Unraveling the link between microbial biogeochemical cycles and mercury transformations in oxygen-depleted submarine groundwater discharges

Coastal aquifers are sensitive land-ocean transitional zones receiving nutrient-rich water due mainly to fertilizing practices that may increase microbial activity and reduce oxygen (O2) availability. The diverse microbial communities inhabiting these systems may have a crucial role in biogeochemical cycles including metal transformations such as mercury (Hg). Yet, the factors determining the microbial Hg transformations in coastal aquifers is poorly understood. The increasing depletion of O2 in coastal waters from submarine groundwater discharges (SGDs) may modify the biogeochemical processes and hence modulates the Hg speciation and its export to the sea. To shed light on this, the MIMOA project aims at defining the role of nutrient-enriched SGDs in microbial Hg cycling of coastal areas by combining microbial, chemical, and educative dimensions. This project will rely on the synergy of my background in biogeochemical cycles and anoxic environments with extensive expertise in Hg biogeochemistry and metagenomics of the host (Dr. Bravo). This will be complemented by the essential expertise in biochemistry of low O2 zones and analytic/environmental chemistry of the two secondment supervisors (Dr. Garcia-Robledo and Dr. Amouroux). By getting trained in bioinformatic analyses, gene detection and chemistry, I will explore the effects of O2 depletion from SGDs on microbial Hg transformations in an eutrophication context and transfer this knowledge to the general audience through science outreach and education assisted by Plàncton company as a placement. MIMOA outcomes will significantly contribute to global Hg budget by revealing the importance of Hg export through depleted O2 SGDs, having long-term consequences on marine food web contamination and improve awareness of general audience on their anthropic footprint in coastal zone; boosting my career opportunities as a prominent researcher in microbial ecology and biogeochemistry, after my research period in Latin America.