A 4000-year record of parallel collapse in the ecological niche of Black Sea top predators

Marine ecosystems face multifaceted threats stemming from historical overexploitation and environmental degradation. Despite existing research, there are notable gaps in understanding the long-term dietary dynamics of marine organisms in the context of anthropogenic impacts. To address these gaps, we utilized stable isotope analysis as a proxy for dietary niche and examined changes in the Black Sea over a 4000-year period, focusing on ancient and contemporary samples from cetaceans ( Phocoena phocoena , Delphinus delphis , Tursiops truncatus ) and fish ( Scophthalmus maximus ). Among the ancient samples, the isotopic data from all four species revealed a wide and generally overlapping average dietary niche. In contrast, contemporary cetacean and fish samples exhibited niche compression, indicative of a fundamental shift in the Black Sea marine ecosystem from Antiquity to the present day. Our analyses provide ecologically significant temporal perspectives, shedding light on critical trends and changes essential for conservation efforts aimed at addressing contemporary ecological challenges in degraded marine systems.