Benthic Foraminiferal Distribution and their Environmental Significance of Selected Red Sea Coastal Ecosystems, Saudi Arabia

Abstract

The present study uses benthic foraminiferal abundance and diversity indices in the coastal bottom sediments of the Farasan Island, Southern Cornich of Jeddah (SCJ) and Rabigh areas, Saudi Arabia to identify the ecological controls on their distribution. A total of 20 recent sediment samples were collected from the studied sites. Grain size analysis, CaCO₃ content and organic matter were determined. Multivariate analyses were applied to test and represent the diversity indices and distribution of benthic foraminiferal assemblage. Two main benthic foraminiferal assemblages; A and B have been distinguished. The assemblage-A includes a high abundance of T. trigonula (33%), S. communis (30%), Q. bosciana (21%), E. striatopunctatum (18%) with low diversity indices in the Rabigh coastal sediments indicating high ecological stress. The Farasan ecosystem is dominated by sub-assemblage-B1 P. planatus (55%), S. orbiculus (27%), N. calcar (15%), Q. limbata (14%), which totally ranges between 60%-82%, indicating a highly oxic marine environment and normal ecology stress. Sub-assemblage-B2 such as P. planatus (39%),C. hemprichii (26%), V. neostriata (15%),Q. costata (10%) dominate the Southern Corniche of Jeddah (SCJ) with relatively high diversity indices, indicating moderate stress ecology or unstable environmental conditions.The cluster and the canonical correspondence analyses (CCA) indicated that the distribution and diversity pattern of benthic foraminifera are controlled by the enrichment of organic matters, CaCO₃ contents, and sediments grain size characteristics. The concept of differentiation between these ecosystems is probably related to several factors, such as seasonal flash floods carrying a considerable amount of dissolved nutrients and mangrove communities on the Rabigh coast. In contrast, it is negligible on the south Jeddah coast and absence on Farasan Island.