PARTICULATE FLUXES OF ORGANIC-COMPOUNDS AND THEIR RELATIONSHIP TO ZOOPLANKTON FECAL PELLETS IN THE NORTHWESTERN MEDITERRANEAN-SEA

Sediment trap experiments were conducted in the northwestern Mediterra nean (Ligurian sea) in 1987 in the course of the DYFAMED project. The particles collected during 9-15 day intervals from February through Ju ly at 200 m and from April through May at 2000 m depth were analysed f or organic carbon, nitrogen, fatty acids and n-alkanes. Concentrations in these particles were compared to those in freshly-produced zooplan kton fecal pellets collected from several cruises during the same peri od. In winter, high mass fluxes were encountered at 200 m; the organic material was characterized by a. relatively high proportion of n-alka nes and C24 fatty acid which are characteristic of refractory (old) or ganic matter and a low content of the more labile fatty acids. During the spring and summer period, fluxes contained undegraded phytoplankto n and zooplankton material. In the 2000 m trap samples, refractory org anic matter was still present, but the fresh input was very low and ha d evidently been consumed in the upper water column. There was no tend ency toward a higher content in bacterial fatty acid markers in zoopla nkton fecal pellets and 200 m sediment trap material. Based on the ass umption that all n-alkanes in trap collections originate from sinking fecal pellets, end-member calculations indicate that intact zooplankto n fecal pellets are important contributors to vertical particulate flu xes at 200 m. The maximum contribution is estimated to be between 10% (in summer) and 30% (spring) using n-alkane marker concentrations.