太湖两种水生植物群落对沉积物中氮素的影响

Influence of Two Different Species of Aquatic Plant Communities on the Concentration of Various Nitrogen Forms in Sediment of Lake Taihu

2012年6月对太湖贡湖湾、南部湖区以及东西山之间水域的两种水生植物——马来眼子菜（Potamogetonmalaianus）和荇菜（Limnanthemunnymphoides）群落内外的沉积物进行样品采集，调查了沉积物中的氮素分布现状．结果表明：①草藻过渡型湖区（贡湖湾）马来眼子菜群落内部0-25cm的沉积物中Org—N和TN的含量分别比群落外部高38．06％和25．65％．②草型湖区新生植物群落的形成可以促进沉积物（0—25cm）中各形态氮含量的降低，其中马来眼子菜群落内沉积物（0-25cm）中TN、Org—N、Nn4＋-N和NO3--N的含量较群落外平均降低了43．29％，50．78％，7．09％和10．86％；荇菜群落内部比外部分别降低了4．65％，4．63％，5．01％和2．76％，可以发现马来眼子菜群落的促进作用比荇菜群落明显．③植物群落的存在可以影响沉积物的理化性质．相关性分析显示，植物群落外沉积物的pH与TN显著正相关（P〈0．05，n=24），植物群落内部沉积物中pH与沉积物中NH4＋-N呈显著负相关（P〈0．05，n=24），与硝态氮呈显著正相关（P〈0．05，n=24）；植物群落内部和外部沉积物的Eh均与TN显著正相关（GMN，P〈0．01，R=0．9228＊＊;NMN，P〈0．01，R=0．8277＊＊；GMW，P〈0．05，R=0．74899；NMW，P〈0．05，R=0．6637＊），但较群落外部而言内部的相关性更强．

To investigate the spatial distribution of nitrogen in the sediment from both internal and external sites of Potamogeton malaianus and Limnanthemun nymphoides communities, levels of various forms of nitrogen were quantified in sediment samples collected from Gonghu Bay, the southern region and the intermediate area between East and West mountains of Lake Taihu in June 2012. The results showed that：① Within the algae-type region in Gonghu Bay, the contents of organic （Org-N） and total nitrogen （TN） in the internal sediment （0-25 cm） from P. malaianus communities were higher than those of the external sediment, by 38.06% and 25.65%, respectively. ②In the non-algal region, the contents of TN, Org-N, NH4＋-N and NO3--N in the internal sediments from P. malaianus communities were lower by 43.29% , 50.78% , 7.09% and 10.86% compared to those in the external sediments; for L. nymphoides communities, the contents of TN, Org-N, NH4＋ -N and NO3- -N in the external sediments were lower by 4.65% ,4.63% ,5.01% and 2.76% compared to the internal sediments. These values suggested that the promotion in reducing sedimentary nitrogen was more effective by the P. malaianus community than by the L. nymphoides community. ③ A significant positive correlation （P 〈 0. 05, n = 24） was found between pH and TN within the external sediments and between pH and NO3- -N within the internal sediments （ P 〈 0.05, n = 24）, while a significant negative correlation （ P 〈 0. 05, n= 24） was found between pH and NH4＋-N of both aquatic plant communities. The redox potential （Eh） was also found to be significantly positively correlated with TN in both the internal and external sediments of P. malaianus communities （GMN, P 〈0. 01, R =0. 922 8 ＊ ＊ ; NMN, P 〈0. 01, R =0.8277＊＊ ; GMW, P〈0.05, R=＊ ; NMW, P〈0.05, R=0.6637＊）. It is therefore concluded that the presence of aquatic plant communities could impact the physical and chemical properties of the sediments.