Sediment trap illustrates taxon-specific seasonal signals in Southern Ocean zooplankton

Abstract

Southern Ocean zooplankton provide globally significant ecosystem services through their role in carbon sequestration, nutrient cycling and food webs. However, the remote and extreme nature of the Southern Ocean creates significant logistical difficulties for studying zooplankton all year round. Here, for the first time in the Southern Ocean, we present the seasonal occurrence of the zooplankton assemblage in the Northeast Scotia Sea using a sediment trap deployed throughout 2018 (P3 observation site, 52.80˚ S, 40.14˚ W). Results show that copepods and pteropods dominated trap abundance, representing 25.0–68.3% and 13.4–72.5% respectively, followed by amphipods (1.0–7.2%) and hydrozoa (0.2–15.6%). The dominant signal in copepods was consistent with previous observations using traditional (net) sampling methods while the relative contribution of pteropods, amphipods and hydrozoa was increased in our trap. Further, zooplankton showed taxon-specific seasonal signals, with a relatively high number of individuals throughout winter, including an increase in hydrozoa occurrences. This observation highlights the importance of zooplankton as source of nutrition for the benthic community in the winter. Our data reiterate the utility of sediment traps for observing zooplankton in remote locations and sampling specific taxa that might be otherwise understudied.