Limits...
Acute and additive toxicity of ten photosystem-II herbicides to seagrass.

Wilkinson AD, Collier CJ, Flores F, Negri AP - Sci Rep (2015)

Bottom Line: We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides.The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses.This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/F(m)'.

View Article: PubMed Central - PubMed

Affiliation: College of Marine and Environmental Sciences, James Cook University, Townsville, Queensland, 4811, Australia.

ABSTRACT
Photosystem II herbicides are transported to inshore marine waters, including those of the Great Barrier Reef, and are usually detected in complex mixtures. These herbicides inhibit photosynthesis, which can deplete energy reserves and reduce growth in seagrass, but the toxicity of some of these herbicides to seagrass is unknown and combined effects of multiple herbicides on seagrass has not been tested. Here we assessed the acute phytotoxicity of 10 PSII herbicides to the seagrass Halophila ovalis over 24 and/or 48 h. Individual herbicides exhibited a broad range of toxicities with inhibition of photosynthetic activity (∆F/F(m)') by 50% at concentrations ranging from 3.5 μg l(-1) (ametryn) to 132 μg l(-1) (fluometuron). We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides. The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses. This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/F(m)'.

No MeSH data available.


Related in: MedlinePlus

Concentration-response curves for inhibition of∆F/Fm’ by herbicidemixtures.Inhibition was measured at 24 h for binary and complex (10)herbicide mixtures, relative to each solvent control. Bars representSE ± n = 9.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4663499&req=5

f2: Concentration-response curves for inhibition of∆F/Fm’ by herbicidemixtures.Inhibition was measured at 24 h for binary and complex (10)herbicide mixtures, relative to each solvent control. Bars representSE ± n = 9.

Mentions: The response of H. ovalis to the four mixtures tested (binary and complex)were also plotted as concentration-response curves (Fig.2). The four curves largely overlapped across the range of Toxic Units(TUs) indicating little difference in the response of∆F/Fm’ between thedifferent mixtures and this was confirmed by the calculated IC50which ranged between 0.85 TU – 0.95 TU (3).For additivity using the Concentration Addition (CA) method, the IC50of each of the mixtures would be expected to be close to 1 TU, whichwas determined by the individual concentration-responses (Table2). The reference mixtures of[diuron + diuron] and[atrazine + atrazine] exhibited IC50s of0.90 TU – 0.95 TU indicating slightly moresensitive responses to both herbicides than was observed during the individualherbicide assays. F-test analysis indicated a significant difference within the4-way mixture comparison (F3,24 = 3.21,p < 0.05). The post-hoc analysis indicated thatthe IC50 of [diuron + atrazine] was slightly(11%) but significantly lower (i.e. more potent) than the IC50 of[atrazine + atrazine] (Table 3).This indicates a possible synergistic interaction; however, there was nosignificant difference between the IC50 of the[diuron + atrazine] mixture and the other mixtures(Table 3).


Acute and additive toxicity of ten photosystem-II herbicides to seagrass.

Wilkinson AD, Collier CJ, Flores F, Negri AP - Sci Rep (2015)

Concentration-response curves for inhibition of∆F/Fm’ by herbicidemixtures.Inhibition was measured at 24 h for binary and complex (10)herbicide mixtures, relative to each solvent control. Bars representSE ± n = 9.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663499&req=5

f2: Concentration-response curves for inhibition of∆F/Fm’ by herbicidemixtures.Inhibition was measured at 24 h for binary and complex (10)herbicide mixtures, relative to each solvent control. Bars representSE ± n = 9.
Mentions: The response of H. ovalis to the four mixtures tested (binary and complex)were also plotted as concentration-response curves (Fig.2). The four curves largely overlapped across the range of Toxic Units(TUs) indicating little difference in the response of∆F/Fm’ between thedifferent mixtures and this was confirmed by the calculated IC50which ranged between 0.85 TU – 0.95 TU (3).For additivity using the Concentration Addition (CA) method, the IC50of each of the mixtures would be expected to be close to 1 TU, whichwas determined by the individual concentration-responses (Table2). The reference mixtures of[diuron + diuron] and[atrazine + atrazine] exhibited IC50s of0.90 TU – 0.95 TU indicating slightly moresensitive responses to both herbicides than was observed during the individualherbicide assays. F-test analysis indicated a significant difference within the4-way mixture comparison (F3,24 = 3.21,p < 0.05). The post-hoc analysis indicated thatthe IC50 of [diuron + atrazine] was slightly(11%) but significantly lower (i.e. more potent) than the IC50 of[atrazine + atrazine] (Table 3).This indicates a possible synergistic interaction; however, there was nosignificant difference between the IC50 of the[diuron + atrazine] mixture and the other mixtures(Table 3).

Bottom Line: We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides.The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses.This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/F(m)'.

View Article: PubMed Central - PubMed

Affiliation: College of Marine and Environmental Sciences, James Cook University, Townsville, Queensland, 4811, Australia.

ABSTRACT
Photosystem II herbicides are transported to inshore marine waters, including those of the Great Barrier Reef, and are usually detected in complex mixtures. These herbicides inhibit photosynthesis, which can deplete energy reserves and reduce growth in seagrass, but the toxicity of some of these herbicides to seagrass is unknown and combined effects of multiple herbicides on seagrass has not been tested. Here we assessed the acute phytotoxicity of 10 PSII herbicides to the seagrass Halophila ovalis over 24 and/or 48 h. Individual herbicides exhibited a broad range of toxicities with inhibition of photosynthetic activity (∆F/F(m)') by 50% at concentrations ranging from 3.5 μg l(-1) (ametryn) to 132 μg l(-1) (fluometuron). We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides. The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses. This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/F(m)'.

No MeSH data available.


Related in: MedlinePlus