Stella Berger, Christian Dilewski, Alexis Guislain, Iordanis Magiopoulos, Sébastien Mas, Behzad Mostajir, Jens Nejstgaard, David Parin, Paraskevi Pitta, Tanguy Soulié, Katerina Symiakaki, Anastasia Tsiola, Francesca Vidussi During a Transnational Access of JERICO-S3, called the 'Joint JERICO-S3 and AQUACOSM-plus study on Baltic Sea heatwaves', twelve indoor mesocosms were used to simulate different levels of MHWs at the Finnish Environment Institute (SYKE) in Helsinki from late August to early September 2022, in order to study their impact on the Baltic Sea plankton communities. Severe anomalous warming events, known as Marine Heat Waves (MHWs), are expected to increase under continued global warming. Although the effect of the temperature increase has been investigated in multiple systems, little is known…