Seagrass-rafted large benthic foraminifera transported into the deep Red Sea

Abstract

[eng] Large shallow-marine foraminifera tests occur in deep-sea carbonate sediments of the northern RedSea as a minor but recurring component among the remains of otherwise pelagic and deep-marinebenthic biogenic assemblages. In this study of sediments recovered along the northern shore of SaudiArabia, the symbiont-bearing taxa Sorites variabilis, S. orbiculus, Amphisorus hemprichii, Amphisteginalobifera, A. lessonii and A. radiata were identified in samples from between 430 to 1,000 m depth.These foraminifera are dwelling in shallow-water environments, associated with coral reefs andseagrass habitats. The seemingly erratic occurrence of photosymbiotic benthic organisms in deep-seasediments was explained by the finding of such foraminifera tests along with seagrass (e.g., Halophilaleaves) and macroalgae remains in pristine preservational states in the sediment of the Umluj brinepool below ~ 638 m depth. This indicates a passive transport process by rafting attached to floatingmacrophytes to these off-platform settings. The abundant seagrass and oceanographic conditionsalong the Arabian Peninsula may facilitate the transport of epiphytes and associated taxa offshore.Such long-distance transport mechanisms could further contribute to the rapid (co-)dispersal of someof these organisms into new habitats. Passive rafting should thus be considered in interpretation ofsedimentary records and biogeographic patterns.