3. Geomorphology and Reef Building in the SE Gulf

The Gulf, a subtropical epicontinental sea, is home to the northernmost coral reefs on the western boundary of the Indo-Pacific. The basin has an area of 250,000 sq. km and is shallow and semi-restricted, which combined with its high-latitude and the presence of mountainous plateaus and deserts nearby, make the Gulf’s climate the most extreme endured by reef-building corals anywhere in the world (Riegl et al. 2011, Chaps.​ 2, 7, and 9). Despite the hostile conditions, the Gulf is home to about 40 species of scleractinian and 31 species of alcyonacean corals, representing an impoverished but typical segment of that of the Indo-Pacific. The Gulf is unique in many respects, most notably in terms of its water chemistry, inclement climate (hot summers but also cold winters), and the hardiness of the corals that inhabit it. These factors conspire to prevent the development of spectacular reef edifices, like those that exist in the adjacent Red Sea, but nonetheless the expression of coral growth is as varied and interesting as the prevailing climate. The Gulf marks the separation between the stable Arabian foreland, atop which the U.A.E. sits, and the unstable Iranian fold belt. This positioning generates a specific geological set-up which conveys primary control on the geomorphology of the basin and in turn, the opportunities for reef development. Of particular note is the influence that salt tectonics play in the creation of offshore banks and islands, all of which support coral communities. Secondary and more recent modification has been exerted by the flooding of the Gulf during the last transgression, with the majority of the basin having lain sub-aerially exposed for considerable periods in the last 100,000 years. This complex and rich genesis brings the Gulf to a crossroads in the present day; we witness an unprecedented level of coastal development and modification fueled by rising economic prosperity on the back of vast hydrocarbon discoveries. Many areas of spectacular coral growth have been lost to construction, but some remain, for now. This chapter will detail the status of these ecosystems and the factors that have shaped them through time.