Coral reef development on the Gulf of Aden coast is severely constrained by the low temperature caused by seasonal upwelling resulting in the domination of hard substrates by brown algae, and soft substrates by seagrass. Only two species have been recorded along the Saudi Arabian Red Sea coast, Avicennia marina, which is widespread, and Rhizophora mucronata , found at only six sites. They are found in such areas as broad coastal plains, protected shores, over shoals and spits, and in lagoons. While mangroves are found scattered along much of the Red Sea coast, the main concentration is in the southern Red Sea where factors such as increased sediment creates an environment more conducive to their development. This increased development in the soil also coincides with areas of greatest agricultural potential.
Mangroves are also important nesting sites for several species of birds.
Development of coastal recreation facilities and coastal villages in the Ras Hatiba area north of Jeddah, shrimp aquaculture along the southern Red Sea coast and extensive landfill operations in Tarut Bay and Qatif Island and the Gulf War oil spill in Mardumah Island and Tanajib in the Eastern Province have all contributed to decline of the region's coastal mangroves. Mangrove systems are a valuable and ecologically significant habitat with many uses to humans. The high productivity sustained through detrital food chains contributes to resident and migratory animals and birds and to trophic balances in associated ecosystems. Seagrasses Seagrasses are fairly widespread along the Red Sea coast although they are more common in the southern Red Sea. Of the 11 seagrass species in the entire Red Sea, ten have been recorded along the Saudi Arabian coast.