中文摘要：

氮负荷较高的富营养湖泊中,着生藻大量增加,而牧食者数量却逐渐减少,进而导致沉水植物衰退或消亡;为了探究氮浓度过高对螺类生长的影响,本文基于受控实验,探讨了不同水体氮浓度（1 mg/L,4 mg/L,7 mg/L）培养下的着生藻碳氮计量特征对铜锈环棱螺（Bellamya aeruginosa）生长的影响效应。结果表明,4 mg/L处理组的着生藻和螺体内的碳和氮含量均高于1 mg/L和7 mg/L处理组,而碳氮比则低于这2个处理组;1 mg/L处理组的着生藻和螺体内的碳和氮含量最低,其碳氮比最高。着生藻氮含量与螺体内氮含量呈显著正相关关系（r=0.877,P〈0.001）。水体氮浓度为1 mg/L处理组的螺生长率和体长均高于4 mg/L和7 mg/L处理组,4 mg/L处理组的螺生长率和体长最低。研究结果显示,着生藻氮元素含量在一定范围内会随着水体氮浓度的增加而升高,着生藻氮含量与螺体内的氮含量变化一致,作为螺食物的着生藻氮含量增加时,螺体内氮含量也相应随之增加。环棱螺食物质量的下降与着生藻中化学元素含量的改变有关,这可能是螺生长受到抑制的重要原因。

英文摘要：

Snails are an important component of fresh water ecosystems and feed primarily on periphyton.Research has reported that the herbivore populations often decline in eutrophic lakes with high nitrogen levels,leading directly to increased periphyton biomass and indirectly to the degradation of submerged macrophytes.However,the effect of high nitrogen concentration on the growth of freshwater snails has not been well documented.Thus,we conducted a controlled experiment to better understand how the C∶N ratio of periphyton,cultured under different nitrogen concentrations,effects the growth of Bellamya aeruginosa.Periphyton for the experiment was cultured for one month in light incubators simulating natural conditions and Bellamya aeruginosa,collected from Meiliang Bay of Taihu Lake,were acclimated for one month in aquaria.At the beginning of the experiment,the concentrations of nitrogen and phosphorus were set to target concentrations by adding solutions of KNO_3 and KH_2PO_4.The initial concentrations of N were 1 mg/L,4 mg/L and 7 mg/L,with an initial P concentration of 0.1 mg in all treatments.Four glass slides with cultured peripyton and four snails were placed into each aquarium.After 35 days,the shell length and biomass of snails were measured and the carbon and nitrogen content of periphyton and snails determined.Results show that the content of both carbon and nitrogen in both periphyton and snails was highest at a nitrogen concentration of 4 mg/L and lowest at 1 mg/L and there was a significant positive correlation between periphyton nitrogen content and snail nitrogen content（r=0.877,P〈0.001）.The C∶N ratio of periphyton and snails was lowest at 4 mg/L and highest at 1 mg/L.The growth rate and snail length was highest at a nitrogen concentration of 1 mg/L and lowest at 4 mg/L.These findings indicate that the nutritional value of periphyton increased with nutrient levels up to a certain level and that the changes in the nitrogen content of snails closely followed changes in nitrogen content of periphyto