Predator-prey interactions between the heterotrophic protist Polykrikos kofoidii and strains of three dinoflagellate species of Alexandrium (A. catenella, A. limii, A. pseudogonyaulax)

The ingestion rates of the heterotrophic protist Polykrikos kofoidii feeding on different species of Alexandrium were determined by means of incubation experiments in well-plates. In the first experiment P. kofoidii was subjected to monoalgal prey consisting of either lytic goniodomin producing A. pseudogonyaulax (Limfjord, Denmark, strain L4-B9) or a non-lytic paralytic shellfish toxin producing Alexandrium catenella (Scottish east coast North Sea, strain Alex 5). In the second experiment P. kofoidii was subjected to prey mixtures consisting of A. pseudogonyaulax (strain L4-B9) and A. catenella (strain Alex 5) or goniodomin producing non-lytic A. limii (Shioya Bay, Japan, strain Atay99Shio-02), whereby one prey was dyed with the fluorescent dye CMAC. The experiments were carried out between December 2 and 5, 2022 and on January 18, 2023 in the laboratories at the Alfred-Wegener-Institute in Bremerhaven, Germany.