太湖水体溶解性氨基酸的空间分布特征

Spatial distribution of dissloved amino acids in Lake Taihu,China

为探索氨基酸(DAAs)组分特征对生物可利用性溶解有机质(DOM)的示踪及定量表征可能性,对太湖3个湖区(北太湖:藻型湖区,东太湖:草型湖区,南太湖:农业污染湖区)水体DAAs浓度、组分特征及其空间变化进行了调查研究,并对控制其量、质空间分布的因素加以讨论。结果表明夏季太湖水体DAAs的浓度范围为0.27—3.95μmol/L,平均值为(1.38±1.17)μmol/L,与湖泊、海洋中研究中报道结果相近。北太湖、南太湖、东太湖3个湖区的DAAs浓度平均值分别为(2.59±0.71)μmol/L,(0.48±0.14)μmol/L,(0.48±0.16)μmol/L,北太湖DAAs浓度及对有机碳氮的贡献都明显高于其他湖区,DAAs组分中以苯丙氨酸和赖氨酸为主,而在南太湖和东太湖,赖氨酸都是最主要的DAAs组分。表明水体的DAAs组分特征能对湖泊营养状态及生态类型的变化做出响应,可以作为指示湖泊营养状态的生物标记物。DAAs也可以作为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。根据氨基酸对有机碳的贡献估算出北太湖的活性溶解性有机碳相对含量为(17.65±17.84)%,显著高于南太湖和东太湖。但由于太湖高度的空间异质性,还需要在今后的研究工作中进行相关的室内实验,建立适用于太湖的经验公式。

Amino acids （AAs） are important bio-available components of organic matter （OM） and are the major forms of organic nitrogen （ON） in aquatic ecosystem. They also represent significant fractions of OM in recent coastal marine sediments, water column particles and dissolved organic matters. They are typically labile composed relative to bulk OM and ON, and account for a considerable portion of the particulate OC and ON recycled in both water column and sediments, and therefore are an important nutrient form. Owing to the different AAs monomers have different biogeochemical stability, AAs are often used as an indicator of organic matter sources and as an index of OM degradation potential. Changes in amino acid composition exhibit consistent trends and demonstrate the degradation of cellular organic matter as it sinks through water column and is incorporated into sediments. Due to the labile character of AAs, the percentage of OC and N represented by amino acid （AA-C/OC% and AA-N/ON% ） and the percentage of total amino acids have proven to be useful degradation indicators. They are sensitive at different stages of OM alteration and appear uncompromised by source variation. Dissolved amino acids （DAAs） characteristics were investigated in water of Lake Taihu, a large, shallow and eutrophic freshwater lake in China. The northern lake is characterized by phytoplankton dominance, high water turbidity, and severe Microcystis spp. algal blooms. In contrast, eastern lake is characterized by submersed vegetation, clear water, and diverse communities of fishes and invertebrates. The main upstream land use types of south Taihu were classified by the mountain forests andfarmland. DAAs concentrations in Taihu ranged from 0.27 to 3.95 regional differences in concentrations and yields of DAAs suggested Ixmol/L, with a mean value of 1.38 μmol/L. The large that DOM produced in situ is an important source of bio- reactive of organic matter in waters of Taihu. The spatial distributions of DAAs concentrations in Taihu were less variable than those previously reported from other aquatic environments. DAAs concentrations of north Taihu were significantly higher than south lake and east lake, with mean values of （2.59±0.71） μmol/L in north Taihu, （0.48±0. 14） μmol/L in south Taihu, and （0.48±0.16）μmol/L in east Taihu, respectively （P〈0.001）. Based on the relationship between amino acid yields and percent labile DOC, （17.65±17.84）% of fresh DOC in north lake is labile, which is higher than in south lake or east lake. The results showed internal sources mainly from the decomposing of phytoplankton should be the main source of DAAs in Taihu, and DAAs was important fraction of DOM. DAAs compositions were dominated by Phenylalanine （PHE） and lysine （LYS） in north lake, while only LYS in south and east lake. Compositions and concentrations of DAAs can be possible used as an indicator, which could provide useful information about the nutritional Status and bio-available DOM in Lake Taihu. But because of high spatial heterogeneity in Taihu, we need to establish DAAs-liable DOC linear model for Lake Taihu, by the means of the algal-dominated and macrophyte-dominated DOM degradation experiments.