Micronekton is an important, yet poorly known, component of the trophic chain, which partly contributes to the storage of CO₂ in the deep ocean thanks to biomass vertical migrations. In this study, we characterize the ideal sampling regions to estimate the amount of biomass that undergoes theses migrations. We find that observations made in warm, nondynamic and productive waters reduce the error of the estimation by 20 %. This result should likely serve for future in situ network deployment.

Oxygen minimum zones (OMZs) are ocean areas severely depleted in oxygen as a result of physical, chemical, and biological processes. Biologically, organic material is produced in the sea surface and exported to deeper waters, where it respires. In the Bay of Bengal (BoB), an OMZ is present, but there are traces of oxygen left. Our study now suggests that this is because one key process, nitrogen fixation, is absent in the BoB, thus preventing primary production and consecutive respiration.

The patterns observed in the composition of polychaete assemblages were attributed to variations in food supply at the regional scale and nodule density at the local scale. The high levels of species replacement were mainly driven by rare species, leading to regional species pool estimates between 498 and 240 000 species. The high proportion of singletons seems reflect an under-sampling bias that is currently preventing the assessment of potential biodiversity loss due to nodule mining.

In this paper, we assessed four methods (total alkalinity anomaly, calcium anomaly, ⁴⁵Ca incorporation, and ¹³C incorporation) to determine coral calcification of a reef-building coral. Under all conditions (light vs. dark incubations and ambient vs. lowered pH levels), calcification rates estimated using the alkalinity and calcium anomaly techniques as well as ⁴⁵Ca incorporation were highly correlated, while significantly different results were obtained with the ¹³C incorporation technique.

Many wetland systems exhibit lumpy, or uneven, soil surfaces where higher points are called hummocks and lower points are called hollows. We found that, while hummocks extended only ~ 20 cm above hollow surfaces, they exhibited distinct plant communities, plant growth, and soil properties. Differences between hummocks and hollows were the greatest in wetter sites, supporting the hypothesis that plants create and maintain their own hummocks in response to saturated soil conditions.

We investigated the spatial distribution of dissolved Fe during spring 2014, in order to understand the processes influencing the biogeochemical cycle in the North Atlantic. Our results highlighted elevated Fe close to riverine inputs at the Iberian Margin and glacial inputs at the Newfoundland and Greenland margins. Atmospheric deposition appeared to be a minor source of Fe. Convection was an important source of Fe in the Irminger Sea, which was depleted in Fe relative to nitrate.

Vegetation typically responds to variation in temperature and rainfall within days. Yet seasonal changes in meteorological conditions, as well as decadal climate variability, additionally shape the state of ecosystems. It remains unclear how vegetation responds to climate variability on these different timescales. We find that the vegetation response to climate variability depends on the timescale considered. This scale dependency should be considered for modeling land–atmosphere interactions.

We found that glaciers with basal temperatures near the melting point mobilize more solutes, nutrients, and microbes from the underlying substrate and are more likely to promote in situ biogeochemical activity than glaciers with basal temperatures well below the melting point. The temperature at the base of glaciers is therefore an important control on the biogeochemistry of ice near glacier beds, and, ultimately, the potential solutes, nutrients, and microbes exported from glaciated watersheds.

Mitigating emissions of the greenhouse gas N₂O requires understanding of the relative contribution of its producing processes in response to environmental variables. We show, using isotopic analysis, that N₂O emissions from a nitrifying system were sensitive to oxygenation, temperature and NH₄⁺ concentrations with nitrite reduction being the main N₂O source. Temperature appears to be the main control on N₂O production, due to its dissimilar effects on ammonium and nitrite oxidizing activities.

We studied the organisation and dynamics of actin in foraminifera. Actin is one of the key structural proteins in most lifeforms. Our investigations show that in foraminifera it forms small granules, around 1 µm in diameter, that display rapid movement. This granularity is unusual in comparison to other organisms. We suppose that these granules are most likely involved in the formation of all types of pseudopods responsible for movement, food capturing, biomineralisation, and other functions.

