Geochemistry and benthic foraminifera of the nearshore sediments from Yanbu to Al-Lith, eastern Red Sea coast, Saudi Arabia

Abstract

The nearshore waters and sediments along 500 km of the eastern Red Sea coast from Yanbu to Al-Lith were investigated in regard to environmental parameters (temperature, salinity, dissolved oxygen and pH), sediment grain size, organic matters, carbonates, metal concentrations (Fe, Mn, Zn, Cu, Cr, Pb, Ni and Co) and benthic foraminifera in order to document and give a broad view about the present environmental status of this shorline area. The results showed that the studied nearshore sediments were mainly composed of biogenic sandy sediments with very low metal concentrations indicating an existence in a natural state. However, in the nearshore sediments of Jeddah coast, these metals became frequent showing the highest concentrations indicating urbanization activities. In the other hand, the organic matter showed no relations with these metals indicating its typical marine sources. The benthic foraminifera of these nearshore sediments were low due to modification by taphonomic processes and were visually (and by the CCA) divided into three faunal assemblages. The Coscinospira hemprichii-Varidentella neostriatula assemblage increased northwards, following the subtle northward increase of salinity, and this could be used as a high salinity indicator in the Red Sea fossil sediments. Whereas, the Neorotalia calcar-Neoeponides bradyi assemblage increased southward, probably, as a result of a profusion of seagrasses and filamentous algae. The Quinqueloculina seminula assemblage showed no increase/decrease either towards the north or the south, indicating their tolerance for a wide range of environmental conditions and showing, however, their preferences to soft, muddy substrates.