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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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