Recent microbial endoliths have fine zonation within the intertidal and supratidal areas along the carbonate coast of Bermuda. This zonation correlates with a gradual change in the rock surface relief and color. The diversity and abundance of the endoliths were determined for seven sites with different degrees of slope and wave exposure around Bermuda. Within each site there is a gradual reduction in the number of species and a shift in the dominance of a species from subtidal to supratidal. By grouping of species, it is possible to identify community composition changes for each site and to establish the principal microbial endolith associations representative of the Bermuda Coast. A given assemblage of endolithic organisms occupies a certain relative position with respe t to mean sea level and wave exposure, and is characterized by the microrelief of the biokarst. Preliminary work on the endoliths of Jamaica and Florida suggests that the endolith-community profile for Bermuda may be typical of the entire Caribbean area.

The microbial endolithic assemblages can be recognized on the basis of (SEM-studied) resin casts of their boreholes. Thus, by comparison with recent assemblages, fossil microborings can be interpreted.

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