TEMPERATURE AND SALINITY EFFECTS ON GROWTH OF A NON‐CHAIN‐FORMING STRAIN OF FYMNODINIUM CATENATUM (DINOOHYCEAE) ESTABLISHED FROM A CYST FROM RECENT SEDIMENTS IN THE SOUND (øRESUND), DENMARK1

The athecate, marine dinoflagellate Gymnodinium catenatum Graham 1943 was cultured from a resting cyst found in sediment samples from The Sound, Denmark. Gymnodinium catenatum has not previously been registered alive in Danish waters, although fossilized cysts have been found in old sediments. The description (morphology and ultrastructure) of the strain established from the cyst complied with earlier studies of G. catenatum with the exception that chains longer than two cells were never see. Fitting the growth rates of the motile stage of G. catenatum to a linear model showed a signified influence of temperature and salinity. Maximal division rate was 0.4 div‐day−1 at 20–25°C and 20% salinity. Gymnodinium catenatum causes paralytic shellfish poisoning in other parts of the world, but the toxicity of the Danish strain has not been determined. Possible explanations for the presence of G. catenatum in Danish waters ware discussed.