The fate of macroalgal carbon under microbial anaerobic respiration: A critical factor in macroalgae cultivation for climate change mitigation.

Decoupling salinity and carbon function during hydrothermal carbonization of anaerobic digestate.

How light and aggregate size shape oxygen profiles in photogranules.

Methane (CH4) production is commonly associated with anaerobic microbial respiration, yet substantial CH4 production has been observed in aerobic surface waters, presenting the "aerobic methane paradox". Clarifying the mechanism behind aerobic CH4 production is essential for refining the global CH4 budget. Here, we demonstrate that sunlight-driven photochemical processes can effectively produce CH4 across various surface waters, including river, lake, and seawater. The CH4 formation rates ranged from 0.4 ± 0.1 to 0.7 ± 0.1 μmol/m2/h in the daytime, which were 2.3- to 3.9-fold higher as compared to those driven by the decomposition of organic matter by methanogenic archaea in the nighttime. Such aerobic CH4 production stems from the rapid oxidation of naturally abundant methyl donors (e.g., dimethyl sulfoxide) by a photochemically produced hydroxyl radical (•OH), which yields a methyl radical (•CH3) and subsequently leads to CH4 production. Simulations on CH4 productions across varying seasons, latitudes, altitudes, and regions at the global scale suggest that the photochemical processes contribute to 35.3-70.7% of marine CH4 emissions. Our study highlights a ubiquitous yet previously overlooked photochemical source of CH4 production in surface waters, shedding light on the "aerobic methane paradox", which has implications on the global CH4 budget.

Soil microbes are key drivers of nutrient cycling in terrestrial ecosystems. It is crucial to better understand how soil microbial communities are linked to soil functions to predict the consequences of global climate change. Earlier studies have shown that the resistance and resilience of microbial respiration differed across regional or continental scales, which may be influenced by abiotic and biotic factors. However, the resistance and resilience of microbial respiration at a local scale, such as slope aspect, remain unclear. In this study, we examined the soil microbial community structure using phospholipid fatty acid (PLFA) analysis and the resistance and resilience of soil microbial respiration to drying-rewetting perturbations using soils collected from north- and south-facing slopes in a cool-temperate forest in northern Japan. Our results showed that the fungi-to-bacteria ratio and microbial stress indicators (the ratio of saturated to monounsaturated fatty acids, Sat:Mono) were significantly lower on the north-facing slopes than on the south-facing slopes. The resistance and resilience of microbial respiration were also lower on the north-facing slopes than on the south-facing slopes. Resistance and resilience were significantly related to bacterial biomass and microbial stress indicators, suggesting that the soil bacterial community on north-facing slopes, which is dominated by stress-intolerant bacteria, is more vulnerable to drying and rewetting than that on the south-facing slopes. These results provide insights into how the stability of soil functions can vary at a local scale, highlighting the importance of topography in predicting the consequences of environmental changes. • Slope aspects influence soil microbial community structure in a cool-temperate forest, with north-facing slopes dominated by bacteria and south-facing slopes dominated by fungi. • Slope aspects influence the resistance and resilience of soil microbial respiration to drying-rewetting. • The resistance and resilience of soil microbial respiration were significantly related to specific abiotic factors and indicators of soil microbial community structure.

Recent studies report high carbon export efficiencies in Arctic regions with seasonal sea ice compared to ice-free regions, yet the mechanisms behind this enhanced export remain unclear. In the marginal ice zone (MIZ), where pack ice meets open ocean, eddies and filaments frequently form. To investigate carbon export mechanisms in such frontal systems, we combined direct in situ observations of export processes and physical oceanography using free-drifting sediment traps, Marine Snow Catchers, and in situ optics during a Fram Strait expedition in July 2020. Dense Atlantic Water (AW) subducted beneath lighter surface meltwater and Polar Water (PW), structuring biogeochemical and biological processes, including chlorophyll distribution, primary production, zooplankton abundance, microbial respiration, and aggregate formation. We observed three main mechanisms supporting carbon export; (i) deep aggregate formation driven by the subduction of chlorophyll-rich AW, (ii) diatom ballasting of aggregates, including slow-sinking Phaeocystis colonies, and (iii) cryogenic mineral ballasting in PW aggregates, which increased sinking velocities up to tenfold. High carbon fluxes occurred in the AW and at the front, while export in PW was lower, highlighting the role of water mass characteristics and ballasting in regulating export efficiency. The results suggest that continued Atlantification and expansion of the MIZ could enhance carbon export across larger Arctic areas as sea ice retreats.

