Evaluation of range of sites on river discharging into the ocean.

TC (total coliforms) and E. coli MPN/100ml. FWAs – ppb.

Microbial results.

Compared to previous sampling results, with the exception of site 9, low levels of E. coli were detected in all samples. These levels would not be considered a problem. The levels of E. coli at site 9, were very high and warrant further investigation.

Molecular Markers

Faecal pollution was detected in all samples except those taken from site 3. Only site 4 indicated the presence of human faecal pollution. The ruminant Bacter oidetes marker was detected in sites 2, 6 and 9.

Fluorescent whitening agents

FWA analysis by HPLC was undertaken on five of the samples, with FWA1 detected only in the sample from site 4, with a level of 0.2. This level would support the detection of human faecal pollution.

Faecal sterol analysis

Results from faecal sterol analysis of sites 1, 4 and 7 suggest that contamination at site 4 was consistent with the presence of human faecal pollution. The source of the sterols in the other two samples could not be determined, but were not indicative of human faecal contamination. Low levels of sterols identified at site 7 suggested a cautious interpretation of ratios indicating non-human faecal pollution.

LOQ= limit of quantitation

Key points

Site 9 clearly had the highest level of contamination. The molecular markers and FWAs suggested it was not of human source, while Bacteriodetes ruminant marker suggested animal source. Further investigation identified this site was being used as an illegal dump for animal effluent waste.

The low levels of E. coli in the other samples would normally suggest that there was no need to apply faecal source tools, and that if applied, a definitive results is less likely. Site 4, however, did indicate a human source of pollution, which subsequent testing confirmed.