Evidence of sewage input to inner shelf sediments in the NE coast of Brazil obtained by molecular markers distribution

Coprostanol (5β-cholestan-3β-ol) and other fecal steroids were used as markers to trace the input of sewage to the shelf along the coast of Sergipe and Alagoas States, in NE Brazil. Surface sediment samples in shallow regions (<50 m depth) on the shelf were collected adjacent to four fluvial systems, whose drainage basins exhibit distinct levels of human influence. Highest coprostanol concentrations were observed in the area under influence of the Sergipe River (58.6 ± 74.6 ng g−1; maximum of 184.1 ng g−1), whereas in the Vaza-Barris (18.9 ± 23.6 ng g−1) and the Piaui/Real (12.3 ± 6.7 ng g−1) rivers the levels of coprostanol were near the method's limit of detection. Nearby the São Francisco River, the largest in the NE Brazil, coprostanol was virtually absent. The findings of the present study, supported by coprostanol-based diagnostic ratios, revealed that, when sanitation is lacking in the coastal region, even a small-sized river like the Sergipe River can effectively contribute to the export of sewage-derived organic matter to the inner continental shelf in the studied region.