Sediment Transport in Northern Safaga Bay (Red Sea, Egypt) as a Mechanism for Coral Community Differentiation

Northern Safaga Bay is a mixed siliciclastic/carbonate environment with both Aeolian and fluvial sediment input. Aeolian transport is prevalent in the north, the more important fluvial import is limited to wadis in the southwest. External and autochthonous sediment supply led to a distinct coral community differentiation. Two groups are found: (1) determined by hydrodynamic energy (strong waves/low currents – Acropora, medium waves/ medium currents – Porites, weak waves/high currents – Millepora dominant); (2) determined by light, suspension, and sedimentation (high light, low suspension, low sedimentation- Porites carpet; low light, high suspension moderate sedimentation – Sarcophyton carpet; all 3 moderate – Faviid carpet, degrading in low light, high suspension and sedimentation in diversity and coverage, in deeper water/low sedimentation – platy coral association). The northern part of the pay showed a slightly sediment influenced Acropora community. The western margin of the bay, along which fine grain sizes are transported in suspension, is characterized by the Sarcophyton carpet. In the southern sector, where episodic fluvial sediment import happens and sediment settles due to reduced current the sediment stressed community occurs