Table 2.
Comparison of IC10 and IC20 (µg l−1) values of herbicides, aged herbicides and DEA, the transformation product of atrazine for Symbiodinium sp. and Dunaliella sp. These ICX values represent the concentration of parent herbicide in the toxicity assays that inhibit ∆F/Fm′ by X = 10 and 20% and were derived from the concentration-response curves in Fig. 1. Of the three transformation products tested, only DEA inhibited ∆F/Fm′ by >20%.
| IC10 parent | IC10 aged | IC20 parent | IC20 aged | |
|---|---|---|---|---|
| Symbiodinium sp. | ||||
| Diuron | 0.64 (0.57–0.71) | 0.17 (0.12–0.24) | 0.68 (0.58–0.79) | 0.34 (0.32–0.36) |
| Atrazine | 8.6 (8.0–9.3) | 7.2 (6.5–8.0) | 14 (13–15) | 12 (11–13) |
| Ametryn | 0.47 (0.43–0.51) | 0.43 (0.41–0.46) | 0.82 (0.77–0.87) | 0.80 (0.76–0.83) |
| Hexazinone | 5.3 (4.5–6.7) | 10 (8.7–12) | 12 (11–14) | 17 (16–19) |
| Simazine | 21 (19–23) | 22 (20–24) | 34 (32–36) | 35 (32–38) |
| DEA | 103 (93–115) | — | 218 (203–233) | — |
| Dunaliella sp. | ||||
| Diuron | 1.02 (0.94–1.10) | 0.63 (0.58–0.69) | 1.74 (1.65–1.84) | 1.27 (1.19–1.34) |
| Atrazine | 12 (11–14) | 5.9 (5.0–7.1) | 18 (16–20) | 11 (10–12) |
| Ametryn | 0.70 (0.65–0.74) | 0.75 (0.72–0.78) | 1.23 (1.17–1.28) | 1.35 (1.31–1.38) |
| Hexazinone | 16 (15–17) | 18 (17–20) | 10 (9.2–11) | 10 (9.0–11) |
| Simazine | 31 (29–33) | 31 (26–38) | 17 (15–18) | 16 (14–18) |
| DEA | 157 (142–173) | — | 310 (290–332) | — |