This study investigates the role of genotypic diversity in enhancing ecosystem recovery after climatic extremes, specifically a heat wave that occurred in 2003 across Europe. The experiment was conducted in a coastal ecosystem dominated by the seagrass *Zostera marina* in the southwestern Baltic Sea. The researchers manipulated the genotypic diversity of *Z. marina* by planting plots with different numbers of genotypes (monocultures, three-genotype treatments, and six-genotype treatments) while maintaining a constant number of plants per plot. The results showed that increasing genotypic diversity enhanced biomass production, plant density, and faunal abundance, even under near-thermal water temperatures due to the extreme warming event. The positive effects were attributed to genotypic complementarity rather than selection of particularly robust genotypes. The study highlights the importance of maintaining both genetic and species diversity to enhance ecosystem resilience in the face of increasing climatic variability and uncertainty.This study investigates the role of genotypic diversity in enhancing ecosystem recovery after climatic extremes, specifically a heat wave that occurred in 2003 across Europe. The experiment was conducted in a coastal ecosystem dominated by the seagrass *Zostera marina* in the southwestern Baltic Sea. The researchers manipulated the genotypic diversity of *Z. marina* by planting plots with different numbers of genotypes (monocultures, three-genotype treatments, and six-genotype treatments) while maintaining a constant number of plants per plot. The results showed that increasing genotypic diversity enhanced biomass production, plant density, and faunal abundance, even under near-thermal water temperatures due to the extreme warming event. The positive effects were attributed to genotypic complementarity rather than selection of particularly robust genotypes. The study highlights the importance of maintaining both genetic and species diversity to enhance ecosystem resilience in the face of increasing climatic variability and uncertainty.