太湖梅梁湾沉积物中氮铁硫转化细菌的毫米级垂向分布及对氮磷迁移转化的潜在影响

本研究在太湖梅梁湾采集沉积柱,采用一种自制的毫米级柱状沉积物自动垂向分层切割装置对表层50 mm沉积物进行垂向切割(间隔2 mm),结合高通量测序技术分析沉积物中细菌群落的毫米级垂向分布;同时采用毫米级高分辨透析技术和薄膜扩散梯度技术(DGT)分析溶解态和DGT可获取态铵态氮(NH₄⁺-N)、硝态氮(NO₃^--N)、Fe、P的垂向分布特征。结果显示,沉积物中细菌群落与溶解态和DGT可获取态氮铁磷浓度在垂向上呈现显著的异质性。细菌硝酸盐还原主要发生在-16～0 mm沉积物深度,这可能导致了溶解态和DGT可获取态NO₃^--N含量在该沉积物深度的明显减少。细菌铁还原主要分布在-32～-18 mm沉积物深度,细菌硫酸盐还原主要分布在-50～-34 mm的沉积物深度;细菌硫酸盐还原是导致沉积物溶解态和DGT可获取态铁磷浓度从-32 mm随沉积物的深度增加而显著增加的主要原因。本研究加深了对富营养化湖泊沉积物中细菌影响氮磷在垂向上迁移转化的认识。

Millimeter-scale vertical distribution of bacterial groups involved in nitrogen, iron and sulfur cycling and its potential influence on the migration and transformation of nitrogen and phosphorus in sediments of Meiliang Bay, Lake Taihu

In this study, sediment cores were collected in Meiliang Bay, Lake Taihu. The surface 50 mm sediment were sliced at 2 mm section using the self-made device to analyze the vertical distribution of bacterial communities in sediment with high-throughput sequencing technology. High-resolution dialysis and diffusive gradients in thin films technology (DGT) with resolution of millimeter were used to analyze the vertical distribution of dissolved and DGT-labile ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), Fe and P. Results indicated that the composition of bacterial community, concentrations of dissolved and DGT-labile NH₄⁺-N, NO₃^--N, Fe and P changed significantly across the sediment depth. Bacterial nitrate reduction process mainly occurred at the sediment depth from -16 mm to 0 mm, which should cause an obvious decrease in the concentrations of dissolved and DGT-labile NO₃^--N in this sediment depth. Bacterial iron reduction process mainly distributed in the sediment depth from -32 mm to -18 mm, while bacterial sulfate reduction process mainly dominated in the sediment depth from -50 mm to -34 mm. Bacterial sulfate reduction was the main cause for the significant increase of dissolved and DGT-labile Fe and P concentrations in the sediment depth from -32 mm. This study has deepened the understanding of the bacterial influence on the vertical migration and transformation of nitrogen and phosphorus in eutrophic lake sediments.