Structure and Spatial Distribution of Mesozooplankton Communities in the Atlantic Sector of the Southern Ocean

Abstract—The article discusses the composition and spatial distribution patterns of mesozooplankton communities in the waters of the Bransfield Strait, Antarctic Sound, Powell Basin of the Weddell Sea, and off the Antarctic Peninsula and South Orkney Islands during the austral summer of 2022. Among the mesozooplankton communities, two groups were revealed to be the most abundant: copepods Calanoides acutus, Metridia gerlachei and Oithona spp., and euphausiids Euphausia superba. The maximum abundance and biomass of mesozooplankton were found in warm Antarctic surface water (AASW) off the South Orkney Islands. Correspondingly, the minimum values were found in cold modified Transitional Weddell Sea Water (TWW) off the Antarctic Peninsula. Copepods was concentrated in the Bransfield Strait near the South Shetland Islands with a sea surface temperature (SST) of –0.5 to 0.5°С and sea surface salinity (SSS) of 34.5–34.6‰; krill E. superba eggs and larvae at different stages of development was concentrated in waters off the South Orkney Islands with SST values of 1–2°С and SSS values of 34.3–34.5‰. Four groups of mesozooplankton communities with different composition, abundance, and taxonomic dominance were identified. The results of this and future studies have practical implications for monitoring the state of the changing ecosystem of the Southern Ocean.