Linking long-term changes of the zooplankton community to the environmental variability at the EPEA Station (Southwestern Atlantic Ocean)

Abstract

A significant sea surface temperature increase has been reported for the Southwestern Atlantic Ocean between 20° S-50° S over the last decades. Zooplankton organisms are highly sensitive to temperature rise. They play a very important role in marine ecosystems by providing themain pathway of energy transfer from primary producers to consumers. Seasonal and interannual(2000-2017) variability of metazooplankton in relation to environmental changes, particularly tem-perature, were analyzed at the EPEA station (38° 28′ S-57° 41′ W). Copepods, appendicularians,cladocerans, chaetognaths, and lamellibranch larvae were identified and quantified. Temperature exhibited a positive interannual trend during the series, whereas the Simpson parameter showed a decreasing tendency and salinity remained almost constant. Adults, copepodites, and nauplii of small copepods belonging to Oithonidae (mostly Oithona nana) and Paracalanidae-Clausocalanidae families dominated the metazooplankton community during the study period. Three groups of taxa with different seasonal patterns of variability were clearly identified. Members of Oithonidae exhib-ited positive interannual trends, whereas lamellibranch larvae and Calanidae showed negative inter-annual trends. A direct influence of temperature anomaly on these changes is suggested as well as possible indirect effects of this anomaly upon zooplankton through different phytoplankton frac-tions. Under the current scenario of climate change, the maintenance of this time-series becomes crucial in order to evaluate the eventual transfer of the environmental variability to the local foodwebs through planktonic organisms.