Fig 1.
LC50 dose-response curve for B. longirostris.
Average percent mortality of B. longirostris collected in May 2016 following a 48-hr exposure at 25°C to a range of microcystin-LR concentrations. Data corrected for control percent mortality. Error bars represent standard deviation. N = 6. Different letters indicate significant difference (p-value<0.05, Fisher’s LSD). One-way ANOVA: p<0.0001. F5,30 = 139.96. R2 = 0.96.
Fig 2.
Probit analysis of the effect of microcystin-LR on B. longirostris mortality.
Percent mortality converted to empirical probits versus log of the microcystin-LR concentrations [36]. Log-LC50 = 1.42, based on linear regression with 100 μg L-1 concentration treatment omitted: y = 0.6666x+4.0531. R2 = 0.602. LC50 = 26.3±4.6 μg L-1.
Fig 3.
Temperature and microcystin-LR exposure from 25°C-35°C.
Average percent mortality of B. longirostris collected in June 2016 over a range of temperatures when exposed to the LC50 of 26.3 μg L-1 microcystin-LR for 48-hrs. Temperature control treatments did not contain microcystin-LR. Error bars represent standard deviation. N = 9. Different letters indicate significant difference (p-value<0.05, Fisher’s LSD). ANCOVA: p <0.0001. R2 = 0.80. F1,1 = 23.18. Temperature one-way ANOVA: R2 = 0.84. p-value <0.0001. F4,30 = 40.23. Temperature plus Toxin one-way ANOVA: R2 = 0.68. p-value <0.0001. F4,30 = 15.92.
Fig 4.
Temperature and microcystin-LR exposure from 15°C-25°C.
Average percent mortality of B. longirostris collected in April 2017 over a range of temperatures when exposed to the LC50 of 26.3 μg L-1 microcystin-LR for 48-hrs. Temperature control treatments were without microcystin-LR. Error bars represent standard deviation. N = 9. Different letters indicate significant difference (p<0.05, Fisher’s LSD). ANCOVA: p<0.0001. R2 = 0.88. F1,1 = 92.48. Temperature one-way ANOVA: R2 = 0.21. p<0.05. F4,44 = 2.27. Temperature plus Toxin one-way ANOVA: R2 = 0.90. p<0.0001. F4,41 = 85.37.
Table 1.
Common zooplankton species and their corresponding LC50 values when exposed to dissolved microcystin-LR.
Dashes indicate value not reported.