| With the discharging of a variety of nutrients, heavy metals and other pollutants into the Wetland of Poyang Lake continuously and the intensity of human disturbance enhanced, the aquatic ecosystem and submerged plant communities in Poyang Lake have been affected seriously. In this paper, we selected some typical lakeside wetland area in Poyang Lake included Nanjishan Wetland in Xinjian County,Wucheng Town in Yongxiu County,Baishazhou Wetland and Longkou Wetland in Poyang County, Zhouxi Wetland and Xiyuan Wetland in Duchang County and other area as the study area. We investigated the submerged plants and the communities,and also collected the water and sediments samples in Autumn of 2013 and Spring of 2014. We determined the contents of the nutrients included Total Nitrogen(TN),Total Phosphorus(TP), Chemical Oxygen Demand(COD), Organic Carbon(OC), and the heavy metals included copper, lead and cadmium in the water samples and sediments samples. On the basis of the investigated and determined data, we studied the species, distribution, communities and biodiversity of the submerged plants, we also evaluated the water eutrophication by using the evaluation standard of parameter methods of water body eutrophication and the TSIM regression model evaluation methods, and also evaluated the heavy metals pollution in sediments by using both the Geo-accumulation index methods and the potential ecological risk index methods; and analyzed the principal environmental factors in the water and sediment affecting the submerged plant communities by using Pearson Correlation Analysis methods and Detrended Canonical Correspondence Analysis(DCCA)methods. This research paper get the support and funding by the national natural science foundation of China(D41161035): "The community structure of submerged plant in Poyang Lake wetland and its typical factor of water environment quantitative research".The main results are as follows:(1) We found 15 submerged plant species in 9 families, 11 genera in the investigated area in the two different seasons, and we found 11 submerged plant species in 7 families, 9 genera in the investigated areas in the spring of 2014. Among the submerged plant species, Chara vulgaris is one kind of submerged algae, other submerged plants are aquatic vascular plants. Valliisneria spiralis and Hydrilla vertivilla were widely distributed in the study areas. Chara vulgaris and Najas marina were relatively rare distributed. We also found 12 submerged plant community types in the study areas, and V. spiralis communities and V. spiralis+H. vertivilla communities were more common distributed than other communities. We found V.spiralis was the dominant plant in different sampling sits, and we found somedifferences existed among the composition and dominant species in different sampling sites. The species diversity of submerged plants in Baisha Lake and Changhu Lake in Najishan Wetland were more than other sampling sites and the evenness of the species distribution were also more relatively higher than other sampling sites. On the contrary, the diversity of submerged plants in the wetland of Zhouxi Town and Xiyuan Town in Duchang County, Baishazhou Wetland in Poyang County were lower than that of other sampling sites. In the two different seasons, the composition and biodiversity of submerged plants in Najishan Wetland included Baisha Lake, Changhu Lake and Sanniwan Lake remained relatively stable; and the dominant plants in Nanjishan Wetland were V. spiralis, H.vertivilla and N. minor, but the submerged plant community types were different; the species diversity of Baishahu Lake and Changhu Lake changed slightly in two different seasons, and the biodiversity of the submerged reduced with the submerged species reduced and the uneven distribution of submerged plants in Sanniwan Lake in Nanjishan Wetland.(2) The order of the water quality in the different investigated sampling sites are as follows, the water quality in sampling sites of Baishazhou Wetland and Wucheng Wetland is better than that of Nanjishan Wetland, and better than that of Duchang Wetland sampling sites, and which is better than that of Longkou Wetland. The contents of Total Nitrogen(TN), Total Phosphorus(TP) and Chemical Oxygen Demand(COD) of the first 3 investigated sampling sites reached Ⅲ class water environment quality standard, and the water quality in the sampling sites of Longkou Wetland was the worst, the content of Total Nitrogen(TN) exceeded out the range of the fifth class water environment quality standard in some sampling sites of Longkou Wetland. The results of the two eutrophication assessment methods showed that the water body of the different sampling siteswere in eutrophic state. We analyzed comprehensively the contents of Total Nitrogen, Total Phosphorus and Organic Carbon(OC) in sediments, we found the contents of Nutrient salts in sediments in Sanniwan Lake and Changhu Lake of Nanjishan Wetland were higher than that of other sampling sites, and the contents of of Nutrient salts in sediments in the Wetland in Duchang County and Longkou Wetland in Poyang county was more lower than that of other sampling sites. The organic matter in sediments were mainly derived from the aquatic plants of different wetland sampling sites and the organic matters were the main resources of the nitrogen. The results showed that the water quality in Nanjishan Wetland could reach to the third class water environment quality standard basically in different two seasons; and the water body of Nanjishan Wetland was in middle eutrophic state in Autumn, and which was in rich eutrophic state in Spring. The contents of the nutrient substance in the water body of the two different seasons had significant differences, and the contents of nutrient substance in sediment had no significant difference in the two different seasons.