As this site is naturally poor in dissolved iron, which is a source of development for Fe-oxidising bacteria, in situ colonisation experiments are carried out. Using a mineral substrate, synthetic basaltic glass enriched in Fe(II), enrichment cultures can be carried out while maintaining the conditions of the environment, in particular the pressure, temperature and nutrient supply of the growth medium for the microorganisms. We use geomicrobiological colonizers (photo on the left), consisting of pierced glass tubes filled with Fe(II)-enriched basaltic glass and iron shots (ballast from the Nautile), distributed on a weighted support. The colonisers are installed with the aid of the Nautile, using biological sampling boxes to avoid contamination in the water column.