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- Title
Microbial Assemblages and Metabolic Activity in Organic‐Rich Subterranean Estuaries: Impact of Climate and Land Use Changes.
- Authors
Adyasari, Dini; Dimova, Natasha T.; Ní Chadhain, Sinéad M.; Waska, Hannelore
- Abstract
Microbial communities in subterranean estuaries mediate biogeochemical reactions of coastal groundwater discharging into the oceans; however, studies on their response to abrupt environmental changes caused by climate and land use alterations are still limited. In this study, we conducted a controlled laboratory study using combined geochemical and metagenomic approaches to investigate microbial structures and their metabolic pathways under a wide range of nitrate (NO3− ${{\text{NO}}_{3}}^{-}$) inputs, saline solutions, and incubation times. These factors served as proxies for land use, salinization of the shallow aquifer, and climate changes. We found a highly reducing habitat and an amplification of genes related to denitrification, sulfate reduction, and methanogenesis processes. Core communities consisting of Clostridia, Bacilli, Alphaproteobacteria, Gammaproteobacteria, and Desulfobaccia were observed across all treatments. The metabolic prediction of plant‐derived organic matter (i.e., tannin and lignin) degradation was not affected by NO3− ${{\text{NO}}_{3}}^{-}$ inputs or salinity because of it being implemented by core communities and the abundance of electron donors and acceptors. Quantification of denitrification genes shows that they are susceptible to NO3− ${{\text{NO}}_{3}}^{-}$ inputs and seawater ions. Long‐term incubation allowed sufficient time for microbes to degrade less labile DOM, promoting the re‐release of buried solid phase organic matter into the active carbon cycle and increasing the relative abundance of biofilm or spore‐forming taxa while decreasing that of rare taxa. Our results illustrate the sensitivity of microbial assemblages to environmental changes and their capacity to altering the C and N cycles in coastal areas, further affecting coastal water quality and ecosystem‐scale biogeochemistry. Plain Language Summary: This study investigated how microbial communities in subterranean estuaries (STE) respond to climate and land use changes. Understanding microbial responses is essential, considering microbes control the degradation of terrestrial‐derived solutes transported to the ocean. STE sediments collected from different seasons were incubated with different nitrate inputs, saline solution, and incubation times to represent changing groundwater quality, sea level rise, and groundwater residence time, respectively. The relative proportions of core microbial groups (Clostridia, Bacilli, Alphaproteobacteria, Gammaproteobacteria, and Desulfobaccia) were stable across all treatments; however, less adaptable groups did not survive long incubation times. Seawater addition negatively affected nitrate removal, while changing environmental parameters did not significantly impact plant‐derived organic matter degradation. The study highlights how microbial communities and metabolic processes related to the carbon and nitrogen cycles are susceptible to environmental change. Ultimately, these changes in the microbial community can affect water quality and ecosystem health in coastal areas. Key Points: Core microbial communities, fermenters, and methanogens contributed to plant‐derived particulate organic matter‐to‐dissolved organic matter (DOM) degradation in subterranean estuariesDenitrification is influenced by NO3− ${{\text{NO}}_{3}}^{-}$ concentrations and seawater ionsLong‐term incubation time allowed for less labile DOM microbial degradation and negatively influenced rare taxa
- Subjects
CLIMATE change; CARBON cycle; ELECTRON donors; COASTAL ecosystem health; ESTUARIES; NITROGEN cycle; TERRITORIAL waters; WATER quality; COASTAL sediments
- Publication
Journal of Geophysical Research. Biogeosciences, 2024, Vol 129, Issue 3, p1
- ISSN
2169-8953
- Publication type
Article
- DOI
10.1029/2023JG007660