Animation: Olivier Ragueneau & Gabriel Dulaquais

A better understanding of oceanic biogeochemical cycles requires describing and understanding input and output, and their variability. To this end, we are working on the different interfaces with the ocean, since these interfaces are external sources and sinks of matter whose intensity and importance vary according to the element considered. These interfaces are generally the site of strong physico-chemical gradients and are extremely sensitive to different anthropogenic pressures.

Sediments, the ocean-atmosphere interface, and hydrothermal springs are the sources of metals for the ocean. Our findings showing that bacterial concentrations in rainwater samples are related to the increase in iron-specific ligand concentrations that can impact organic speciation of iron, our objective is to better understand the interactions between iron and bioaerosols and their fate in the ocean water column. In hydrothermal environments, our objective is to identify and describe the chemical reactions that determine the organic complexing of metals.

The land-sea continuum is an interface strongly impacted by anthropogenic pressures. The physico-chemical gradients in estuaries control river inputs of biogenic (Si, N) and metallic elements. Our team continues to improve our understanding of the dynamics of these elements along the land-sea continuum by studying the changes that occur through adsorption/desorption, coagulation, complexing or degradation processes and by characterizing the composition and physico-chemical role of organic matter that influences their bioavailability/toxicity.

In addition, our work in the Bay of Vilaine should lead us to participate in the development of a nutrient limitation scheme that could restore eutrophic ecosystems. By improving our knowledge of the Brest Rade we wish to use climate change scenarios to model the evolution of nutrient fluxes in the coastal zone. These scenarios can be combined with scenarios of changes in agricultural practices in the watersheds in collaboration with AMURE’s team of economists.