The coccoliths are major contributors to the particulate inorganic carbon in the ocean. They are extremely difficult to weigh because they are too small to be manipulated. We propose a universal method to measure thickness and weight of fine calcite using polarizing microscopy that does not require fine-tuning of the light or a calibration process. This method named "bidirectional circular polarization" uses two images taken with two directions of a circular polarizer.

Initial evidence suggests human ignitions or landscape changes caused most Amazon fires during August 2019. However, confirmation is needed that meteorological conditions did not have a substantial role. Assessing the influence of historical weather on burning in an uncertainty framework, we find that 2019 meteorological conditions alone should have resulted in much less fire than observed. We conclude socio-economic factors likely had a strong role in the high recorded 2019 fire activity.

In this study, we demonstrated distinct nitrogen isotope effects for nitric oxide (NO) production from major microbial and chemical NO sources in an agricultural soil. These results highlight characteristic bond-forming and breaking mechanisms associated with microbial and chemical NO production and implicate that simultaneous isotopic analyses of NO and nitrous oxide (N₂O) can lead to unprecedented insights into the sources and processes controlling NO and N₂O emissions from agricultural soils.

We quantify global plant water uptake durations after rainfall using satellite-based plant water content measurements. In wetter regions, plant water uptake occurs within a day due to rapid coupling between soil and plant water content. Drylands show multi-day plant water uptake after rain pulses, providing widespread evidence for slow rehydration responses and pulse-driven growth responses. Our results suggest that drylands are sensitive to projected shifts in rainfall intensity and frequency.

The unique observations by a Biogeochemical Argo float in the NW Pacific Ocean captured the impact of a super typhoon on upper-ocean physical and biological processes. Our result reveals typhoons can increase the surface chlorophyll through strong vertical mixing without bringing nutrients upward from the depth. The vertical redistribution of chlorophyll contributes little to enhance the primary production, which is contradictory to many former satellite-based studies related to this topic.

Recording land surface temperatures using drones offers new options to predict evapotranspiration based on energy balance models. This study compares predictions from three energy balance models with the eddy covariance method. A model II Deming regression indicates interchangeability for latent heat flux estimates from certain modeling methods and eddy covariance measurements. This complements the available methods for evapotranspiration studies by fine grain and spatially explicit assessments.

We studied ecosystem- and plant-community-level carbon (C) exchange between subarctic mire and the atmosphere during 2017–2018. We found strong spatial variation in CO₂ and CH₄ dynamics between the main plant communities. The earlier onset of growing season in 2018 strengthened the CO₂ sink of the ecosystem, but this gain was counterbalanced by a later drought period. Variation in water table level, soil temperature and vegetation explained most of the variation in ecosystem-level C exchange.

We investigated the nutrient assimilation characteristics of deep-water-induced phytoplankton blooms across the subtropical North and South Pacific Ocean. Nutrient drawdown ratios of dissolved inorganic nitrogen to phosphate were anomalously low in the western North Pacific, likely due to the high phosphate uptake capability of low-phosphate-adapted phytoplankton. The anomalous phosphate uptake might influence the maintenance of chronic phosphate depletion in the western North Pacific.

Increasing drought frequency can jeopardize the restoration of the CO₂ sink function in degraded peatlands. We explored the effect of the summer drought in 2018 on vegetation development and CO₂ exchange in a rewetted fen. Drought triggered a rapid spread of new vegetation whose CO₂ assimilation could partially outweigh the drought-related rise in respiratory CO₂ loss. Our study shows important regulatory mechanisms of a rewetted fen to maintain its net CO₂ sink function even in a very dry year.

We analyse the seasonal cycle of O₂ and estimate an annual O₂ budget in the north-western Mediterranean deep-convection region, using a numerical model. We show that this region acts as a large sink of atmospheric O₂ and as a major source of O₂ for the western Mediterranean Sea. The decrease in the deep convection intensity predicted in recent projections may have important consequences on the overall uptake of O₂ in the Mediterranean Sea and on the O₂ exchanges with the Atlantic Ocean.

The reintroduction of American bison creates multiple environmental benefits. Ruminants like bison also emit methane – a potent greenhouse gas – to the atmosphere, which has not been measured to date in a field setting. We measured methane efflux from an American bison herd during winter using eddy covariance. Automated cameras were used to approximate their location to calculate per-animal flux. From the measurements, bison do not emit more methane than the cattle they often replace.

Endolithic microhabitats have been described as the last refuge for life in arid and hyper-arid deserts where life has to deal with harsh environmental conditions, such as those in the Atacama Desert. In this work, three different endolithic microhabitats occurring in gypcrete rocks of the Atacama Desert are characterized, using both microscopy and molecular techniques, to show if the architecture of each microhabitat has an influence on the microbial communities inhabiting each of them.

We quantified the lateral and vertical subsurface flow (SSF) and P concentrations of three beech forest plots with contrasting soil properties during sprinkling experiments. Vertical SSF was 2 orders of magnitude larger than lateral SSF, and both consisted mainly of pre-event water. P concentrations in SSF were high during the first 1 to 2 h (nutrient flushing) but nearly constant thereafter. This suggests that P in the soil solution was replenished fast by mineral or organic sources.

