Microbial Ecophysiology Group, Faculty of Biology/Chemistry, University of Bremen, Bremen, Germany; MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
Microbial Ecophysiology Group, Faculty of Biology/Chemistry, University of Bremen, Bremen, Germany; Instituto Antártico Argentino, San Martín, Buenos Aires, Argentina; Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina.
Environ Int. 2021 Nov;156:106602. doi: 10.1016/j.envint.2021.106602. Epub 2021 May 26.
Colonization of newly ice-free areas by marine benthic organisms intensifies burial of macroalgae detritus in Potter Cove coastal surface sediments (Western Antarctic Peninsula). Thus, fresh and labile macroalgal detritus serves as primary organic matter (OM) source for microbial degradation. Here, we investigated the effects on post-depositional microbial iron reduction in Potter Cove using sediment incubations amended with pulverized macroalgal detritus as OM source, acetate as primary product of OM degradation and lepidocrocite as reactive iron oxide to mimic in situ conditions. Humic substances analogue anthraquinone-2,6-disulfonic acid (AQDS) was also added to some treatments to simulate potential for electron shuttling. Microbial iron reduction was promoted by macroalgae and further enhanced by up to 30-folds with AQDS. Notably, while acetate amendment alone did not stimulate iron reduction, adding macroalgae alone did. Acetate, formate, lactate, butyrate and propionate were detected as fermentation products from macroalgae degradation. By combining 16S rRNA gene sequencing and RNA stable isotope probing, we reconstructed the potential microbial food chain from macroalgae degraders to iron reducers. Psychromonas, Marinifilum, Moritella, and Colwellia were detected as potential fermenters of macroalgae and fermentation products such as lactate. Members of class deltaproteobacteria including Sva1033, Desulfuromonas, and Desulfuromusa together with Arcobacter (former phylum Epsilonbacteraeota, now Campylobacterota) acted as dissimilatory iron reducers. Our findings demonstrate that increasing burial of macroalgal detritus in an Antarctic fjord affected by glacier retreat intensifies early diagenetic processes such as iron reduction. Under scenarios of global warming, the active microbial populations identified above will expand their environmental function, facilitate OM remineralisation, and contribute to an increased release of iron and CO from sediments. Such indirect consequences of glacial retreat are often overlooked but might, on a regional scale, be relevant for the assessment of future nutrient and carbon fluxes.
新无冰区被海洋底栖生物占据，这增加了波特尔湾（南极半岛西部）沿海表层沉积物中大型藻类碎屑的埋藏量。因此，新鲜的、不稳定的大型藻类碎屑是微生物降解的主要有机物质（OM）来源。在这里，我们使用添加了粉碎的大型藻类碎屑作为 OM 来源、乙酸盐作为 OM 降解的主要产物和针铁矿作为反应性氧化铁的沉积物培养物来研究波特尔湾中沉积后微生物铁还原的影响，以模拟原位条件。腐殖质类似物蒽醌-2,6-二磺酸（AQDS）也被添加到一些处理中，以模拟电子穿梭的潜力。大型藻类促进了微生物铁还原，并且在添加 AQDS 时，其还原作用增强了 30 倍。值得注意的是，虽然单独添加乙酸盐不会刺激铁还原，但单独添加大型藻类会。从大型藻类降解中检测到乙酸盐、甲酸盐、乳酸盐、丁酸盐和丙酸盐作为发酵产物。通过结合 16S rRNA 基因测序和 RNA 稳定同位素示踪，我们从大型藻类降解物到铁还原物重建了潜在的微生物食物链。Psychromonas、Marinifilum、Moritella 和 Colwellia 被检测为大型藻类和发酵产物（如乳酸盐）的潜在发酵菌。属 delta 变形菌纲的成员包括 Sva1033、脱硫单胞菌和脱硫穆萨菌以及弧菌（前厚壁菌门，现为 Campylobacterota）作为异化铁还原菌。我们的研究结果表明，冰川退缩影响的南极峡湾中大型藻类碎屑的埋藏量增加，加剧了早期成岩过程，如铁还原。在全球变暖的情况下，上述活性微生物种群将扩大其环境功能，促进 OM 再矿化，并有助于从沉积物中释放更多的铁和 CO2。冰川退缩的这种间接后果往往被忽视，但在区域尺度上，可能与未来营养物质和碳通量的评估有关。
