Seasonal and Interannual Dynamics of the Abundance of the Black Sea Alien Species Pseudodiaptomus marinus Sato, 1913 (Copepoda, Calanoida, Pseudodiaptomidae) in the Crimean Coastal Waters: Influence of the Temperature Factor

Observation on the occurrence of the Black Sea alien species Pseudodiaptomus marinus were initiated since this species was reported in coastal waters of Crimea, in 2016. Current study is focused on the 170-500 mu m microplankton fraction represented by nauplii and first copepodite stages. These data were complemented by the mesoplankton fraction abundance contributed by copepodite stages II-V and adults. Samples were collected by plastic bottles at the sea surface and by Juday and Apstein plankton nets in the upper 10 m layer. Nauplial stages of P. marinus were observed during the first three years after species invasion, in September, at the sea surface temperature range from 21.1 to 25.5 degrees C. From 2019 to 2020, specimens appeared in July, at temperatures from 25.8 to 26.0 degrees C. The presence of specimens in samples has been observed by the end of November or December, at sea surface temperature of 13.1 or 8.6 degrees C, respectively. The maximal abundance was observed in the inner part of the Sevastopol Bay. The correlation value of 0.7-0.9 was estimated between the abundance and sea surface temperature throughout the year. Interannual variations of the abundance were associated with an integrative indicator of temperature (in particular, the sum of active temperatures).