Seasonal upwelling influence on trophic indices of mesozooplankton in a coastal food web estimated from δ15N in amino acids

•Changes in mesozooplankton food web dynamics were evaluated in response to upwelling.•Higher phytoplankton availability during upwelling events induces herbivory.•Negative relationship between upwelling intensity and zooplankton trophic position.•Metazoan and microbial food webs are optimally coupled at low upwelling intensities.•Upwelling disruption leads to shorter and more efficient food webs.