Long-term dynamics of the copepod invader Oithona davisae in coastal waters of the Black Sea

Abstract

The results of a six-year monitoring of the abundance of the recent alien copepod Oithona davisae in the nearest coastal waters of Sevastopol are presented. It is shown that the seasonal cycle of O. davisae begins in late May–early June. The copepod reaches its maximum abundance in August–September. Then it decreases continuously until the complete disappearance of the species from plankton. The annual variability of the peaks of abundance is of a sinusoidal character with a two-year period and is related to temperature conditions of warm period of the year. The long-term trend of the invader is characterized by a general increase in its number. A record abundance of O. davisae over the period of observations was registered in 2014: up to 388 thousand ind. per m³ in the open coastal waters, and up to 1.25 million ind. per m³ in the mouth of the bay.