Role of the Variability of Abiotic Environmental Parameters in the Population Dynamics of Invasive Ctenophores in the Black Sea

Abstract

The multidecade, seasonal, and interannual variability of hydrometeorological parameters of the Black Sea has been analyzed with reference to the population dynamics of invasive ctenophores. Polynomial approximations of average annual time series indicate a nonlinear character of the long-term variability of the studied parameters. Two 20- and 40-year intervals with multidirectional trends of parameter changes have been revealed. The effect of variability of abiotic factors on the two main ecosystem drivers, i.e., invasive ctenophore Mnemiopsis leidyi A. Agassiz, 1865 and its predator Beroe ovata Bruguière, 1789, has been analyzed. M. leidyi invaded the Black Sea in the 1980s, followed by the B. ovata invasion in the 1990s. The M. leidyi invasion caused degradation of the ecosystem at all trophic levels, including fish resources. The subsequent introduction of its predator, B. ovata, provided a significant restoration of the ecosystem and fish resources in the Black Sea; this process still continues in the Sea of Azov. The interannual dynamics of both ctenophores follows water temperature changes, but only if it varies within the limits favorable for these species. In the case of exceeding these limits, a sharp reduction of their population magnitudes occurs.