Hydrodynamics and zooplankton assemblages in Prydz Bay, East Antarctica, during the austral summer of 2017

Abstract

Vertical distribution of zooplankton biovolume, abundance and community composition in the twilight zone are important to better understand their role in carbon and energy transfer that mediate the food web structure in the Prydz Bay. Qualitative and quantitative zooplankton studies were carried out in January 2017, using a multi plankton sampler (mouth area: 0.25 m2; 200-microns mesh size) in the ice-free domain of the Prydz Bay. In this study, we investigated the diel variation of zooplankton biovolume and community structure between the surface water layer and 500 m depth at every six hours intervals for a period of 48 h at about 68° S latitude, 74° E longitude in the Prydz Bay. Besides, relationship between the zooplankton assemblages and diffrent water masses were also discussed. We found an abrupt increase in zooplankton biovolume within the mixed layer depth on day 1 (13:15 h). Apart from high, localized contributions from chaetognaths, appendicularians and polychaete larvae, mesozooplankton was numerically dominated by copepods, and densities were highest near the surface most of the times. Two water masses were identified based on the signatures of temperature and salinity: Antarctic Surface Water (ASW) and Shelf Water (SW). ASW had a higher proportion of Calanoides acutus, Calanus propinquus and Oithona similis, while Metridia gerlachei, and Heterorhabdus austrinus were mostly encountered in SW. Our results will help to predict the short term temporal variations of copepods assemblages and other zooplanktons according to the dynamics of hydrographic features in Prydz Bay.