Influence of invader ctenophores on bioluminescence variability off the coast of Western Crimea

Abstract

In the second half of the XX century, Black Sea ecosystem has undergone significant changes: a number of storm winds and upwellings decreased, precipitation abundance increased, coastal waters salinity decreased, temperature increased; moreover, ctenophores invaded. As a result, in the late 1980s, Black Sea pelagic ecosystem abruptly got restructured. This research is based on the studies performed in 1965–1966 and 2007–2012 near Sevastopol (Western Crimea) using the remote sensing data. Analysis of satellite data over the past 20 years showed the presence of positive dynamics in surface water temperature in Sevastopol water area. In the mid-1960s, the annual bioluminescence was characterized by seasonal peaks of dinophytes luminescence. In recent years, this rhythm has changed due to ctenophores invasion. The increase in Mnemiopsis leidyi abundance leads to a decrease in bioluminescence of luminous microalgae being consumed by these ctenophores. Due to Beroe ovata invasion and reproduction, M. leidyi biomass decreased; as a result, bioluminescence increased.