Quantifying the Role of the Invasive Copepod Oithona davisae Ferrari F.D. and Orsi, 1984 (Copepoda: Cyclopoida) in the Diet of the Planktivorous Ctenophore Mnemiopsis leidyi A. Agassiz, 1865 in Coastal and Deep-Sea Areas of the Black Sea

Feeding rates and predation intensity of the cyclopoid copepod Oithona davisae Ferrari F.D. and Orsi, 1984 by the ctenophore Mnemiopsis leidyi A. Agassiz, 1865 were analyzed across several areas of the Black Sea from 2008 to 2022. Under in situ conditions in Sevastopol Bay, on the Sevastopol shelf, off the southern coast of Crimea, and in deep-sea areas, the feeding rate, estimated from gut contents and prey digestion time, ranged from 0.01 to 0.76 mg organic C per individual per day. On average, the ctenophore removed 1–20% of individuals from local crustacean subpopulations per day. Predation on O. davisae was the highest in the eutrophic–mesotrophic Sevastopol Bay during the summer–autumn period of 2009–2011. In years with high prey and predator abundance, M. leidyi likely exerted a significant effect on the population dynamics of O. davisae in the Black Sea.