Compositional and temporal evolution of particle fluxes in the open Algero–Balearic basin (Western Mediterranean)

In the frame of the EU-funded ADIOS project, the aim of this paper is to present the results of the total mass and the major constituent (organic matter, calcium carbonate, opal and lithogenics) fluxes obtained in the central part of the Algero–Balearic Basin (ABB). Two identical mooring lines, named A and B were equipped with three automated sediment traps and three current meters at 250 m, 1440 m and 2820 m of water depth, and another one, named C, was equipped with five sediment trap–current meter pairs at the corresponding depths of 250 m, 845 m, 1440 m, 2145 m and 2820 m. The samples were collected during an annual period, from April 2001 to May 2002 over sampling periods of 15–30 days.The presented particle fluxes data constitute the first one-year experimental study carried out in the open ABB, a region in which the continental inputs are expected to be minimums. This fact explains why the values of the mean annual fluxes were the lowest found in the whole Western Mediterranean Sea, ranging from 11.30 mg·m− 2 day− 1 (2145 m; station C) to 112.75 mg m− 2 day− 1 (250 m; station A).The temporal evolution of the particle fluxes in the upper waters shows the dominance of the atmospherically derived particles during summer and autumn, and a clear biological control during winter related to the primary productivity pathway. Along the whole water column, the calcium carbonate appears as the main relative contributor of the biogenic material (26%–30%), and the opal content presents the lowest values (6%–8%), suggesting that the study area is a carbonate-dominated ecosystem.Otherwise, even if the particles are derived from the atmosphere or internally produced by biological processes, it is clear that their transference from the upper to the deeper ocean is controlled by the stabilization of the water column and the distribution of the water masses in the Western Mediterranean Sea. In this context, the input of the Tyrrhenian Deep Water (TDW) into the AB7B at 800–1500 m of water depth strongly affects the distribution of the particle fluxes in the basin, being responsible of the minimum concentration zone at intermediate depths. Furthermore, current meter and flux data indicate a high influence of the Gulf of Lions water mass formation by spreading of dense cold water along the whole ABB, leading up to a maximum of particulate matter at depths higher than 2000 m.