Benthic foraminifera assemblage change along the southeastern Mediterranean inner shelf due to fall-off of Nile-derived siliciclastics
Hyams-Kaphzan, Orit; Almogi-Labin, Ahuva; Sivan, Dorit; Benjamini, Chaim
published: Jun 1, 2008
ArtNo. ESP155024803007, Price: 29.00 €
The southeastern Mediterranean continental shelf is dominated by sediments derived from the Nile River, which gradually decrease along the Israel coast to the northeast. We here report on how this sedimentary transition, across a variety of rocky, sandy and silty-clayey substrates, affects the abundant, diverse benthic foraminifera that are highly sensitive to changing environmental parameters. Because of patchy distribution and seasonality, comparison of these substrates in the long-term is best done by time-averaged, dead assemblages of foraminifera. We studied the dead benthic foraminifera from 7 east-west oriented transects extending from 3 to 30 m water depth, supplemented by 8 box corer samples taken along a north-south transect at ∼ 40 m depth. There were 350 benthic foraminifera species present. The abundance, diversity and composition of the assemblages change significantly, correlating with substrate, depth, and geographical position relative to the Nile littoral cell. Approximately 66 are common to the Gulf of Aqaba, Red Sea, of which about half are probably Lessepsian invaders, entering the Mediterranean since the opening of the Suez Canal. The foraminifera clustered into four well-defined assemblages. They are mainly substrate controlled, with siliciclastic-rich sandy, rocky, and silty-clayey substrate assemblages south of Haifa, still part of the Nilotic province, and carbonate-rich rocky and sandy-silty assemblages from north of Haifa. These assemblages clearly fall into two distinct provinces, each with a number of substrates: The laterally distal end of the "Nilotic" province on the southern shelf, with low concentrations of foraminifera and low diversity assemblages on siliciclastic substrates, and a "Levantine" province north of Haifa Bay, with a much more abundant and diverse foraminiferal fauna on carbonate substrates.