Diversity and distribution of benthic foraminifera in the Al-Kharrar Lagoon, eastern Red Sea coast, Saudi Arabia

Abstract

High-resolution benthic foraminiferal study was carried out on the surficial bottom sediments of the Al-Kharrar Lagoon (KL), north of Rabigh City, eastern Red Sea coast, Saudi Arabia. One hundred thirty surface sediments samples were collected from the lagoon during March 2014 to investigate the benthic foraminiferal diversity, abundance, distribution and controlling factors. The lagoon’s water environmental parameters such as temperature, salinity, dissolved oxygen and pH,water depth, sediment grain size, organic matter and carbonate were also studied. Statistical techniques were applied to test the reliability of collected data and to facilitate the interpretation. The results showed that faunal density and diversity were with averages of 135±300 dead tests/g and 23±10 displaying the highest values (3000 and 44) only in some intertidal areas, respectively. The Q-mode cluster analysis as well as the spatial distribution of the benthic foraminifera allowed the division of KL into five environmental biotopes such as the southern tip, the mid-eastern side, the inlet, the whole intertidal-subtidal and, the deeper area. These biotopes were dominated by five major assemblages such as an intertidal assemblage (Quinqueloculina seminula-Q. laevigata and Affinetrina quadrilateralis-Neorotalia calcar), an inlet Amphistegina lessonii assemblage, an intertidal-subtidal assemblage (Peneroplis planatus-Coscinospira hemprichii-Sorites orbiculus) and deep-water assemblage (Spiroloculina communis-Triloculina serrulata-T. trigonula). The canonical correspondence analysis indicated that the intertidal-subtidal assemblage is positively correlated with high salinity, temperature, and bioclastic sandy substrates with algal mats, sea-grasses and macro-algae, reflecting their preferences to warm, dry climatic conditions. The deep-water assemblage showed positive relationships with pH, deep muddy substrates enriched in organic matter, and negatively correlated with high temperature and salinity. The inlet assemblage is also correlated with the deeper waters where hard to coarse-grained substrates predominate.