Benthic nitrogen fixation and sulfate reduction were investigated in the Peruvian oxygen minimum zone. The data suggest a coupling of both activities to a large extent, but that also sulfide and organic matter availability are controlling the benthic diazotrophy in this area. The molecular analysis confirms the presence of heterotrophic diazotrophs. This work improves our understanding of N cycling in OMZ sediments and the understanding of N sources in the marine environment.

In this paper, several methods for the retrieval of the refractive indices are used in three different examples modeling different shapes and particle size distributions. The error associated with each method is discussed and analyzed. It is finally demonstrated that those inverse methods using a genetic algorithm provide optimal estimations relative to other techniques that, although faster, are less accurate.

Diatoms are the dominant primary producers of the most productive and best fishing areas of the modern ocean, the coastal upwelling systems. This turns them into important contributors to the biological pump and climate change. To help untangle their response to warming climate, we compare the worldwide diatom sedimentary abundance (SDA) to environmental variables and find that the capacity of diatoms to take up silicic acid sets an upper limit on global export production in these ocean regions.

We present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types, and use the model to assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean. Our results suggest that observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton growth.

The VAHINE experiment in the New Caledonia lagoon (SW Pacific) targeted the dynamics of nutrient pools and fluxes, N₂ fixation, and the composition and productivity of the microbial communities. To connect this information to the actual activities of diverse microbial taxa, we present the analysis of the community-wide gene expression for 23 days. The results from this experiment provide insight into the microbial activities in a low-nutrient, low-chlorophyll ecosystem and within a mesocosm.

Tropical montane forests represent a significant portion of Andean land cover, however, soil-atmosphere methane exchange in these ecosystems is under studied. Here we report on soil methane cycling in montane forests of the southern Peruvian Andes. These soils acted as a net sink for atmospheric methane and variation in uptake across the studied forests was best explained by nitrate inhibition of oxidation and/or limitations on the inward diffusion of methane from the atmosphere into the soil.

The global coastal ocean took up 0.1 Pg C yr⁻¹ of anthropogenic carbon during 1993–2012 based on new biogeochemical simulations with an eddying 3-D global model. That is about half of the most recent estimate, an extrapolation based on surface areas. It should not be confused with the continental shelf pump, perhaps 10 times larger, which includes natural as well as anthropogenic carbon. Coastal uptake of anthropogenic carbon is limited by its offshore transport.

The marine cyanobacterium Trichodesmium spp. forms massive blooms important to carbon and nitrogen cycling in the oceans that often collapse abruptly. We investigated a Trichodesmium bloom in the lagoon waters of New Caledonia to specifically elucidate the cellular processes mediating the bloom decline. We demonstrate physiological, biochemical, and genetic evidence for nutrient and oxidative stress that induced a genetically controlled programmed cell death (PCD) pathway leading to bloom demise.

Diatoms and biomarkers have been recently used for palaeoclimate reconstructions in the Southern Ocean. Few sediment-based ecological studies have investigated their relationships with environmental conditions. Here, we compare high-resolution sedimentary records with meteorological data to study relationships between our proxies and recent atmospheric and sea surface changes. Our results indicate that coupled wind pattern and sea surface variability act as the proximal forcing at that scale.

A decade-long drainage on an Arctic floodplain has altered dominant plant species and soil temperature regimes. Consequently, CO₂ exchange rates between the atmosphere and the terrestrial ecosystem were modified: CO₂ uptake rates by the terrestrial ecosystem decreased and CO₂ emission rates to the atmosphere increased. Ongoing global warming may thaw ice-rich permafrost and make some regions drier in the Arctic, and this will reduce carbon accumulation in the terrestrial ecosystem.

Using a synthetic dataset, we show how to best determine the mean source signature, δ_S, at high temporal resolution using continuous CO₂ and δ¹³C(CO₂) data. We apply this method to measured data from Heidelberg and find a distinct seasonal cycle of δ_S. Disentangling this record into its source components requires the isotopic end members of CO₂ from the biosphere and those from the fuel mix. They can be estimated from the δ_S record, but only when their relative share is close to 100 %.

This research provides spatial data on gross emissions from the land use sector for the tropical region for the period 2000–2005. This sector contributes up to 24 % of the global emissions, but there is little understanding of where the hotspots of emissions are, how uncertain they are, and what the human activities behind these emissions are. Data provided here should assist countries to identify priority areas for mitigation action and contrast the effectiveness of their current measures.

Atmospheric models of CO₂ require estimates of land CO₂ fluxes at relatively high temporal resolutions because of the high rate of atmospheric mixing and wind heterogeneity. However, land CO₂ fluxes are often provided at monthly time steps. Here, we describe a new dataset created from 15 global land models and 4 combined products in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP), which we have converted from monthly to 3-hourly output.

We present in this study a highly diverse and complex chemodiversity of dissolved organic matter (DOM) in the Amazon Basin analyzed by modern ultrahigh-resolution mass spectrometry and optical property analyses. DOM within the Rio Madeira (white water), Rio Negro (black water) and Rio Tapajós (clear water) area showed a large overlap of thousands of molecular formulae, but also unique signatures were apparent for each region, with significant correlations to colored DOM.

We have evaluated 11 machine learning (ML) methods and two complementary drivers' setup to estimate the carbon dioxide (CO₂) and energy exchanges between land ecosystems and atmosphere. Obtained results have shown high consistency among ML and high capability to estimate the spatial and seasonal variability of the target fluxes. The results were good for all the ecosystems, with limitations to the ones in the extreme environments (cold, hot) or less represented in the training data (tropics).