Vertical characteristics of bacterial community and the interaction of dissolved organic matter in sediments of a shallow lake, China

Abstract

Bacteria and dissolved organic matter (DOM) play a pivotal role in the biogeochemical cycling of lake sediments. However, the vertical characteristics of bacterial communities in lake sediments and their interactions with DOM remain limited understood. This study focuses on the sediment bacteria of Liangzi Lake, identifying their community structure, key driving factors, and interactions with DOM along a vertical profile (0–120 cm). The dominant phyla in the shallow (0–36 cm), middle (36–72 cm), and deep (72–120 cm) sediments were identified as Chloroflexi and Actinobacterota, Firmicutes and Chloroflexi, and Proteobacteria and Firmicutes, respectively. Pb, Cd, Sb, As, TN (total nitrogen), and TC (total carbon) were the key driving factors of bacterial communities in shallow sediments, while C:N (the ratio of TC to TN), TS (total sulfur), and Cr played a dominant role in shaping bacterial communities in middle sediments. Based on co-occurrence network, shallow sediments showed the highest connectivity between bacterial communities and DOM components, followed by the deep and middle layers. Among them, Chloroflexi and Acidobacteriota exhibited significant interactions with fluorescent components, accounting for over 50 % of the total edges, with the strongest association observed with the tryptophan-like component. In addition, functional groups involved in the C cycle (83.03 %) were the most abundant, especially enriched in the shallow sediments. These results offer a support for understanding geo-microbiological processes and C storage in lacustrine sediment profiles.