Effects of nitrogenous and phosphorus nutrients on the growth of toxic dinoflagellate Alexandrium catenella

Abstract

Alexandrium catenella, the causative dinoflagellate of paralytic shellfish poisoning and red-tide, has been grown in axenic and batch conditions to determine the effects of nitrogen and phosphorus on its growth. This organism could use NH4+-, NO3--, and NO2--N, as a sole nitrogen source, but could not use urea and twenty amino acids, except glutamine. And this species could utilize both inorganic and organic phosphorus compounds, as a sole phosphorus source. The half-saturation constant for growth (KS) of inorganic nitrogen and phosphate were 3.3-7.7 μM N and 0.72 μM P respectively. The minimum cell quota of nitrogen and phosphorus were 7.0-7.3 pmol-N/cell and 0.32 pmol-P/cell respectively. The maximum specific growth rate (μmax) was 0.47-0.55 day-1 under nutrient saturated conditions. The relatively large KS and small μmax by A. catenella compared to other typical red-tide phytoplankton species suggest that this organism could not be a dominant species under inorganic nitrogen and/or phosphate limited waters. The present study reveals that A. catenella is suitable to grow in eutrophied coastal waters of elevated organic phosphorus concentration.