This study addresses the role played by vertical diffusion in the nutrient enrichment of the Levantine intermediate waters, a process particularly relevant inside thermohaline staircases. Thanks to a high profiling frequency over a 4-year period, BGC-Argo float observations reveal the temporal continuity of the layering patterns encountered during the cruise PEACETIME and their impact on vertical and lateral transfers of nitrate between the deep reservoir and the surface productive zone.

Large amounts of soil organic matter stored in permafrost-affected soils from Arctic Russia are present as undecomposed plant residues. This large fibrous organic matter might be highly vulnerable to microbial decay, while small mineral-associated organic matter can most probably attenuate carbon mineralization in a warmer future. Labile soil fractions also store large amounts of nitrogen, which might be lost during permafrost collapse while fostering the decomposition of soil organic matter.

Zooplankton are the smallest animals in the ocean and important food for fish. Despite their importance, zooplankton have been relatively undersampled. To better understand the zooplankton community in the Gulf of Mexico (GoM), we developed a model to simulate their dynamics. We found that heterotrophic protists are important for supporting mesozooplankton, which are the primary prey of larval fish. The model developed in this study has the potential to improve fisheries management in the GoM.

We measured CO₂ and CH₄ fluxes and quantified the global warming potential of different surface areas in a recently created urban wetland in Southern Finland. The ecosystem has a small net climate warming effect which was mainly contributed by the open-water areas. Our results suggest that limiting open-water areas and setting a design preference for areas of emergent vegetation in the establishment of urban wetlands can be a beneficial practice when considering solely the climate impact.

Monthly measurements of dissolved methane (CH₄), a potent greenhouse gas, were conducted at Boknis Eck (BE), a time-series station in the southwestern Baltic Sea, from June 2006. In general CH₄ concentrations increased with depth. High concentrations in the upper layer were linked to saline water inflow. Eckernförde Bay emitted CH₄ to the atmosphere throughout the monitoring period. No significant trend was detected in CH₄ concentrations or emissions during 2006–2017.

We assess 21st century projections of marine biogeochemistry in the CMIP6 Earth system models. These models represent the most up-to-date understanding of climate change. The models generally project greater surface ocean warming, acidification, subsurface deoxygenation, and euphotic nitrate reductions but lesser primary production declines than the previous generation of models. This has major implications for the impact of anthropogenic climate change on marine ecosystems.

Seamounts are globally abundant submarine structures that offer great potential to study the impacts and interactions of environmental gradients at a single geographic location. In an exemplary way, we describe potential mechanisms by which a seamount can affect the structure of pelagic and benthic (sponge-)associated microbial communities. We conclude that the geology, physical oceanography, biogeochemistry, and microbiology of seamounts are even more closely linked than currently appreciated.

Boron isotope ratios (δ¹¹B) of foraminifera are a promising proxy for seawater pH and can be used to constrain pCO₂. In this study, we derived calibrations for new foraminiferal taxa which extend the application of the boron isotope proxy. We discuss the origin of different δ¹¹B signatures in species and also discuss the potential of using multispecies δ¹¹B analyses to constrain vertical pH and pCO₂ gradients in ancient water columns to shed light on biogeochemical carbon cycling in the past.

Results of the first globally resolved simulations of terrestrial carbon and nitrogen (N) cycling and N₂O emissions over the past 21 000 years are compared with reconstructed N₂O emissions. Modelled and reconstructed emissions increased strongly during past abrupt warming events. This evidence appears consistent with a dynamic response of biological N fixation to increasing N demand by ecosystems, thereby reducing N limitation of plant productivity and supporting a land sink for atmospheric CO₂.

Anoxic sediments mostly contain much more organic matter than oxic ones, and therefore organic matter in anoxic settings is often considered to be preserved better than in oxic settings. However, through the analysis of the same fossil dinoflagellate cyst species from both oxic and anoxic settings, we show that at a molecular level the preservation in the oxic sediments may be better since in the anoxic setting the cyst macromolecule has been altered by postdepositional modification.

