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The impact of leisure scuba diving on coral reefs is described for the resort of Sharm el Sheikh on the Red Sea. It is established that significant damage is caused by this activity and presents a serious problem in environmental management. Sources of damage are investigated; the main problem is shown to be connected with the use of cameras. Some immediate control measures are discussed but it is recognised that total control may be difficult given the economic importance of the activity to the resort.

Surveys of the mangal along the Red Sea coast of Saudi Arabia form the basis of this study. Both soft-bottomed mangals and the less well known hard-bottomed mangals are represented. The distribution of Avicennia marina, the dominant mangrove species, is discontinuous in the northern part of the Red Sea. Its development increases southwards, and mean height is inversely correlated both with latitude (P

Echinostrephus molaris (de Blainville) is a small Indo‐pacific echinoid which burrows in coral reef limestone. Normally individuals do not leave the burrows so they cannot graze on algae growing around the burrow mouth. E. molaris catches floating algal particles with its long aboral spines. When a particle touches one of these organs or a tube‐foot in the area, the surrounding spines converge and grip it. Captured fragments are lowered to the test by further tube‐foot and spine action and are then passed across the ambitus towards the mouth. They are held by the oral tube‐feet and the shorter curved oral spines which aid ingestion. The behavioural and structural modifications shown for this habit are discussed. Burrowing and particle collecting have allowed E. molaris to occupy a particular niche on the reef. A similar method of food gathering is reported for Echinometra mathaei (de Blainville).