The most abundant zooplankton species are Acartia spp. and Calanus helgolandicus. Crab larvae are also important during winter months along the Portuguese coast. In recent years, copepod species such as Temora stylifera, characteristic of warmer waters, have appeared or increased in abundance (e.g.) related to increases in sea surface temperature. The seasonal cycle of zooplankton biomass is characterized by a bimodal pattern along the western Iberian coast, with peak biomass in April and August, caused by seasonal upwelling. Copepod abundance remains high throughout the year, with the highest abundances from August through November along the Iberian coast. The interannual variation of zooplankton abundance and biomass does not show clear trends in the ecoregion except for Galicia, where it couples with the upwelling cycles. There are differences in the structure of the zooplankton community along the north Iberian coast.