An integrated appraisement of multiple faecal indicator bacteria and sterols in the detection of sewage contamination in subtropical tidal creeks

The quality of water bodies has been regulated by national environmental agencies and based on faecal indicator bacteria, such as thermotolerant coliforms Escherichia coli and Enterococcus sp. Additionally, faecal sterols (mainly coprostanol) have been used to corroborate sewage discharge in marine environments. In this study, faecal material input was evaluated in two sampling campaigns in transects of two tidal creeks using bacterial and chemical indicators to both compare and establish the water quality in a South Atlantic subtropical estuary. The Itibere tidal creek (S1) was classified as "contaminated" by faecal material, while the Pew tidal creek (S2) presented variable water quality according to the sampling period and sewage indicators considered in this evaluation. Then, the integrated application of chemical and bacterial indicators was applied for tidal creeks with different sewage contamination levels and under distinct environmental conditions and confirmed that Enterococcus sp. and coprostanol are the most suitable for estuarine environments.