Dispersal of endolithic microorganisms in vesicular volcanic rock: Distribution, settlement and pathways revealed by 3D X‐ray microscopy

Pleistocene basanitic rocks of Vesteris Seamount in the Greenland Sea had been found to exhibit an endolithic habitat largely consisting of marine fungi that dwell within abundant vesicles, therefore representing cryptoendoliths. For the first time, we demonstrate that 3D X‐ray microscopy can unravel how microorganisms access and migrate through vesicular rock. The fossil assemblages occur within a set of vesicles connected by microcracks. Such microcracks, which are ubiquitous features in submarine volcanic rocks, enable the dispersal of marine microorganisms in the rock. This study suggests that this pathway for the colonization of marine volcanic rocks forms in consequence of early tensional stress due to variable rates of cooling of the lava flow. Subsequently, the interconnected vesicles get populated by rock‐dwelling microorganisms. This cryptoendolithic habitat exists at least since the Paleoproterozoic.