Presumably BiOS-induced zooplankton invasion from the western Mediterranean to the east, eventually introduced by Acartia (Hypoacartia) adriatica (Crustacea: Copepoda)

Abstract

Mediterranean is well-known of its’ rich biodiversity among the semi-enclosed seas which was affected from atmospheric-sea interactions coupled with globally ocean oscillations and El Nino as well as from the basin-wise decadal Bimodal Oscillating System (BiOS) and the Atlantic rim current. Besides invasion of non-indigenous species (NIS) in Levant Sea, to the Turkish coastal water recent introduction of Mediterranean indigenous species (IS) which are common in West Mediterranean and Adriatic Sea is noteworthy to mention. Introductions through BIOS may put extra burden on the ecosystem of the Levant Sea which is already threatened by NIS invasions. During a study on mesozooplankton distribution along the Turkish Mediterranean coastal waters in summer 2019, one calanoid copepod species, Acartia (Hypoacartia) adriatica which is widely distributed in Italian coasts was identified for the first time for the Levant Sea and found numerous at one of 67 sampling stations in the study area. Furthermore, abundances of five phytoplankton species (two of them common in Adriatic Sea) were estimated to be 50 to 100 fold higher at this particular station compared to the rest of the stations. Physicochemical (relatively lower salinity and unusual high nutrient levels for the summer period in Levantine basin) and biological properties of this single station fell apart from the neighboring stations. Near-past records (17 gelatinous specimens recorded in the Turkish seas in 2019-2020; all species present in West Mediterranean Sea) of other specimens were harmonized as a consequence of the BiOS. The present study suggests that i) zooplankton may have been transported to this region by a different mechanism rather than well-known routes and vectors (Suez Canal, ship ballast water and aquaculture), ii) the BiOS may be another vector for new species introductions into Levant Sea, and iii) between-sea-to-sea introduction of NIS or IS could not be ignored for their effects on already established ecosystem specific to Mediterranean.