Das Projekt "Exzellenzcluster 80 (EXC): Ozean der Zukunft" wird vom Umweltbundesamt gefördert und von Helmholtz-Zentrum für Ozeanforschung Kiel (GEOMAR), Forschungsbereich 3: Marine Ökologie, Forschungseinheit Evolutionsökologie Mariner Fische durchgeführt. Global climate change leads to the emergence and increase of diseases in marine ecosystems. In eelgrass, Zostera marina, mass mortality possibly induced by the protist Labyrinthula zosterae (wasting disease) was first observed in the 1930s and since then appeared circumpolar coinciding with environmental stress. Despite the ecosystem consequences of eelgrass loss, little is known on distribution and virulence of L. zosterae, any background infection level of Z. marina, and the environmental triggers for epidemics. We will quantify L. zosterae in European Z. marina-populations with quantitative PCR (targeting rDNA ITS region). Differences among L. zosterae-strains will be identified by microsatellite analysis and correlated with Z. marina genetic structure. The virulence of strains of different origin will be experimentally tested against different eelgrass hosts, with and without stress. Our results will reveal how the host-pathogen-genotype-interaction is affected by environmental stress, resulting in marine epidemics with massive ecological consequences.