Abstract

Recent benthic foraminiferal distribution patterns in the Mediterranean Sea are investigated in relation to water depth, substrate characteristics and food availability. Patterns of presence/absence abundances, and foraminiferal diversities differ between the main eastern and western Mediterranean basins. The small basins in the Sicily Strait show the closest affinity with the western basin. The primary result of the present study is that no high resolution Mediterranean-wide bathymetric zonation can be determined because the modern benthic distribution patterns appear to be governed by interactions between water depth, substrate, and food supply. We can, however, define a broad subdivision between “shallow-water” and “deep-water” assemblages, which can be traced throughout the Mediterranean Sea. The deep-water (>1000 m) assemblage is characterized by low diversity and consists of Glomospira charoides, Gyroidinoides circularis/orbicularis, Gyroidinoides altiformis, Anomalinoides minimus, Robertinoides translucens and Biloculinella/Nummoloculina spp. The shallow-water assemblage has higher diversities and consists of Cassidulina crassa, Cassidulina laevigata/carinata, and Bulimina marginata.

Decreasing primary productivity values from west to east result in a similar decrease in organic flux to the sea floor and, therefore, in lower food availability to the benthic fauna. This trend might explain why species with low food demands, such as Gyroidinoides circularis/orbicularis and Glomospira charoides are more abundant in the eastern Mediterranean. Deep infaunal species such as Globobulimina spp., Chilostomella spp., and Brizalina alata seem to prefer high amounts of sedimentary organic carbon and thrive on sediments with low carbonate concentrations. This results in a distribution more or less restricted to areas with highest primary productivity values. Maxima of this group are consequently found in the Alboran Sea, off Algeria, and in the northern Aegean Sea.

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