Recent terrestrial and carbonate fluxes in the pelagic eastern Mediterranean; a comparison between sediment trap and surface sediment

A sediment trap mooring was deployed in the central eastern Mediterranean f rom November 1991 to August 1994. At 3000 m water depth, total mass, Al, Ca , Mg, Sr and Th-230 fluxes recovered by the sediment trap are highly season al, with highest fluxes during early spring in 1992 and 1993, and during la te-spring/early-summer in 1994. Comparison of historic annual satellite-der ived chlorophyll records (coastal zone colour scanner) with the trap flux t ime series indicates a lag of 4-6 months between maximum primary production in the surface ocean and maximum flux recorded by the trap. Only the flux of coccospheres to the trap is at a maximum similar to 1 month after maximu m pigment concentrations in surface waters, a value commonly found in other areas. Quantification of the inorganic (lithogenic) flux to the trap indic ates that Saharan dust is likely to be the major contributor to the trap ma ss flux, The trapping efficiency of the sediment trap, as calculated from t he intercepted Th-230 flux, is only 23%, and the trap Al-flux is similarly x4 lower than Al fluxes measured in nearby uppermost sediments. Compared wi th surface sediments, the trap-intercepted carbonate fluxes are even lower (x9) than the corresponding lithogenic fluxes. This is partly due to the ve ry low abundance of large (>32 mu m) foraminifera and pteropods found in th e trap material compared to the surface sediment. We speculate that the per iod of our sediment trap deployment was insufficiently long to recover epis odical large fluxes, such as may be triggered by North Atlantic Oscillation variations. (C) 2000 Elsevier Science B.V. All rights reserved.