Soil organic carbon (SOC) storage and persistence are strongly controlled by reactive metal phases, particularly organically complexed aluminum (Al) and iron (Fe) and short-range-order (SRO) minerals. However, their global relevance and the specific metal phases involved remain uncertain due to substantial variability in parent material, soil age, and rock-climate-SOC interactions. Andisols, derived from volcaniclastic materials and enriched in SOC and reactive metals, provide an ideal system to assess metal-SOC associations across broad pedogenic gradients. We compiled a global Andisol database of over 2850 soil samples across 34 countries, covering wide ranges of mean annual temperature (-2 degrees C to 30 degrees C), precipitation (60-6000 mm y(-1)), and soil pH in water (3.1-9.3). Most samples clustered within pH 4.5-6.5, corresponding to an Al-buffered domain where soil pH is predominantly regulated by Al hydrolysis reactions and equilibria among reactive Al pools. Generalized additive mixed model analyses identified organically complexed Al (pyrophosphate-extractable Al, Al-p) as the strongest global predictor of SOC (relative importance = 40%) after accounting for soil depth. SRO Al minerals (acid oxalate-extractable Al minus Al-p) showed moderate importance (relative importance = 10%), whereas reactive Fe and clay content had minor effects. Exchangeable calcium contributed significantly only at pH > similar to 6.3, consistent with a transition toward base-cation buffering. The persistence of strong SOC-Al-p relationships within the Al-buffered domain, together with consistent pH-dependent shifts in reactive Al and Fe pools, suggests that complexation with pedogenic Al released through weathering may exert a first-order control on mineral-protected SOC beyond Andisols and provides a mechanistic basis for incorporation into global-scale models. Identifying dominant stabilization mechanisms remains critical for determining whether SOC persistence is primarily regulated by carbon inputs, metal supply, or their combined effects. Given its integration of organically complexed and SRO Al phases and its broad data availability, acid oxalate-extractable Al emerges as the most practical proxy for mineral-protected SOC at the global scale.

Abstract Full‐pattern fitting of X‐ray powder diffraction (XRPD) data using reference materials has attracted increasing attention as a high‐throughput method to determine the contents of long‐range‐ordered (i.e., crystalline) materials in soils. We hypothesized that this XRPD method can also be used to quantify short‐range‐ordered (SRO) materials with low crystallinity, despite their much weaker and broader diffraction. To obtain soil samples with a wide range of allophane and organic matter (OM) contents, surface and subsurface soils were collected from five profiles in northern Japan. A full factorial design was used to identify the optimal combination of reference SRO materials, including allophane, OM, and phytolith, for XRPD method using full‐pattern fitting. The allophane and OM contents determined by XRPD were broadly but unexpectedly consistent with those obtained by conventional methods. In addition, the allophane and OM contents determined by XRPD showed significant positive correlations with phosphate absorption coefficient and cation exchange capacity, respectively (Spearman's rank correlation, p < 0.001), consistent with the relationships observed by the conventional methods. These results suggest that, although accurate quantification of samples with low contents (i.e., OM < 10 wt.%) remains challenging, state‐of‐the‐art XRPD method using full‐pattern fitting alone provides a promising new approach for rapid evaluation of soil properties and functions through the quantification of both crystalline and low‐crystalline materials.

Mangrove restoration is being increasingly employed to restore degraded coastal ecosystems and strengthen blue carbon (C) sequestration. Nevertheless, total ecosystem carbon (TEC) evaluations often omit deep soils, causing inaccurate estimates of C stored in restored mangroves. This study investigated a 10–14-year chronosequence restoration in Central Thailand using Avicennia alba to quantify TEC stocks across aboveground biomass, coarse roots and fine roots (≤2 mm in diameter), and soil organic carbon (SOC) at a depth of 3 m, as well as changes in total ecosystem carbon (ΔTEC). TEC stocks increased from 695.6 to 828.2 Mg C ha−1 with stand age, with SOC accounting for >80% of total stocks. The ΔTEC was substantial—21.06 Mg C ha−1 yr−1 at 1 m—and was largely associated with SOC, whereas the increase in biomass C was estimated at 10.11 Mg C ha−1 yr−1. Depth-integrated estimates indicated higher values when deeper soil layers were included. SOC stocks increased with stand age throughout the 0–3 m profile; increases up to 2 m were associated with vegetation-derived inputs, as indicated by δ13C shifts and fine root presence. However, soils at 2–3 m retained estuarine signatures that were not clearly associated with vegetation-derived inputs. This study highlights the importance of including deep soil layers in C assessments and emphasizes that interpretations of ecosystem C change should consider depth-dependent controls. These findings emphasize the importance of young mangrove restorations as emerging C sinks, particularly through substantial soil C storage.

The interaction between dissolved organic matter (DOM) and microbial communities is a critical yet understudied driver of biogeochemical cycling in aquatic ecosystems. Understanding these interactions is essential to elucidating chemical and microbial dynamics that sustain ecosystem functioning. Here, we combined non-targeted ultrahigh-resolution mass spectrometry (FT-ICR MS)-based environmental metabolome analysis with microbiome analysis to conduct the first comprehensive investigation of DOM-microbe linkages in both the epilimnion (5 m and thermocline) and oxygenated hypolimnion (60 and 85 m) of a deep freshwater lake throughout the stratification period, with Lake Biwa (Japan) as a model system. To facilitate the interpretation of DOM-microbe networks, we developed an integrated compound category classification (IC3) framework for assigning molecular formulae (MFs) to putative compound categories. Using a compositional data analysis framework with proportionality-based association, we identified covarying MFs and bacterial taxa in the hypolimnion, which exhibited substantially more complex networks than the epilimnion. These networks encompassed 1704 MFs and 14 bacterial ASVs, representing the majority of total FT-ICR MS peak intensity and 22% of the total ASV abundance, underscoring stronger DOM-microbe coupling in deep waters. Several hypolimnion specialist lineages exhibited cluster-specific associations with N-rich and oxidized MFs, consistent with niche differentiation within deep-water heterotrophy. Although network edges do not resolve causality, these patterns provide testable hypotheses about substrate preferences and metabolic pathways shaping hypolimnetic DOM. Our study offers the first high-resolution insights into DOM-microbe associations in the hypolimnion of a deep freshwater lake and establishes a framework for more efficient and robust analyses of such interactions.

Compositional data (CoDa) are prevalent in environmental research. They represent parts of a whole, such as percentages, proportions, and relative or absolute abundances. They are arrays of positive data that convey relevant information in the ratios between their components. Standard statistical techniques developed for real random observations often yield spurious results and are therefore unsuitable for CoDa, which has unique geometric properties. CoDa analysis is now widely acknowledged across various research fields, ranging from geoscience to social science, with a recent surge in popularity in microbial genomics. However, its adoption remains limited in natural organic matter (NOM) research, despite NOM data from key analytical tools such as mass spectrometry, fluorescence spectroscopy, and nuclear magnetic resonance spectroscopy all being compositional. Given the structural similarity between NOM and high-throughput sequencing data, for which CoDa analysis has been successfully adopted, we argue that CoDa analysis should also be consistently integrated into NOM research to prevent analytical pitfalls and misleading inferences. A few pioneering studies have applied CoDa analysis to NOM data, and a wide array of useful open-source tools are already available. This paper discusses step-by-step the application of CoDa analysis to NOM research, using ultrahigh-resolution mass spectrometry data as an illustrative example. The goal of the study is to provide the community with an overview of CoDa analysis and guide them on how to use it in practice.

Mangroves are important sources of dissolved organic matter (DOM) that contribute to marine carbon sequestration. Porewater acts as a key intermediate reservoir through which mangrove-derived DOM is mobilized and transported to adjacent coastal waters. Despite this importance, the spatiotemporal variability in porewater dissolved organic carbon (DOC) concentration and molecular composition within mangrove ecosystems remains poorly understood. This study applied a chronosequence approach across four mangrove plantations of different ages (10-18 years) in Thailand to investigate the spatiotemporal variability in DOC concentration and molecular composition using ultrahigh-resolution mass spectrometry (FT-ICR MS). Temporal variation was inferred from the10-18-year age sequence, including mudflats as a reference, while spatial variation was assessed along seaward-to-landward transects within each plantation. DOC concentrations increased landward but showed no significant dependence on forest age, indicating that porewater DOC is primarily regulated by spatial gradients associated with tidal dilution and vegetation distribution rather than by forest development. In contrast, DOM molecular composition responded to both distance from the seaward edge and forest age. At landward sites in older forests, the relative abundances of aromatic and sulfur-containing compounds increased, coinciding with a molecular index indicative of sulfidic porewater. The enrichment of sulfur-containing compounds and high values of the molecular index are consistent with abiotic sulfurization of porewater DOM under sulfate-reducing redox conditions. This study shows that mangrove forest development alters the quality of porewater DOM, with implications for the contribution of mangrove-derived recalcitrant carbon to porewater pools, carbon cycling, and long-term carbon persistence in blue carbon ecosystems.

Soil organic carbon (SOC) comprises particulate (POC) and mineral-associated organic carbon (MAOC), which differ in formation, stabilization, and loss mechanisms. While the current global distribution of POC and MAOC is characterized, their vulnerability under future climate scenarios remains unclear. Using 3284 topsoil (0-30 cm) observations from six continents, we identify high-latitude soils as global hotspots of SOC vulnerability under shared socioeconomic pathway scenarios (SSP126, SSP245, and SSP585). Under a high-emission scenario (SSP585), high-latitude soils are projected to lose substantial POC by 2100, accounting for about 81 ± 10% of total SOC losses. These declines are driven by the high proportion of SOC stored as POC (fPOC) and its high temperature sensitivity. We show that fPOC is a robust indicator of SOC vulnerability to climate change. Globally, the projected POC decline corresponds to a cumulative carbon dioxide (CO2) release of 81.34 Pg CO2-equivalent by 2100, highlighting the importance of preserving POC to mitigate climate feedbacks.

Prediction of the impact of anthropogenic disturbances and global change on Organic Carbon (OC) pools in mangrove soils requires a detailed understanding of the mechanisms underlying OC stabilization. Using density fractionation to physically separate OC fractions with varying degrees of mineral association and protection, this study aimed to assess distributions of these fractions and the geochemical factors influencing the most dominant and refractory mineral-associated, High-density Fraction (HF). We conducted forest-wide soil sampling in the Gaburumata mangrove forest on Ishigaki Island, Japan, along three transects (upstream, midstream, downstream) and at five depths (until 100 cm). The OC in HF (OCHF) was the oldest (median Delta 14C value of-13.81 parts per thousand) and contributed most significantly to bulk soil OC (43 %-63 %) and total nitrogen (64 %-85 %). Among the extractable metals analyzed (aluminum [Al], iron [Fe], calcium [Ca], and magnesium [Mg]) with different crystallinity, only organically complexed Al and Fe showed strong positive correlations with OCHF. Together with high OCHF:Fe ratios that surpassed the maximum sorptive capacity of Fe oxides, these results indicate that co-precipitation of OC and Fe was the dominant mode of organo-mineral associations. The low clay content reduced the importance of Ca and Mg on OCHF, as these divalent cations typically facilitate OC stabilization through cation bridging between negatively charged clay surfaces and organic matter. Furthermore, the Delta 14C-OC relationship suggested efficient incorporation of mangrove-derived modern C into HF, in addition to the pre-existing old C. Thus, mangrove expansion may enhance stable soil OC pools as well as increase plant biomass and litter. Overall, this study proposes a biogeochemical mechanism for how stable mangrove OC is newly formed, as well as maintained, with ramifications for global mangrove expansion and plantation efforts.

The interaction between dissolved organic matter (DOM) and microbial communities is a critical yet understudied driver of biogeochemical cycling in aquatic ecosystems. Understanding these interactions is essential for elucidating the chemical and microbial dynamics that sustain ecosystem functionings. Here, we combined non-target ultra high-resolution mass spectrometry-based environmental metabolome analysis with microbiome analysis to conduct the first comprehensive investigation of DOM-microbe linkages in both the epilimnion and oxygenated hypolimnion of a deep freshwater lake throughout the stratification period, with Lake Biwa (Japan) as a model system. To facilitate interpretation of DOM-microbe networks, we developed an integrated compound category classification (IC3) framework for assigning molecular formulae (MFs) to specific compound categories. Using a compositional data analysis framework, we identified specific MFs and bacterial taxa that covaried in the hypolimnion, which exhibited substantially more complex networks than the epilimnion. These networks encompassed 1705 out of the 1755 common MFs, representing the majority of total peak intensities, underscoring stronger DOM-microbe coupling in deep waters. Hypolimnion specialist bacteria were associated with specific MFs and co-ocuuring taxa, providing environmental metabolomic evidence for substrate preference and potential symbiotic relations. Notably, more than three-fourths of these MFs in relative abundance were classified as recalcitrant, including lipid-, lignin-, tannin-like, and carboxyl-rich alicyclic molecules, suggesting the capability of hypolimnion specialists to use or produce these compounds. Our study offers the first high-resolution insights into DOM-microbe associations in a deep freshwater lake and establishes a framework for more efficient and robust analyses of such interactions. ### Competing Interest Statement The authors have declared no competing interest. Japan Society for the Promotion of Science, JP22H03733, JP22H00382, JP22K15182, JP21H03584, JP22H03723 Japan Science and Technology Agency, JPMJFR231C, JPMJFR2273

