Abstract

Seasonal and inter-annual fluctuations in the zooplankton composition and abundance from West Antarctica are relatively well known. Nonetheless, there is scarce information about the zooplankton structure in Antarctic waters at shorter time and spatial scales. In this study, we analyzed short-term (i.e., days) temporal and spatial (i. e., km) variation in mesozooplankton from a shallow embayment (South Bay, Doumer Island, 64 degrees 52 ' S, 63 degrees 35 ' W) and surrounding zones off the Western Antarctic Peninsula (WAP), during the austral summer 2022. A total of 110 taxonomic groups were identified in the samples. Meroplankton (Asteroidea, Polychaeta, and Nemertea larvae) was more abundant inside the bay, while the opposite trend was observed for the holoplankton (Copepoda, Appendicularia, and Chaetognatha). Copepods numerically dominated the samples, particularly Oithona spp., Calanoides acutus, and Paraeuchaeta sp. Only meroplankton showed significant differences in the composition and abundance between zones, although alpha-diversity indices showed similar values inside and outside the bay. A Multivariate Regression Tree indicated that the pH (node 1) was the primary predictor separating zooplankton assemblages, followed by the east-west wind stress (Tau-U, node 2), and water stability (node 3). This study highlights the importance of shallow bays in the WAP for the aggregation of planktonic stages of benthic and demersal taxa.