The climate benefit of carbon sequestration (CBS) is a metric developed to quantify avoided warming by two separate processes: the amount of carbon drawdown from the atmosphere and the time this carbon is stored in a reservoir. This metric can be useful for quantifying the role of forests and soils for climate change mitigation and to better quantify the benefits of carbon removals by sinks.

Seasonal hypoxia in the nearshore bottom waters frequently occurs in the Pearl River estuary. Aerobic respiration is the ultimate cause of local hypoxia. We found an elevated level of polyunsaturated aldehydes in the bottom water outside the estuary, which promoted the growth and metabolism of special groups of particle-attached bacteria and thus contributed to oxygen depletion in hypoxic waters. Our results may be important for understanding coastal hypoxia and its linkages to eutrophication.

Our study is of interest to atmospheric scientists and environmental microbiologists, as we show that clouds can be considered a medium where bacteria efficiently degrade and transform amino acids, in competition with chemical processes. As current atmospheric multiphase models are restricted to chemical degradation of organic compounds, our conclusions motivate further model development.

Here we used multi-proxy analyses from Lake Oltina (Romania) and quantitatively examine the past 6000 years of the forest steppe in the lower Danube Plain, one of the oldest areas of human occupation in southeastern Europe. We found the greatest tree cover between 6000 and 2500 cal yr BP. Forest loss was under way by 2500 yr BP, falling to ~20 % tree cover linked to clearance for agriculture. The weak signs of forest recovery over the past 2500 years highlight recurring anthropogenic pressure.

Controls of pyrogenic carbon (PyC) redistribution under rainfall are largely unknown. However, PyC mobility can be substantial after initial rain in post-fire landscapes. We conducted a controlled simulation experiment on plots where PyC was applied on the soil surface. We identified redistribution of PyC by runoff and splash and vertical movement in the soil depending on soil texture and PyC characteristics (material and size). PyC also induced changes in exports of native soil organic carbon.

We developed a simple method to refine existing open-ocean maps towards different coastal seas. Using a multi-linear regression, we produced monthly maps of surface ocean fCO₂ in the northern European coastal seas (the North Sea, the Baltic Sea, the Norwegian Coast and the Barents Sea) covering a time period from 1998 to 2016. Based on this fCO₂ map, we calculate trends in surface ocean fCO₂, pH and the air–sea gas exchange.

Reconstructing ancient atmospheric CO₂ is an important aim of palaeoclimate science in order to understand the Earth's climate system. One method, the alkenone proxy based on molecular fossils of coccolithophores, has been recently shown to be ineffective at low-to-moderate CO₂ levels. In this paper I show that this is likely due to changes in the biogeochemistry of the coccolithophores when there is low carbon availability, but for much of the Cenozoic the alkenone proxy should have utility.

Coccolithophores are important calcifying phytoplankton with an overlooked life cycle. We compile a global dataset of marine coccolithophore abundance to investigate the environmental characteristics of each life cycle phase. We find that both phases contribute to coccolithophore abundance and that their different environmental preference increases coccolithophore habitat. Accounting for the life cycle of coccolithophores is thus crucial for understanding their ecology and biogeochemical impact.

Total denitrification, i.e. N₂O and (N₂O + N₂) fluxes, of repacked soil cores were analysed for different combinations of soils and water contents. Prediction accuracy of (N₂O + N₂) fluxes was highest with combined proxies for oxygen demand (CO₂ flux) and oxygen supply (anaerobic soil volume fraction). Knowledge of denitrification completeness (product ratio) improved N₂O predictions. Substitutions with cheaper proxies (soil organic matter, empirical diffusivity) reduced prediction accuracy.

We report here the first year-long high-frequency pH data set for an Arctic lagoon that captures ice-free and ice-covered seasons. pH and salinity correlation varies by year as we observed positive correlation and independence. Photosynthesis is found to drive high pH values, and small changes in underwater solar radiation can result in rapid decreases in pH. We estimate that arctic lagoons may act as sources of CO₂ to the atmosphere, potentially offsetting the Arctic Ocean's CO₂ sink capacity.

Flexible foil chamber design and the anchored deployment might be useful techniques to enhance the robustness and the accuracy of CO₂ measurements in low-order streams. Moreover, the study demonstrates the value of analytical and numerical techniques for the estimation of gas exchange velocities. These results may contribute to the development of novel procedures for chamber data analysis which might improve the robustness and reliability of chamber-based CO₂ measurements in first-order streams.

A large amount of organic carbon (OC) in soil is protected against decay by bonding to minerals. We studied the release of mineral-bonded OC by NaF–NaOH extraction and H₂O₂ oxidation. Unexpectedly, extraction and oxidation removed mineral-bonded OC at roughly constant portions and of similar age distributions, irrespective of mineral composition, land use, and soil depth. The results suggest uniform modes of interactions between OC and minerals across soils in quasi-steady state with inputs.