Heterotrophic CO2 fixation is a significant yet underappreciated CO2 flux in environmental carbon cycling. In contrast to photosynthesis and chemolithoautotrophy – the main recognized autotrophic CO2 fixation pathways – the importance of heterotrophic CO2 fixation remains enigmatic. All heterotrophs – from microorganisms to humans – take up CO2 and incorporate it into their biomass. Depending on the

Permafrost degradation in the catchment of major Siberian rivers, combined with higher precipitation in a warming climate, could increase the flux of terrestrially derived dissolved organic matter (tDOM) into the Arctic Ocean (AO). Each year, ∼ 7.9 Tg of dissolved organic carbon (DOC) is discharged into the AO via the three largest rivers that flow into the Laptev Sea (LS) and East Siberian Sea (ESS)

The Indian Ocean Rim hosts many of the world's underdeveloped and emerging economies that depend on the ocean resources for the livelihoods of the populations of millions. Operational ocean information services cater to the requirements of managers and end-users to efficiently harness those resources and to ensure safety. Fishery information is not the only operational service that will be needed to

Peatlands are diverse wetland ecosystems distributed mostly over the northern latitudes and tropics. Globally they store a large portion of the global soil organic carbon and provide important ecosystem services. The future of these systems under continued anthropogenic warming and direct human disturbance has potentially large impacts on atmospheric CO2 and climate.We performed global long-term projections

Abstract. Subduction associated with mesoscale eddies is an important but difficult to observe process that can efficiently export carbon and oxygen to the mesopelagic zone (100–1000 db). Using a novel BGC-Argo dataset covering the western North Pacific (20–50° N, 120–180° E), we identified imprints of episodic subduction using anomalies in dissolved oxygen and spicity, a water mass marker. These subduction

The African baobab, Adansonia digitata L., has great paleoclimatological potential because of its wide distributional range and millennial length life span. However, dendroclimatological approaches are hampered by dating uncertainties due to its unique, parenchyma-dominated stem anatomy. Here, securely dated time series of annual wood increment growth and intra-ring stable isotopes of carbon and oxygen

Sea-level rise demands for protection measures of endangered coastlines crucial for the local population. At the island of Sylt in the SE North Sea, shoreline erosion is compensated by replenishment with sand dredged from an offshore extraction site. We studied the long-term effects of sand extraction on bathymetry, geomorphology, habitats and benthic fauna. Sand extraction created dredging holes about

Filaments and fronts play a crucial role for a net offshore and downward nutrient transport in Eastern Boundary Upwelling Systems (EBUSs) and thereby reduce regional primary production. Most studies on this topic are based on either observations or model simulations, but only seldom are both approaches are combined quantitatively to assess the importance of filaments for primary production and nutrient

Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution

Abstract. The flow of carbon through terrestrial ecosystems and the response to climate is a critical but highly uncertain process in the global carbon cycle. However, with a rapidly expanding array of in situ and satellite data, there is an opportunity to improve our mechanistic understanding of the carbon (C) cycle’s response to land use and climate change. Uncertainty in temperature limitation on

An experiment was conducted to investigate the effect of seasonally asymmetric warming on ecosystem respiration (Re), CH4 uptake, and N2O emissions in alpine grassland of the Tianshan of central Asia, from October 2016 to September 2019. The annual means of Re, CH4, and N2O fluxes in growing season were 42.83 mg C m−2 h−1, −41.57 µg C m−2 h−1, and 4.98 µg N m−2 h−1, respectively. Furthermore, warming

Abstract. The aquatic eddy covariance technique stands out as a method for benthic O2-flux measurements because it measures non-invasively, but in the conventional instruments, the spatial separation of the measuring locations of the velocity and O2 sensors causes a time-shift that can be substantial and difficult to correct. Here we introduce a triple O2-sensor-eddy covariance instrument (3OEC) that

