太湖北部水体溶解性氨基酸分布特征及其环境意义

为探讨溶解性氨基酸(DAAs)在太湖水体中作为指示有机质来源及降解特征生物标记物的可能性,对太湖北部不同水域2种分子量级(胶体态:1kDa~0.5mm;真溶解态:<1kDa)的DAAs的空间分布、分子量分布、组成变化及对DOM的相对贡献等方面进行了调查研究.结果表明,太湖水体DAAs大多数以真溶解态存在,平均占DAAs的90%.不同湖区DAAs的含量及分子量组成不同,梅梁湾污染河口区、中心区、湾口区及太湖湖心区DAAs的含量分别为14.5, 34.7, 59.8, 24.0nmol/L,其中真溶解态的比例分别为94%, 88%, 89%及90%. DAAs的空间分布说明太湖的浮游生物内源是太湖DAAs的主要来源.组氨酸、精氨酸、赖氨酸、丝氨酸、酪氨酸是现存的主要氨基酸.氨基酸的成分变化能反映有机质从高分子量向低分子量转变的降解趋势,可作为指示溶解性有机质(DOM)降解的生物标记物.氨基酸碳(AA-C)与溶解性有机碳(DOC)的比值可以作为DOM生物降解性的评价参数,反映湖泊水体中与生物活性相关的DOM动态变化.

Distribution of dissolved amino acids and its environmental significance in water of Taihu Lake, China

The concentrations and molecular weight of dissolved amino acids (DAAs) were investigated in water of Taihu, a large, shallow and eutrophic freshwater lake in China. DAAs were mainly existed as “true dissolved” form in the lake water, which colloidal form average occupied 10% of DAAs. Concentration of DAAs showed a significant spatial heterogeneity, which was lowest in river mouth and was highest in the mouth of Meiliang Bay, a hypereutrophic bay of Taihu and serious Microcystis algal bloom happened each summer. Generally, histidine, arginine, lysine, serine and tryptophan were the main forms of DAAs in the water of Taihu. Internal sources mainly from the decomposing of plankton should be the main source of DAAs in Taihu. The composition of DAAs was also possible used as an indicator of biological degradation state of the organic matter in the lake.