Red Sea coral reefs are the northernmost in the Indian Ocean. Most of the Red Sea coast is rimmed by shallow submarine shelves and extensive fringing reef systems, by far the dominant reef type found here.
Red Sea fringing reef platforms are over 5000 years old, and the entire coastal reef complex extends along some 2,000 km (1,240 miles) of shoreline.
Most such reefs grow directly from the shoreline. The dominant, most actively growing corals include most notably highly branched species of the genera Acropora and Porites.
The Red Sea also contains numerous offshore reefs that defy classic reef type categorization.
Included in this catch-all category are atoll-like rings of coral, elongated coral ridges that rise abruptly from considerable depths on both sides, and peculiar complex reef patterns of odd shapes.
Such Red Sea coral reef formations are almost certainly the result of the active and unusual tectonic forces that have been at work here for millennia and continue today.
There are a few true atolls in the Red Sea (several off the coast of Sudan), but no true barrier reefs.
The geological history of the Red Sea region is distinctive, and there is only slow and restricted water (and larval) exchange between this sea and the remainder of the Indo-Pacific region as a whole.
Thus, Red Sea reefs have developed a number of features that distinguish them from reefs found throughout most of the rest of this vast oceanic area.
Particularly important in the light of global warming predictions is the fact that Red Sea corals have developed an unusually high tolerance to the extreme temperatures, salinity, and occasional turbidity (caused by huge seasonal dust storms) that occur in the region. Such conditions that would be lethal or highly damaging to most hard corals found elsewhere.
Also, water clarity is exceptional in the Red Sea because of the lack of river discharge and low rainfall. Thus, Red Sea reefs are not heavily impacted by the suspension and dissipation of fine sediments that plague reefs in tropical oceans near large land masses.
The Al Wadj Bank, Saudi Arabia
Red Sea coral reefs are particularly well developed in the north and central portions (off the coasts of Egypt, Saudi Arabia, Sudan), with large sizable offshore reef complexes containing small islands, fringing reefs, and a variety of reef-associated habitats (see photo, above).
Further south, coral growth is somewhat inhibited by the influx of nutrient laden water where the Indian Ocean enters the Red Sea. This surface waters of the more southerly areas are also subject to far greater mixing with deeper water caused by strong winds coming off a high mountainous coast.
In general, the marine biota of Red Sea coral reefs is characterized by high endemism. For example, of the 1200 or so coral reef fish species recorded, about 10% are endemic (found nowhere else).
About 300 hard coral species have been recorded from the Red Sea as a whole. The Egyptian coast alone supports about 200 species of reef building corals belonging to almost 50 genera. This represents about four times the hard coral diversity found on Caribbean reefs, and is comparable to the coral diversity found in the Maldives and Seychelles in the Indian Ocean.
Nonetheless, the biodiversity of Red Sea reefs does not rival that of reefs of the richest parts of the Indo-Pacific region.
Despite the extreme conditions characteristic of the region, Red Sea coral reefs are generally healthy. Coral reefs range widely in condition and cover, with up to 85% living coral cover at the best sites and over 50% live coral cover at many other locations. There is usually minimal coral bleaching evident, although some localized outbreaks are reported from time to time.
Still, many Red Sea coral reefs situated near urban centers and other developed parts of the coast have been heavily damaged or lost due to the predicatable effects of poorly planned or regulated population expansions and coastal development, along with associated declines in water quality.
In some of the once most pristine reef areas, insufficiently managed dive tourism (damage from anchors and recreational scuba divers) has also taken its predictable toll on the reefs.
A fringing reef rims the shore of Egypt’s Ras Mohammed National Park
Studies of diver effects on reefs suggest that continued dive tourism expansion at some of the more popular tourist destinations would be ill-advised and will inevitably lead to serious reef degradation.
A growing number of marine number of protected areas (MPAs) have been established in the Red Sea to help alleviate some of these problems. Ras Mohammed National Park was established by Egypt in 1983 and includes miles of healthy fringing reefs. The Red Sea Marine Peace Park in the Gulf of Aqaba was founded in 1994 by the governments of Jordan and Israel to preserve and protect the area’s coral reefs.
The Red Sea is an extension of the Indian Ocean, lying between the Arabian Peninsula and Africa, with a surface are roughly equal to the US state of California.
The only natural connection between the Red Sea and the rest of the Indian Ocean is Bab el Mandeb, a narrow strait that transitions into the Gulf of Aden.
To the north, the Red Sea splits into two narrow branches (the Gulf of Suez and the Gulf of Aqaba) that flank the Sinai Peninsula.
Overall, the Red Sea is a comparatively shallow body of water with an average depth of only about 1600 feet. However, it is in reality a young ocean in the early stage of formation.
As the African and Arabian continents slowly rift apart, new oceanic crust is formed and slowly but surely the Red Sea is gradually widening. The tectonic forces at work are most evident in the deep narrow trench (Rift Valley) that runs most of the length of the sea at its center, reaching a maximum depth of over 8,600 feet (2,600 m) below sea level.
The region surrounding the Red Sea is one of the hottest, driest areas on earth. The extreme air temperatures result in very high levels of evaporation, making this one of the hottest and saltiest bodies of seawater in the world.
Map of the Red Sea and surrounding region
The average salinity is 40 parts per thousand (ppt), as compared to about 35-36 (ppt) in the tropical Indian, Pacific, and Atlantic Oceans. Recent measurements found surface water temperatures to be 28 degrees C. (82 degrees F.) in winter and up to 34 degrees C. (93 degrees F.) in summer.
Scuba diving and snorkeling on the fringing reefs of the Red Sea became popular soon after the publicity, books, and films of the expeditions of Hans Hass and Jacques Cousteau in the 1950s and 1960s were widely disseminated.
Today, the most popular dive destinations along the northern coast of the Gulf of Aquaba (known as the “Red Sea Riviera”) include Eilat in Israel and Aqaba in Jordan. Other popular destinations in the Gulf of Aquaba on the the Egyptian side of Sinai are Dahab and Taba.
Further south, along the western shore of the Red Sea, reef diving is well supported at Marsa Alam, El Gouna, Safaga, and Hurghada.
The very popular Egyptian reef diving center of Sham-el-Sheikh, located on the southern tip of the Sinai, has undergone rapid expansion recently.
Shallow reefs, clear water, and abundant marine life
In the most southerly portions of the Red Sea, recreational diving (or tourism of any kind) is presently considered risky because of the presence of pirates originating from uncontrolled zones of Somalia. The situation is even worse in the Gulf of Aden between Somalia and Yemen.
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