Based in the Mauritanian upwelling system, the article describes a Lagrangian study of biogeochemical processes within a freshly upwelled body of water as it advects offshore. We report rates of primary production, nitrogen assimilation, and regeneration and describe how these processes relate to the dynamics of the upwelling regime. This system is perhaps the least studied of the four major eastern boundary upwelling systems and so these measurements provide important new insights.

The ocean is full of eddies and they play a key role for ocean biogeochemistry. In order to understand dinitrogen (N₂) fixation, one major control of oceanic primary production, we investigated three eddies in the eastern tropical South Pacific off Peru. We conducted the first detailed survey and found increased N₂ fixation in the oxygen-depleted cores of anticyclonic mode water eddies. Taken together, we could – for the first time – show that eddies play an important role in N₂ fixation off Peru.

The global warming debate has sparked an unprecedented interest in temperature effects on coccolithophores. We show that sub-optimal growth temperatures lead to an increase in malformed coccoliths in a strain-specific fashion and the inorganic / organic carbon has a minimum at optimum growth temperature. Global warming might cause a decline in coccoliths' inorganic carbon contribution to the "rain ratio", as well as improved fitness in some genotypes by reducing coccolith malformation.

Intensification of dairying is rapid in New Zealand, with unknown impact on stocks of soil carbon (C). We investigated changes of soil C over one year for an irrigated, fertilised, rotationally-grazed pasture and an unirrigated winter grazed pasture. The irrigated pasture gained more C from net CO₂ uptake, excreta deposition and fertiliser application than was lost by grazing. The unirrigated pasture lost a small amount of C. Intensive dairy practices may thus increase soil C in the short term.

We explored the causes and consequences for the evolution of life-history traits (seed dormancy & size) in lodgepole pine in British Columbia, Canada and found that dynamic climate rather than constant geography are the environmental driving forces in seed dormancy and size variations. Evapotranspiration and precipitation are the most critical climate variables and we predicted that levels of seed dormancy in lodgepole pine would increase across large geographical tracts in 2050s.

We compare the carbon budget of a pasture using two different system boundaries: including and excluding grazing cows. We reveal the importance of non-CO₂ fluxes as budget components depending on the chosen system boundaries and discuss the effect of their uncertainties. Budget components were directly measured or derived from cow related measured parameters like milk yield. The resulting carbon budgets of both approaches agree within the limits of uncertainty showing a near-neutral behavior.

A transport-reaction model was used to simulate porewater methane and sulfate concentrations. Model results and sediment slurry incubation experiments show high methane production rates supported by non-competitive substrates and ample dissolved and labile organic matter as well as methane from deeper sediment through bubbles dissolution and diffusion. The shallow methane production and accumulation depths in these sediments promote high methane fluxes to the water column and atmosphere.

Soil organic carbon dynamics are crucial for the global greenhouse gas balance, but their complexity is difficult to model and understand. We therefore often rely on radiocarbon measurements for calibrating models, but their effect on our understanding of the processes is still unclear. We calibrated five model structures on data from a long-term Swiss field experiment in a Bayesian framework to assess the effect of radiocarbon on the parameter and structural uncertainty of a soil carbon model.

Measurements after the Fukushima Dai-ichi accident show that elevated concentrations of Cs-137 still remain in sediments, benthic organisms, and demersal fishes in the coastal zone. The dynamic food chain model has been extended to include benthic organisms. We showed that the gradual decrease of activity in the demersal fish after the accident was caused by the transfer of activity from organic matter deposited on the bottom through the deposit-feeding invertebrates.

Studies investigating the effect of increasing CO₂ levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in aquatic systems. The aim of our study was to analyse effects of elevated CO₂ levels on phosphorus pool sizes and uptake. Therefore, we conducted a CO₂-manipulation mesocosm experiment in the Storfjärden (western Gulf of Finland, Baltic Sea) in summer 2012. We compared the phosphorus dynamics in different mesocosm treatment

Based on the eddy covariance method we investigate the ecosystem–atmosphere exchange of CH₄ and CO₂ at a eutrophic shallow lake as a challenging ecosystem often evolving during peatland rewetting. Both open water and emergent vegetation are net emitters of CH₄ and CO₂, but with strikingly different release rates. Even after 9 years of rewetting the lake ecosystem exhibits a considerable carbon loss and global warming impact, the latter mainly driven by high CH₄ emissions from the open waterbody.

The studies were initiated to investigate potential changes in the important coastal upwelling system off NW Africa and to evaluate the role of mineral dust for carbon sequestration into the deep ocean. For this purpose, we deployed time series sediment traps in the deep water column off Cape Blanc, Mauritania. A more than two-decadal sediment trap record from this coastal upwelling system is now presented with respect to deep ocean mass fluxes, flux components and their longer term variability.

The microbial communities of up to 2.3 km depth of Precambrian crystalline bedrock fractures share features with serpenization-driven microbial communities in alkaline springs and subsurface aquifers. This study suggests that phylotypes belonging to Burkholderiales and Clostridia are possible "keystone microbial species" in Outokumpu deep biosphere. Many of the keystone species belong to the rare biosphere with low abundance but a wide range of carbon substrates and a capacity for H2 oxidation.

Is the ocean’s biological carbon pump stable or changing? The Carbon Flux Explorer (CFE), capable of year-long missions without tending ships, was invented to address this question. The CFE dives to 1000 m depths and drifts with currents to optically measure the downward flux of sinking carbon using imaging methods. During wintertime tests in California coastal waters, the CFE observed fluxes ∼10 times higher than previously reported. Traditional approaches have undersampled > 1 mm aggregates.

Biological nitrogen (N) fixation is an important source of N for food webs in tropical and subtropical oceans. However, uptake pathways remain poorly understood. This study found that fixed N contributed a third of total zooplankton N in the New Caledonia lagoon. Fixed N reached the zooplankton through 1) direct grazing on N fixers and 2) grazing on phytoplankton that had taken up N released by fixers. We report the first record of direct zooplankton grazing on the unicellular N fixer UCYN-C.

In this study we investigated marine algae as a source of CH₄ in oxic surface waters of oceans. Algae-derived CH₄ may explain the CH₄ oversaturating state within the surface mixed layer, sometimes also termed the "oceanic methane paradox". This finding of an overlooked source of CH₄ in marine environments will be of considerable importance to scientists in many disciplines because algae play a crucial role in organic matter cycling in marine and freshwater ecosystems.

Hydrophilic surfaces influence the structure of water close to them and may thus affect the isotope composition of water. Across a wide range of materials, fractionation became linearly more negative with increasing volumetric solid : water ratio and even exceeded −44 ‰ for ²H. This has major implications for the interpretation of the isotopic composition of extracted water, especially when the solid : water ratio is larger than 0.5 or for processes occurring at the solid–water interface.