Burford et al. (2014) analyzed the effects of N and P concentrations on cell division and on the production of cylindrospermopsins in C. raciborskii in experiments with phytoplankton communities dominated by this species and obtained from tropical reservoirs. The amount of toxin per cell increased significantly in treatments where there was an increase in phosphorus without an increase in the rate of cell division. In this paper, positive and significant correlations were found between saxitoxina and DO (r = 0.61, p < 0.001) and orthophosphate (r = 0.57, p < 0.001) concentrations, whereas negative correlations were found with the temperature (r = −0.71, p < 0.001) and pH (r = −0.56, p < 0.001) (Table 2).
Pearson's correlation coefficient (r) and significance (p) between environmental parameters and saxitoxin concentration for the 56 integrated samples from the Itupararanga Reservoir water column
| Parameter . | Correlation (r) . | Significance (p) . |
|---|---|---|
| Temperature | −0.71 | 0.000 |
| DO | 0.61 | 0.000 |
| NO2 | 0.43 | 0.001 |
| Orthoposphate | 0.52 | 0.000 |
| Total nitrogen | −0.38 | 0.004 |
| Total phosphorus | −0.57 | 0.000 |
| Alkalinity | −0.56 | 0.000 |
| Total organic carbon | −0.40 | 0.002 |
| Parameter . | Correlation (r) . | Significance (p) . |
|---|---|---|
| Temperature | −0.71 | 0.000 |
| DO | 0.61 | 0.000 |
| NO2 | 0.43 | 0.001 |
| Orthoposphate | 0.52 | 0.000 |
| Total nitrogen | −0.38 | 0.004 |
| Total phosphorus | −0.57 | 0.000 |
| Alkalinity | −0.56 | 0.000 |
| Total organic carbon | −0.40 | 0.002 |