Vertical Stratification of Dissolved Organic Matter Linked to Distinct Microbial Communities in Subtropic Estuarine Sediments

Abstract

Dissolved organic matter (DOM) provides carbon substrates and energy sources for sediment microbes driving benthic biogeochemical processes. The interactions between microbes and DOM are dynamic and complex and require the understanding based on fine-scale microbial community and physicochemical profiling. In this study, we characterized the porewater DOM composition in a 300-cm sediment core from the Pearl River estuary, China, and examined the interactions between DOM and archaeal and bacterial communities. DOM composition were highly stratified and associated with changing microbial communities. Compared to bacteria, the amplicon sequence variants of archaea showed significant Pearson correlations (r ≥ 0.65, P < 0.01) with DOM molecules of low H/C ratios, high C number and double bond equivalents, indicating that the distribution of archaea was closely correlated to recalcitrant DOM while bacteria were associated with relatively labile compounds. This was supported by the presence of auxiliary enzyme families essential for lignin degradation and bcrABCD, UbiX genes for anaerobic aromatic reduction in metagenome-assembled genomes of Bathyarchaeia. Our study demonstrates that niche differentiation between benthic bacteria and archaea may have important consequences in carbon metabolism, particularly for the transformation of recalcitrant organic carbon that may be predominant in aged marine sediments.

Carbon metabolism and biogeography of candidate phylum “Candidatus Bipolaricaulota” in geothermal environments of Biga Peninsula, Turkey

“…For the pangenomic analysis, the MAGs to compare against our study were downloaded from public databases deposited as a part of research efforts (Takami et al, 2012;Jungbluth et al, 2017;Parks et al, 2017;Hao et al, 2018;Kadnikov et al, 2019;Smith et al, 2019;Youssef et al, 2019;Liu et al, 2020;Reysenbach et al, 2020;Zhou et al, 2020;Bhattarai et al, 2021;Schneider et al, 2021;Wang et al, 2021;Brazelton et al, 2022;Speth et al, 2022). Supplementary Table 2 provides information on the 23 origins of all the genomes examined in this study.…”

Dissolved Organic Matter Sources in High Arsenic Groundwater From a Sand‐Gravel Confined Aquifer

“…From our previously conducted incubation experiments, it was also found that the consumption of more labile organic molecules produced more abundant microbially derived OM, and resulted in stronger Fe(III) oxide reduction and higher dissolved As concentrations (Qiao et al., 2020). Similarly, a greater extent of DOM degradation was also found to be responsible for higher dissolved Fe(II) and NH 4 + concentrations and more negative δ 13 C‐DIC values in the Pear River estuarine sediment porewater (Wang et al., 2021) and lower dissolved NO 3 − concentrations in coastal groundwater (Adyasari et al., 2021). Overall, the stronger DOM degradation state may cause more reducing conditions and drive the fundamental biogeochemical processes, especially Fe(III) oxide reduction and As release, in the aquifer systems (Figure 9).…”

“…Groundwater DOM contains thousands of diverse molecules, which can be categorized into labile pools being preferentially utilized as microbial substrates and recalcitrant ones that are resistant to microbial degradation (Mladenov et al., 2015). The former DOM type can act as electron donors for microbially mediated Fe(III) oxide reduction to trigger the release of As (Qiao et al., 2020; Tufano et al., 2008; Wang et al., 2021), while the latter may promote As release via electron shuttling, competition, and complexation (Huang et al., 2015; Kulkarni et al., 2017; Mladenov et al., 2015). Therefore, identification of the groundwater DOM compositions and the relevant degradation pathways is vital in assessing the underlying mechanism of groundwater As mobilization (Postma et al., 2016; Wang et al., 2019).…”

“…Regarding both the biodegradable and recalcitrant DOM molecules, Flerus et al (2012) established a degradation index (I_deg) based on the ratio of the intensity of five significantly positively correlated formulas to the sum intensity of the five positively correlated and five negatively correlated formulas with marine 14 C-DOC aging, which can reflect the average degradation state of DOM (Adyasari et al, 2021;Koch et al, 2014). The index has also been used in other studies of marine DOM (Koch et al, 2014;Lechtenfeld et al, 2014;Mentges et al, 2017), marine sediment porewater DOM (Rossel et al, 2020), estuarine sediment porewater DOM (Wang et al, 2021), coastal groundwater DOM (Adyasari et al, 2021), andgroundwater DOM (McDonough et al, 2022). Nevertheless, the degradation state of DOM in As-prone groundwater is unknown, which significantly limits our understanding of DOM roles in As mobilization.…”

Linking Bacterial Communities to Optical-Derived Properties of Porewater DOM in Sediments in the Coastal East China Sea

“…However, some recent studies revealed that some parts of DOM in marine sediments have the potential to be bio-reactive (Rossel et al, 2016;Cai et al, 2019;Tobias-Hünefeldt et al, 2021). Since prokaryotes (especially for bacteria) are the pivotal component responsible for transformation of DOM in marine sediments (Wang et al, 2021), it is important to investigate the interactions, between DOM and bacteria in marine sediments. For all heterotrophic and some autotrophic bacteria in sediments, stepwise processes during the decomposition of sedimentary DOM sever as their main carbon and electron donors source (Burdige and Komada, 2015;Mahmoudi et al, 2017), and porewater DOM was believed as the most active delegate in sedimentary DOM pools (Derrien et al, 2019).…”