湖泊草、藻来源溶解性有机质及其微生物降解的差异

太湖生态类型多样,存在着水环境差异比较显著的草、藻型湖区,其水体中溶解性有机质(DOM)的来源及组分特征也存在较大差异.为了检验草、藻来源的DOM组分特征及其微生物降解机制的差异性,分别选取太湖藻型湖区的蓝藻水华及草型湖区的优势水生植物马来眼子菜进行室内细菌降解实验.结果表明,浮游植物及沉水植物的细菌降解都能快速释放营养盐和有机质,而且释放的DOM均以极具活性的类蛋白荧光组分为主.草源和藻源DOM在组分构成上存在显著差异,藻源DOM以类色氨酸组分为主,而草源DOM荧光物质则基本上以类酪氨酸组分C3为主,草、藻来源DOM的荧光组分差异与野外调查结果相似.经过细菌的降解利用,草、藻来源的DOM类蛋白荧光强度都迅速减弱,藻源性溶解物质相对容易被细菌降解利用,在2 d之内就能降解约70%,而草源性DOM的降解速率则较低,通常降解转化周期则为更长时间.

Different degradation mechanism of dissolved organic matter derived from phytoplankton and macrophytes in Lake Taihu, China

Lake Taihu has high spatial variability including regions dominated by phytoplankton or macrophytes. There are multiple sources of DOM in Lake Taihu including allochthonous river input and autochthonous biological degradation. We investigate the production of DOM from the decomposition of Algae pulp and P. malaianus in well-controlled laboratory experiments, respectively. The protein-like fluorescence was the most important component in both algal-dominated DOM and macrophyte-dominated DOM. However, the tryptophan-like fluorescence was the most important component in the algal-dominated DOM, while the tyrosine-like fluorescence in the southeastern macrophyte-dominated DOM. These results were similar with field investigations. In the experiment, about 70% of the total algal-dominated DOM was found to be readily degradable in 2 days, while degradation cycle of macrophyte-dominated DOM took longer time.