Vertical structuring of zooplankton communities during a short-term study in the Bransfield Strait, Antarctica

Abstract Phytoplankton and zooplankton organisms are important constituents of the Antarctic marine food-web and play important roles in carbon export. This study analysed the composition and vertical distribution of zooplankton in association with phytoplankton community composition over a 20 h in February 2017 at a fixed station in the central basin of the Bransfield Strait. The water column was stratified, resulting in the dominance of cryptophytes in phytoplankton community. The zooplankton community showed a vertical distribution patterns linked to water column dynamics and food availability, which led an accumulation of salps at the surface during all sampling periods. Calanoid copepods were the main taxa in deeper layers. The consistent presence of salps at the surface highlights their potential role in shaping community structure. If sustained over longer periods, such dominance may influence trophic pathways and carbon flux by altering grazing pressure on phytoplankton and enhancing vertical carbon export through dense, fast-sinking fecal pellets. These findings contribute to a better understanding of zooplankton vertical distribution over short time periods and underscore the importance of further investigating the ecological implications of salp dominance in Antarctic ecosystems.