Selak Lorena, Meier Dimitri V, Marinović Maja, Čačković Andrea, Kajan Katarina, Pjevac Petra, Orlić Sandi
Ruđer Bošković Institute, Bijenička cesta 54, Zagreb, 10000, Croatia.
Nordic Center for Earth Evolution (NORDCEE), University of Southern Denmark, Odense, Denmark.
Environ Microbiome. 2025 Jun 17;20(1):73. doi: 10.1186/s40793-025-00739-w.
Climate change-induced salinization poses a global threat to freshwater ecosystems and challenges microbial communities driving crucial biogeochemical processes, particularly methane cycling. This study examined the impact of salinization and the accompanying sulfate concentration increases on microbial community dynamics and methane cycling in coastal freshwater lake sediments. We show that sulfate enrichment in sediment profiles enables the proliferation of distinct sulfate-reducing bacteria (SRB) that reshape microbial niches by competing with methanogens and promoting sulfate-dependent anaerobic oxidation of methane (AOM). Freshwater SRB clusters, which compete with some methanogens for substrates but also degrade organic compounds into methanogenesis precursors, are replaced by the SEEP-SRB groups that form syntrophic relationships with ANME-1 in salinized sediments. As seawater intrudes and reshapes microbial communities, a methane pocket forms that escapes both aerobic and anaerobic oxidation. Underneath this methane pocket, SRB play a key role in enabling sulfate-dependent AOM, facilitating methane consumption at higher sediment depths. While all microorganisms demonstrated some physiological adaptability potential to elevated osmotic stress, SRB exhibited the highest resilience to increased salinity. These findings highlight how salinization-induced geochemical shifts, particularly sulfate enrichment, directly affect microbial community assembly and impact methane cycling in coastal freshwater ecosystems.
气候变化导致的盐碱化对淡水生态系统构成全球威胁，并给驱动关键生物地球化学过程（尤其是甲烷循环）的微生物群落带来挑战。本研究考察了盐碱化以及随之而来的硫酸盐浓度增加对沿海淡水湖沉积物中微生物群落动态和甲烷循环的影响。我们发现，沉积物剖面中的硫酸盐富集使得不同的硫酸盐还原菌（SRB）得以增殖，这些细菌通过与产甲烷菌竞争并促进依赖硫酸盐的甲烷厌氧氧化（AOM）来重塑微生物生态位。淡水SRB菌群与一些产甲烷菌竞争底物，但也会将有机化合物降解为甲烷生成前体，在盐碱化沉积物中，它们被与ANME-1形成共生关系的SEEP-SRB菌群所取代。随着海水入侵并重塑微生物群落，会形成一个既逃避好氧氧化又逃避厌氧氧化的甲烷库。在这个甲烷库下方，SRB在促进依赖硫酸盐的AOM过程中发挥关键作用，有助于在沉积物较深部位消耗甲烷。虽然所有微生物都表现出一定的对渗透压升高的生理适应潜力，但SRB对盐度增加的恢复力最强。这些发现凸显了盐碱化引发的地球化学变化，尤其是硫酸盐富集，如何直接影响微生物群落组装并影响沿海淡水生态系统中的甲烷循环。
