Sea-ice-related environmental drivers affect meiofauna and macrofauna communities differently at large scales (Southern Ocean, Antarctic)

Abstract

The structure and drivers of Southern Ocean meiofauna and macrofauna were investigated together in one extensive study. From the tip of the Antarctic Peninsula to the southeastern Weddell Sea, we classified the investigated stations into 5 categories according to their summer sea-ice cover: (I) none (Drake Passage), (II) irregular (Bransfield Strait), (III) seasonal (northwestern Weddell Sea), (IV) high (South Filchner Trough), and (V) constant (North Filchner Trough). The categories differed significantly in primary-production-related characteristics in the water column and food availability at the seafloor. Almost all ice-cover categories differed significantly in meiofauna communities (32-500 µm, 20 taxa, 585 825 individuals). Fewer regions differed significantly in macrofauna (>500 µm, 19 taxa, 3974 individuals) or the combined meiofauna and macrofauna communities. Environmental drivers explained >66% of the variation among different communities and differed for the faunal size classes: for meiofauna (84.2%), sea-ice cover (1 yr) and availability of fresh food (chlorophyll a [chl a]) were most important, whereas 1 yr ice cover, chl a, and total organic carbon were decisive drivers for macrofauna (66.6%). Grain size, water depth, water-column chl a, long-term ice cover, seafloor temperature, and the carbon/nitrogen ratio influenced communities to a lesser extent. We demonstrated a stronger relationship with sea-ice cover in meiofauna communities than in macrofauna communities, and we recommend including meiofauna in future assessments of the influence of environmental changes on Southern Ocean ecosystems.