<I>In-situ</I> observation of deep water corals in the northern Red Sea waters of Saudi Arabia

Abstract

Three sites offshore of the Saudi Arabia coast in the northern Red Sea were surveyed in November 2012 to search for deep-water coral (DWC) grounds using a Remotely Operated Vehicle (Fig. 1). A total of 156 colonies were positively identified between 400 and 760 m, and were represented by seven species belonging to Scleractinia (3), Alcyonacea (3) and Antipatharia (1). The scleractinians Dasmosmilia valida Marenzeller (1907), Eguchipsammia fistula (Alcock, 1902) and Rhizotrochus typus Milne-Edwards and Haime, 1848 were identified to species level, while the octocorals Acanthogorgia sp., Chironephthya sp., Pseudopterogorgia sp., and the antipatharian Stichopathes sp., were identified to genus level. Overall, the highest abundance of DWC was observed at Site A1, the closest to the coast. The most abundant species in the study area was D. valida, which lives attached to rocky substrates and represented 42% of the total coral population at site A1. Water column attributes at this depth were quite homogenous with temperature ca. 21.6 °C, salinity ca. 40.56, dissolved oxygen ca. 1.75 ml L-1 and current velocity from 0.6 to 34.5 cm s-1 with a mean value of 9.5 cm s-1. Interestingly, these DWC can cope with high temperature and salinity, compared to those in other regions.