Andisols store a large amount of soil organic carbon (SOC) per area, yet their global SOC stocks remain uncertain. Here, we synthesized a global Andisol database of >2850 soil samples from 34 countries, covering a wide range of climatic and pedogenic environments. We estimated that the area-weighted global SOC stock (median depth: 107 cm) was 320 +/- 46 Mg C ha(-1) which is 50-70% higher than the most recent estimates for Andisols (top 1 m). The global SOC inventory in Andisols was estimated as 30.0 +/- 4.2 Pg C, approximately 2% of the global SOC inventory. These refined estimates highlight the disproportionally high SOC storage of Andisols relative to their limited extent.

Mangrove-fringed estuaries are intertidal ecosystems discharging significant amounts of dissolved organic matter (DOM) into coastal oceans. DOM in these ecosystems is derived from autochthonous production, fluvial input, and mangrove porewater outwelling; however, differentiating between these sources remains challenging. Our incomplete understanding of the biogeochemical factors controlling DOM dynamics and its relationship with nutrient and trace metal cycling still hinders the formulation of elemental budgets in coastal environments. Here, we relate the DOM composition in a mangrove-fringed estuary in North Brazil (Amazonia) to the redox conditions at the formation sites. We combined molecular DOM analyses via ultrahigh-resolution mass spectrometry (FT-ICR-MS) with parallel factor analysis of excitation-emission fluorescence matrices (EEM-PARAFAC), nutrient and redox-sensitive trace metal analyses. During low tide, the influx of oxygen-depleted porewater carried terrigenous DOM, inorganic nutrients, and trace metals into the mangrove-fringed creeks. Precipitation of metal(hydr)oxides and microbial turnover controlled nutrient and trace metal dynamics in the estuary. The highest inorganic nitrogen concentrations within the upper mangrove-fringed estuary indicated outwelling from mangrove sediments as an essential source. Phosphate concentrations were highest within the lower mangrove-fringed estuary, where available phosphate likely exceeded precipitation with iron(hydr)oxides. We tracked the DOM transport to the coastal ocean using a novel molecular index derived from sulfidic porewater (ISuP). Outwelling of recalcitrant DOM from mangrove habitats is relevant in the context of blue carbon storage. Therefore, applying our molecular proxy (ISuP), together with trace-metal and optical DOM analyses, is a powerful approach for differentiating contributions of diverse DOM sources in highly complex coastal ecosystems.

Around one-third of the world’s most carbon-rich ecosystems, mangrove forests, have already been destroyed in Thailand owing to coastal development and aquaculture. Improving these degraded areas through mangrove plantations can restore various coastal ecosystem services, including CO2 absorption and protection against wave action. This study examines the biomass of three coastal mangrove plantations (Avicennia alba) of different ages in Samut Prakarn province, Central Thailand. Our aim was to understand the forest biomass recovery during the early stages of development, particularly fine root biomass expansion. In the chronosequence of the mangrove plantations, woody biomass increased by 40% over four years from 79.7 ± 11.2 Mg C ha-1 to 111.7 ± 12.3 Mg C ha−1. Fine root biomass up to a depth of 100 cm was 4.47 ± 0.33 Mg C ha−1, 4.24 ± 0.63 Mg C ha−1, and 6.92 ± 0.32 Mg C ha−1 at 10, 12, and 14 year-old sites, respectively. Remarkably, the fine root biomass of 14-year-old site was significantly higher than those of the younger sites due to increase of the biomass at 15–30 cm and 30–50 cm depths. Our findings reveal that the biomass recovery in developing mangrove plantations exhibit rapid expansion of fine roots in deeper soil layers.

