Spring-summer temporal dynamics of the zooplankton community in a flooded inlet of a sub-Antarctic river (Tierra del Fuego National Park)

Abstract

Understanding the dynamics of zooplankton communities is essential given their key role in aquatic food webs and their value as indicators of ecosystem health. This study examined the temporal variation of micro- and mesozooplankton communities in a flooded estuarine area influenced by glacial meltwater, during the spring-summer period, considering both temporal and diel scales. Physical, chemical, biological, and meteorological parameters were measured, and their relationships with zooplankton composition were analysed. Three microzooplankton and fourteen mesozooplankton taxa were identified. The dominant groups were copepod nauplii and adults and the cladoceran Podon leuckarti. Zooplankton composition varied among periods and between daytime and nighttime, with Podon leuckarti and Oithona similis contributing most to diel differences. Zooplankton composition was influenced by water temperature, salinity, microphytoplankton biomass, wind intensity, and time of day, with seasonal effects explaining the largest share of variability. Our results provide insights into zooplankton dynamics in a sub-Antarctic estuarine ecosystem across two temporal scales. We propose a possible mechanism in which zooplankton are transported into this shallow floodplain mainly by tidal advection and subsequently benefit from the favourable environmental conditions present during the season of highest diversity (spring-summer). This area may also function as an important feeding habitat for other aquatic organisms.