Present-day coccolith fluxes recorded in central eastern Mediterranean sediment traps and surface sediments

Ziveri, P., Rutten, A., De Lange, G.J., Thomson, J. and Corselli, C. (2000) Present-day coccolith fluxes recorded in central eastern Mediterranean sediment traps and surface sediments. Palaeogeography, Palaeoclimatology, Palaeoecology, 158 (3/4), 175-195. (doi:10.1016/S0031-0182(00)00049-3).

Abstract

Two sediment traps were deployed in time series collection from November 1991 to August 1994 at 3000 and 3500 m, respectively, above and below the oxygenated sea water/anoxic brine interface in the Bannock Basin, central eastern Mediterranean. Here, the coccolithophore flux and its contribution to the carbonate particulate flux are presented for the 3000 m trap and compared with the record in eastern Mediterranean surface sediments. A marked seasonal variation is observed in the fluxes of total mass, total coccoliths and whole coccospheres, with flux maxima in late winter and spring. The annual coccolith flux of 1×1010 coccoliths m?2 year?1 measured in the deep waters of Bannock Basin is much lower than published data from most other oceanographic settings, even when corrected for the trap efficiency of ~23% calculated from the 230Th flux. The biogenic and lithogenic fluxes are primarily controlled by coccolithophore production and Saharan dust input, respectively. The calculated coccolith and coccosphere settling rates, estimated from the comparison of maximum pigment concentration in the surface ocean and arrival of maximum flux at 3000 m water depth, ranged from 17 to 25 m day?1 for coccoliths and 100 m day?1 for coccospheres. At the study site, carbonate dissolution is a minor process at both the trap depth and at the sea floor in both oxic and anoxic conditions, and there is a high preservation of coccolith CaCO3. Coccolithophores are the main contributor to the biogenic carbonate flux, followed by thoracosphaerids. Emiliania huxleyi and Florisphaera profunda followed by Syracosphaera, Helicosphaera carteri and Calcidiscus leptoporus are the dominant species in the sediment trap and surface sediments.

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