Influence of temperature, salinity and light on growth rates of Alexandrium tamarense (Dinoflagellata, Dinophyceae) from the continental shelf close to Patos Lagoon estuary

Abstract

The dinoflagellate Alexandrium tamarense (Lebour) Balech potentially produces saxitoxins which can be accumulated through the food web and cause a serious disease called PSP (Paralytic Shellfish Poisoning) in higher-level consumers, including humans, birds and mammals. There were obtained 13 strains through cysts germination and motile cells isolation that were kept in culture, under constant conditions of temperature (20°C), light intensity (ca. 350 μmol.m-2.s-1), salinity (31) and nutrients (f/2 medium without silicate), until the experiments were carried out. Assays were performed to determine optimal environmental conditions for growth, after acclimation to respective test conditions. Although relatively high growth rates (0.3 div.day-1) were found under a wide range of temperature (7 to 25°C), light intensity (over 80 μmol.m-2.s-1) and salinity (7 to 32), highest growth rates up to 0.7 div day-1 were measured under restricted ranges of temperature (15 to 20°C), light intensity (above 150 μmol.m-2. s-1) and salinity (26 and 31). These growth rates are among the highest reported for Alexandrium tamarense under laboratory conditions and represent a potentiality for high cell concentrations during fast growth in the southern Brazilian coastal waters.