The importance of euendolithic microbial communities as a palaeontological tool for the reconstruction of ancientsedimentary basin history has been widely acknowledged (Golubic et al. 1975, 1984, Vogel et al. 1995, 1996). This tool can be improved by better knowledge of the relationship between modern microendoliths (rock-penetrating microorganisms) and the environmental conditions they thrive in. The aim of a long-term study conducted on Lee Stocking Island, Bahamas, was to point out factors that control occurrence, distribution and composition of microbial euendolithic populations. The experimental design and first results are published in Radtke 1993, Kiene et al. 1995, Vogel et al. 1996, Gektidis 1997. This paper deals with one aspect of microendolithic development: the progress and change of community structure in time. Microendolithic biocoenoses are excellent bathymetric indicators (Golubic 1975, Gektidis 1997). However their potential use as indicators for different water depths is influenced by the continuous growth of the endolithic communities themselves and the surrounding benthic microflora. This process will have to be taken into consideration when, following a uniformitarian approach, fossil basins are to be reconstructed by analyzing the fossil microendolithic ichno-communities.