Organic Contamination of San Vicente Bay, Chile STEPHEN M. MUDGE * and CARMEN GLORIA SEGUELà  School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Anglesey LL59 5EY, UK àFaculty of Science, Universidad Cat olica de la Sant  õsima Concepci  on, Campus San Andres, Paicav  õ 3000, Concepc  õon, Chile Surface sediment samples from 16 sites in San Vicente Bay were analysed for a range of lipid biomarkers and hydrocarbons. Coprostanol and cholesterol were used to indicate regions of sewage contamination: ratios reached 1.1 adjacent to known discharge points. The fatty alcohol data were used to highlight regions of bacterial and ter- restrial biomass. The bacterial fatty acid 18:1x7 co-varied with the odd/even fatty alcohol ratio and the coprostanol/ cholesterol ratio con®rming the regions of aerobic bacte- rial activity near the sewage outlets. The ¯uoranthene/ pyrene ratio together with the ratio between the (three or less/four or more) ring aromatics and total concentration of aromatics demonstrate the extent of crude oil and pyrogenic contamination in the sediments. San Vicente Bay was divided into three principal regions on the basis of this analysis: (a) the highly contaminated northern end with strongly reducing sediments and high concentrations of organic matter, (b) the region adjacent to the sewage outlets with associated bacterial biomass, and (c) the re- maining central and southern areas relatively unaected by the northern discharges. Partial Least Squares path modelling suggests the latter region received less than 50% of the material discharged at the northern end of the Bay. Ó 1999 Published by Elsevier Science Ltd. All rights reserved. Keywords: sterols; fatty acids; fatty alcohols; PAH; hydrocarbons; San Vicente; Chile; PLS; multivariate statistics. Introduction San Vicente Bay (36°45 0 S, 73°10 0 W) is close to Talc- ahuano, the principal naval base of Chile and Con- cepci on, the third largest city (Fig. 1). The land surrounding both this bay and Concepci  on Bay to the north is home to several heavy industries such as steel manufacture and oil re®ning. The cold upwelling located approximately 5 miles from the coast has led to the development of a substantial ®shing industry both at the subsistence level as well as large commercial ¯eets. These Bays receive several waste discharges from these indus- tries together with fuel oils and greases spilled during engine operation and sewage from several large urban areas including Talcahuano (popn. 228,000). The water quality is poor in many areas and large blooms of phytoplankton and bacteria have been ob- served (Ahumada et al., 1984). In a previous study of sediments from these two bays, lipid biomarkers and other organic matter failed to indicate the primary source of organic matter to the bays (Mudge and Seguel, 1997). This study concentrates on San Vicente Bay which has 8 monitored industrial inputs to the north and east with a mean ¯ow of 530 m 3 h 1 . In contrast, the southern end of Bay is relatively undeveloped and the Universidad Cat olica de la Sant  õsima Concepci  on have a marine ®eld station located near Lenga at the SW edge of the Bay. The sewage that is discharged into the Bay is derived from 3 piped and a number of diuse sources. These account for 363 litres per second (ESSBIO, un- published report). Sediment samples were analysed for typical lipid biomarkers such as sterols, fatty alcohols, fatty acids as well as aliphatic and aromatic hydrocar- bons more usually associated with anthropogenic con- tamination. Sterols have often been used to indicate the source of organic matter, especially sewage through use of cop- rostanol (Grimalt et al., 1990; Nichols and Espey, 1991). Coprostanol (5b-cholestan-3b-ol) is formed in the hu- man gut by bacteria (Grimalt et al., 1990) and can be used to trace the fate of human faeces in the marine environment. One of the more useful measures is the ratio with cholesterol since this ``normalises'' for the total lipid content as cholesterol is present in most or- ganisms (Chan et al., 1998). Other measures include ratios to the total sterols, cholestanol (5a-cholestan-3b- ol) plus cholesterol (cholest-5-en-3b-ol) and cholestanol plus coprostanol (Chan et al., 1998). An isomer of coprostanol, epi-coprostanol (5b-cholestan-3a-ol) is formed during the treatment of wastewaters and sewage sludge digestion. The ratio between epi-coprostanol and Marine Pollution Bulletin Vol. 38, No. 11, pp. 1011±1021, 1999 Ó 1999 Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0025-326X/99 $ - see front matter PII: S0025-326X(99)00132-0 *Corresponding author. Tel.: +44-1248-351151; fax: +44-1248- 716367; e-mail: s.m.mudge@bangor.ac.uk 1011