanophyta species,48 Chlorophyta species,53 Bacillariophyta species.The number of phytoplankton species of seven reservoirs displayed a decreasing trend spatially as follows:Letan,Qiaogong,Dahua,Pingban,Longtan,Yantan,Tianshengqiao-I.The phytoplankton species in the downstream was more abundant than in the upstream.Although there are differences existed,the dominant algae of seven reservoirs were Bacillariophyta,Chlorophyta and Cyanophyta species.(2)The average value of phytoplankton density was 10.57×104 ind./L.The value of Bacillariophyta density was the largest one,which was 4.02×104 ind./L on average,accounting for 38.07%of the total average density;The value of Cyanophyta density took the second place,which was 2.98×104 incd./L,accounting for 28.19%;The value of Chlorophyta density was 2.64×104 ind./L,accounting for 24,96%.The ratio of Pyrrophyta,Euglenophyta,Xanthophyta and Cryptophyta respectively were 5.14%,1.70%,1.15%and 0.80%.The value of phytoplankton density of seven reservoirs displayed a decreasing trend spatially as follows:Pingban,Qiaogong,Letan,Yantan,Dahua,Longtan.,Tianshengqiao-I.The average value of phytoplankton density of downstream was greater than upstream,which was larger than midstream.(3)The average value of phytoplankton biomass was 2332.54×10-4 mg/L.The value of Bacillariophyta biomass was the largest one,which was 1486.18×10-4 mg/L on average,accounting for 63.72%of the total average biomass;The value of Chlorophyta biomass took the second place,which was 324.85×10-4 mg/L,accounting for 13.93%;The proportion of Pyrrophyta,Euglenophyta,Cyanophyta,Xanthophyta and Cryptophyta was smaller,respectively accounting for 9.46%,7.24%,4.84%,0.47%and 0.35%.The value of phytoplankton biomass of seven reservoirs displayed a decreasing trend spatially as follows:Letan,Qiaogong,Dahua,Yantan,Pingban,Longtan,Tianshengqiao-I;it increased from upstream to downstream roughly.(4)The dominant species of phytoplankton in Hongshui River were as follows:Bacillariophyta granulate,Fragilaria crotonensis,Fragilaria capucina,Fragilaria pinnata in Bacillariophyta;Pediastrum simplex,Pediastrum simplex var.gracillimum,Spirogyra in Chlorophyta;Microc'ystis aeruginosa,Oscillatoria Formosa in Cyanophyta;Ceratium hirundinella in Pyrrophyta.The dominant species of phytoplankton in seven reservoirs was different.Microcystis aeruginosa was the main dominant species in Tianshengqiao-I reservoir;Ceratium hiundimella was the main dominant species in Pingban reservoir;Fragilaria crotonensis,Bacillariophyta granulate and Fragilaria capucina was the main dominant species in other reservoirs.(5)The average value of Margalef diversity index(d),Shannon-Weirner diversity index(H'),and Pielou diversity index(J)of plhytoplankton respectively were 4.47,2.21 and 0.49,whose water quality assessment all were light pollution.It means that the present water quality status of Hongshui River is light pollution.The assessment of these three indexes showed that the water quality of upstream was better than midstream and downstream;the midstream was polluted more seriously.2.Structure of the zooplankton communities(1)89 species of zooplankton in Hongshui River were detected,which belonged to 4 kinds and 46 genuses,among which there were 23 Protozoa species,36 Rotifera species,22 Cladocera species,8 Copepoda species.The proportion of Protozoa,Rotifera,Cladocera and Copepoda which accounted for the total species respectively were 25.84%,40.45%,24.72%,8.99%.The number of zooplankton species of seven reservoirs in Hongshui River displayed a decreasing trend spatially as follows:Qiaogong,Yantan,Pingban,Dahua,Letan,Longtan,Tianshengqiao-I.The zooplankton species increased from upstream to downstream roughly;the dominant algae of seven reservoirs were Cladocera and Rotifera.(2)The average value of zooplankton density was 376 ind./L.The value of Cladocera density was the largest one,which was 140 ind./L on average,accounting for 37.31%of the total average density;The value of Rotifera density took the second place,which was 103 ind./L,accounting for 27.48%;The value of Copepoda and Protozoa density was 80 ind./L and 53 ind./L,respectively account,ing for 21.25%and 13.97%.The value of zooplankton.density of seven reservoirs displayed a decreasing trend spatially as follows:Pingban,Qiaogong,Yantan,Dahua,Longtan,Letan,Tianshengqiao-I.The average value of zooplankton density of upstream was greater than downstream,which was larger than midstream.(3)The average value of zooplankton biomass was 2.939 mg/L.The value of Cladocera biomass was the largest one,which was 1.538 mg/L on average,accounting for 52.34%of the total average biomass;The value of Copepoda biomass took the second place,which was 1.104 mg/L,accounting for 37.57%;The proportion of Rotifera and Protozoa was smaller,respectively accounting for 9.39%and 0.70%.The value of zooplankton biomass of seven reservoirs displayed a decreasing trend spatially as follows:Pingban,Yantan,Longtan,Dahua,Tianshengqiao-I,Qiaogong,Letan;it increased from upstream to downstream of Hongshui River roughly.(4)The dominant species of zooplankton were as follows:Difflugia corona,Arcella vulgaris in Protozoa;Brachionus angularis,Brachionus budapestiensis,Brachionus calyciflorus,Keratella valga,Keratella cochlearis,Trichocerca bicristata in Rotifera;Bosmina longirostris,Simocephlaus vetulus,Diaphanosoma paueispinosum,Moina affinis in Cladocera;Mesocyclops leuckarti,Cyclops strenus in Copepoda.The main dominant species of seven reservoirs in Hongshui River all were Rotifera and Cladocera species.(5)The average value of H',d and J indexes of zooplankton respectively were 1.79,5.16 and 0.49.The water quality assessment of d and J were light pollution,while the water quality assessment of was moderate pollution.It showed that the water quality of upstream was better than midstream and downstream of Hongshui River roughly.