Table 1.
Comparison of ICX (µg l−1) values of standard parent herbicides and aged mixtures (after 330 d) from each herbicide. These ICX values represent the concentration of parent herbicide in the toxicity assays that inhibit ∆F/Fm′ by X = 10, 20 or 50% and were derived from the concentration-response curves in Fig. 1 (the concentrations of transformation products are not considered here). Differences in ICXs between pure and aged herbicide solutions were assessed using the F-test in GraphPad and were considered significant when < 0.05. The diuron vs aged diuron solutions had significantly different IC10 and IC20 values for both algal species and the IC50 values for Symbiodinium sp. were different. IC10 and IC20 values for all herbicide and algal species can be found in Table 2. All r2 > 0.97.
| ICX | ICX parent | ICX aged | F(df) | P value | |
|---|---|---|---|---|---|
| Symbiodinium sp. | |||||
| Diuron | IC50 | 1.4 (1.3–1.6) | 0.95 (0.92–0.99) | F (1,84) = 34.1 | <0.0001 |
| IC20 | 0.68 (0.58–0.79) | 0.34 (0.32–0.36) | F (1,84) = 74.3 | <0.0001 | |
| IC10 | 0.64 (0.57–0.71) | 0.17 (0.12–0.24) | F (1,84) = 136 | <0.0001 | |
| Atrazine | IC50 | 34.5 (32–35) | 32 (27–38) | F (1,110) = 0.352 | 0.5541 |
| Ametryn | IC50 | 2.2 (2.1–2.3) | 2.3 (2.2–2.4) | F (1,93) = 2.13 | 0.1475 |
| Hexazinone | IC50 | 45.7 (40–53) | 51 (46–56) | F (1,89) = 3.41 | 0.068 |
| Simazine | IC50 | 84 (77–92) | 72.5 (63–83) | F (1,74) = 1.59 | 0.2111 |
| Dunaliella sp. | |||||
| Diuron | IC50 | 4.4 (4.2–4.6) | 4.1 (3.8–4.5) | F (1,103) = 0.980 | 0.3245 |
| IC20 | 1.74 (1.65–1.84) | 1.27 (1.19–1.34) | F (1,103) = 62.1 | <0.0001 | |
| IC10 | 1.02 (0.94–1.10) | 0.63 (0.58–0.69) | F (1,103) = 63.4 | <0.0001 | |
| Atrazine | IC50 | 35 (32–38) | 40 (35–47) | F (1,95) = 1.96 | 0.1652 |
| Ametryn | IC50 | 3.4 (3.2–3.6) | 3.7 (3.5–3.8) | F (1,81) = 17.3 | 0.0789 |
| Hexazinone | IC50 | 38 (36–40) | 40 (38–43) | F (1,87) = 2.24 | 0.1384 |
| Simazine | IC50 | 87 (79–96) | 103 (73–146) | F (1,78) = 0.841 | 0.3618 |