The mechanisms underlying stabilization of soil organic matter (SOM) in coastal ecosystems, including mangrove forests, are poorly understood, limiting our ability to predict the consequences of disturbances. Here, we introduce density fractionation to mangrove soils to identify the distribution and properties of the functional components of SOM with regard to degradation state, stability, and origin, namely, the high-density fraction (HF), free low-density fraction (f-LF), and mineral-associated LF (m-LF). Three soil cores (1 m) were collected in a mangrove forest on Ishigaki Island, Japan and cut into 10 cm intervals and analyzed. The massive production of mangrove fine roots resulted in a high abundance of LFs throughout the cores, which markedly differed from terrestrial soils. Relative abundance of LFs together accounted for 38%–66% of total soil C. The m-LF was as abundant as f-LF and 1.6 times higher in relative abundance than the global average of terrestrial soils. The C/N ratios and δ13C values clearly increased with depth in all fractions, which was attributed to the increased contribution from roots. We found a consistent pattern in Δ14C values of density fractions. HF was the oldest with Δ14C between -149‰ and -97‰ followed by m-LF (between -130‰ and -87‰) and then f-LF (between -89‰ and 78‰), suggesting that mineral association may be pivotal in long-term carbon storage in the mangrove mineral soil. Our analysis successfully identified meaningful functional components of mangrove SOM, yet several questions remained unanswered, including a large variability in Δ14C in different cores. Future studies would benefit from a coupled analysis of quantity and quality of density fractions and geochemical factors in the mangrove soil.

Identifying drivers of the molecular composition of dissolved organic matter (DOM) is essential to understand the global carbon cycle, but an unambiguous interpretation of observed patterns is challenging due to the presence of confounding factors that affect the DOM composition. Here, we show, by combining ultrahigh-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, that the DOM molecular composition varies considerably among 43 lakes in East Antarctica that are isolated from terrestrial inputs and human influence. The DOM composition in these lakes is primarily driven by differences in the degree of photodegradation, sulfurization, and pH. Remarkable molecular beta-diversity of DOM was found that rivals the dissimilarity between DOM of rivers and the deep ocean, which was driven by environmental dissimilarity rather than the spatial distance. Our results emphasize that the extensive molecular diversity of DOM can arise even in one of the most pristine and organic matter source-limited environments on Earth, but at the same time the DOM composition is predictable by environmental variables and the lakes' ecological history.

Accelerated glacier melt and runoff may lead to inputs of labile dissolved organic matter (DOM) to downstream ecosystems and stimulate the associated biogeochemical processes. However, still little is known about glacial DOM composition and its downstream processing before entering the ocean, although the function of DOM in food webs and ecosystems largely depends on its composition. Here, we employ a set of molecular and optical techniques (UV-vis absorption and fluorescence spectroscopy, 1H NMR, and ultrahigh-resolution mass spectrometry) to elucidate the composition of DOM in Antarctic glacial streams and its downstream change. Glacial DOM consisted largely of a mixture of small microbial-derived biomolecules. 1H NMR analysis of bulk water revealed that these small molecules were processed downstream into more complex, structurally unrecognizable molecules. The extent of processing varied between streams. By applying multivariate statistical (compositional data) analysis of the DOM molecular data, we identified molecular compounds that were tightly associated and moved in parallel in the glacial streams. Lakes in the middle of the flow paths enhanced water residence time and allowed for both more DOM processing and production. In conclusion, downstream processing of glacial DOM is substantial in Antarctica and affects the amounts of biologically labile substrates that enter the ocean.

Mangroves are increasingly recognized as an important component of regional and global carbon cycles especially for their high carbon storage capacity. Global estimation of mangrove soil organic carbon (SOC) storage requires detailed regional studies, but estimates of SOC data in deep soils are currently missing in many countries. Furthermore, little is explored on the molecular composition of mangrove SOC. Here, we assessed the SOC stock in a Trat mangrove forest (Thailand) by collecting deep soils (3.5 m) and analyzed the SOC composition for better understanding its potential sources and influencing factors. The Trat mangrove forest had four times higher SOC stock than has been considered for Thai mangrove forests, with the per-area SOC stock of nearly 1000 Mg C ha-1 which rivals that of Indo-Pacific mangrove forests. The SOC composition analyzed by C/N ratios and spectroscopic techniques differed by tree species and depth. Compositional data principal component analysis revealed that a biological factor (root abundance) had stronger influences than the soil texture (sand versus clay) on the abundance and composition of mangrove SOC. Although surface soil (~1 m) C density was largely controlled by the recent vegetation, deep soil C density reflected other historical processes. This study contributed to a refined estimate of Thailand mangrove SOC stock and revealed that factors influencing SOC abundance and composition differ by tree species and depth.