Abstract. Grasslands cover around two thirds of the land area of Great Britain (GB) and are important reservoirs of terrestrial biological carbon (C). Outside a few well-monitored sites the quantification of C dynamics in managed grasslands is made complex by the spatio-temporal variability of weather conditions combined with grazing and cutting patterns. Earth observation (EO) missions produce high-resolution

The West Antarctic Ice Sheet (WAIS) is one of the largest potential sources of future sea-level rise, with glaciers draining the WAIS thinning at an accelerating rate over the past 40 years. Due to complexities in calibrating palaeoceanographic proxies for the Southern Ocean, it remains difficult to assess whether similar changes have occurred earlier during the Holocene or whether there is underlying

There is growing interest in developing spatially resolved methane (CH4) isotopic source signatures to aid in geographic source attribution of CH4 emissions. CH4 hydrogen isotope measurements (δ2H–CH4) have the potential to be a powerful tool for geographic differentiation of CH4 emissions from freshwater environments, as well as other microbial sources. This is because microbial δ2H–CH4 values are

Abstract. In the oligotrophic waters of the Mediterranean Sea, during the stratification period, the microbial loop relies on pulsed inputs of nutrients through atmospheric deposition of aerosols from both natural (Saharan dust) and anthropogenic origins. While the influence of dust deposition on microbial processes and community composition is still not fully constrained, the extent to which future

Coastal waters globally are increasingly impacted due to the anthropogenic loading of nitrogen (N) from the watershed. To assess dominant sources contributing to the eutrophication of the Little Narragansett Bay estuary in New England, we carried out an annual study of N loading from the Pawcatuck River. We conducted weekly monitoring of nutrients and nitrate (NO3-) isotope ratios (15N / 14N, 18O / 16O

A significant proportion of the global carbon emissions to the atmosphere originate from agriculture. Therefore, continuous long-term monitoring of CO2 fluxes is essential to understand the carbon dynamics and balances of different agricultural sites. Here we present results from a new eddy covariance flux measurement site located in southern Finland. We measured CO2 and H2O fluxes at this agricultural

Floodplain soils polluted with high levels of mercury (Hg) are potential point sources to downstream ecosystems. Repeated flooding (e.g., redox cycling) and agricultural activities (e.g., organic matter addition) may influence the fate and speciation of Hg in these soil systems. The formation and aggregation of colloids and particles influence both Hg mobility and its bioavailability to microbes that

Abstract. The production and consumption of ammonium (NH4+) are essential upper-ocean nitrogen cycle pathways, yet in the Southern Ocean where NH4+ has been observed to accumulate in surface waters, its mixed-layer cycling remains poorly understood. For surface samples collected between Cape Town and the marginal ice zone (MIZ) in winter 2017, we found that NH4+ concentrations were five-fold higher

Abstract. Emissions from biomass burning (BB) are a key source of atmospheric tracer gases that affect the atmospheric carbon cycle. We estimated four types of global BB emissions using a bottom-up approach and by combining the remote sensing products related to fire distribution with two aboveground biomass (AGB) and two land cover classification (LCC) distributions. The sensitivity of the estimates

Abstract. Large herbivore grazing has been shown to substantially alter tundra soil and vegetation properties as well as carbon fluxes, yet observational evidence to quantify the impact of herbivore introduction into Arctic permafrost ecosystems remains sparse. In this study we investigated growing season CO2 and CH4 fluxes with flux chambers on a former wet tussock tundra inside Pleistocene Park,

Abstract. Dynamics of ocean boundary currents and associated shelf processes can influence onshore/offshore transport of water, critically impacting marine organisms that release long-lived pelagic larvae into the water column. The western rock lobster, Panulirus cygnus, endemic to Western Australia, is the basis of Australia's most valuable wild-caught commercial fishery. After hatching, western rock

Dissolved organic matter (DOM) connects aquatic and terrestrial ecosystems, plays an important role in carbon (C) and nitrogen (N) cycles, and supports aquatic food webs. Understanding DOM chemical composition and reactivity is key for predicting its ecological role, but characterization is difficult as natural DOM is comprised of a large but unknown number of distinct molecules. Photochemistry is

