Aliphatic hydrocarbon pollution and macrobenthic assemblages in ceuta harbour: a multivariate approach

The aliphatic hydrocarbon composition of sediments from Ceuta harbour, North Africa, was studied to determine the sources, levels and effects of these hydrocarbons on macrofauna com- position by considering indices and concentration ratios in multivariate analyses. A total of 21 stations (15 inside and 6 outside the harbour) were sampled using a van Veen grab. High hydrocarbon con- centrations (496 to 6972 ppm), the dominance of the UCM (unresolved complex mixture) in relation to the resolved alkanes, and values close to the unity ( ≈ 1) of the CPI (carbon preference index) and pristane:phytane ratio indicated anthropogenic origins of the hydrocarbons. Ceuta harbour is char- acterised by intense traffic, and frequent loading and dumping related to shipping operations. Fur- thermore, 2 urban effluent outfalls of Ceuta city flow into the harbour. The relationship between macrofauna and the above-measured parameters was evident in canonical correspondence analysis (CCA). Variation in species composition at different sample stations was related to the ratios of maltenes to other hydrocarbons, pristane:phytane and, especially, maltenes:asphaltenes, which turned out to be the main factor discriminating between internal and external stations according to species distribution. The crustaceans Corophium runcicorne and C. sextonae , the mollusc Parvi- cardium exiguum and the polychaete Pseudomalacoceros tridentata were only found at internal sta- tions, while the polychaetes Jasmineira elegans and Scoloplos armiger were present only at external stations. The abundance of the crustaceans Apseudes latreilli , Leptochelia dubia and Pariambus typicus , and the polychaetes Capitella capitata , Nereis falsa and Potamilla reniformis , differed sig- nificantly between the internal and external stations. Although the asphaltene fraction is potentially hazardous to sediment macrofauna, due to its high molecular weight and its slow degradation, the r elationship between the distribution of marine organisms and the presence of asphaltenes has never been explored in previous studies