(3) The contents of the three kinds of heavy metals in the water samples waslower than the surface water environmental quality standard of second class criterion except the contents of lead in the water of the sampling sites in Zhouxi Town of Duchang County. The order of the contents of the three kinds of heavy metals in the water samples was that the copper contents in water is more than that of lead in water,and which was more than that of cadmium in water. The contents of the three kinds of heavy metals in Longkou wetland were relatively more than those of other sampling sites, and which were the least in Baishazhou. The highest value of the contents of copper or cadmium in the water or sediments were found in the sampling sites of Longkou wetland in Poyang County, and the highest value of the contents of lead in the water or sediments were found in the sampling sites of Zhouxi wetland in Duchang County. There were significant differences in the contents of copper and lead, and there was no significant difference in the contents of cadmium in the water or sediments in the two different seasons in the sampling sites of Nanjishan Wetland.Both of the results of the Geo-accumulation Index methods and the Potential Ecological Risk Index methods indicated that the heavy metals pollution in the sediments of the sampling sites in Longkou Wetland was moderate polluted, and which was the most serious heavy metal-polluted area, and the other sampling sites were polluted under the moderate pollution. The results of Potential Ecological Risk Index methods showed that the heavy metals pollution in the sediments in the Wetland of Nanjishan was slight polluted in the different two seasons.(4) The results of the Pearson correlation analysis methods showed that showed that there were significant negative correlations among the fresh weight of submerged plants and the water environment factors included water transparency(SD), water level depth, Total Nitrogen contents(TN) and so on. And the Pearson correlation analysis result of showed highly significant negative correlation between the depth of water level and the species diversity, and there were significant correlations among the water environment factors included Total Nitrogen(TN), Total Phosphorus(TP),copper,lead and etc., and the sediment environment factors included Organic Carbon(OC) and Total Nitrogen(TN), and the species diversity of submerged plants. The results of the Detrended Canonical Correspondence Analysis methods of the submerged plants and environment factors, indicated that the first ordination axis mainly reflected the water transparency(SD) and the water level depth, while the second ordination axis reflected the the contents of copper. On the basis of the above analysis, we found that the main environmental factors which affected the submerged macrophytes communities were water transparency(SD) and water level depth in Poyang Lake in Spring of 2014, and the other environmental factors included the contents of Total Nitrogen(TN), Total Phosphorus(TP) and copper in the water were also the significant influenced environmental factors. There were no significant correlations among the diversity of the submerged aquatic plants and the environmental factors in the Autumn of 2013, and there were significant negativecorrelations among the diversity of the submerged aquatic plants and the water environmental factors included the water transparency(SD), water depth and etc. in the Spring of 2014.In conclusion, the water quality of the most sampling sites in the wetland of Poyang Lake could reach to the third class water environment quality standard. The heavy metals pollution in the sediments of the most sampling sites were slight pollution except Longkou wetland in Poyang County were the moderate pollution.The main environmental factors which affected the submerged plant communities were water transparency(SD) and water depth in Poyang Lake. The most of the submerged plant community distributed in the areas which are shallow and the water quality is well. On one hand, in some sampling sites such as Nanjishan Wetland, the water level was relatively shallower and the water quality were relatively better in the same time than that of other sampling sites, and the submerge plant species were more and the species diversity were richer than other sampling sites.On the other hand,where the water level were more deeper and the water quality were worse in other some sampling sites such as in Duchang county, the number of the submerged plant species and the species diversity index were both more less. The comparison results of the environmental factors of the water or sediments and the structure of the submerged plant communities in different seasons showed that the structure of submerged plant communities were relatively stable in Nanjishan Wetland; and the contents of the pollutants in the water changed greatly, while the contents of pollutants in the sediments were relatively stable; and the water quality in the spring of 2014 were worse than that of the autumn of 2013; the influence of the environmental factors on the submerged plant communities in the spring of 2014 were much stronger than that of the autumn of 2013. |
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