Alternation magnitudes of organic matter composition determines priming effect of biodegradable microplastics on lake carbon emission.

Microplastic (MP) pollution may influence aquatic greenhouse gas (GHG) emissions by altering dissolved organic matter (DOM)-microbe coupling, yet reported effects remain inconsistent across ecosystems and exposure regimes. Here, we synthesized evidence from 16 studies to quantify the net effects of MPs on CO2, CH4, and N2O fluxes under ambient DOM conditions. Our meta-analysis indicates that MP exposure significantly increases CO2 emissions and decreases N2O fluxes, whereas CH4 responses show a non-significant positive trend with high variability. Exposure duration and polymer identity emerge as key moderators, indicating that MP effects are context-dependent rather than uniform. Short-term exposure tends to suppress carbon mineralization, whereas long-term exposure is more often associated with GHG production, consistent with a time-dependent trajectory potentially shaped by polymer aging. Mechanistically, this pattern may reflect initial DOM adsorption and humification that reduce substrate availability, followed by the release of bioavailable MP-derived compounds that may stimulate microbial respiration, methanogenesis, and denitrification. Overall, MPs reshape aquatic carbon and nitrogen cycling within the overarching framework of DOM, which may ultimately influence GHG emissions under certain conditions. These findings provide a quantitative basis for reconciling conflicting observations and improving predictions of the climate relevance of MP pollution in aquatic ecosystems.

Coupled effects of glyphosate on soil carbon cycling regulated by dose, time, and environment: A global meta-analysis.

ABSTRACT Transition from conventional to no-till vegetable production systems (NTVPS) has been shown to improve soil quality, but the timeline for crop yield responses remains uncertain. This study aimed to evaluate the effects of NTVPS implementation on broccoli (Brassica oleracea var. italica) and maize (Zea mays) production and soil properties using six cover crop treatments: monocultured black oats (Avena strigosa Schreb), four winter cover crop mixtures and a bare soil control. In a two-year field experiment, dry matter production, nitrogen accumulation, broccoli and maize yields, and soil chemical, physical and biological parameters were measured. The cover crop mixtures significantly increased subsurface organic matter in year two, and principal component analysis showed that the Avena strigosa, Secale cereale and Vicia sativa mix was associated with organic matter content, potassium levels, carbon mineralisation and soil density, whilst the Secale cereale, Pisum sativum and Brassica rapa mix was associated with phosphorus availability and microbial respiration rates, and monocultured oats favoured soil physical attributes. In the initial 2 years of the NTVPS, chemical attributes including P, K, Ca and base saturation showed consecutive increases. The maize achieved dual agronomic-economic benefits (maize + pearl millet dry matter: 3.68 t ha−1; maize ear yield: 8.7 t ha−1). In the early stages of NTVPS, the cover crops drove improvements in soil quality characteristics, and whilst broccoli yields were lower in the cover crop treatments, the production of the maize was unaffected. Therefore, long-term monitoring is essential to determine if, and when, crop productivity gains materialise.

Global environmental change is reshaping phenological patterns across ecosystems, yet belowground phenological responses remain poorly characterized. Using a flux-based framework, we derived phenological metrics from 2100 site-years of paired root and microbial respiration time series across 163 sites worldwide. Our meta-analysis shows that root and microbial phenology typically shift asymmetrically in direction and magnitude under global change, except for a warming-induced symmetric advance in season onset. Warming and nitrogen addition extended root growing season, whereas microbial season lengthened under warming and reduced precipitation but shortened following partial vegetation removal. These phenological shifts were largely decoupled from changes in respiration fluxes, indicating a distinct dimension of ecosystem responses to global change. Such phenological adjustments critically influence carbon dynamics, as warming-driven extensions of the microbial season alone could increase global heterotrophic respiration by 2.5 ± 0.8 Pg C yr-1 (mean ± SE). Our results provide flux-based empirical guidance for representing root and microbial phenology as distinct, driver-sensitive processes in Earth system models, thereby improving projections of ecosystem carbon dynamics.

