Coprostanol as sewage tracer in McMurdo Sound, Antarctica

Abstract

Sediment cores from the vicinity of sewage outfalls off McMurdo Station as well as surface grab samples from different locations in the McMurdo Sound, Antarctica were analysed for coprostanol (5β-cholestan-3β-ol) and epicoprostanol (5β-cholestan-3α-ol) to assess the degree of sewage addition to the Sound. Sediment samples close to the point source contain as much as 3 mg g −1 dry sediment of coprostanol, whereas samples farther from the source, for example from New Harbour and Granite Harbour, contain only trace levels to 40 ng g −1. Coprostanol in the sediments of latter locations most likely originates from seals rather than from sewage outfalls. It appears that sewage particles are very quickly incorporated into the sediment layers close to the discharge point in the eastern Sound. However, significant levels (930 ng g −1) of fecal sterols were detected in Cape Armitage surface sediments, indicating that the sewage plume could also have reached the seawater intake station, situated in between the outfall and Cape Armitage sampling site. These results suggest the need for a sound environmental monitoring and assessment of the existing wastewater practices in the region.