The Impact of Sewage Discharge in a Marine Embayment: A Stable Isotope Reconnaissance

Stable isotope analyses, δ13C and δ15N, of sewage tolerant benthic invertebrates seaward of a sewage effluent discharged in a marine embayment, the Firth of Forth, East Scotland, suggest that the polychaete worm Nereis virens is a suitable species for identifying biological assimilation of sewage derived organic matter. The sewage isotopic signal is not strongly recorded in the sediment due to the combined action of tidal movement, wind-induced wave action and benthic invertebrate grazing of particulate matter on the sea-bed. δ13C of the plankton is significantly different from the effluent, but δ15N is not which precludes its use as a trace.