Association of organic carbon (OC) with reactive iron (FeR) represents an important mechanism by which OC is protected against remineralisation in soils and marine sediments. Recent studies indicate that the molecular structure of organic compounds and/or the identity of associated FeR phases exert a control on the ability of an OC–FeR complex to be extracted by the citrate–bicarbonate–dithionite (CBD)

Tree phenology is a major driver of forest–atmosphere mass and energy exchanges. Yet, tree phenology has rarely been monitored in a consistent way throughout the life of a flux-tower site. Here, we used seasonal time series of ground-based NDVI (Normalized Difference Vegetation Index), RGB camera GCC (greenness chromatic coordinate), broadband NDVI, LAI (leaf area index), fAPAR (fraction of absorbed

Abstract. Peat growth is a frequent phenomenon in European river valleys. The presence of peat in the floodplain stratigraphy makes them hotspots of carbon storage. The long-term dynamics of alluvial peatlands are complex due to interactions between the peat and the local river network, and as a result, alluvial peatland development in relation to both regional and local conditions is not well understood

Severe droughts are expected to become more frequent and persistent. However, their effect on autumn leaf senescence, a key process for deciduous trees and ecosystem functioning, is currently unclear. We hypothesized that (I) severe drought advances the onset of autumn leaf senescence in temperate deciduous trees and (II) tree species show different dynamics of autumn leaf senescence under drought

Upscaling plant biomass distribution and dynamics is essential for estimating carbon stocks and carbon balance. In this respect, the Russian Far East is among the least investigated sub-Arctic regions despite its known vegetation sensitivity to ongoing warming. We representatively harvested above-ground biomass (AGB; separated by dominant taxa) at 40 sampling plots in central Chukotka. We used ordination

Vegetation optical depth (VOD) from microwave satellite observations has received much attention in global vegetation studies in recent years due to its relationship to vegetation water content and biomass. We recently have shown that VOD is related to plant productivity, i.e., gross primary production (GPP). Based on this relationship between VOD and GPP, we developed a theory-based machine learning

Biological rock crusts (BRCs) are ubiquitous features of rock surfaces in drylands composed of slow-growing microbial assemblages. BRC presence is often correlated with rock weathering, soiling effect or mitigating geomorphic processes. However, their development rate is still unknown. In this work, we characterised and dated BRCs in an arid environment, under natural conditions, by integrating archaeological

Abstract. The Cretaceous evolution of angiosperm leaves towards higher vein densities enables unprecedented leaf stomatal conductance. Still, simulating and quantifying the impact of such change on plant productivity and transpiration in the peculiar environmental conditions of the Cretaceous remains challenging. Here, we address this issue by combining a paleo proxy-based model with a fully atmosphere-vegetation

Abstract. We investigate in which ways marine biologically-mediated heating increases the surface atmospheric temperature. While the effects of phytoplankton light absorption on the ocean have gained attention over the past years, the impact of this biogeophysical mechanism on the atmosphere is still unclear. Phytoplankton light absorption warms the surface of the ocean with consequences for the air-sea

Abstract. Photosynthetically-active foraminifera are important carbonate producers contributing nearly 5 % of the reef and nearly 1 % of the total global calcium carbonate budgets. The abilities to be photosynthetically active, foraminifera realize by endosymbiosis with microalgae or by sequestering plastids (kleptoplasts) of digested algae. These ecological behaviors are a great advantage for the

Climate change in the Arctic is leading to shifts in vegetation communities, permafrost degradation and alteration of tundra surface–atmosphere energy and carbon (C) fluxes, among other changes. However, year-round C and energy flux measurements at high-latitude sites remain rare. This poses a challenge for evaluating the impacts of climate change on Arctic tundra ecosystems and for developing and

Abstract. Understanding the differences and controlling factors of stable water isotopes in the soil-plant-atmosphere continuum of different vegetation zones has important guiding significance for revealing the hydrological processes and regional water cycle mechanisms.This study selected three different vegetation zones (alpine meadows, forests, and arid piedmont zones) in the Shiyang River Basin

