Reef Destruction and Bleaching in the Red Sea
Yusef Fadlallah: firstname.lastname@example.org
In 1998 extensive surveys (habitat mapping project) were carried out in nearshore and offshore reefs at two locations along the eastern coast of the Red Sea, Saudi Arabia. One location (16°40 N to 17°10 N), along the Jaizan coast near the boarder with Yemen, was surveyed during February 1998. The other location (22°33' N to 22°58' N, along the coast of Rabigh -140 km north of Jeddah), was surveyed during December 1998. The survey in Jaizan was the first for that area, whereas the Rabigh location was surveyed once before during October 1997.
Fringing reefs do not occur in the southern mudflat-mangrove dominated coastline off Jaizan. However, many offshore reef banks and islands occur 15-30 km from the coast. However, the corals throughout these offshore reefs are dead . Observations suggest that mortality occurred during the past decade, very likely from intensive trawling operations (we observed more than 20 shrimp trawlers in one location) that cause direct mechanical damage as well as increased sediment loading on the reefs. Acropora and Pocillopora apparently constituted the main reefal communities. However, gently sloping portions of the reef islands also contained colonies of Porites of considerable sizes. These were all dead. The only live corals Throughout the entire survey site (about 100 km of coastline), that were observed were the small and hardy Siderastrea.
Fringing reefs and reef banks off Rabigh contained extensive live communities of hard and soft corals and associated fish populations when the area was surveyed in October 1997. The same area apparently suffered wide scale catastrophic mortality that may have resulted from bleaching during the summer (August-September 1998). The fringing reefs were especially affected. Hard (including Millepora) and soft corals were wiped out (95+ percent) on the top of the reef, at the reef crest and back reef, and significant mortality occurred down to 15 m depth along the reef edge. Acropora was especially hardly hit, and the hardy Pocillopora verrucosa, Stylophora pistillata and Porites were not spared.Millepora that were observed to dominate extensive stretches of the reef crest along the coast during the survey of 1997 apparently suffered mortality approaching 100 percent.
The offshore (25 km from the coast) reef banks of Rabigh were not spared. Mortality of corals was estimated to be around 70 percent on a previously surveyed location. Some of the corals were still bleaching at the time of the survey. Habitat destruction and natural phenomena (sediment loading) are responsible for the demise of corals in Jaizan (southern Red Sea). The Farasan Archipelago is only 20 km to the west of the offshore survey location in Jaizan. We have no information on the condition of the corals in the reefs there.
Temperature stress is apparently responsible for bleaching and subsequent mortality of corals in the Rabigh (central Red Sea). Although the mortality observed in Rabigh was locally (50 km x 20 km) extensive, we do not have any other information that would suggest wide scale coral bleaching and mortality along the Saudi coast of the Red Sea.
Center for Environment and Water
Research Institute - King Fahd University of Petroleum and Minerals
Dhahran 31261, Saudi Arabia
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