New invasive copepod Oithona davisae Ferrari and Orsi, 1984: seasonal dynamics in Sevastopol Bay and expansion along the Black Sea coasts

Seasonal and interannual dynamics of abundance of the recent invader Oithona davisae (Copepoda: Cyclopoida) were investigated in Sevastopol Bay from October 2005, when the species appeared in the plankton, to December 2009. The study was based on bi‐weekly plankton sampling at three stations located within and adjacent to Sevastopol Bay, Crimea, Northern Black Sea. The abundance of O. davisae increased steadily in Sevastopol Bay in 2006–2009. The species was more abundant at the centre of the bay than at its mouth. During the investigated period, an absolute maximum of the invader abundance at the centre of Sevastopol Bay was observed in early December 2008 (91,650 ind. m⁻³) and at the mouth of the bay in late October 2007 (46,200 ind. m⁻³). The maximum contribution of O. davisae to the total copepod abundance was about 99%. Expansion of the invasive copepod along the Black Sea coasts is reported. Changes in structure of the zooplankton community for the last 20 years that preconditioned the invasion of the new copepod species in the Black Sea as well as the changes in the community structure caused by O. davisae are discussed.