Impact of anthropogenic activities and natural inputs on oceanographic characteristics of water and geochemistry of surface sediments in different sites along the Egyptian Red Sea Coast

Abstract

The surface sediments and sea water interactions were studied in five different sites along the Egyptian Red Sea coast. There are commutative and correlative relations between these constituents, therefore, any alterations occur in the sediments and sea water will be directly reflected on the marine environment. Sixty-five sediment samples were collected and also the oceanographic characteristics of surface sea water such as salinity, pH and total dissolved salts (TDS) were measured in situ for the same five localities (El-Hamrawein Harbour, Sharm el Bahari, Abu Dabab, Qola'an and Shalatein). The oceanographic properties of sea water show high salinity (42.55 and 42.59 psu) and total dissolved salts values (31.77 and 31.73 mg/L^-1) in both Qola'an and Shalatein, also Abu Dabab and Qala'an areas shows high pH values (8.00 and 8.04) due to the presence of dense sea grass cover. The sediment types generally changes from sand to slightly gravelly sand or muddy sand, also the surface sediments are mainly medium sand, moderately to poorly sorted. Geochemically, the factor controlling the carbonate content of studies sediments includes material supply of biogenic and terrigenous components. Therefore, sediments of El-Hamrawein, Sharm el-Bahari, Abu Dabab and Shalatein areas are terrigenous sediments, while sediments of Qola'an area south Marsa Alam are highly carbonates. In general, organic matter (4.82%) is higher in the sediments relative to adjacent areas due to high contributions of terrestrial materials by wadis and anthropogenic factors.

Key words: Grain size, geochemistry, oceanographic, sediments, seawater, Red Sea, Egypt.