Temperate forests play a major role in the global carbon and water cycles, sequestering atmospheric CO₂ on annual timescales. This research examined the annual carbon and water dynamics of two similar (age, soil, climate, etc.) eastern North American temperate forests of different species composition (i.e., broadleaf vs. needleleaf). Ultimately, fluxes of the deciduous forest were found to be less sensitive to temperature and water limitations – conditions expected with future climate warming.

Non-structural carbohydrates (NSCs) are an important set of molecules that help plants to grow and respire when photosynthesis is restricted by extreme climate events. In this paper we present a simple model of NSC storage and assess the effect that it has on simulations of vegetation at the ecosystem scale. Our model has the potential to significantly change predictions of plant behaviour in global vegetation models, which would have large implications for predictions of the future climate.

We provide evidence that the greenhouse gas methane (CH₄) is enclosed in calcareous glacier-forefield sediments across Switzerland. Geochemical analyses confirmed that this ancient CH₄ has its origin in the calcareous parent bedrock. Our estimate of the total quantity of CH₄ enclosed in sediments across Switzerland indicates a large CH₄ mass (~10⁵ t CH₄). We produced evidence that CH₄ is stable in its enclosed state, but additional experiments are needed to elucidate its long-term fate.

The anthropogenic nitrogen deposition has led to an increase in nitrate relative to phosphate in the upper oligotrophic waters; however, this anthropogenic nitrogen signal is unclear in the North Atlantic. We analyzed datasets from repeated measurements on meridional and zonal transects in the upper North Atlantic between the 1980s and 2010s and found that the anthropogenic nitrogen signal has been found only in the upper western North Atlantic.

Biological nitrogen fixation (BNF) plays an important role in the global nitrogen cycle. However, the fixation rate has usually been measured or estimated at a particular observational site. This study develops a BNF model considering the symbiotic relationship between legume plants and bacteria. The model is extensively calibrated with site-level observational data and then extrapolated to the global terrestrial ecosystems to quantify the fixation rate in the 1990s.

This study presents a low-cost way to measure methane emissions applicable in nature and society. This facilitates widespread and affordable methane measurements, which are greatly needed for verifying that greenhouse gas mitigation is effective and for improved quantification of fluxes and how they are regulated. The paper also describes an open-source do-it-yourself methane–carbon dioxide–humidity–temperature logger, to increase the distributed capacity to measure greenhouse gases.

This paper reports the first data about atmospheric deposition of dissolved organic matter (DOM) on the island of Lampedusa. It also shows the implications for the surface marine layer by studying the impact of atmospheric organic carbon deposition in the marine ecosystem. It is a preliminary study, but it is pioneering and important for having new data that can be crucial in order to understand the impact of atmospheric deposition on the marine carbon cycle in a global climate change scenario.

We compare the cycling of Fe and Cd in sulfidic sediments of the Peruvian oxygen minimum zone. Due to the contrasting solubility of their sulfide minerals, the sedimentary Fe release and Cd burial fluxes covary with spatial and temporal distributions of H₂S. Depending on the solubility of their sulfide minerals, sedimentary trace metal fluxes will respond differently to ocean deoxygenation/expansion of H₂S concentrations, which may change trace metal stoichiometry of upwelling water masses.

Peatlands export a large amount of DOC through inland waters. This study aims at identifying the mechanisms controlling the DOC concentration at the outlet of two mountainous peatlands in the French Pyrenees. Peat water temperature and water table dynamics are shown to drive seasonal- and event-scale DOC concentration variation. According to water recession times, peatlands appear as complexes of different hydrological and biogeochemical units supplying inland waters at different rates.

Foraminifera are unicellular marine organisms that play an important role in the marine element cycle. Changes of environmental parameters such as salinity or temperature have a significant impact on the faunal assemblages. Our experiments show that changing salinity in the German Wadden Sea immediately influences the foraminiferal community. It seems that A. tepida is better adapted to salinity fluctuations than H. germanica.

Satellite measurements of solar-induced chlorophyll fluorescence (SIF) provide a global measure of photosynthetic change. This enables scientists to better track carbon cycle responses to environmental change and tune biochemical processes in vegetation models for an improved simulation of future change. We use tower-instrumented SIF measurements and controlled model experiments to assess the state of the art in terrestrial biosphere SIF modeling and find a wide range of sensitivities to light.