Characterization of grazer-induced responses in the marine dinoflagellate Alexandrium tamarense

Harmful algal blooms (HABs) have increased worldwide over the last several decades. The characterization of processes that promote the ecological success of toxic algae species that form such blooms has therefore gained immense importance. The HAB-dinoflagellate Alexandrium tamarense causes outbreaks of Paralytic Shellfish Poisoning (PSP) due to the synthesis of the highly neurotoxic alkaloid saxitoxin and several of its analogues (Paralytic Shellfish Toxins, PSTs). While the ecological function of PST production is still unknown and their allelochemical nature is mainly supposed due to the negative effects they have on some copepod species, there are other unknown secondary metabolites produced by A. tamarense which are definitely known to possess allelochemical properties. These compounds are distinct from PSTs and have a lytic effect on co-occurring competitors and protistan grazers. The investigations in this thesis focus on the analysis of mechanisms that promote the success in grazer interactions related to secondary metabolite synthesis in A. tamarense. The implementation of functional genomic tools enabled a detailed characterization of processes that are induced due to the presence of grazers in A. tamarense. Such induced processes that either decrease grazing pressure and/or provide an advantage over co-occurring species in the presence of grazers can strongly promote a species success.