Organic fertilization and planting interactively regulate soil carbon (C) storage, phosphorus (P) components, and microbial respiration, providing insights for optimizing fertilization regimes in farmland. This study employed a pot experiment with organic fertilization and crop planting as two factors, each at two levels, was conducted to comparatively analyze the changes in soil organic C, P fractions (total organic P/total inorganic P, Po/Pi), and microbial respiration (SIR, substrate-induced respiration) under different treatments (organic fertilizer application, planting crops or not, and their combinations). The results showed that long-term absence of organic inputs significantly reduced soluble C by 33-56% and enhanced organic P mineralization (indicated by a 27% decrease in Po/Pi ratio). Organic fertilizer application increased soluble C by 18-22% in the topsoil (0-5cm), and this increase was greater than that observed in the absence of crops, stimulated microbial respiration (+ 30%), and led to a 3.6-fold accumulation of labile organic P. However, it exacerbated P availability stratification (40% decline in Po/Pi). Crop cultivation increased microbial biomass (+ 15-20%) and improved subsoil P speciation (50% increase in Po/Pi). Combining deep-rooted crop cultivation with surface organic fertilizer application synergistically enhances soil C sequestration.

Microbial perchlorate respiration mediates electron flux to drive synergistic removal of perchlorate and terephthalic acid.

Redox oscillations in riparian zone stimulate carbon loss by enhancing microbial respiration.

Redox gradients, often driven by changes in sediment moisture levels in porous, heterogeneous groundwater systems, create dynamic conditions that may promote the production and transport of colloids within natural waters. While much research has focused on the inorganic composition of colloids, the organic composition remains less well understood. Organic matter (OM) in colloids may associate with minerals, complex metal ions, and serve as an electron donor for microbial respiration; therefore, its composition is of high interest. We examined the composition of porewater OM along a redox gradient in a riparian soil located along the Slate River in Crested Butte, Colorado, USA as a function of depth (90, 130, 200, and 350 cm below ground surface). All depths were oxic to suboxic, except 200 cm, where the products of iron and sulfate reduction were observed concomitant with an increase in dissolved and/or colloidal OM, pH, alkalinity, and conductivity. We investigated the composition of porewater using correlated scanning transmission X-ray microscopy and transmission electron microscopy. We observed a change in the OM chemistry from carboxylate-rich at the 200 cm depth (where it was also enmeshed with non-crystalline iron) to phenol- and substituted-aromatic-rich at other depths. Radiocarbon dating revealed carbon in porewater at 200 cm was younger than depths above and below. Soil porewater can flow down into the underlaying gravel bed during baseflow conditions, thus we speculate whether riparian porewater could transport iron- and carboxylate-rich organic colloids into surrounding surface waters through the gravel bed conduit.

Microplastic and biogeochemical releases from plastic, metal, cement, and fiber coastal restoration materials.

Sustainable agriculture requires maintaining soil health, yet conventional management (CM) practices may not protect soils from stresses such as compaction. This study compared microbial resilience to compaction in two soils collected from sugarcane farms under improved management (IM: minimum tillage, cover cropping and stubble retention) and CM (conventional tillage, no cover crop and stubble retention) practices. Samples were placed in 96-well deep-well plates and compacted using a bespoke device to achieve bulk densities of 0.9 (control), 1.1 (low), and 1.2 g cm⁻³ (moderate). Microbial resistance was assessed 14 days after compaction, and resilience 14 days after stress relief. Under low and moderate compaction, IM soils showed 49.5 % and 45.7 % higher CO₂ emission resistance indices (i.e., the ability of soil to maintain microbial respiration under compaction stress) than CM, indicating greater stability. Microbial biomass carbon and nitrogen were 56.2 % and 47.9 % higher in IM soils under low compaction, compared to CM. Soil microbial metabolic quotient ( q CO₂) was similar across compaction levels within each system, but was 19.5 %–36.3 % lower in IM soils than CM at equivalent compaction, indicating lower microbial stress under IM. Fourteen days after stress relief, q CO₂ in moderately compacted CM soil increased by 41.1 % and 25.0 % compared to control and low compaction. In contrast, IM soil under moderate compaction had 40.6 % lower q CO₂ than CM. The CM showed no effects of compaction on hot water extractable organic carbon content, while compaction of IM showed a 13 % decline compared to its control. Hot water extractable total nitrogen did not vary with compaction within the management systems but was 12 %–15 % higher in IM than CM under the same compaction during the resistance phase. Total mineral nitrogen was unaffected by compaction treatments under each system but was 11 %–13 % higher in IM than CM during resistance phase. These findings highlight the potential of improved management practices to sustain soil health and resilience under compaction stress. • A novel test used to assess microbial functional resilience to compaction stress. • Improved management had higher respiration resistance than conventional management. • Improved management reduced microbial metabolic quotient under compaction stress. • Improved management enhanced microbial functional stability and nutrient retention.

