Though the extent of these communities is unknown, temperature restraints limit the depth at which bacteria can exist (Parkes et al. 2000).  Also, the systems appear to shut down with the end of hydrothermal circulation.  As fluid flow decreases, cells starve and are trapped in the precipitates left in the veins they fluids formerly occupied (Thorseth et al. 2003).  Thorseth et al. concluded that most alteration had taken place prior to 2.5 Ma.  However, in the 2.5 Ma samples, open fractures suggest that cells were active, though at low rates, at during sampling.  By 18 and 25 Ma, no cells or organic carbon were found in the cores (Thorseth et al. 2003).

These microbial communities seem to persist for 1-10 Ma, as at 18 Ma, no carbon was found in the samples (Thorseth et al. 2003).  At 2.5 Ma, it appears that there was microbial activity still ongoing.  However, the extent that these communities can live in different parts of the oceans may be vastly different.  The figure to the left represents the current data, but information is lacking.