基于菌藻对比培养方法的洱海沉积物溶解性有机氮生物有效性评价

Bioavailability of Dissolved Organic Nitrogen in Sediment from Erhai Lake: A Comparative Study on Bacterial and Algae Incubation

为了深入探究DON(溶解性有机氮)在湖泊水生生态系统中的重要营养作用和生态效应,寻找科学的DON生物有效性评价方法,选择洱海不同湖区表层沉积物样品,通过室内接种细菌和铜绿微囊藻进行对比培养,运用三维荧光-平行医疗法(3D EEM-PARAFAC)研究菌藻对比培养条件下湖泊沉积物DON生物有效性及各DON荧光组分生物有效性差异.结果表明:(1)藻类培养条件下洱海表层沉积物DON生物有效性(8.49%~42.5%)略低于细菌培养条件下的生物有效性(10.5%~45.3%).(2)藻培养条件下,DON生物利用率与藻细胞密度增长量呈显著正相关,即藻细胞密度的增长量可作为反映沉积物DON生物有效性的指标.(3)菌类培养过程中DON光谱学特征参数[如SUVA_(254)(254 nm处紫外吸收光谱系数)、S_R (275~295 nm处吸收光谱系数与350~400 nm处吸收光谱系数比值)等]与DON含量相关性总体较细菌培养好;培养液中SUVA_(254)有不同程度下降,S_R 指数均有上升,大分子DON和高芳香性DON可被微生物降解.相比于陆源荧光组分,内源荧光组分的生物有效性较差.(4)相比而言,藻类培养方法能更直观地反映沉积物DON对藻类生长的影响,可在一定程度上作为衡量湖泊沉积物DON生物有效性的指标,即藻类培养方法更适合评价洱海沉积物DON生物有效性.

This study aimed to explore the importance of dissolved organic nitrogen （DON） in the aquatic ecosystem and its ecological effects, and to find a scientific method to evaluate the bioavailability of DON and to provide a basis for further revealing the mechanism of lake eutrophication. Three-dimensional fluorescence excitation- emission matrix （3DEEM-PARAFAC） was used to estimate sediment DON bioavailability. Various components were identified by PARAFAC model according to the fluorescence excitation emission spectra. Surface sediment samples from different regions of Erhai Lake were selected to study the difference of DON content variation by comparing the cultures inoculated with bacteria and algae under room conditions. The variation characteristics for DON structures during incubation were characterized by UV-visible absorption and 3DEEM spectra. The results showed that： （ 1 ） Bioavailability of sediment DON incubated by algae （8.49% -42.5% ） was slightly lower than that by bacteria （10.5%-45.3% ）. （2） Under algae incubation, the DON bioavailability had significant positive correlation with the growth of algae cell density, indicating algae growth could reflect sediment DON bioavailability. （3） The correlation between DON content and its spectroscopy characteristic parameters of 3DEEM, SUVA_254 and Sa during the incubation by bacteria was better than that by algae. SUVA_254 had different declining degree, and SR showed different increasing degree, indicating DON with high molecular weight and aromaticity could be degraded by microorganisms. Compared with terrestrial PARAFAC components, autochthonous components showed higher bioavailability. （4） Compared with bacteria incubation, algae incubation method could reflect the influence of sediment DON on algae growth more directly. It could be used as a method to measure the DON bioavailability of lake sediments to some extent. In conclusion, it is more suitable to evaluate the Erhai sediment DON bioavailability by algae incubation.