Table 3
Linear regression models explaining the abundance of the two dominant species Dolichospermum flos-aquae and Microcystis aeruginosa, and MC-LR concentration in the Foum-Gleita Reservoir (Mauritania). The models result from a forward stepwise selection procedure and explain M. aeruginosa and D. flos-aquae biovolume (log MycBiov and log DolBiov in mm3 L−1) and Microcystin-LR concentration (log [MC-LR] in μg L−1) by the independent variables: dissolved inorganic nitrogen (log DIN in mg L−1), total phosphorus (log TP in mg L−1), and iron (log Fe in mg L−1), and surface water temperature (T in °C) and pH. All regression models were significant (p < 0.0001). The significance of the regression coefficients is indicated by * (0.01 < p < 0.05), ** (0.001 < p < 0.01), and *** (p < 0.001). Number of observations = 36.
| N0 | Dependent variables | Independent variables | Linear model equations | R 2adj | F |
|---|---|---|---|---|---|
| 1 | log DolBiov | log DIN | – 3.356*** + 3.363*log DIN | 0.182 | 4.894 |
| 2 | log DIN + log TP | – 3.723*** + 4.405*log DIN − 1.676***log TP | 0.193 | 9.364 | |
| 3 | log DIN + log TP + T | – 2.983** + 4.394*log DIN − 1.917***log TP − 0.03*T | 0.160 | 3.218 | |
| 4 | log DIN + log TP + pH | – 3.719** + 2.967*log DIN − 17.646**log TP − 1.457**pH | 0.430 | 9.794 | |
| 5 | log DIN + log TP + pH+ log Fe | – 3.027** + 2.631*log DIN − 12.628**log TP − 0.878*pH + 0.015*log Fe | 0.489 | 9.724 | |
| 6 | log MycBiov | log DIN | + 0.775*** − 3.317**log DIN | 0.863 | 111.396 |
| 7 | log DIN + log TP | + 1.614** − 1.355**log DIN + 3.831*log TP | 0.650 | 66.134 | |
| 8 | log DIN + log TP + T | + 2.789*** − 1.389**log DIN + 4.197*log TP − 0.038**T | 0.883 | 89.095 | |
| 9 | log DIN + log TP + T + pH | + 2.823*** − 1.549**log DIN + 4.273*log TP − 0.078*T + 0.238*pH | 0.884 | 67.469 | |
| 10 | log DIN + log TP + T + log Fe | + 2.917*** − 1.942**log DIN + 4.722*log TP − 0.206*T − 0.160***log Fe | 0.902 | 72.470 | |
| 11 | log [MC-LR] | log DIN | – 1.134** + 0.658**log DIN | 0.723 | 92.35 |
| 12 | log DIN + log TP | – 1.233** + 0.425**log DIN − 0.454**log TP | 0.803 | 72.252 | |
| 13 | log DIN + log TP + T | – 1.565*** + 0.415**log DIN − 0.346**log TP + 0.014**T | 0.856 | 70.30 | |
| 14 | log DIN + log TP + T + pH | – 1.257** + 0.390**log DIN − 0.334**log TP + 0.014**T − 0,038*pH | 0.854 | 52.341 | |
| 15 | log DIN + log TP + T + log Fe | – 1.324** + 0.312*log DIN − 0.590*log TP + 0.007**T + 0.019***log Fe | 0.909 | 55.150 |
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