Mangroves
 
 

Mangrove sites are quite rare in the study area. They cover only 6 km of total coastline. The mangroves are found at sheltered sites on soft anaerobic mud. The salt tolerant mangrove trees settle from mean high tide level to the mid eulittoral. Only one single species of mangrove tree, Avicennia marina, occurs in the study area and along the Saudi Arabian Gulf Coast. In association with mangroves, salt marsh halophytes such as Arthrocnemum macrostachyum or Salicornica europaea are common.

 
  Schematic profile of a mangrove habitat at the Gulf coast  
 
profile mangroves
 
  The mangrove-habitat provides food and shelter to small invertebrates such as shrimp and many species of young fish.
Mangrove shores are usually dissected by a branched net of
tidal channels. As the oil of the 1991 Gulf War Oil Spill came along with the tides, it affected primarily the trees along those tidal channels. Trees further away from channels were hardly reached by the oil.
About 50% of the mangrove trees were oiled and around 30% died off either immediately or during the following years.
 
  mangroves

Devastated mangrove area

on Qurma Island

 

Most mangrove sites were not as badly hit by the 1991 Oil Spill as salt marshes because the mangroves are located in more protected areas. Nevertheless, all states of destruction could be seen at the more heavily affected sites. Usually a 10 to 20 metre wide belt of Avicennia plants died in the upper eulittoral.

Most of the Cleistostoma populations were killed in these heavily contaminated areas as well. Towards the mid and lower eulittoral the oiling was less severe and in most cases numbers of individuals and species diversity were higher. The recolonisation by crabs and other burrowing macrofauna started at most sites relatively early in 1992. After the resettlement of crabs the vegetation got the chance to germinate again.

In general, most mangrove sites managed to recover partially until 1993 and nearly fully until 2002. Only a narrow tar covered belt near the HWS and some local calcified tar crusts remained at a few sites. Halophytic plants typical of salt marsh such as Halocnemum, Arthrocnemum or Salicornica, had more problems to recover in comparison to the mangrove trees. This was due to the ability of the mangrove Avicennia marina to form aerial roots, which allow the plants better to compensate for a decreased oxygen concentration within the soil

 
   
   
 
(Barth 2002)
 
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