Evaluation of anthropogenic and biogenic inputs into the western Mediterranean using molecular markers

Aliphatic hydrocarbons (AHs), sterols (ST), and lipid classes were determin ed in suspended particles collected in the Catalan Sea, northwestern Medite rranean. Principal Component Analysis of the data set revealed a clustering of samples depending on the sources of organic matter, i.e., coastal influ enced, open sea and frontal zone. Terrestrial inputs were recognized in par ticles collected in the surface waters, at the vicinities of river outflow (i.e., Rhone and Ebro), by a predominance of C-29 and C-31 n-alkanes, 24-et hylcholest-5-en-3 beta-ol (S12), and the anthropogenic 5 beta(H)-cholestan- 3 beta-ol, coprostanol (S1). Phytoplanktonic molecular markers (n-C-17, 27- nor-24-methylcholesta-5,22E-dien-3 beta-ol cholesta-5, 22-dien-3 beta-ol an d 24-methylcholest-5-en-3 beta-ol) were widespread but relatively more appa rent in the open sea and frontal zones. A similar distribution was observed for lipid classes, with higher concentrations of phospholipids, and an enr ichment in free fatty acids in the areas influenced by river discharges. To tal sterol, the unresolved complex mixture of hydrocarbons and the pristane -phytane ratio were highest at a persistent frontal zone, possibly reflecti ng the combination of a higher primary productivity and fossil hydrocarbon absorption on to suspended particles. Moreover, vertical profiles exhibited a subsurface concentration maximum at 20-30 m water depth, concurrently wi th the chlorophyll. (C) 1999 Elsevier Science B.V. All rights reserved.