铜绿微囊藻培养过程中氨基酸的释放特征及其对水体有机质的贡献

为深入分析铜绿微囊藻水华暴发对水体有机质、氨基酸含量及组成的影响,进一步揭示蓝藻水华暴发对湖泊内源氨基酸和有机质的贡献及养分循环机制,采集太湖北部富营养化区域梅梁湾中的水样,用于在室内培养太湖蓝藻水华优势种——铜绿微囊藻(Microcystis aeruginosa),采用邻苯二甲醛(OPA)柱前衍生-反相高效液相色谱法(HPLC)分析铜绿微囊藻生长、衰亡过程中氨基酸的摩尔浓度及其组成特征的变化,探讨藻类产生的氨基酸和有机质对湖泊水体中有机质、TC(总碳)及DTN(溶解性总氮)的贡献. 结果表明:铜绿微囊藻在生长过程中产生的氨基酸对水体中TC、DTN、TOC(总有机碳)的贡献率分别为23%~37%、46%~93%和46%~83%；在衰亡期,水体中难降解氨基酸(如甘氨酸、丝氨酸、丙氨酸和赖氨酸)的摩尔浓度(c)为60.4 μmol/L,显著高于同时期易降解氨基酸(如酪氨酸、苯丙氨酸、谷氨酸和精氨酸)的摩尔浓度(40.9 μmol/L)；c(D-氨基酸)/c(L-氨基酸)由初始的0.28降至0.09,表明在铜绿微囊藻对数生长至衰亡期间,水体中有机质的降解程度逐渐降低. 研究显示,在水体有机质降解程度降低的同时,氨基酸摩尔浓度逐步增加,因此大量未降解的氨基酸沉积下来成为水体有机质来源之一. 

Release of Amino Acids from Microcystis aeruginosa and Its Contributions to Organic Matter

In order to understand the influence of the blooming of Microcystis aeruginosa on the contents and sources of organic matter (OM), amino acids in the overlying water samples were collected from the eutrophic Meiliang Bay in the northern part of Lake Taihu. The growth process of M. aeruginosa in the water samples was simulated in the laboratory. The influences of the release of amino acids from M. aeruginosa on nutrients, amino acid and OM of the water were analyzed. The contents of fifteen amino acids including D-and L-of amino acid were determined by the pre-column derivatization with o-phthaldialdehyde (OPA) combined with HPLC. The contributions of amino acids and OM produced by M. aeruginosa to the organic matter, total carbon (TC), and dissolved total nitrogen (DTN) were investigated. The results showed that the contributions of M. aeruginosa-derived amino acid to TC, DTN and TOC in the overlying water were 23%-37%, 46%-93% and 46%-83% respectively. The concentration of the refractory amino acids (i.e., glycine, serine, alanine and lysine) was 60.4 μmol/L, which was much higher than the concentration (40.9 μmol/L) of degradable amino acids (i.e., tyrosine, phenylalanine, glutamic acid and arginine). The ratio of D-AA to L-AA decreased from 0.28 to 0.09, which indicated that the degradation degree of organic matter decreased during the period from logarithmic growth phase to decline phase. The results showed that the contents of amino acids increased as the degradation degree of the organic matter decreased. Therefore, large amounts of undegraded amino acids are an important source of organic matter in the overlying water. These results are fundamental to understanding the contributions of algae blooming to endogenous OM and nutrients, which is useful for understanding the cycling of nutrients in lakes.