Microbial respiration is a key biotic driver of climate change. Warming boosts microbial population growth, which increases biomass and respiration, potentially leading to more warming. This feedback might be disrupted by adaptation in thermal performance curves (TPCs) -whose shape describes how temperature drives growth. In this study, we uncover substantial genetic variation (G) in the intrinsic population growth rates (r) of the protist Tetrahymena thermophila, demonstrate a causal link between heritable variation in r and heritable variation in TPC shape, and show how this variation constrains predicted r-TPC shape evolution along specific evolutionary paths across temperatures. We also uncover Gene-by-Environment (G × E) variation in r, which results in specific signatures in TPC shape and predictable temperature-dependent TPC evolution that can erode heritable variation, thus reducing future evolutionary potential. Overall, we show how temperature-dependent evolution in microbial TPC shape-a linchpin of global ecosystem function-is determined by a combination of heritable and non-heritable variation in intrinsic growth rates.

Abstract Deep-rooted plants may build soil carbon (C) stocks, but most research has focused on shallow soils, leaving gaps in our understanding of how shifts in the balance between decomposition and C inputs drive soil C accumulation with depth. Thus, our objectives were to: (1) link depth gradients in root biomass with microbial activity and soil C stocks down to 1 m, and (2) examine the potential of simple C inputs to prime soil C across depths. To this end, we dug 5 quantitative soil pits in Argiudolls under mature perennial miscanthus plots in the SoyFACE Farm (Champaign-Urbana, IL). We added 13 C labeled glucose to our soils to determine the fate of simple C inputs with depth. We found that fine root biomass, total soil C, mineral-associated organic C (MAOC), particulate organic C (POC), and microbial activity (as measured by potential enzyme activity) declined with depth. POC declined more rapidly than MAOC, resulting in an increase in the ratio of MAOC-to-POC. Root biomass, enzyme activity (either acid phosphatase or n-acetyl-glucosaminadase) activity, and microbial respiration explained 74% and 38% of the variability in soil total C and MAOC, respectively, while POC was dependent on root biomass and microbial respiration (47%). Although the incorporation of simple 13 C inputs into MAOC was similar across depths, these inputs led to greater net MAOC losses in shallow soils than in deeper soils between 50 and 100 cm. The divergent impact of simple C inputs across depths may suggest that MAOC in shallow soils is more susceptible to priming losses, while C inputs into deep soils may instead be more persistent. Collectively, our results suggest that depth gradients in soil C stocks represents a balance between inputs, decomposition, and microbial necromass production and that increases in root C inputs by deep-rooted plants may have the potential to build stable MAOC.

As an important ecological barrier of the Yangtze River， Chongqing's spatio-temporal evolution and driving mechanism of net ecosystem productivity （NEP） are of great significance for regional ecological protection and sustainable development. Using the CASA model and soil microbial respiration model， combined with multi-source data such as climate data， vegetation data， and social data， the regional net ecosystem productivity of Chongqing from 2000 to 2020 was estimated. Trend analysis， hotspot analysis， Hurst index， geographical detector， and spatio-temporal geographically weighted regression model were used to analyze the spatio-temporal variation characteristics of NEP and the mechanism of influencing factors. The results showed that： ① The mean value of NEP （C） in Chongqing from 2000 to 2020 was 578.68 g·（m2·a）-1. The urban development area and the urban functional area were the low value area and the cold spot area of NEP， respectively， and the northeast area and the southeast area of Chongqing were the high value area and the hot spot area of NEP. ② The overall change rate of the study area was 5.66 g·（m2·a）-1. The NEP of Chongqing and more than 86.52% of the functional areas showed an increasing trend， but there was a possibility of decreasing NEP in the future. ③ The explanatory power of elevation， temperature， precipitation， and land use type on NEP was strong， and the explanatory power of each factor interaction was improved. The influencing factors of each functional area had spatial and temporal heterogeneity. The urban development area， urban functional area， and northeastern Chongqing were mainly affected by the positive effects of elevation， temperature， and precipitation. The southeast of Chongqing was mainly affected by the negative effects of elevation and temperature. The research results will provide a scientific basis for the sustainable development of each functional area， regional ecological protection， and the realization of the "double carbon target."