To clarify the effects of crab burrows on variation in sediment CO2 flux in mangrove forest, we measured the traits of crab burrows (density and entrance area size) and the CO2 flux rate from sediment surfaces, in areas with and without burrows, in a subtropical mangrove forest on Ishigaki Island, southwestern Japan. Burrow density and entrance area showed significant differences among seasons (warm, middle, and cool) and mangrove zones (upper-, middle-, and downstream), which may have depended on crab phenology, life cycle, and species composition. The sediment CO2 flux rate was significantly higher at plots with crab burrows (B+) than at those without burrows (B−) in each zone and season. However, standardized sediment CO2 flux rate by burrow surface area at B+ plots did not differ significantly from that at B− plots. In addition, there were no significant differences in sediment temperature and sediment water content between the two types of plots. Moreover, the level of microbial respiration differed significantly between sediments collected from the deep part and those collected from either the ground surface part or burrow walls. These results suggest that crab burrows increase sediment CO2 flux from the mangrove forest floor by increasing the sediment–atmosphere interface area, thereby inducing a change to aerobic conditions in the sediments around burrows. Therefore, the seasonal and spatial effect of crab burrows on the forest floor should be considered when evaluating sediment CO2 flux and examining the role of the mangrove ecosystem as a carbon sink.

Despite the recognized organic carbon (OC) sequestration potential of mangrove forests, the ongoing climate change and anthropogenic disturbances pose a great threat to these ecosystems. However, we currently lack the ability to mechanically understand and predict the consequences of such impacts, primarily because mechanisms underlying OC stabilization in these ecosystems remain elusive. Research into OC stabilization has focused on terrestrial soils and marine sediments for decades, overlooking the vegetated coastal ecosystems including mangroves. In terrestrial soils and marine sediments, it is widely accepted that OC stabilization is the integrated consequence of OM’s inherent recalcitrance, physical protection, and interactions with minerals and metals. However, related discussion is rarely done in mangrove soils, and recalcitrance of roots and high net ecosystem production (high primary production and low heterotrophic respiration) have been considered as a primary OC sequestration mechanism in mangrove peat and mineral soils, respectively. This review presents the available information on the mechanisms underlying OC stabilization in mangrove soils and highlights research questions that warrant further investigation. Primary OC stabilization mechanisms differ between mangrove peat and mineral soils. In mangrove mineral soils, physico-chemical stabilization processes are important, yet grossly understudied OC stabilization mechanisms. In mangrove peat, recalcitrance of mangrove roots and the inhibition of phenoloxidase under the anoxic condition may be the primary OC stabilization mechanisms. Salinity-induced OC immobilization likely plays a role in both type of soils. Finally, this review argues that belowground production and allochthonous inputs in mangrove forests are likely underestimated. More studies are needed to constrain C budgets to explain the enigma that mangrove OC keeps accumulating despite much higher decomposition (especially by large lateral exports) than previously considered.

The significance of aquatic lateral carbon (C) export in mangrove ecosystems highlights the extensive contribution of aquatic pathways to the net ecosystem carbon budget. However, few studies have investigated lateral fluxes of dissolved organic carbon (DOC) and inorganic carbon (DIC), partly due to methodological difficulty. Therefore, we evaluated area-based lateral C fluxes in a small mangrove estuary that only had one exit for water exchange to the coast. We sampled water from the mouth of the creek and integrated discharge and consecutive concentration of mangrove-derived C (ΔC). Then, we estimated the area-normalized C fluxes based on the inundated mangrove area. DIC and DOC concentrations at the river mouth increased during ebb tide during both summer and winter. We quantified the ΔC in the estuary using a two-component conservative mixing model of freshwater and seawater. DIC and DOC proportions of ΔC concentrations at the river mouth during ebb tide was between 34% and 56% in the winter and 26% and 42% in the summer, respectively. DIC and DOC fluxes from the estuary were estimated to be 1.36 g C m−2 d−1 and 0.20 g C m−2 d−1 in the winter and 3.35 g C m−2 d−1 and 0.86 g C m−2 d−1 in the summer, respectively. Based on our method, daily fluxes are mangrove area-based DIC and DOC lateral exports that can be directly incorporated into the mangrove carbon budget.

The maximum ammonia oxidation potential (AOP) of a topsoil in Langhovde, East Antarctica was 22.1±2.4 ng N g–1 dry soil h–1 (2 mM ammonium, 10°C, n=3). This topsoil exhibited twin AOP peaks (1 and 2 mM ammonium) at 10°C, but not at 20°C. Six and ten operational taxonomic units (OTUs) were identified for ammonia-oxidizing bacteria (AOB) and archaea (AOA) amoA, respectively. AOB were classified into Nitrosospira; the two dominant OTUs corresponded to the Mount Everest cluster. AOA were classified into three clusters; Nitrososphaera and Nitrosocosmicus were the two dominant clusters.