Anthropogenic impacts recorded in recent sediments of the Western Black Sea

In this study a resin-embedded sediment core from a location below the chemocline in the Western Black Sea was analyzed for its elemental composition by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), recovering a continuous geochemical record on sub-annual resolution for the last 200 years. Relative enrichments in organic carbon, Pb, Fe, S, and Mo, amongst other trace metals, were observed in the depth interval corresponding to the 1990s, suggesting an increased carbon flux to the sediments as well as an anthropogenic pollution signal. Shallow hypoxia and anoxia were observed on the Western Black Sea shelf in the late 20th century as a consequence of eutrophication due to increased nutrient discharge by major rivers. We propose that this expansion of eutrophication of the Western Black Sea shelf was responsible for the enhanced carbon flux to our study site, while the associated anoxia enhanced the shuttling of redox-sensitive elements to locations below the chemocline. It remains to be established whether a subsequent decrease of carbon and metal enrichments at the core top is related to recent improvements of the ecological state of the Western Black Sea shelf.