The distribution of tree sizes across Amazonia can be fitted very well (for both trunk diameter and tree mass) by a simple equilibrium model assuming power law growth and size-independent mortality. We find tree growth to mirror some aspects of metabolic scaling theory and that there may be a trade-off between fast-growing, short-lived and longer-lived, slow-growing ones. Our Amazon mortality-to-growth ratio is very similar to US temperate forests, hinting at a universal property for trees.

Causal inference promises new insight into biosphere–atmosphere interactions using time series only. To understand the behaviour of a specific method on such data, we used artificial and observation-based data. The observed structures are very interpretable and reveal certain ecosystem-specific behaviour, as only a few relevant links remain, in contrast to pure correlation techniques. Thus, causal inference allows to us gain well-constrained insights into processes and interactions.

Lake sediments release the greenhouse gas CH₄. Acetate is an important precursor. Although Amazonian lake sediments all contained acetate-consuming methanogens, measurement of the turnover of labeled acetate showed that some sediments converted acetate not to CH₄ plus CO₂, as expected, but only to CO₂. Our results indicate the operation of acetate-oxidizing microorganisms couples the oxidation process to syntrophic methanogenic partners and/or to the reduction of organic compounds.

In this paper, we demonstrate that high physiological activity levels during the extremely warm winter are allocated into the below-ground biomass and only to a minor extent used for additional plant growth during early spring. This process is so far largely unaccounted for in scenario analysis using global terrestrial biosphere models, and it may lead to carbon accumulation in the soil and/or carbon loss from the soil as a response to global warming.

Continental shelves are the most productive areas in the ocean and can have an important impact on the nutrient cycle as well as the climate system. The one in Yucatán is the largest shelf in the Gulf of Mexico. However, its nutrient budget remains unidentifiable. Here we propose not only a general nutrient budget for the Yucatán Shelf but also the physical processes responsible for its pathway modulation through a physical–biogeochemical coupled model of the whole Gulf of Mexico.

Potential future deep-sea mining of polymetallic nodules at the seafloor is expected to severely harm the marine environment. However, the consequences on deep-sea ecosystems are still poorly understood. This study on surface sediments from man-made disturbance tracks in the Pacific Ocean shows that due to the removal of the uppermost sediment layer and thereby the loss of organic matter, the geochemical system in the sediments is disturbed for millennia before reaching a new equilibrium.

Selenium (Se) is an essential micronutrient for many organisms. Our knowledge of dissolved Se biogeochemical cycling in tropical estuaries is limited. We have found that dissolved organic Se (DOSe) was the major speciation in the peat-draining rivers and estuaries. The DOSe fractions may be associated with high molecular weight peatland-derived carbon compounds and may photodegrade to more bioavailable forms once transported to oligotrophic coastal water, where they may promote productivity.

Current rates of climate and atmospheric change are likely higher than during the last millions of years. Vegetation cannot keep pace with these changes and lags behind climate. We used a vegetation model to study how these lags are influenced by CO₂ and fire in Africa. Our results indicate that vegetation is most sensitive to CO₂ change under current and near-future conditions and that vegetation will be committed to further change even if CO₂ emissions are reduced and the climate stabilizes.

Combined effects of warming and light intensity were estimated in N₂-fixing cyanobacterium Trichodesmium. Its physiological responses to warming were significantly modulated by light, with growth peaking at 27 °C under the light-saturating condition but being non-responsive across the range of 23–31 °C under the light-limiting condition. Light shortage also weakened the acclimation ability of Trichodesmium to warming, making light-limited Trichodesmium more sensitive to acute temperature change.

Chemical composition of plant litter controls C availability for biological N transformation processes in soil. In this study, we showed that easily degradable maize shoots stimulated microbial respiration and mineralization leading to high N₂O formation in litter-associated hot spots. A higher share of slowly degradable C compounds and lower concentrations of water-soluble N restricted N₂O emissions from maize roots. Bacterial community structure reflected degradability of maize litter.

We analysed the ability of 34 climate models to reproduce main factors affecting the coccolithophore Emiliania huxleyi blooms in six Arctic and sub-Arctic seas. Furthermore, we proposed a procedure of ranking and selecting these models based on the model’s skill in reproducing 10 important oceanographic, meteorological, and biochemical variables in comparison with observation data and demonstrated that the proposed methodology shows a better result than commonly used all-model averaging.