Influence of upwelling intensity on environmental variables and phytoplankton community composition in the Peruvian upwelling system during austral summer 2018-2019

Silvia Georgieva

The effect of upwelling intensity on the hydrological structure, phytoplankton biomass and composition on two different time scales (i) a week before cruise sampling and (ii) during sampling was investigated on six cross-shore transects along the Peruvian coast during the austral summer of 2018-2019. The majority of phytoplankton biomass was restricted to the surface along the coastal band, but in areas that experienced strong upwelling a week prior to sampling, high biomass also extended to offshore waters. Several stages of phytoplankton succession were observed, with diatoms mainly dominating in freshly upwelled waters, while a transition to mixed, dinoflagellate-dominated communities was observed in aging waters. Mature offshore waters were characterized by smaller phytoplankton groups, such as haptophytes and pelagophytes.