Reef walking on Red Sea reef flats - Quantifying impacts and identifying motives

Reef walking on the shallow reef flats of fringing reefs is an activity commonly observed on Red Sea coral reefs. Of the 137 in-water observations of reef walkers made at Ras Um Sidd, Sharm El Sheikh, South Sinai, 12.4% caused coral damage. Eighteen incidents of coral damage were recorded, 44.4% being breakages of branching corals, 39.8% abrasions of various growth forms and 16.7% detachments of soft coral colonies. Sediment was stirred-up on 31.4% of observations. Tramplers broke 0.1 branches per minute and raised 1.5 sediment clouds, thereby causing more damage than reported from divers. Damage caused depended on coral community structure and past trampling history, with communities dominated by fragile branching corals being most susceptible to mechanical damage and communities heavily trampled in the past being less susceptible. Given that main motives for reef walking included crossing the reef flat, adjusting gear or communicating, management interventions, such as the construction of a walkway combined with a public awareness campaign, could reduce the numbers of reef walkers by up to 39%.