Morphological study of Naiadinium polonicum (Dinophyceae) reported for the first time in Chilean inland waters

Abstract

Naiadinium polonicum is a dinoflagellate widely distributed in lakes and reservoirs of the Northern Hemisphere, sometimes associated with fish mortality by production of toxins. During May 2013 a massive proliferation of this species was detected in Rapel Reservoir (34°10’S, 71°29’W). In the present paper a morphological study of the species was performed using light and electron microscopical techniques. This is the first record of N. polonicum for Chilean continental waters. The morphological characters of the specimens analyzed are consistent with the descriptions and illustrations found in the literature. In this study, Naiadinium polonicum was considered as a conspecific taxon to Naiadinium biscutelliforme, and we considered the species to be variable with relation to the number and relative size of the intercalary plates (1-2a). Naiadinium polonicum reached a maximum concentration of 2572 cells/mL, and since this phenomenon was observed only once we preliminary attributed the high content of nutrients (66 μgL-1 PT, 645.67 μgL-1 NT) available in the water column as the preponderant factor that probably caused the proliferation.