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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 individual herbicides.Concentration response curves for inhibition of∆F/Fm’ measured at(A) 24 h and (B) 48 h for 10individual herbicides, relative to each solvent control. The four herbicidesin (B) did not reach maximum inhibition of∆F/Fm’ within24 h. Bars representSE ± n = 9.
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f1: Concentration-response curves for individual herbicides.Concentration response curves for inhibition of∆F/Fm’ measured at(A) 24 h and (B) 48 h for 10individual herbicides, relative to each solvent control. The four herbicidesin (B) did not reach maximum inhibition of∆F/Fm’ within24 h. Bars representSE ± n = 9.

Mentions: All herbicides tested inhibited∆F/Fm’ in H. ovalisenabling classical concentration-response relationships to be fitted (Fig. 1) with high levels of confidence (r2values = 0.98–0.99). The herbicideconcentrations that inhibited∆F/Fm’ by 10% (IC10)and 50% (IC50) are listed in Table 2. After24 h, diuron was the most potent of the herbicides, exhibiting thelowest IC50 of 4.3 μgl−1 (Table 2).Fluometruon with an IC50 of 132 μgl−1 was the least potent of the herbicides testedin the 24 h assays. Maximum inhibition of∆F/Fm’ was reachedbefore 24 h for all herbicides8 apart from ametryn,metribuzin, prometryn and hexazinone which reached maximum inhibition by48 h. This additional 24 h of exposure resulted in lowerIC50 values, reducing them by a further 63% to 69% (Fig. 1B and Table 2). The potenciesfor each of the herbicides can be evaluated using the Relative Potencies (ReP)compared to the reference herbicide diuron (IC50diuron/IC50 herbicide) (Table 2). RePvalues > 1 indicate potencies proportionallygreater than diuron and ReP values < 1 indicatepotencies less than diuron.


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 individual herbicides.Concentration response curves for inhibition of∆F/Fm’ measured at(A) 24 h and (B) 48 h for 10individual herbicides, relative to each solvent control. The four herbicidesin (B) did not reach maximum inhibition of∆F/Fm’ within24 h. Bars representSE ± n = 9.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Concentration-response curves for individual herbicides.Concentration response curves for inhibition of∆F/Fm’ measured at(A) 24 h and (B) 48 h for 10individual herbicides, relative to each solvent control. The four herbicidesin (B) did not reach maximum inhibition of∆F/Fm’ within24 h. Bars representSE ± n = 9.
Mentions: All herbicides tested inhibited∆F/Fm’ in H. ovalisenabling classical concentration-response relationships to be fitted (Fig. 1) with high levels of confidence (r2values = 0.98–0.99). The herbicideconcentrations that inhibited∆F/Fm’ by 10% (IC10)and 50% (IC50) are listed in Table 2. After24 h, diuron was the most potent of the herbicides, exhibiting thelowest IC50 of 4.3 μgl−1 (Table 2).Fluometruon with an IC50 of 132 μgl−1 was the least potent of the herbicides testedin the 24 h assays. Maximum inhibition of∆F/Fm’ was reachedbefore 24 h for all herbicides8 apart from ametryn,metribuzin, prometryn and hexazinone which reached maximum inhibition by48 h. This additional 24 h of exposure resulted in lowerIC50 values, reducing them by a further 63% to 69% (Fig. 1B and Table 2). The potenciesfor each of the herbicides can be evaluated using the Relative Potencies (ReP)compared to the reference herbicide diuron (IC50diuron/IC50 herbicide) (Table 2). RePvalues > 1 indicate potencies proportionallygreater than diuron and ReP values < 1 indicatepotencies less than diuron.

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