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The increasing eutrophication of Lake Poyang,the largest freshwater Chinese lake, has taken more and more attention in recent years, but the eutrophication of shallow lakes around Lake Poyang are known rather little. An annual limnological investiga⁃ tion was conducted in the year of 2014 2015 in 3 typical shallow lakes, adjacent to the southwest bank of Lake Poyang at the sub⁃ urb of Nanchang City, Jiangxi Province. Parameters of the water quality and eutrophic level in the three lakes were time⁃serially monitored to deeply understand the seasonally dynamics and the driving mechanism. Results showed that the variation of CODMn in Lake Qingshan, Lake Yaohu and Lake Junshan ranged from 2.6-4.5 mg / L, 2.1-4.6 mg / L and 1.6-1.9 mg / L, respectively. Only Lake Junshan was still not affected by the organic pollution, and significant differences were found between each other among the three lakes. The contents of total nitrogen (TN) and total phosphorus (TP) in the water column of Lake Qingshan and Lake Yaohu largely exceeded the thresholds for eutrophic regime shifts (TN: 0.20 mg / L, TP: 0.02 mg / L),while the concentration of TP was only in Class IV-below V. The main form of nitrogen in the three lakes was soluble, and the main form of phosphorus in these lake were all particulate, except Lake Junshan. The contents of Chl.a in Lake Qingshan, Lake Yaohu and Lake Junshan were 34.65184.48 μg / L, 7.66-120.67 μg / L and 2.42-17.41 μg / L, respectively, and the contents were all lowest in winter. Lake Junshan⁃ was significantly different from both Lake Qingshan or Lake Yaohu in the Chl.a contents, but no significant difference in the Chl.a contents between Lake Qingshan and Lake Yaohu. The trophic states of the three lakes has been assessed with a synthesized trophic state index (TLI).Its found that Lake Qingshan was in the highest eutrophic level( from mild to moderate eutrophication), followed by Lake Yaohu(from mesotrophication to moderate eutrophication) and Lake Junshan (from oligotrophication to mesotrophication) during the studying period. Water temperature was found as one of the important environmental factors affecting the seasonal trophic fluatuation of these lakes. The significant positive relationships were calculated between Chl.a and TN or TP in water column of all lakes through Pearson correlation analysis, while Chl.a was tightly positively correlated with TDN and TDP only in Lake Qingshan and Lake Yaohu. Overall, nitrogen was one of the dominant factors affecting the environmental characteristics in these lakes, and phosphorus was the predominant factor affecting two eutrophic lakes. In the process of nutrient control, effective reduction of the ni⁃ trogen input should be considered in the eutrophic lakes while lowering the phosphorus discharge, especially, during the period of middle water temperature (15-25°C), and systematical regulation should be conducted in the mesotrophic lake ( e.g. Lake Yao⁃ hu) through the combination of N reduction and P sources control, in particular, during the period of high water temperature at more than 25°C .It would provide a new way to protect and manage water environment of these shallow lakes around Lake Poyang.

Comparative limnological study on annual dynamic pattern of nutrients in water column of three suburb lakes adjacent to Lake Poyang