| Eighteen sampling sites along middle and lower reaches of Fenhe River were selected to investigate distribution of phytoplankton and the water quality. During June (wet season) and December (dry season) in 2012, specimens were collected, qualitative and quantitative investigation on the algae and monitoring on physicochemical indexes of the water were studied. Meanwhile, water quality of the middle and lower reaches of Fenhe River were analyzed and evaluated combining all the physicochemical indexes, cell density, dominant species and diversity indexes. Correlation analysis and CCA were conducted to discuss the relationship of algae community construction and the environmental factors, thus providing scientific basis for administer and protection of Fenhe River and other water tourism as well as theoretical basis for the health index and restoration evaluation of water system. The main results showed that:(1) There were 298 species of phytoplankton under the membership of 8 divisions,42 families and 96 genera. Among which Bacillariophyta was the dominant division, a total of 127 species of 27 genera, followed by Chlorophyta,104 species of 41 genera, and Cyanophyta,45 species of 20 genera. Only 22 species of 8 genera followed to Euglenophyta, Cryptophyta, Pyrrophyta, Chrysophyta and Xanthophyta. The number of species in wet season was higher than that of dry season at all sites. The cell density of Bacillariophyta, Chlorophyta and Cyanophyta is relatively high and the others is quite low among all the sampling sites in middle and lower reaches of Fenhe River. Overall the cell density in wet season is higher about 3.93×10/L and in dry season is lower about 2.99×10/L. Dominant species include Cyclotella meneghiniana, Synedra acus, Navicula cryptocephala, Nitzschia palea of Bacillariophyta, Chlorella vulgaris of Chlorophyta, Oscillatoria tennis, Phormidium tenue of Cyanophyta.(2) The water temperatures change largely with seasons in the middle and lower reaches of Fenhe River. The annual average temperature of this river is about 16.1℃ and the flow rate is totally slow, however the conductivity of all sites vary violently during different seasons. The pH is more than 7 at all sites, which seems alkaline. Chemical oxygen demand (COD) ranged from 0.048 mg/L to 2.584 mg/L, total phosphorus ranged from 0.009 mg/L to 4.59 mg/L, total hardness ranged from 2.240 meq/L to 6.410 meq/L, dissolved oxygen ranged from 3.40 mg/L to 12.50 mg/L, ammonia nitrogen ranged from 0.304 mg/L to 6.617 mg/L. The content of five kinds of heavy metals including zinc(Zn)、cadmium(Cd)、chromium(Cr)、 plumbum(Pb) and copper(Cu), are mostly higher at all sites.(3) The middle and lower reaches of Fenhe river was globally evaluated through the Physico-chemical and biological parameters. According to the physical and chemical indicators of COD, total phosphorus, ammonia nitrogen, dissolved oxygen and Cd, Cr, Zn, Pb and Cu, the water quality is respectively between Ⅰ to Ⅴ at all sites。Based on the cell density, the water quality is eutrophic. By the dominant species evaluation, the water quality showed a-ps to P-ps. Shannon-Wieaver species diversity index was between 1 and 3 basically. And Margalef species richness index ranged between 0.5 and 2. Besides, Pielou evenness index ranged between 0.3 and 0.8. In conclusion, the water is contaminated moderately to heavily in middle and lower reaches of Fenhe river.(4) Based on the correlation analysis of phytoplankton cell densities and the Physico-chemical parameters, the results show that cell densities and the physico-chemical parameters have different correlations, cell densities and conductivity, flow rate, total hardness, COD, dissolved oxygen, pH, Cd, Zn and Cu correlated positively in the wet season, cell densities and conductivity, total phosphorus, dissolved oxygen, Cd also have positive correlation in the dry season. The 18 sampling sites were divided into six groups by cluster analysis of physico-chemical parameters, the result shows that Zhaocheng town and Jishan country were severely polluted; the sampling sites were divided into three groups by DCA cluster of phytoplankton dominant species. The water quality of Zhaocheng town and Huojiabao village seem a-ps. Based on the analysis of CCA, during the wet season, most dominant species of Chlorophyta and Euglenophyta have higher correlation with COD, conductivity and ammonia nitrogen. The dominant species of Cyanophyta were influenced greatly by the contents of water temperature and Cr. The distribution of dominant species of Bacillariophyta complicately related with environmental factors. During the dry season, there were higher correlations between the member of Cyanophyta and ammonia nitrogen, total phosphorus, COD. The species of Chlorophyta and Euglenophyta were influenced mainly by the dissolved oxygen and total phosphorus. The bacillariophytes were related mainly with total phosphorus, dissolved oxygen, pH and Cd. |
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