Diversity patterns of bivalves in a coral dominated shallow-water bay in the northern Red Sea – high species richness on a local scale

Abstract

Bivalve species richness in the Northern Bay of Safaga, northern Red Sea, was assessed through original collecting activity in water depths from the intertidal to >50 m and by incorporating selected literature records. One-hundred-and-ninety-three samples, yielding 16,320 shells (dead and living), were taken from a coral-dominated coastal area that covers approximately 75 km². Two-hundred-and-forty-three bivalve species were recognized; this is the highest number of species reported to date for any coastal area of comparable size. This high species richness can be related to the great habitat variety in the bay and the major sampling effort, including quantitative and qualitative samples from hard and soft substrata, which enabled us to detect many rare species. Species accumulation curves suggest that the full range of species in the bay was considerably under-estimated. Additional species would most likely be detected at depths from 20–50 m, where sampling intensity was much lower than in shallower parts of the bay. Additional species are also likely to be small and rare; they will probably have unusual life habits and will probably be detected in bulk samples from soft substrata, from systematic sampling in cryptic habitats and from commensal associations. The consideration of dead shells in this survey helped us to recognize species that were rare or that colonize very specialized habitats. The probability of finding them alive within a reasonable time was low, with a reasonable number of samples, or without destructive sampling methods. Surveys of this type may help to identify areas of conservation importance, especially where living bivalves are only present in low numbers.

Keywords:

• Mollusca
• diversity
• Red Sea
• Indian Ocean
• habitat
• sampling intensity

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

Field work was supported by R. Golebiowski, K. Kleemann, A. Mansour, J. Nebelsick, P. Pervesler, W. Piller, C. Rupp and F. Steininger. The processing of sediment samples was supported by O. Abdelghany, S. Salek and U. Sattler. Bivalve identifications and nomenclature were supported by H. Dekker, H. Dijkstra, R. Janssen, E. Neubert, O. Schultz, J. Taylor, and E. Wawra. Discussions with J. Hohenegger and M. Stachowitsch improved the manuscript. The help of the Austrian Cultural Institute of the Austrian Embassy in Cairo, the Department of Geology of the University of Assiut/Qena and the Department of Geology of the South Valley University, Qena, made field work possible. The manuscript benefited from numerous comments by B. G. Tunberg and from the careful and constructive reviews by R. Bieler and M. Oliverio. The study was financially supported by the projects P5877 and P10715-Geo of the Austrian Science Fund (FWF) to F.F. Steininger, and by project H-140/2000 of the Hochschuljubiläumsstiftung der Stadt Wien to M. Zuschin.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark