Deep-sea benthic foraminifera from the central Red Sea

The distribution of living (Rose Bengal-stained), dead and fossil benthic f oraminifera was investigated in six short cores (multicores, 30-32 cm total length) recovered from the central Red Sea. The ecological preferences as well as the relationship between the live and dead/fossil assemblages (pres erved down-core) were examined. The sites, located along a W-E profile and between the depth of 366 and 1782 m, extend from the center of the oxygen m inimum zone (OMZ, similar to 200-650 m), through its margin at similar to 6 00 m, and down to the well-aerated deep-water environment, Live (Rose-Benga l stained) and coexisting dead foraminifera were studied in the upper 5 cm of each of the sites, and the fossil record was studied down to similar to 32 cm, Q-mode Principal Component Analysis was used and four distinct foram iniferal fossil assemblages were determined, These assemblages follow diffe rent water mass properties. In the center of the OMZ, where the organic car bon content is highest and the oxygen concentration is lowest (less than or equal to0.5 mi O-2/1), the Bolivina persiensis-Bulimina marginata-Discorbi nella rhodiensis assemblage dominates, The slightly more aerated and lower organic-carbon-content seafloor, at the margin of the OMZ is characterized by the Neouvigerina, porrecta-Gyroidinoides cf, G, soldanii assemblage. The transitional environment, between 900-1200 m, with its well-aerated and ol igotrophic seafloor, is dominated by the Neouvigerina ampullacea-Cibicides mabahethi assemblage. The deeper water (>1500 m), characterized by the most oxygenated and oligotrophic seafloor conditions, is associated with the As trononion sp, A-Hanzawaia sp. A assemblage, Throughout the Red Sea extremely high values of temperature and salinity ar e constant below similar to 200 m depth, but the flux of organic matter to the sea boor varies considerably with bathymetry and appears to be the main controlling factor governing the distribution pattern of the benthic foram inifera, Comparison between live and the dead/fossil assemblages reveals a large difference between the two. Processes that may control this differenc e include species-specific high turnover rates, and preferential predation and loss of fragile taxa (either by chemical or microbial processes). Signi ficant variations in the degree of loss of the organic-cemented agglutinant s were observed down core. This group is preserved dawn to 5-10 cm at the s hallow OMZ sites and down to greater depths at well-aerated and oligotrophi c sites. The lower rate of disintegration of these forms, in the deeper loc ations of the Red Sea, may be related to low microbial activity. This resul ts in the preservation of increasing numbers of organic-cemented shells dow n-core.