Organic pollution is a serious environmental problem for the coastal zones of seas. The study tested the hypothesis that allochthonous organic carbon derived from St. Petersburg wastewaters is a significant basal resource of carbon for the benthic food webs. We analyzed stable isotope composition of carbon and nitrogen in suspended organic matter in the Neva Estuary and in the tissues of macroinvertebrates and fish. The Stable Isotope Bayesian mixing model showed that waste waters were an important source of carbon for the most of consumers in the Neva Estuary. The autochthonous carbon produced by phytoplankton was a significant source of carbon only for some macroinvertebrates. The main consumers of the carbon derived from waste waters were tubificid worms, chironomid larvae and alien polychaete, which currently dominate in the zoobenthos of the estuary. These species replaced the former dominants, native crustaceans, which to a lesser extent use anthropogenic carbon.
Keywords: Gulf of Finland; Macroinvertebrates; Organic pollution; Stable isotopes (Bayesian mixing model).
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