Atlantic Ocean 4 Atlantic Ocean (Southwest) 4 Brazil-Malvinas Confluence 4 Southwestern Atlantic 4 abundance 4 biomass 4 chlorophyll 4 community structure 4 copepods 4 crustacean 4 normalized biomass size spectra population density 4 population distribution 4 size structure 4 summer 4 trophic level 4 upper ocean 4 zooplankton 4