Abstract. The influence of human activities on the role of inland waters in the global carbon (C) cycle is poorly constrained. In this study, we investigated the impact of human land use on the degradation of terrestrial dissolved organic matter (DOM) and its potential impact on bacterial respiration in ten independent catchments of the Lake Geneva Basin. Sites were selected along a gradient of human

Wildfires are the major disturbance in boreal ecosystems and are of great importance for the biogeochemical cycles of carbon (C) and nutrients. However, these fire-induced impacts are hard to quantify and are rarely assessed together at an ecosystem level incorporating both aquatic and terrestrial environments. Following a wildfire in Sweden in an area with ongoing monitoring, we conducted a pre-fire

Tropospheric ozone (O3) and nitrogen deposition affect vegetation growth and, thereby, the ability of the land biosphere to take up and store carbon. However, the magnitude of these effects on the contemporary and future terrestrial carbon balance is insufficiently understood. Here, we apply an extended version of the O–CN terrestrial biosphere model that simulates the atmosphere to canopy transport

Abstract. As global change continues to progress, there is a growing interest in assessing any local levers that could be used to manage the social and ecological impacts of rising CO2 concentrations. While habitat conservation and restoration have been widely recognized for their role in carbon storage and sequestration at a global scale, the potential for managers to use vegetated habitats to mitigate

The ocean response to carbon emissions involves the combined effect of an increase in atmospheric CO2, acting to enhance the ocean carbon storage, and climate change, acting to decrease the ocean carbon storage. This ocean response can be characterised in terms of a carbon–concentration feedback and a carbon–climate feedback. The contribution from different ocean basins to these feedbacks on centennial

A quasi-tropical cyclone (QTC) observed over the Black Sea on 25–29 September 2005 caused an exceptionally strong anomalous autumn coccolithophore bloom that lasted for more than 1.5 months. The QTC induced intense upwelling, causing a decrease in sea surface temperature of 15 ∘C and an acceleration of the cyclonic Rim Current up to extreme values of 0.75 m s−1. The Rim Current transported nutrient-rich

For decades, predominant soil biogeochemical models have used conceptual soil organic matter (SOM) pools and only simulated them to a shallow depth in soil. Efforts to overcome these limitations have prompted the development of the new generation SOM models, including MEMS 1.0, which represents measurable biophysical SOM fractions, over the entire root zone, and embodies recent understanding of the

Abstract. Zero Emissions Commitment (ZEC), the expected change in global temperature following the cessation of CO2 emissions has recently been assessed by the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). ZECMIP concluded that the component of ZEC from CO2 emissions will likely be close to zero in the decades following the cessation of emissions. However, of the 18 Earth system

Uptake and release patterns of dissolved organic matter (DOM) compounds and co-transported nutrients are entangled, and the current literature does not provide a consistent picture of the interactions between the retention processes of DOM fractions. We performed plateau addition experiments with five different complex DOM leachates in a small experimental stream impacted by diffuse agricultural pollution

While there is agreement that global warming over the 21st century is likely to influence the biological pump, Earth system models (ESMs) display significant divergence in their projections of future new production. This paper quantifies and interprets the sensitivity of projected changes in new production in an idealized global ocean biogeochemistry model. The model includes two tracers that explicitly

Abstract. We evaluate a range of blue intensity (BI) tree-ring parameters in eight conifer species (12 sites) from Tasmania and New Zealand for their dendroclimatic potential, and as surrogate wood anatomical proxies. Using a dataset of ca. 10–15 trees per site, we measured earlywood maximum blue reflectance intensity (EWB), latewood minimum blue reflectance intensity (LWB) and the associated delta

To understand the vertical variations in carbon fluxes in biologically productive waters, four autonomous carbon flux explorers (CFEs), ship-lowered CTD-interfaced particle-sensitive transmissometer and scattering sensors, and surface-drogued sediment traps were deployed in a filament of offshore flowing, recently upwelled water, during the June 2017 California Current Ecosystem – Long Term Ecological

