Effects of nutrients on growth and nodularin production of Nodularia strain GR8b

To determine the effects of nutrients on growth and toxin production of Nodularia strain GR8b, several nutrient concentrations were tested in batch and chemostat cultures. in batch cultures, phosphate (55-5,500 pg L-1) and nitrate (100-30,000 mug L-1) concentrations were applied, whereas in chemostat cultures, phosphate concentrations (5-315 mug L-1) were tested. Intra- and extracellular toxin concentrations, together with biomass parameters, were measured. In the batch cultures with low phosphate concentrations, chlorophyll a and protein contents were reduced, but dry weights and cell numbers were not significantly affected. The highest nitrate concentrations resulted in reduced dry weight concentrations. Nodularin concentration per dry weight, nodularin to protein ratio, and dissolved nodularin were highest at the end of the experiment, but were not influenced by the nutrient concentrations. Nodularin concentration per cell was also rather constant under the varying nutrient concentrations. In the chemostat cultures, the biomass increased with high phosphate concentrations. However, the phosphate concentrations did not have statistically significant effects on nodularin production rates.