| This study focused on phytoplankton characteristics and eutrophication status of the large and medium-sized lakes in Jiangxi Province in October 2013 and July 2014.These lakes included Poyang lake, Junshan lake, Zhu lake, Chi lake, Sai lake, Qili lake, Taipo lake, Nanbei lake, Xinmiao lake and Chenjia lake. The main results are as follows.1. A total of 220 species of phytoplankton from 107 genera in 8 phyla were observed in October 2013 and July 2014. Among them, there were 57 species in Cyanophyta, 122 species in Chlorophyta, 27 species in Bacillariophyta, 4 species in Euglenophyta, 2 species in Chrysophyta, 4 species in Dinophyta, 2 species in Xanthophyta, 1 species in Cryptophyta. 79 species of phytoplankton were observed in Chenjia lake, 94 species were observed in Chi lake, 122 species in Junshan lake, 84 species in Nanbei lake, 142 species in Poyang lake, 88 species in Qili lake, 101 species in Sai lake, 92 species in Taipo lake, 55 species in Xinmiao lake, 99 species in Zhu lake.2. The average abundance and biomass of phytoplankton were 1.03×108 cells/L,7.656 mg/L in Chenjia lake. 1.59×107 cells/L, 2.134 mg/L in Chi lake. 1.67×107cells/L, 2.348 mg/L in Junshan lake, 9.7×107 cells/L, 9.545 mg/L in Nanbei lake,1.13×106 cells/L, 0.477 mg/L in Poyang lake, 7.87×107 cells/L, 8.770 mg/L in Qili lake, 5.69×107 cells/L, 6.871 mg/L in Sai lake, 2.31×108 cells/L, 8.436 mg/L in Taipo lake, 7.79×107 cells/L, 5.820 mg/L in Xinmiao lake, 1.75×107 cells/L, 1.334 mg/L in Zhu lake.3. The dominant species were mainly from Bacillariophyta and Chlorophyta in October 2013, and from Cyanophyta and Chlorophyta in July 2014. Pielou’s index was ranged from 0.38 to 0.74 and from 0.34 to 0.74 in October 2013 and July 2014,respectively. Shannon wiener index was ranged from 1.2 to 2.8 and from 1.22 to 2.56 in October 2013 and July 2014, respectively.4. The proportions of water-bloom cyanobacteria abundance were from 37% to94% in October 2013 and from 25% to 95% in July 2014, respectively. The proportion of water-bloom cyanobacteria biomass were from 3% to 45% and from18% to 61%, respectively. The proportions of water-bloom cyanobacteria abundance were lower than those of biomass. The proportions of water-bloom cyanobacteria biomass in October 2013 was significantly higher than those in July 2014, indicating that the risk of cyanobacteria blooms in October 2013 was higher than that in July2014.5. Water transparence as represented in SD were from 0.13 m to 1.66 m in October 2013 and from 0.29 m to 1.6m in July 2014. The concentrations of total nitrogen were from 0.212 mg/L to 1.27 mg/L and from 0.670 mg/l to 3.928 mg/L. The concentrations of total phosphorus were from 0.05 mg/L to 0.42 mg/L and 0.02 mg/L to 0.14 mg/L. COD were from 2.863 mg/L to 8.514 mg/L and from 2.193 mg/L to23.206 mg/L. The concentrations of Chlorophyll a were from 4.35 μg/L to 100.02μg/L and from 7.75 μg/L to 105.25 μg/L.6. The status of eutrophication of large and medium-sized lakes in October 2013 was higher than in July 2014. Half of the lakes were eutrophic in October 2013, and nighty percent of lakes were eutrophic in July 2014. Chi lake was mesotrophic both in October 2013 and July 2014. Zhu lake was mesotrophic and lightly eutrophic,respectively. Junshan lake was mesotrophic and lightly eutrophic, respectively. Sai lake was meso-eutrophic and lightly eutrophic. Poyang lake was mesotrophic and meso-eutrophic. Taipo lake was lightly eutrophic and meso-eutrophic. Chenjia lake was both meso-eutrophic. Xinmiao lake was mesotrophic and meso-eutrophic. Qili lake was lightly eutrophic and meso-eutrophic. Nanbei lake was all meso-eutrophic.7. The abundance and biomss of cyanobacteria were significantly correlated with COD and p H in October 2013. The biomass of cyanobacteria was significantly correlated with SD and Total nitrogen in July 2014. This could be explained by the fact that higher concentration of total nitrogen can promote the growth of cyanobacteria. |
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