Understanding the impact of a complex environmental matrix associated with climate change on the European marshes engineer species Spartina martima

•Impact of a complex environmental matrix on S. maritima performance was evaluated.•Temperature and atmospheric CO2 increments had synergic injury effects.•These conditions drastically reduced plant growth and increased its senescence.•Carbon assimilation, light-harvesting and photoprotective impacts were found.•Atmospheric CO2 enrichment would limit stomata ability to cope with heat excess.