Contribution and acclimatization of the swarming tropical copepod Dioithona oculata (Farran, 1913) in a Mediterranean coastal ecosystem

Abstract

In this study, tropical oithonid copepod Dioithona oculata was recorded for the first time in the Mediterranean Sea. Thisspecies is distinguished easily by its large ocular lenses and by the number of setae on the endopod of the maxillule. The study wasconducted seasonally in the coastal area of İskenderun Bay between April 2013 and December 2016. D. oculata was first observed inOctober 2013 in the study area (Station 4; 3.1 ind. m–3); after this period, this species became an important contributor to zooplanktonassemblages in October with the highest level seen in 2016 (Station 4, 834.5 ind. m–3).The proportion of this species in the copepodcommunity varied from 0.14% (2014) to 29.4% (2016), and the highest proportions, observed in October 2016, were at Stations 3 and4 (51.1% and 65.3%, respectively). Females dominated the D. oculata population and the ratio of female to male was 5.6 ± 7 on average.Copepodit stages were also observed in the population.Altogether, these data indicate that the D. oculata population increased year after year. In addition, the presence of copepodits in thepopulation suggests that this species was established and successfully acclimatized to the conditions, becoming an important componentof the zooplankton community in the İskenderun Bay ecosystem.