ИСТИНА

Сalanoid copepods of the genus Pseudocalanus play an important role in the pelagic communities of the White Sea, being one of the dominant groups in terms of abundance and composing a significant portion of the total zooplankton biomass. Two species co-occur in the White Sea: P. acuspes and P. minutus, although historically zooplankton studies have grouped them together due to the very insignificant morphological differences between the species, particularly at juvenile stages. In this study we examine the species-specific distribution and population structure of Pseudocalanus in the White Sea, based on material collected on a transect through the Kandalaksha Bay from aboard the RV “Professor Zenkevich” in August 2018. Species identification at juvenile stages was accomplished using species-specific PCR. The abundance of this group was 200-400 ind m-3 and increased towards the southern end of the transect. The populations of both species were mainly composed of later copepodite stages (CIII-CV), yet the population structure of the two species was significantly different. This suggests that these species are at different stages of their life cycle, likely exploiting different production sources, which allows them to co-exist in one environment.