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| Effects of Freshwater Mussels Hyriopsis cumingii on Plankton Community Structure in an Intensive Grass Carp Ctenopharyngodon idellus Pond |
| ZHENG Zonglin ,ZHENG Shuming,WANG Guangjun,ZHAO Zheng |
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Abstract Twenty thousand 1 year old freshwater mussel H yriopsis cumingii was stocked into 2 grass carp Ctenopharyngodon idellus (with body weight of 50 g) ponds of each 0 .8 hm2 and water depth of 1 .8 m at stocking density of 12 000 per pond polycultured with silver carp Hypophthalmichthys molitrix with body weight of 24—100 g at stocking density of 500 individuals per pond and bighead carp A ristichthys no-bilis with body weight of 150 g at stocking density of 100 individuals per pond ,2 same size and stocking ponds without freshwater mussel as control ponds .The species and biomass of phytoplankton were deter-mined in the ponds in a 24 day interval to look insight on effects of freshwater mussel on phytoplankton community structure .The results showed that there were the phytoplankton of 94 species ,48 genera ,6 phyla in the fish-mussel polyculture ponds ,while 91 species ,42 genera ,6 phyla were observed in the con-trol ponds ,with the dominant species accounting for 47 .8% in the fish-mussel polyculture ponds ,and 41.8% in the control ponds ,with Cyclotella and Synedra in Bacillariophyta ,besides Chlorella ,Scenedes-mus and Closterium in Chlorophyta .The Shannon-Wiener diversity index of phytoplankton was found from 1.24 to 1 .41 in the fish mussel polyculture ponds and from 1 .26 to 1 .36 in the control ponds .The density of the phytoplankton were varied from 539 .23 × 104ind/L to 1289 .53 × 104ind/L in the fish-mussel polycul-ture ponds and from 669 .57 × 104 ind/L to 1608 .50 × 104 ind/L in the control ponds ,with the biomass of 6 .68—12 .47 mg/L in the fish-mussel polyculture ponds and 8 .40—18 .62 mg/L in the control ponds .The growth and reproduction of phytoplankton was to some extent restrained in the fish mussel plyculture ponds ,indicating that fish- mussel polyculture can change phytoplankton community structure ,and en-hance the ability to automatically adjust the water ,and more conducive to aquaculture .
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Received: 25 December 2015
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