太湖水体溶解性氨基酸的空间分布特征

Abstract

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 and farmland. DAAs concentrations in Taihu ranged from 0. 27 to 3. 95 μmol / L,with a mean value of 1.38 μmol / L. The large regional differences in concentrations and yields of DAAs suggested 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 macrophytedominated DOM degradation experiments.