In coastal regions, rivers and streams may be important sources of nutrients limiting to primary production in marine waters; however, sampling is still rarely conducted across the land-to-ocean aquatic continuum, precluding conclusions from being drawn about connectivity between freshwater and marine systems. Here we use a more-than-4-year dataset (2014–2018) of nutrients (nitrogen, phosphorus, silica

Headwater streams drain >70 % of global land areas but are poorly monitored compared with large rivers. The small size and low water buffering capacity of headwater streams may result in a high sensitivity to local hydrological alterations and different carbon transport patterns from large rivers. Furthermore, alpine headwater streams on the “Asian water tower”, i.e., Qinghai–Tibetan Plateau, are heavily

Small boreal lakes are known to contribute significantly to global CH4 emissions. Lake Lovojärvi is a eutrophic lake in southern Finland with bottom water CH4 concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 µM). We studied the biogeochemical processes involved in CH4 removal by chemical profiling and through incubation experiments

Biogeochemistry has an important role to play in many environmental issues of current concern related to global change and air, water, and soil quality. However, reliable predictions and tangible implementation of solutions, offered by biogeochemistry, will need further integration of disciplines. Here, we refocus on how further developing and strengthening ties between biology, geology, chemistry

Abstract. Two Argo floats equipped with oxygen, chlorophyll (Chl), backscatter, and nitrate sensors conducted daily vertical profiles of the water column from a depth of 2000 m to the sea surface in the western North Pacific from January to April of 2018. Data for calibrating each sensor were obtained via shipboard sampling that occurred when the floats were deployed and recovered. Float backscatter

Abstract. Leading an effective response to the accelerating crisis of anthropogenic climate change will require improved understanding of global carbon cycling. A critical source of uncertainty in Earth Systems Models (ESMs) is the role of microbes in mediating both the formation and decomposition of soil organic matter, and hence in determining patterns of CO2 efflux. Traditionally, ESMs model carbon

Abstract. The subsurface is a temporally dynamic and spatially heterogeneous compartment of the Earth's Critical Zone, and biogeochemical transformations taking place in this compartment are crucial for the cycling of nutrients. The impact of spatial heterogeneity on such microbially mediated nutrient cycling is not well known which imposes a severe challenge in the prediction of in situ biogeochemical

Abstract. Chromium (Cr) and its isotopes hold great promise as tracer of past oxygenation and marine biological activity due to the different chemical properties of its two main oxidation states, Cr(III) and Cr(VI), and the associated fractionation during redox transformations. However, to date the Cr cycle remains poorly constrained due to insufficient knowledge about sources and sinks and the influence

Abstract. Tropospheric O3 damages leaves and directly inhibits photosynthesis, posing a threat to terrestrial carbon sinks. Previous investigations have mostly relied on sparse in-situ data or simulations using land surface models. This work is the first to use satellite data to quantify the effect of O3 exposure on gross primary productivity (GPP). O3-induced GPP reductions were estimated to vary

Abstract. This study assesses marine biological production of organic carbon based on the diel variability of bio-optical properties monitored by two BioGeoChemical-Argo (BGC-Argo) floats. Experiments were conducted in two distinct Mediterranean systems, the Northwestern Ligurian Sea and the Central Ionian Sea during summer months. We derived particulate organic carbon (POC) stock and gross community

South Asian vegetation provides essential ecosystem services to the 1.7 billion inhabitants living in the region. However, biodiversity and ecosystem services are threatened by climate and land-use change. Understanding and assessing how ecosystems respond to simultaneous increases in atmospheric CO2 and future climate change is of vital importance to avoid undesired ecosystem change. Failed reaction

Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom water conditions, phosphorus release from the sediment is elevated, which further stimulates primary production. It is commonly assumed that re-oxygenation could break this “vicious cycle” by increasing the sedimentary phosphorus retention. Recently, a deep-water inflow into