Science Highlights

Some recent GEOTRACES science findings are reported below.

Who produces methylmercury in the global ocean?

The UNEP Minamata Convention was ratified in August 2017 and aims to protect human health from mercury exposure by reducing anthropogenic, inorganic, mercury emissions. The most toxic and biomagnifying mercury species, methylmercury, is not emitted from anthropogenic or natural sources, but produced in the ocean from inorganic mercury. Marine mercury methylation has been confirmed for […]


Oceanic Margins as sources of lithogenic particulate and dissolved iron in the North Pacific Ocean

Three GEOTRACES Japanese cruises on board the R/V Hakuho Maru allowed establishing basin-scale and full-depth sectional distributions of total dissolvable iron (tdFe), dissolved iron (dFe), and labile particulate iron (lpFe=tdFe – dFe) in the North Pacific Ocean. Zheng and Sohrin (2019, see reference below) also discuss aluminum (Al) and manganese (Mn) data in this work. […]


Informative zinc isotopic fractionation in the Southern Ocean

Ellwood and co-workers (2020, see reference below) established the distribution of dissolved and particulate zinc (dZn and pZn respectively) and its isotopes in the Subantarctic Zone South of Tasmania. Concentration profiles show that zinc has a longer regeneration length scale than phosphorus and of cadmium, but shorter than copper. Modelling of the particulate profiles produced […]


Is the global primary production at it’s maximum rate?

Lauderdale and co-authors (2020, see reference below) are seriously questioning the paradigm establishing that marine phytoplankton growth is limited by iron on a global scale. Iron availability to marine microbes is facilitated by binding with organic molecules which, in turn, are produced by microbes. The authors hypothesize this forms a reinforcing cycle between biological activity […]


Can phytoplankton help us determine the bioavailability of iron in the world ocean?

Joint Science Highlight with US Ocean Carbon and Biogeochemistry (OCB). Iron (Fe) is a key element to life but in seawater it is present at extremely low concentrations. The scarcity of this important micronutrient limits phytoplankton growth in large swaths of the global ocean with consequences to the marine food-web and carbon cycling. Understanding the […]


The Colloidal Hourglass: North Atlantic Iron Distribution Controlled by Dynamic Colloidal Phase

K. Kunde and colleagues (2019, reference below) show that a highly dynamic colloidal iron phase in the upper ocean and at the seafloor boundary controls the distribution of dissolved iron at key sources and sinks across the subtropical North Atlantic Ocean, while the ocean interior is marked by an equilibrium partitioning between the soluble and […]


A unique insight into the properties of iron aerosols in the Arctic Ocean

Gao and co-workers (2019, see reference below) collected size-segregated aerosols over 8 segments of the 2015 US GEOTRACES cruise (GN01) across the Arctic Ocean. They show that: aerosol iron (Fe) had a single-mode size distribution, peaking at 4.4 μm in diameter, suggesting regional dust sources of Fe around the Arctic Ocean, Fe in the coarse-mode […]


A review constituting the half-way mark of GEOTRACES

After a brief reminder on the motivation and foundation processes of the international and ambitious programme GEOTRACES, Bob Anderson (2020, see reference below) proposes an overview of many results of GEOTRACES activities related to the three guiding themes of the programme: (1) fluxes and processes at ocean interfaces (2) internal cycling of TEIs, and 3) […]


Unprecedented iron delivery from the Congo River margin to the South Atlantic Gyre

The Congo River is the world’s second largest river by discharge volume and the only major river discharging into an eastern boundary region. Despite of its size, the Congo River plume and its influence on trace element cycles and ocean primary productivity is poorly constrained. During GEOTRACES cruise GA08, Vieira and co-workers (2020, see reference […]