International Journal of Research in Environmental Science (IJRES) Volume 7, Issue 1, 2021, PP 38-53 ISSN No. (Online) 2454-9444 DOI: http://dx.doi.org/10.20431/2454-9444.0701005 www.arcjournals.org International Journal of Research in Environmental Science (IJRES) Page | 38 Environmental Genomics and Biodiversity of Macro- and Microbenthic Communities in the Red Sea Coast of Jeddah City SAMAH SULAIMAN 1* , BAESHEN, M. N. 2 , ALI AL-KELDI 3 , HAYAM S. ABDELKADER 4 Department of Biology, College of Science, University of Jeddah, Jeddah, Saudi Arabia. 1. BACKGROUND Kingdom of Saud Arabia covers about 80% of Arabian Peninsula; it occupies an area of about 2,250,000 square kilometers (El Raey, 2010). The country has an arid climate with an average annual rainfall of 70.5 mm along the broad coastal Tihamah plains of Red Sea (Hariri, 2012). The largest section of Saudi Arabian's Red Sea coastline (Figure 1) extends about 1800 km to the west; from Jordan to Yemen (Khalil, 2017). The Red Sea is a young environment that began to form after the northeast African continental crust began to divide and drift eastward (Berumen et al, 2019). The present dimensions and structure of the Red Sea are the result of a combination of geological and climatic processes, including the spreading between the African and Arabian plates, associated volcanism in the mid- Tertiary, and eustatic sea-level fluctuations (Di Battista et al., 2016). Tertiary faulting in the area between Africa and Arabia led to the formation of the Red Sea rift. Red Sea Red Sea Mountains are characterized by a steep western edge and a gently east-dipping Arabian Shield. The landmass lies between the mid-latitudes; in a typically arid area dependent on winter rains in the north and monsoon winds in the south. The Red Sea lies as an elongated, north-south oriented oceanic basin extending from 30°N to 12° 40'N between Asia and Africa (Rasul and Stewart, 2015). It is surrounded by desert landscapes where rivers are scarce, with a modest area (438,000 km2) (Alsaffar, 2018). Red Sea countries include Egypt, Sudan, Eritrea, and Djibouti on the west coast, with Saudi Arabia and Yemen on the east coast. The Red Sea has many fascinating geomorphological characteristics, such as its extreme depths, particularly along its long axis, and the unusually high elevations along much of its rough shoulder. The oceanic spreading centers in the Red Sea are profoundly bound to the depths (Rasul and Stewart, 2015). its depths range from shallow along the coral coasts (50 m) to deep in the shelf/offshore areas (500-1000 m) or in the trench itself (at least 1000 m) (1000 m). Marine environments are broadly divided into two aquatic environments: a pelagic and a near-bottom or benthic. Within the pelagic environment, water is divided into the neritic province, which includes water above the continental shelf and is characterized by high nutrient content resulting from solutes in river runoff, and the oceanic province, which includes all open water beyond the continental shelf (Dupuy et al., 2015). In addition, the benthic environment is divided into a number of unique ecological zones based on depth, seafloor topography and vertical gradients of physical parameters; in particular, the balance between stabilizing and destabilizing biotic effects (Schratzbergera and Ingels, 2020). These are: a) the supralittoral (above the high-water mark but not submerged), b) the intertidal or littoral zone, c) offshore water, and d) the sublittoral or ambient zone. The sediments of the continental shelf that affect marine organisms generally originate from the land (Joydas and Borja, 2019). The intertidal soft sediment habitat is classified as one of the most productive ecosystems on earth; mainly due to the primary production of highly diverse collections of benthic diatoms (Dupuy et al., 2015). Haeckel coined the term benthos in 1891, which is derived from the Greek verb βαos, noun βένθος (váthos, rank, degree), related to bathos, depth, bathys, deep, high, meaning depth of the sea (Zaleha, *Corresponding Authors: SAMAH SULAIMAN, Department of Biology, College of Science, University of Jeddah, Jeddah, Saudi Arabia.