Deep-sea mining of earth minerals is expected to grow in the next decades. The increase in deep-sea mining activities may lead to the release of toxic concentrations of metals into the surrounding seabed. Increased concentrations of heavy metals can disturb important ecosystem services provided by microbial communities, such as growth, nutrient cycling activity, and microbial diversity. However, the consequences of metal exposure on microbial ecosystem functions in deep-sea conditions are currently unknown. The overarching goal of this project is to evaluate the impacts of heavy metal exposure on microbial growth, metabolism, and diversity in deep-sea conditions. We propose the following specific objectives: 1. Determine the effects of heavy metal exposure on growth and N2O reduction metabolism in a model bacterial culture, under deep-sea conditions. 2. Examine the effects of heavy metal exposure on the transcriptome of a model bacterial culture, under deep-sea conditions. 3. Determine the impacts of heavy metal exposure on overall N2O fluxes from deep-sea sediments. 4. Evaluate the impacts of heavy metal exposure on the biological and functional diversity of deep-sea complex microbial communities. This research will apply a mixed experimental approach in controlled conditions to address the stated objectives. We will combine the use of bacterial axenic cultures with the study of complex microbial communities under deep-sea conditions (low temperature and high hydrostatic pressure). We will use pressurized bioreactors and hyperbaric chambers to test the effects of two representative metals (copper and cadmium) on bacterial growth, metabolic reduction of N2O, expression of functional genes, and functional diversity. The mining of the deep seafloor is still at an early stage of implementation. This research presents a unique opportunity to assess the environmental risks of an anthropogenic activity before it begins to shape the ecosystem.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 101038095