In this study, we discuss the regional variability in the fractional solubility of trace elements (Al, Ti, Fe, Mn, Co, Ni, Cu, Zn, Cd, Pb) from aerosol samples collected during three cruises to the North Atlantic Ocean. We present data that provides a solubility window, covering a conservative, lower limit to an upper limit, the maximum potentially soluble fraction, and discuss why this upper limit could be used to represent the biologically available fraction in some regions.

We present the particulate biogenic barium distributions in the North Atlantic for the first time with the objective of estimating mesopelagic carbon remineralisation fluxes. The remineralisation fluxes balanced or slightly exceeded the upper-ocean carbon export fluxes. This is a key result as the North Atlantic is generally assumed to be efficient in transferring carbon to the deep ocean, but during our study, the North Atlantic was characterized by a near-zero carbon sequestration efficiency.

We first report the mercury distribution in the water section across the subpolar and subtropical gyres of the North Atlantic Ocean (GEOTRACES-GA01 transect). It allows the characterisation of various seawater types in terms of mercury content and the quantification of mercury transport associated with the Atlantic Meridional Overturning Circulation. It shows the nutrient-like biogeochemical behaviour of mercury in this ocean.

We document 2.5 yr of dinoflagellate cyst production in the Cariaco Basin using a sediment trap record. Each species' production pattern is interpreted in the context of the physico-chemical (e.g., temperature, nutrients) and biological (other planktonic groups) environment. Most species respond positively to upwelling, but seem to be negatively impacted by an El Niño event with a 1-year lag. This work helps understanding dinoflagellate ecology and interpreting fossil assemblages in sediments.

The Papagayo upwelling system is a natural laboratory for studying ecosystems' response to ocean acidification (OA). We measured pH and pCO₂ in situ with high temporal resolution and compared them with data available from upwelling season. Local coral reefs are exposed to acidic and undersaturated waters in upwelling and non-upwelling events. These restrictive conditions occur alongside local stressors, potentially decreasing reefs' resilience and increasing their vulnerability under future OA.

The Southern Ocean accounts for a large portion of the variability in oceanic CO₂ uptake. However, the drivers of these changes are not understood due to a lack of observations. In this study, we used an ensemble of gap-filling methods to estimate surface CO₂. We found that winter was a more important driver of longer-term variability driven by changes in wind stress. Summer variability of CO₂ was driven primarily by increases in primary production.

Our analysis of ion input–output budget illustrates that hydrochemical responses to typhoon storms are distinctly different from those of regular storms. In addition, even mild land use change may have large impacts on nutrient exports/losses. We propose that hydrological models should separate hydrochemical processes into regular and extreme conditions to better capture the whole spectrum of hydrochemical responses to a variety of climate conditions.

Absorption of carbon dioxide (CO₂) realized by humans is decreasing the ocean pH (ocean acidification). Single-celled organisms (microbes) support the Antarctic ecosystem, yet little is known about their sensitivity to ocean acidification. This study shows a shift in a natural Antarctic microbial community, with CO₂ levels exceeding 634 μatm changing the community composition and favouring small cells. This would have significant flow effects for Antarctic food webs and elemental cycles.

The patterns of the large- and fine-scale surface circulation on biogeochemical and biological distributions are examined in the western tropical South Pacific (WTSP) in the context of the OUTPACE oceanographic cruise. The combined use of in situ and satellite data allows for the identification of water mass transport pathways and fine-scale structures, such as fronts, that drive surface distribution of tracers and microbial community structures.

Plants have typical daily carbon uptake and water loss cycles. However, these cycles may change under periods of duress, such as water limitation. Here we identify two types of patterns in response to water limitations: a tendency to lose more water in the morning than afternoon and a decoupling of the carbon and water cycles. The findings show differences in responses by trees and grasses and suggest that morning shifts may be more efficient at gaining carbon per unit water used.

This paper presents some of the first high-resolution measurements of a biologically-produced climate-active sulfur gas (dimethylsulfide – DMS) ever made in the Canadian Arctic, taken using two novel high-resolution sampling techniques aboard an icebreaker in the summer of 2015. We show increased concentrations of DMS and its precursors in frontal zones and areas of high sea ice accumulation. Our results provide a snapshot of climate-active gas dynamics in a rapidly changing Arctic.

Coral reefs provide critical shoreline protection and important services, such as marine habitat, tourism, fishing, and recreation. However, coral reefs are being threatened by global climate change. If we are to understand how reefs will response to climate change, we must also understand how local conditions may impact the reefs. Our study offers a first glimpse into how human inputs of nutrients might add an additional stressor to reef health.

In this paper we investigate how the CO₂ exchange between the land vegetation and the atmosphere varies from year to year. We quantify the relation between variations in the CO₂ exchange and variations in air temperature. For this quantification, we use long-term measurements of CO₂ in the air at many locations, a simulation code for the transport of carbon dioxide through the atmosphere, and a data set of air temperature. The results help us to understand the mechanisms of CO₂ exchange.

This work is part of the Mermex and ChArMEx projects of the MISTRALS program. It aims at studying the impacts of phosphorus deposition from contrasted sources on the biogeochemical cycles of the Mediterranean Sea. The results show that combustion-related phosphorus deposition effects dominate P deposition over the northern Mediterranean, whereas dust-derived phosphorus deposition effects dominate in the southern part.

Manganese nodules are a deep-sea mineral resource considered for mining. This paper provides insights into measuring the distribution of manganese nodules at meter resolution. Nodule abundance was determined by autonomous robots using cameras and echo sounders. Based on the meter-scale abundance measurements, environmental impacts of simulated deep-sea mining were assessed. The spatial extent of a sediment plume was determined and showed correlation to small variations in seafloor topography.

Variabilities of phytoplankton physiology and size-fractionated growth could be related to the physical dynamics of a frontal system. While the river plume increased growths of three phytoplankton size classes, both nano- and picocells became saturated at the frontal zone. Vertical mixing/upwelling improved phytoplankton growth on both sides of the front by altering nutrient concentrations and ratios. These are important for understanding physically driven ecosystem dynamics in the shelf sea.

We performed N budgets to assess the role of N₂ fixation on production and export in the western tropical South Pacific Ocean. We deployed a combination of techniques including high-sensitivity measurements of N input and sediment traps deployment. We demonstrated that N₂ fixation was the major source of new N before atmospheric deposition and upward nitrate fluxes. It contributed significantly to organic matter export, indicating a high efficiency of this region to export carbon.