To quantify the impact of El Nino–Southern Oscillation (ENSO) climate events on the methane budget, we studied the correlation between CH₄ time series and ENSO indices. We find that ENSO explains less than one-third of the variability in CH₄ levels and their stable carbon isotopes, which constrain the source processes of emissions. ENSO forcing of the CH₄ cycle is too small, episodic, and regional to force atmospheric trends, which are more likely caused by agricultural or industrial emissions.

Processes involved in the formation of deep-sea carbonate rocks remain controversial. It is reported in present study that macrofaunal burrowing may trigger the dissolution of the original calcite above the saturation horizon and thus drive deep-sea carbonate lithification on mid-ocean ridges. The novel mechanism proposed here for nonburial carbonate lithification at the deep-sea seafloor sheds light on the potential interactions between deep-sea biota and sedimentary rocks.

Understanding how water flows through ecosystems is needed to provide society and policymakers with the scientific background to manage water resources sustainably. Stable isotopes of hydrogen and oxygen in water are a powerful tool for tracking water fluxes, although the heterogeneity of natural systems and practical methodological issues still limit their full application. Here, we examine the challenges in this research field and highlight new perspectives based on interdisciplinary research.

We investigated the surface particulate organic carbon export fluxes in the North Atlantic with the objective of better understanding the biological carbon pump. Our results highlighted that exports depended on the intensity and stage of the bloom, the phytoplankton size and community structures. After comparing with primary production, we concluded that, during our study, the North Atlantic behaves like most of the highly productive areas in the world's ocean, with a low export efficiency.

Trees are very important for the water and carbon cycles. Climate and weather models often assume constant vegetation parameters because good measurements are missing. We used affordable accelerometers to measure tree sway of 19 trees in the Amazon rainforest. We show that trees respond very differently to the same weather conditions, which means that vegetation parameters are dynamic. With our measurements trees can be accounted for more realistically, improving climate and weather models.

Methylmercury accumulates in marine organisms and is produced by bacterial processes in sediment systems. To date, the contribution of these processes to the marine water column is poorly understood. We measured noncellular production and breakdown of methylmercury in equatorial Pacific waters. We observed enhanced production in filtered waters that suggests noncellular processes result in rapid mercury transformations and, in turn, control methylmercury concentrations in the open ocean.

The formation rates of oxygen to nitrogen anomalies in the subtropical North Pacific and North Atlantic were estimated from time series data. We find that vertically migrating phytoplankton, which traverse ~ 100–150 m in the upper ocean over days to acquire nutrients from waters at depth and return to the surface for photosynthesis, likely explain the observed anomalies and help sustain surface ocean productivity and the biological pump throughout the annual cycle in the subtropical ocean.

Organisms living in natural environments have to cope with constantly fluctuating conditions in order to compete and survive. Hereby, membrane lipids may play an integral role. This study demonstrates that the lipid repertoire and lipid modifications in marine picoplankton living in oxygen minimum zones may be larger than previously thought. The abundant presence of non-phosphorus lipids hint at nutrient limitation within deeper depths of the ocean, even though these are not considered as such.

Diatoms can dominate the Arctic Ocean spring bloom, the key annual event for regional food webs. Diatom growth requires silicon and this nutrient has been declining in the European Arctic. This study communicates an unprecedented combination of silicon-cycling measurements around Svalbard during the spring and shows that dissolved silicon can limit diatom production. These results suggest an important coupling of silicon and carbon cycling during the spring bloom in the European Arctic.

Rewetting drained peatlands may lead to prolonged emission of the greenhouse gas methane, but the underlying factors are not well described. In this study, we found two rewetted fens with known high methane fluxes had a high ratio of microbial methane producers to methane consumers and a low abundance of methane consumers compared to pristine wetlands. We therefore suggest abundances of methane-cycling microbes as potential indicators for prolonged high methane emissions in rewetted peatlands.

Global warming has altered Arctic phytoplankton communities, with unknown effects on deep-sea communities that depend strongly on food produced at the surface. We compared the responses of Arctic deep-sea benthos to input of phytodetritus from diatoms and coccolithophorids. Coccolithophorid carbon was 5× less recycled than diatom carbon. The utilization of the coccolithophorid carbon may be less efficient, so a shift from diatom to coccolithophorid blooms could entail a delay in carbon cycling.

How long does C cycle through terrestrial ecosystems is a critical question for understanding land C sequestration capacity under future rising atmosphere [CO₂] and climate warming. Under climate change, previous conventional concepts with a steady-state assumption will no longer be suitable for a non-steady state. Our results using the new concept, C transit time, suggest more significant responses in terrestrial C cycle under rising [CO₂] and climate warming.

During the OUTPACE cruise conducted in the oligotrophic to ultra-oligotrophic region of the western tropical South Pacific, two contrasted regions were sampled in terms of N₂ fixation rates, primary production rates and nutrient availability. The aim of this work was to investigate the role of N₂ fixation in the differences observed between the two contrasted areas by comparing two simulations only differing by the presence or not of N₂ fixers using a 1-D biogeochemical–physical coupled model.

The unicellular microalga Tetraselmis cordiformis (Chlorophyta) was recently discovered to form intracellular mineral inclusions, called micropearls, which had been previously overlooked. The present study shows that 10 Tetraselmis species out of the 12 tested share this biomineralization capacity, producing amorphous calcium carbonate inclusions often enriched in Sr. This novel biomineralization process can take place in marine, brackish or freshwater and is therefore a widespread phenomenon.

Metabolic rates are sensitive to environmental conditions and can skew geochemical measurements. However, there is no way to track these rates through time. Here we investigate the controls of test porosity in planktonic foraminifera (organisms commonly used in paleoclimate studies) as a potential proxy for metabolic rate. We found that the porosity varies with body size and temperature, two key controls on metabolic rate, and that it can respond to rapid changes in ambient temperature.

Arctic soils store vast amounts of frozen carbon that will thaw, fueling microbes that produce carbon dioxide and methane greenhouse gases. We compared methane producing and oxidizing activities in incubated soils and permafrost of Arctic tundra to improve estimates of net emissions. The methane oxidation profile in these soils differs from temperate ecosystems: maximum methane oxidation potential occurs in suboxic soils and permafrost layers, close to the methanogens that produce methane.

With global warming, thawing of permafrost releases dissolved organic matter (DOM) into streams. By analyzing DOM along an alpine stream on the Qinghai–Tibet Plateau, we found DOM was mainly from the active layer, but with deepening of the active layer, the contribution of the deep permafrost layer increased, causing a change in the chemical composition of DOM. From the head- to downstream, DOM is undergoing rapid degradation, but some components are persistent and can be transported downstream.

Environmental effects of ocean acidification and trace gases have drawn much attention in recent years and existing studies reveal that the response of communities and trace gases to ocean acidification is still not predictable and requires further study. The present study examined the effect of elevated pCO₂ on trace gas production and phytoplankton during an ocean acidification mesocosm experiment.

The first atmospheric iron (Fe) deposition model intercomparison is presented in this study, as a result of the deliberations of the United Nations Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP; http://www.gesamp.org/) Working Group 38. We conclude that model diversity over remote oceans reflects uncertainty in the Fe content parameterizations of dust aerosols, combustion aerosol emissions and the size distribution of transported aerosol Fe.

Minor changes in the biogeochemical model equations lead to major dynamical changes. We assessed this structural sensitivity for the MEDUSA biogeochemical model on chlorophyll and nitrogen concentrations at five oceanographic stations over 10 years, using 1-D ensembles generated by combining different process equations. The ensemble performed better than the default model in most of the stations, suggesting that our approach is useful for generating a probabilistic biogeochemical ensemble model.

Accounting for the vegetation signal is critical for comprehensive CO₂ budget assessment in China. We model and evaluate hourly vegetation carbon dioxide (CO₂) exchange (mass per unit area per unit time) in northern China from 2005 to 2009. The model is driven by satellite and meteorological data, is linked to ground-level ecosystem observations, and is applicable to other time periods. We find vegetation uptake of CO₂ in summer is comparable to emissions from fossil fuels in northern China.

We explored the relationship between chemical composition and the temperature sensitivity of moss decomposition using 959-day lab incubations. Mass loss was low despite the predominance of carbohydrates, indicating the persistence of labile C. Scanning electron microscopy revealed little change in the moss cell-wall structure. These results suggest that the moss cell-wall matrix protects labile C from decomposition, contributing to the globally important stocks of moss-derived C.

A large anomalously warm water patch appeared in the NE Pacific in winter 2013–14 and persisted through 2016. Its effect on biological carbon export was determined using O₂ and dissolved inorganic carbon data from a profiling float and a surface mooring. Results show the carbon export decreased after the first year when warmer water invaded and then returned to the previous value, with a similar trend in phytoplankton abundance and corresponding changes in phytoplankton community composition.