Comparison of Sterol Biomarkers for Sewage with other Measures in Victoria Harbour, B.C., Canada

Abstract

A lipid biomarker survey was conducted in Victoria Harbour, Canada, to compare the distribution of sewage-derived organic matter with existing results from bacterial studies. Previous surveys [Miller (1993) Report prepared by Capital Regional District Engineering Department, Victoria, B.C. Canada and Milleret al. (1995) Report prepared by CRD Environmental Services Group and Aquatic Science Consultants Ltd., B.C., Canada] of sewage contamination in the harbour were based principally on infrequent faecal coliform counts. The use of lipid biomarkers to determine time-averaged concentrations of sewage components in sediments may be a more appropriate method for defining areas where sewage is causing environmental or human health risks. 5β-Coprostanol was measured together with other sterols, fatty acids and fatty alcohols. Generally, sewage contamination shown by these lipid biomarkers was coincident with high faecal coliform counts from previous studies. However, this survey suggests, contrary to faecal coliform counts, that Portage Inlet was a region where sewage had accumulated in the sediments, possibly due to nearby overflow facilities or tidal pumping. Although the bacterial counts were low, sewage-derived organic matter was accumulating in the slack areas. In sediments of the Gorge and West Bay there were low faecal biomarker concentrations; this was probably due to the strong tidal currents which do not allow faecal matter to settle in sediments. Faecal coliform counts, however, indicated poor water quality in these same regions but this probably reflects fresh discharges passing through this area without leading to settlement.