The influence of cyanobacteria on oil polluted intertidal soils at the Saudi Arabian Gulf shores

In 1991 the second Gulf War lead to the largest oil spill in human history. Over 770 km of coastline from southern Kuwait to Abu Ali Island (Saudi Arabia) were smothered with oil and tar, erasing most of the local plant and animal communities. In the following year cyanobacteria colonized most of the oil polluted shores. In the study area at the Saudi Arabian Gulf coast north of Jubail three different processes were observed that followed the extensive formation of cyanobacterial mats. The first one is desiccation, cracking, and peeling of the cyanobacterial mats, thereby removing the uppermost part of the oiled sediment. The second is the resettlement of burrowing macrofauna like crabs and benthic animals such as gastropods, which outcompete the cyanobacteria again. The third process is further extensive growth of cyanobacteria building thick laminated mats. These layers, completely seal the surface and hence produce an anaerobic milieu which inhibits oil degradation. As long as such cyanobacteria exist, they will prevent microbial oil degradation as well as any resettlement by macrofauna.