Vertical migration of Siphonophora (Cnidaria) and their productivity in the Croker Passage, the Antarctic

• Published in: Polish polar research 2014-01, Vol.35 (1), p.115-131
• Main Authors: Panasiuk-Chodnicka, Anna A, Zmijewska, Maria I, Manko, Maciej
• Format: Article
• Language: English
• Subjects: Autumn; Cnidaria; Dimophyes arctica; Marine; Population structure; Siphonophora; Summer; Vertical distribution; Water column; Winter; Zooplankton
• ISSN: 0138-0338; 2081-8262
• DOI: 10.2478/popore-2014-0007

The population structure, seasonal and diel changes in vertical distribution of two siphonophore species, Dimophyes arctica and Pyrostephos vanhoeffeni, in Croker Passage (Antarctic Peninsula) are examined, and compared with the results obtained by other au− thors in various oceanic areas. Zooplankton samples were taken at discrete depth intervals between 0 and 1200 m during day and night shifts, in both summer and winter seasons. Dimophyes arctica was present both in polygastric and eudoxid forms, with the latter being dominant throughout the entire study period. The results obtained demonstrate that Antarc− tic waters clearly enhance the reproductive ability of this species when compared with spec− imens from other oceanic regions. Maximum densities of Dimophyes arctica were recorded in December in the 200-400 m depth horizon. However, high concentrations of eudoxids were also recorded at deeper parts of the water column. Pyrostephos vanhoeffeni was, in contrast, most abundant in autumn and winter, and both species were found to proliferate and disperse or sink further down the water column during autumn and winter. Daily verti− cal migration was observed only during the summer period.