EVIDENCE FOR CYANOBACTERIAL INPUTS AND HETEROTROPHIC ALTERATION OF LIPIDS IN SINKING PARTICLES IN THE ALBORAN SEA (SW MEDITERRANEAN)

The different sources of lipid compounds present in sinking particles collected in a sediment trap mooring deployed in the Alboran Sea (SW M editerranean) were elucidated using the molecular marker concept. A si gnificant contribution of cyanobacterial lipids was identified based o n the occurrence of a series of 3- and 5-methylalkanes and dimethylalk anes. Further evidence of cyanobacterial inputs was obtained by princi pal component analysis of all data showing diploptene and n-alkanes in the range C-14-C-22 clustered together with those branched alkanes. T he use of methyl and dimethyl alkanes to trace cyanobacterial sources in the water column is proposed with advantage to sterols which are us ually masked by phytoplanktonic sterols. The sterol distribution indic ates phytoplankton as a major source with a contribution from heterotr ophic zooplanktonic. Both fossil and biogenic sources can be contribut ors to the large unresolved complex mixture (UCM) found in these sampl es. (C) 1998 Elsevier Science B.V.