Despite the observed coexistence between these species, when the cell density data were analyzed, with a dominance of alternating periods, C. raciborskii biomass was on average 500 times greater than that of M. contortum and was the main contributor to the cyanobacteria dominance in the reservoir considering the cell volume and biovolume of C. raciborskii. The mean, minimum and maximum values, as well as the standard deviations for the quantified parameters are shown in Table 1.
Variation range (average, maximum, minimum and standard deviations) of the physical, chemical and biological data of samples (n = 56) collected at the Itupararanga Reservoir
| Parameters . | Average . | Minimum . | Maximum . | Standard deviation . |
|---|---|---|---|---|
| Temperature (°C) | 21.8 | 16.8 | 26.4 | 4.1 |
| pH | 7.1 | 2.9 | 8.9 | 0.9 |
| DO (mg·L−1) | 6.4 | 2.0 | 9.3 | 2.0 |
| Conductivity (μS·cm−1) | 64.3 | 27.8 | 96.1 | 9.2 |
| Nitrate (μg·L−1) | 0.5 | 0.2 | 0.8 | 0.1 |
| Nitrite (μg·L−1) | 0.5 | 0.0 | 1.8 | 0.5 |
| Ortophosphate (μg·L−1) | 3.2 | 0.3 | 8.5 | 1.8 |
| Total Kjeldahl nitrogen (μg·L−1) | 200 | 0 | 700 | 200 |
| Total phosphorus (μg·L−1) | 23.9 | 8.3 | 42.5 | 7.7 |
| Turbidity (NTU) | 9.8 | 3.1 | 13.4 | 1.7 |
| Alkalinity (meq·L−1) | 0.5 | 0.2 | 0.8 | 0.1 |
| Total organic carbon (mg·L−1) | 4.3 | 1.7 | 6.7 | 0.8 |
| Chlorophyll a (μg·L−1) | 27.6 | 6.6 | 46.4 | 10.7 |
| Pheophytin (μg·L−1) | 3.7 | 0.5 | 15.9 | 3.2 |
| Saxitoxin (μg·L−1) | 0.14 | 0.04 | 0.20 | 0.05 |
| Saxitoxin per trichome (10−3 pg) | 13.3 | 4.5 | 29.9 | 6.2 |
| Total phytoplankton density (org·mL−1) | 3.7 × 104 | 9.1 × 103 | 6.1 × 104 | 1.2 × 104 |
| M. contortum density (org·mL−1) | 1.7 × 104 | 1.1 × 103 | 4.1 × 104 | 1.1 × 104 |
| C. raciborskii density (org·mL−1) | 1.4 × 104 | 3.2 × 103 | 4.3 × 104 | 9.6 × 103 |
| M. contortum biovolume (μm3·mL−1) | 2.9 × 104 | 1.6 × 103 | 1.8 × 105 | 2.8 × 104 |
| C. raciborskii biovolume (μm3·mL−1) | 6.5 × 106 | 1.9 × 106 | 1.8 × 107 | 4.2 × 106 |
| Parameters . | Average . | Minimum . | Maximum . | Standard deviation . |
|---|---|---|---|---|
| Temperature (°C) | 21.8 | 16.8 | 26.4 | 4.1 |
| pH | 7.1 | 2.9 | 8.9 | 0.9 |
| DO (mg·L−1) | 6.4 | 2.0 | 9.3 | 2.0 |
| Conductivity (μS·cm−1) | 64.3 | 27.8 | 96.1 | 9.2 |
| Nitrate (μg·L−1) | 0.5 | 0.2 | 0.8 | 0.1 |
| Nitrite (μg·L−1) | 0.5 | 0.0 | 1.8 | 0.5 |
| Ortophosphate (μg·L−1) | 3.2 | 0.3 | 8.5 | 1.8 |
| Total Kjeldahl nitrogen (μg·L−1) | 200 | 0 | 700 | 200 |
| Total phosphorus (μg·L−1) | 23.9 | 8.3 | 42.5 | 7.7 |
| Turbidity (NTU) | 9.8 | 3.1 | 13.4 | 1.7 |
| Alkalinity (meq·L−1) | 0.5 | 0.2 | 0.8 | 0.1 |
| Total organic carbon (mg·L−1) | 4.3 | 1.7 | 6.7 | 0.8 |
| Chlorophyll a (μg·L−1) | 27.6 | 6.6 | 46.4 | 10.7 |
| Pheophytin (μg·L−1) | 3.7 | 0.5 | 15.9 | 3.2 |
| Saxitoxin (μg·L−1) | 0.14 | 0.04 | 0.20 | 0.05 |
| Saxitoxin per trichome (10−3 pg) | 13.3 | 4.5 | 29.9 | 6.2 |
| Total phytoplankton density (org·mL−1) | 3.7 × 104 | 9.1 × 103 | 6.1 × 104 | 1.2 × 104 |
| M. contortum density (org·mL−1) | 1.7 × 104 | 1.1 × 103 | 4.1 × 104 | 1.1 × 104 |
| C. raciborskii density (org·mL−1) | 1.4 × 104 | 3.2 × 103 | 4.3 × 104 | 9.6 × 103 |
| M. contortum biovolume (μm3·mL−1) | 2.9 × 104 | 1.6 × 103 | 1.8 × 105 | 2.8 × 104 |
| C. raciborskii biovolume (μm3·mL−1) | 6.5 × 106 | 1.9 × 106 | 1.8 × 107 | 4.2 × 106 |