Krupp, F. & Fleming, R. (eds.), Establishment of a Marine Habitat and Wildlife Sanctuary for the Gulf Region. Final report of phase III. Jubail, Frankfurt a.M.

Results of Long-term (1991-1995) Monitoring of the Intertidal Biota after the 1991 Gulf War Oil Spill

A b s t r a c t: Quantitative surveys of the intertidal macrobiota were conducted between 1991-95 along permanent transect lines (PTLs) within the impacted area between Ras az-Zaur and Abu Ali, and at control unpolluted sites to the south of the region. Results reveal that during the study period this oil has weathered, largely disappearing from rocky shores and reducing in extent on soft sediment shores. A sequence of weathering and the formation of overlying algal mats was observed on all shores except at the higher levels of the littoral fringe. By December 1991 between 50-100 % mortality of biota had occurred on the upper shore as a result of pollution. However, by 1995 species diversity ranged from normal to 60 % on the upper shore, and species diversity on the lower shore was similar to that found on unpolluted shores. Species abundances also increased during the survey period and reached or exceeded levels found at lower shore levels on control shores. At higher shore levels densities remain lower than normal at some sites due in part to slow population increases of species without planktonic larvae. High fluctuations in individual species numbers on PTLs appears to be due to a lack of balanced community structure, although this rapidly improved during 1995. However, as control shores show great seasonal and annual fluctuation, care is needed in interpretation. Towards the end of the monitoring period there was comparable influx of the same species on both control and PTL shores indicating return to community stability.