"Plastisphere", microbial communities colonizing plastic debris, has sparked global concern for marine ecosystems. Microbiome inhabiting this novel human-made niche has been increasingly characterized; however, whether the plastisphere holds crucial roles in biogeochemical cycling remains largely unknown. Here we evaluate the potential of plastisphere in biotic and abiotic denitrification and nitrous oxide (N2O) production in estuaries. Biofilm formation provides anoxic conditions favoring denitrifiers. Comparing with surrounding bulk water, plastisphere exhibits a higher denitrifying activity and N2O production, suggesting an overlooked N2O source. Regardless of plastisphere and bulk water, bacterial and fungal denitrifications are the main regulators for N2O production instead of chemodenitrification. However, the contributions of bacteria and fungi in the plastisphere are different from those in bulk water, indicating a distinct N2O production pattern in the plastisphere. These findings pinpoint plastisphere as a N2O source, and provide insights into roles of the new biotope in biogeochemical cycling in the Anthropocene.
Abstract Flooded paddy soils after rewetting dry soils accompanied by extensive nitrogen fertilizer input are important anthropogenic N 2 O emitters due to the denitrification process. Owing to multiple complex denitrifying N 2 O sources, however, the extent to which biotic (fungal or bacterial) and abiotic (chemical) denitrification contribute to total N 2 O emissions remains largely unquantified. Here we sampled across eight provinces where most of the flooded paddy soils were in China to explore microbial and abiotic denitrification potentials and decipher N 2 O dynamics. N 2 O isotopocules and site preference (δ 15 N SP ) analyses found that in most of the sampled paddy soils, fungi‐mediated denitrification was the largest N 2 O contributor (51%–63%); while bacterial and chemical denitrifications contributed 12%–31% and 12%–28% of N 2 O emissions, respectively. Further, using 15 N labeling, a significant spatial heterogeneity of denitrification performance was observed among these flooded paddy soils. As indicated by variance partitioning and regression analyses, this heterogeneity was mainly determined by soil properties (especially soil organic carbon and total nitrogen) rather than by denitrifying communities. Our findings provide insights into the establishment of predictive models of future N 2 O emission from global paddy soils considering both the biotic and abiotic contributions.
Abstract Despite the critical role of soil microbial communities in biomass production and ecosystem functioning, previous research primarily focussed on microbial structure without functional insights, especially for rare species. This study addresses this gap by exploring the functional potential of both abundant and rare bacterial communities across various land uses and soil groups in the Lower Namoi Valley, Australia. By integrating plant‐beneficial bacteria (PBB) and Functional Annotation of Prokaryotic Taxa (FAPROTAX) databases, we show that rare species exhibited higher alpha diversity and multifunctionality than abundant species. Cropping enhanced the biodiversity of abundant functional bacteria in fine‐textured soils, which promoted crop growth through increased PBB and carbon cycling. Conversely, rare functional bacteria exhibited consistently lower biodiversity in croplands. Random forest models and linear regression analyses identified land use as a significant factor influencing the biodiversity of rare functional bacterial communities, likely through plant–soil feedback systems. These findings underline the importance of land use in shaping bacterial community functionality and call for conservation strategies to protect soil biodiversity, especially rare species, to ensure sustainable soil ecosystems and support future food production.
The estuarine plastisphere, a novel ecological habitat in the Anthropocene, has garnered global concerns. Recent geochemical evidence has pointed out its potential role in influencing nitrogen biogeochemistry. However, the biogeochemical significance of the plastisphere and its mechanisms regulating nitrogen cycling remain elusive. Using
Ocean acidification in nitrogen-enriched estuaries has raised global concerns. For decades, biotic and abiotic denitrification in estuarine sediments has been regarded as the major ways to remove reactive nitrogen, but they occur at the expense of releasing greenhouse gas nitrous oxide (N2 O). However, how these pathways respond to acidification remains poorly understood. Here we performed a N2 O isotopocules analysis coupled with respiration inhibition and molecular approaches to investigate the impacts of acidification on bacterial, fungal, and chemo-denitrification, as well as N2 O emission, in estuarine sediments through a series of anoxic incubations. Results showed that acidification stimulated N2 O release from sediments, which was mainly mediated by the activity of bacterial denitrifiers, whereas in neutral environments, N2 O production was dominated by fungi. We also found that the contribution of chemo-denitrification to N2 O production cannot be ignored, but was not significantly affected by acidification. The mechanistic investigation further demonstrated that acidification changed the keystone taxa of sedimentary denitrifiers from N2 O-reducing to N2 O-producing ones and reduced microbial electron-transfer efficiency during denitrification. These findings provide novel insights into how acidification stimulates N2 O emission and modulates its pathways in estuarine sediments, and how it may contribute to the acceleration of global climate change in the Anthropocene.
Land use and soil properties have important impacts on soil microbial communities, which are critical to sustainable land management and ecosystem functioning. However, the specific responses of microbial abundant and rare sub-communities to land use changes in distinct soil types are still not well understood. To address this, we collected soil samples from the surface layers of 13 soil classes, each comprising long-term intensive agricultural lands (cropping and pasture lands) and natural lands (undisturbed national parks and state forests) in the lower Namoi Valley of New South Wales, Australia. Using cluster analysis, two distinct soil groups, discriminated mainly on texture and therefore named Coarse-textured and Fine-textured groups, were identified based on a suite of soil properties. High-throughput sequencing results revealed that land use changes had a more pronounced impact on the structure of rare sub-communities compared to abundant sub-communities. Abundant sub-communities exhibited a higher prevalence in cropping environments than in natural lands in fine-textured soils and showed higher diversity in both soil groups. Conversely, rare sub-communities displayed a reversed trend, consistently demonstrating lower abundance and diversity in cropping lands. This suggests narrower niches, reduced environmental adaptability, and biotic homogenisation resulting from cropping practices. Cropping led to a reduction of 53.7 % of bacterial richness (observed ASVs) and 5.16 % of the relative abundance of rare sub-communities in coarse-textured topsoils, while fine-textured topsoils experienced a decrease of 67.1 % of ASVs and 7.62 % in relative abundance. Taken together, our findings underscore the importance of considering soil heterogeneity when assessing land use impacts on the response of bacterial communities to environmental changes, as well as the need to protect rare sub-communities for sustainable agricultural practices.
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