New invasive copepod species from the Levantine Sea, north-eastern Mediterranean: Oithona davisae (Ferrari and Orsi, 1984) (Cyclopoida: Oithonidae)

Iskenderun Bay is a hotspot for bioinvasions in the Mediterranean Sea, where alien species are frequently introduced, easily settle, and therefore, can often be encountered. The small-sized invasive copepod Oithona davisae (Ferrari and Orsi, 1984) has rapidly spread in several ecosystems worldwide, including the Black Sea, Wadden Sea, Marmara Sea, Adriatic Sea, and Aegean Sea, becoming an integral part of the pelagic communities there. Here. we report O. davisae in Iskenderun Bay, in the north-eastern part of the Mediterranean Sea, and provide information on its spatiotemporal variation and assess its potential impact on the seasonal abundance and biomass of the mesozooplankton community, at present and in the near future. Zooplankton abundance and biomass were at their lowest levels in winter (1066 +/- 313 ind. m(-3), 1.9 +/- 0.8 mg m(-3)) and highest in spring (7738 +/- 1583 ind. 18.5 +/- 5.8 mg m(-3)). However, the relative abundance of oithonid copepods was highest during the winter (35.7 +/- 10%). The proportion of copepodites in the oithonid assemblage was high in spring (72.5 +/- 9.3%), summer (72.7 +/- 13.3%) and winter (68.5 +/- 3.6%) but the relative abundance of male oithonids remained low across all seasons. Oithona davisae was observed only in the autumn. in abundances of 8.4 to 12.6 ind. m(-3). These low abundances could be attributed to the new arrival of this species and the relatively large mesh size used in this study (200 mu m). Nevertheless, the successful introduction and assimilation into other mesozooplankton communities elsewhere, rapid adaptability and wide tolerance to environmental conditions of O. davisae, suggest that this species may become a dominant part of the zooplankton community across the Levantine Basin in the venv near future.