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Biological Assessment of Oil Spill Clean-up Sites in Dawhat ad-Dafi and Dawhat al-Musallamiya

A b s t r a c t: Clean-up sites encompassing rock, sand, mud, salt-marsh and mangrove habitats, were surveyed and compared to similar control sites where clean-up operations had not been conducted. At rocky sites most tar was removed within a year by natural processes and no differences, due to clean-up operations, were observed between biota at artificially cleaned sites and sites left to recover naturally. Similarly, no effects of clean-up operations were observed at a salt-marsh or a lightly oiled mangrove site. On the sand shore, clean-up operations appear to have actually delayed recovery at the top shore where no discernible reduction in the amount of oil that the sediment contained, was found. At a mud flat, diversity and abundance of organisms at the lower end of the cleaned zone are higher than at non cleaned areas, but the upper shore of both remains abiotic. At a heavily oiled mangrove, oil entrapment techniques during collection activities nearby may have increased the degree of oiling at the site. Improvement due to subsequent clean-up operations was difficult to assess objectively because a comparable mangrove control site was not found. Nevertheless, in this case the efforts made are thought to have been beneficial due to the sheer mass of standing oil removed. The overall results of this survey indicate that for most cases clean-up operations result in only a marginal ecological improvement over time, if at all, and that in at least one case they have retarded biological recovery. They are more likely to be of benefit if carried out immediately after beaching of oil, while it is still fresh.