The interaction between fluid flow and biofilm growth in fractured rock

We investigate the interaction between fluid flow and biofilm growth in fractured rock, with a view toward understanding the impacts of this interaction on seafloor hydrothermal fluid venting. We present a preliminary model that predicts the conditions under which a biofilm may attain steady state, the thickness of such a steady state film, and the effect of the film on the permeability of the porous rock matrix as well as on interstitial fluid velocities. In particular, the model predicts that a biofilm can only attain a stable thickness when a precise relationship holds between parameters representing the fluid velocity, bacterial substrate ingestion, and sloughing off of the film into the fluid stream. Conversely, when this condition does not hold, the biofilm either grows to fill all available space or no biofilm can be supported.