Effect of oil pollution on euendolithic cyanobacteria of the Arabian Gulf.

Microbial euendoliths (true borer) cyanobacteria are carbonate-boring microorganisms found in modern and ancient marine environments. Modern euendoliths include a wide range of prokaryotes as well as eukaryotes, which have been reported world-wide. The importance of euendolithic cyanobacteria concerns their role in bio-erosion of calcium carbonate substrates and as ecological indicators of shallow, tropical and subtropical marine environments. Arabian Gulf ooids from four sites along the east coast of Saudi Arabia have been bored and inhabited by several species of euendolithic cyanobacteria. This assemblage of different species exists simultaneously within the same ooid grain. Comparisons of 1989 and 1992 data reveal a drastic reduction in active euendoliths, and the average numbers of colonies in these ooids. This study reveals the harmful effect of the 1991 oil spill on these unique microorganisms residing in these ooids.