Establishment of Oithona brevicornis Giesbrecht, 1892 (Copepoda: Cyclopoida) in the Black Sea

Long-term, regular studies of coastal plankton communities were resumed in 2002, based on bi-weekly plankton casts at three stations located within and adjacent to Sevastopol Bay, Crimea, northern Black Sea. In October 2005 two adult females of Oithona brevicornis were initially discovered in a sample taken during a routine plankton survey. Within one month after this discovery O. brevicornis began to appear in the samples regularly. In November 2005 the total abundance of O. brevicornis exceeded 1000 ind./m in the central part of the Bay. From April 2006, O. brevicornis disappeared completely from net catches and was absent until July 2006 when this species reappeared. The peak abundance of this species – 42667 ind./m – was recorded at the central station within the Bay at the end of October 2006. The possible route of invasion and the seasonal dynamics of this new copepod species in the Black Sea coastal region are discussed.