Effect of abiotic factors in vegetative growth of Alexandrium catenella from cysts in laboratory

Alexandrium catenella is a toxic dinoflagellate that causes harmful algal blooms in the marine inland sea of southern Chile. To gain an insight about the effect of temperature, salinity, photoperiod and nutrient levels in culture medium growth vegetative polyclonal cells of A. catenella (strain ACO90610 QUE-Q) from sediment cysts (Quellon, Chile) were cultivated. The strain was studied in different experiments by cells count using the Utermohl method, every 2 days during 56 days. Effect of salinity (15, 20, 25, 30) using as control seawater with 31 of salinity; temperature (10, 15 and 20 degrees C) photoperiod (12: 12, 16: 08 and 8: 16 L: D) and was determinated nutrients, with L1 medium at different proportions of NaNO3 and NaHPO4. The results showed that cells of A. catenella grew in all range of salinities tested, showing a greater growth rate at 30 (3788 cells mL(-1) on day 26; mu= 0.18 div d(-1)). At 20 degrees C, temperature decrease the growth rate (<1500 cells mL(-1); mu = 0.11 div d(-1)) while at 10 degrees C and 15 degrees C stimulate the growth (> 3000 cells mL(-1); mu = 0.12 div d(-1)). The culture medium without nitrates and phosphates inhibit growth rates, while L1 and L1/ 2 support growth (> 2800 cells. L-1; mu = 0.08 and 0.06 div d(-1), respectively). Different photo-period treatments have similar results (mu = 0.05, 0.07 and 0.08 div d(-1)) reaching 2000 cells mL(-1) at the end of the experiment. These results suggest that the cultured strain responded to changes in temperature, photoperiod and differ ent nutrient concentrations.