A microbialite/algal ridge fringing reef complex, Highborne Cay, Bahamas

Microbial deposition plays an important role in the construction of a present-day fringing reef complex at Highborne Cay, Bahamas. This reef consists of an algal ridge that grades shoreward to a back reef lagoon with a diversity of microbial buildups, Intertidal stromatolites and thrombolites form tabular mounds several meters in diameter and up toa meter thick in the nearhore zone. Shallow subtidal stromatolites form ridges and columnar heads up to half a meter high in the sandy lagoon. A tufa-like rock forms ridges at the bases of some of the thrombolites. The algal ridge is composed mainly of the branching crustose coralline alga, Neogoniolithon strictum, which, until recently, was not known to form algal ridges. The coralline algae are commonly coated with micritic crusts of possible microbial origin. This unusual reef is an ideal system for geomicrobiological studies.