The apparent respiration quotient (ARQ) changes according to which substrates microbes consume, allowing sources of soil respiration to be traced. In a forest soil warming experiment, ARQ had a strong seasonal pattern that reflected a shift from respiration being fueled by sugars and organic acids derived from roots during the growing season to respiration being fueled by dead microbes during winter. ARQ values also changed with experimental warming.

Constants of global biogeochemical ocean models are often tuned by hand to match observations of nutrients or oxygen. We investigate the effect of this tuning by optimising six constants of a global biogeochemical model, simulated in five different offline circulations. Optimal values for three constants adjust to distinct features of the circulation applied and can afterwards be swapped among the circulations, without losing too much of the model's fit to observed quantities.

To better understand the mercury (Hg) content in northern soils, we measured Hg concentration in peat cores across a 1700 km permafrost gradient in Siberia. We demonstrated a northward increase in Hg concentration in peat and Hg pools in frozen peatlands. We revised the 0–30 cm northern soil Hg pool to be 72 Gg, which is 7 % of the global soil Hg pool of 1086 Gg. The results are important for understanding Hg exchange between soil, water, and the atmosphere under climate change in the Arctic.

We studied the contribution of litter-derived carbon (C) in the formation of subsoil organic matter (OM). Soil core sampling, ¹³C field labeling, density fractionation, and water extractions were used to track its contribution to different functional OM fractions down to the deep subsoil. We show that while migrating down the soil profile, OM undergoes a sequence of repeated sorption, microbial processing, and desorption. However, the contribution of litter-derived C to subsoil OM is small.

Seafloor imaging is widely used in marine science and industry to explore and monitor areas of interest. The selection of the most appropriate imaging gear and deployment strategy depends on the target application. This paper compares imaging platforms like autonomous vehicles or towed camera frames and different deployment strategies of those in assessing the megafauna abundance of polymetallic-nodule fields. The deep-sea mining industry needs that information for robust impact monitoring.

In this study, we investigate whether bubbles transport sediments containing arsenic and cyanobacteria from the bottom to the top of a polluted lake. We measured arsenic and cyanobacteria from bubble traps in the lake and from an experimental bubble column in the laboratory. We found that bubble transport was not an important source of arsenic in the surface waters but that bubbles could transport enough cyanobacteria to the surface to exacerbate harmful algal blooms.

This study looks at forest abiotic responses to canopy openness and debris deposition that follow a hurricane. We find that recovery to full canopy may take over half a decade and that recovery of humidity, soil moisture, and leaf saturation under the canopy is not monotonic and may temporarily look recovered before the response is over. Furthermore, we find that satellite data show a quicker recovery than field data, necessitating caution when looking at responses to hurricanes with satellites.

Recent observations from today’s oceans revealed that oxygen concentrations are decreasing, and oxygen minimum zones are expanding together with current climate change. With the aim of understanding past climatic events and their relationship with oxygen content, we looked at the fossils, called benthic foraminifera, preserved in the sediment archives from the Peruvian margin and quantified the bottom-water oxygen content for the last 22 000 years.

The fluxes of soil organic carbon (OC) transport from land to sea are poorly constrained, mostly due to the lack of a specific tracer for soil OC. Here we evaluate the use of specific molecules derived from soil bacteria as a tracer for soil OC in a small river catchment. We find that the initial soil signal is lost upon entering the aquatic environment. However, the local environmental history of the catchment is reflected by these molecules in the lake sediments that act as their sink.

Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas of the sea floor. We describe community composition of microbes associated with nodules of the Peru Basin. Our results show that nodules provide a unique ecological niche, playing an important role in shaping the diversity of the benthic deep-sea microbiome and potentially in element fluxes. We believe that our findings are highly relevant to expanding our knowledge of the impact associated with mining.

CH₄ emissions from reservoirs are responsible for the majority of the climatic forcing of these ecosystems. The origin of the recurrent CH₄ supersaturation in oxic waters is still controversial. We found that the dissolved CH₄ concentration varied by up to 4 orders of magnitude in the water column of 12 reservoirs and was consistently supersaturated. Our findings suggest that photosynthetic picoeukaryotes can play a significant role in determining CH₄ concentration in oxic waters.

A reaction-transport model to assess the potential non-turbulent methane flux from the East Siberian Arctic sediments to water columns is applied here. We show that anaerobic oxidation of methane (AOM) is an efficient filter except for high values of sedimentation rate and advective flow, which enable considerable non-turbulent steady-state methane fluxes. Significant transient methane fluxes can also occur during the building-up phase of the AOM-performing biomass microbial community.

Net community production sets the maximum quantity of phytoplankton carbon available for the marine food web and longer-term storage in the deep ocean. We compared two approaches to estimate this critical variable from autonomous measurements of mixed-layer dissolved oxygen and particulate organic carbon, observing a significant discrepancy between estimates in an upwelling zone near the Oregon coast. We use this discrepancy to assess the fate of organic carbon produced in the mixed layer.

The response of Cymodocea nodosa to environmental changes was reported during a 15-month period. The meadow decline was triggered in spring by the simultaneous reduction of available light in the water column and the creation of anoxic conditions in the rooted area. This disturbance was critical for the plant since it took place during its recruitment phase when metabolic needs are maximal and stored reserves minimal. The loss of such habitat-forming seagrass is a major environmental concern.

The coasts of Peru encompass the richest fisheries in the entire ocean. It is therefore very important for this country to understand how the nearshore marine ecosystem may evolve under climate change. Fine-scale numerical models are very useful because they can represent precisely the evolution of key parameters such as temperature, water oxygenation, and plankton biomass. Here we study the evolution of the Peruvian marine ecosystem in the 21st century under the worst-case climate scenario.