BENTHIC FORAMINIFERAL DISTRIBUTION (LIVING AND DEAD) FROM A PERMANENTLY STRATIFIED MARGINAL SEA (MARMARA SEA, TURKEY)

Detailed examination of four sediment fractions between 63-500 mu m showed that benthic foraminiferal assemblages (undifferentiated living + dead) collected from 23 surface-sediment samples along the Marmara Sea coast were dominated by smaller (63-mu m fraction, cluster analysis of species with >= 5% relative abundance revealed three main assemblages, which were associated with the general hydrography of the Marmara Sea. The first assemblage (0-35 m), is dominated by Ammonia tepida, Ammonia spp., and Elphidium spp. Their distribution is linked to organic matter and river sediment discharge and Black Sea surface inflow. The second assemblage (28-50 m) is dominated by Bulimina aculeata, Bo. variabilis, Nonionella turgida, and Bulimina elongata. This assemblage is affected by salinity fluctuations due to seasonal vertical mixing. The third assemblage (36-320 m) has the highest density and diversity, and includes C. carinata, Brizalina spathulata, Br. dilatata, Valvulineria bradyana, Globocassidulina subglobosa, Bulimina marginata, B. costata, Discorbinella bertheloti, Melonis barleanum, and Gyroidina umbonata. This reflects the greater environmental stability of the Mediterranean undercurrent

Benthic Foraminiferal Composition from the Brackish-Marine Transition Zone of the Marmara Sea, Turkey (Eastern Mediterranean)

Benthic habitat at the continental shelf area of the Marmara Sea is strongly affected by the confluence of the saline Mediterranean and brackish Black Sea waters. Benthic foraminiferal composition and abundance (undifferentiated living and dead) in 19 surface sediment samples taken from water depths between 15 and 67m from the northern Marmara shelf was studied as tracers of the Mediterranean and Black Sea water masses in the area. Faunal analysis showed that a distinct change occured at about 40m water depth. Two main assemblages were identified based on cluster analysis of the quantitative benthic foraminiferal data. They are the Asterigerinata mamilla-Lobatula lobatula-Neoconorbina terquemi assemblage (Shallower assemblage) at 20-38m water depth and Brizalina spathulata-Cassidulina carinata-Bulimina aculeata assemblage (Deeper assemblage) distributed at 43-67m. Comparison between the depth distribution of representative species and basin-averaged salinity gradient clearly shows that faunal shift follows the hydrological boundary