Microfacies of the biotic crusts from two Aegean submarine caves (Eastern Mediterranean)

This work extends the knowledge on bioconstructions growing in cryptic marine environments with the characterization of the biotic crusts found in the Eastern Mediterranean Sea. The walls and vaults of Fara and Agios Vasilios Caves (Lesvos Island, Greece) are covered with bryozoans, serpulids, coralline algae, scleractinian corals and sponges. Skeletons of these organisms are often cemented together to form small bioconstructions. Serpulids, bryozoans and sponges dominate the innermost dark cave sectors. Fine sediments (microcrystalline calcite) deposited via microbial metabolic processes, are a minor component, but testify the presence of bacteria in the crusts. The correlation between microbial activity and abundance of sponges could explain the development of the studied bioconstructions that have smaller sizes (few centimeters) in comparison to larger biostalactites common in other Mediterranean caves.