Bioavailability of Iron and other Trace MetAls in marine Particles – BITMAP

The BITMAP (Bioavailability of Iron and other Trace MetAls in marine Particles) project is proposed by a French female early career researcher, who has gained her PhD in UK, followed by a postdoctoral stay in US. She is currently a postdoctoral researcher in UK.

This novel project proposes to assess the bioavailability of particulate trace metals. This is an extremely important topic as trace metals exert major controls on marine ecosystem features and on the efficiency of the biological pump and as a result, on anthropogenic carbon absorption by the oceans. The biological carbon pump in the ocean is a significant term in the global carbon cycle which transports ~10 Gt C per year from the surface waters to the ocean interior, mainly in the form of settling particles. However in some regions a limitation of trace elements like iron which serves as an essential micronutrient inhibit this primary production.

Up to very recently, it was argued that the phytoplankton mainly has access only to the dissolved phase, rendering the studies of particulate trace metals less attractive. This idea evolved recently and the role of particulate trace metals is more important than initially thought. Also, trace metals concentrations are usually one or two orders of magnitude lower than dissolved concentrations, which usually makes their determination extremely arduous. As a result, we are still largely ignorant on the large scale particulate trace element distributions, sources and sinks for this reservoir and mechanisms of exchanges between particulate and dissolved phases.

Within this context, BITMAP proposes to assess the influence of the size, the origin and the distribution on the bioavailability of particulate trace metals. This project will focus mainly on the following elements: aluminum, manganese, iron, cobalt, copper, zinc, cadmium, phosphorus and barium. To this aim, a combination of tools will be used: biotic and abiotic incubation experiments, chemical leaches, Scanning Electron Microscopy (SEM), and iron isotopes.

BITMAP proposes to provide a complete characterisation of the particulate phase in different size fractions in the Iroise Sea and in the key area of the North Atlantic, which is a key area as it absorbs ~20 % of atmospheric carbon dioxide. Spatial distribution as well as vertical export (using 234Th) of particulate trace metals will be determined for both the reactive and refractory fraction.

BITMAP falls within the framework of two international programmes (GEOTRACES and IMBER), a communication European action (COST) and relates to three French project previously funded by the ANR: SOLWARA, BONUS-GOODHOPE and KEOPS 2.

The results of BITMAP will be very useful to the international scientific community, to the environmental agencies and local authorities. Three participations to major international conferences in marine sciences are scheduled, together with a number of publications in peer reviewed journals and in the general press. An exhibition and conference will be organized at IUEM for the general public after the cruise. The progress and outputs will also be published via the creation of an interactive website, and middle school pupils will be able to ask questions to the scientists involved in BITMAP.
BITMAP will also enable collaborations with many international labs, like for example Rutgers University (US), Stellenbosch University (South Africa) and the National Oceanography Centre (UK).

Finally, BITMAP will be based in Brest, at the Laboratoire de l’Environnement MARin (LEMAR) and will involve two main partners : the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (LEGOS) and the Institut de Physique du Globe à Paris (IPGP).