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Glyphosate-based herbicides reduce the activity and reproduction of earthworms and lead to increased soil nutrient concentrations.

Gaupp-Berghausen M, Hofer M, Rewald B, Zaller JG - Sci Rep (2015)

Bottom Line: However, our knowledge of potential side-effects on non-target soil organisms, even on such eminent ones as earthworms, is still very scarce.Reproduction of the soil dwellers was reduced by 56% within three months after herbicide application.These sizeable herbicide-induced impacts on agroecosystems are particularly worrisome because these herbicides have been globally used for decades.

View Article: PubMed Central - PubMed

Affiliation: Institute of Zoology, University of Natural Resources and Life Sciences Vienna, Gregor Mendel Straße 33, A-1180 Vienna, Austria.

ABSTRACT
Herbicide use is increasing worldwide both in agriculture and private gardens. However, our knowledge of potential side-effects on non-target soil organisms, even on such eminent ones as earthworms, is still very scarce. In a greenhouse experiment, we assessed the impact of the most widely used glyphosate-based herbicide Roundup on two earthworm species with different feeding strategies. We demonstrate, that the surface casting activity of vertically burrowing earthworms (Lumbricus terrestris) almost ceased three weeks after herbicide application, while the activity of soil dwelling earthworms (Aporrectodea caliginosa) was not affected. Reproduction of the soil dwellers was reduced by 56% within three months after herbicide application. Herbicide application led to increased soil concentrations of nitrate by 1592% and phosphate by 127%, pointing to potential risks for nutrient leaching into streams, lakes, or groundwater aquifers. These sizeable herbicide-induced impacts on agroecosystems are particularly worrisome because these herbicides have been globally used for decades.

No MeSH data available.


Activity of horizontally burrowing earthworms before and after the herbicide application (−H, without herbicide; +H, with herbicide).(A) Daily surface cast production, (B) cumulative cast production over the course of the experiment (N = 6, mean ± SE). Red band marks the period when herbicide was applied. P-values from two-sample Wilcoxon tests performed for the pre- and post-herbicide periods.
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f2: Activity of horizontally burrowing earthworms before and after the herbicide application (−H, without herbicide; +H, with herbicide).(A) Daily surface cast production, (B) cumulative cast production over the course of the experiment (N = 6, mean ± SE). Red band marks the period when herbicide was applied. P-values from two-sample Wilcoxon tests performed for the pre- and post-herbicide periods.

Mentions: Herbicide application initially stimulated surface casting activity of L. terrestris, however the number of produced casts ceased dramatically about one week after herbicide application; in contrast the surface casting activity of this species remained nearly constant when no herbicide was applied (Fig. 1A). Not only did exposure to herbicide reduce the number of surface casts produced, it also reduced the mean mass of individual casts (546 ± 202 mg cast−1 vs. 1,408 ± 140 mg cast−1). Compared to non-herbicide treated mesocosms, cumulative cast mass produced by L. terrestris four weeks after herbicide application was reduced by 46% compared to untreated mesocosms (560 g m−2 vs. 1,032 g m−2; P < 0.001; Fig. 1B). Surface casting activity and cast mass production of the soil-dwelling earthworm species, A. caliginosa, was not affected by herbicide application (Fig. 2A,B). Monitoring surface casting activity has recently been proposed as an ecotoxicity test better related to earthworms’ ecological role than standard laboratory tests26. Although the studied earthworm species differ in their feeding behavior, both have been shown to cast on the soil surface when foraging for leaf litter and other organic material2728. The peak in surface casting activity observed after herbicide application was therefore likely the consequence of an increased availability of dead leaf material. Since we provided extra food for earthworms in all treatments (i.e., dried chopped hay spread over the soil surface) which is supposed to increase surface casting activity, the further decrease in casting activity in herbicide-treated mesocosms clearly demonstrates a direct impact of the herbicide. These detrimental effects of the herbicide on earthworm activity are also surprising as soil moisture increased between 3% to 39% after herbicide application (Fig. 1C) reflecting the lack of physiologically active, transpiring plants – however, increased soil moisture commonly stimulates casting activity132930. Another explanation for the reduced surface casting activity after herbicide treatment might also be that L. terrestris avoided plant residues contaminated with glyphosate on the surface. As a consequence these earthworms might have lived in deeper soil horizons and avoided surface foraging and casting. This might also suggest the – albeit not significant – higher water infiltration in mesocosms with this species when exposed to the herbicides (see below). Overall, at the end of the experiment we retrieved 93.3 ± 6.6% and 86.7 ± 9.9% of introduced numbers of L. terrestris and 100.0 ± 0.1% and 100.0 ± 2.6% of introduced numbers of A. caliginosa in –H and +H treatments, respectively.


Glyphosate-based herbicides reduce the activity and reproduction of earthworms and lead to increased soil nutrient concentrations.

Gaupp-Berghausen M, Hofer M, Rewald B, Zaller JG - Sci Rep (2015)

Activity of horizontally burrowing earthworms before and after the herbicide application (−H, without herbicide; +H, with herbicide).(A) Daily surface cast production, (B) cumulative cast production over the course of the experiment (N = 6, mean ± SE). Red band marks the period when herbicide was applied. P-values from two-sample Wilcoxon tests performed for the pre- and post-herbicide periods.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542661&req=5

f2: Activity of horizontally burrowing earthworms before and after the herbicide application (−H, without herbicide; +H, with herbicide).(A) Daily surface cast production, (B) cumulative cast production over the course of the experiment (N = 6, mean ± SE). Red band marks the period when herbicide was applied. P-values from two-sample Wilcoxon tests performed for the pre- and post-herbicide periods.
Mentions: Herbicide application initially stimulated surface casting activity of L. terrestris, however the number of produced casts ceased dramatically about one week after herbicide application; in contrast the surface casting activity of this species remained nearly constant when no herbicide was applied (Fig. 1A). Not only did exposure to herbicide reduce the number of surface casts produced, it also reduced the mean mass of individual casts (546 ± 202 mg cast−1 vs. 1,408 ± 140 mg cast−1). Compared to non-herbicide treated mesocosms, cumulative cast mass produced by L. terrestris four weeks after herbicide application was reduced by 46% compared to untreated mesocosms (560 g m−2 vs. 1,032 g m−2; P < 0.001; Fig. 1B). Surface casting activity and cast mass production of the soil-dwelling earthworm species, A. caliginosa, was not affected by herbicide application (Fig. 2A,B). Monitoring surface casting activity has recently been proposed as an ecotoxicity test better related to earthworms’ ecological role than standard laboratory tests26. Although the studied earthworm species differ in their feeding behavior, both have been shown to cast on the soil surface when foraging for leaf litter and other organic material2728. The peak in surface casting activity observed after herbicide application was therefore likely the consequence of an increased availability of dead leaf material. Since we provided extra food for earthworms in all treatments (i.e., dried chopped hay spread over the soil surface) which is supposed to increase surface casting activity, the further decrease in casting activity in herbicide-treated mesocosms clearly demonstrates a direct impact of the herbicide. These detrimental effects of the herbicide on earthworm activity are also surprising as soil moisture increased between 3% to 39% after herbicide application (Fig. 1C) reflecting the lack of physiologically active, transpiring plants – however, increased soil moisture commonly stimulates casting activity132930. Another explanation for the reduced surface casting activity after herbicide treatment might also be that L. terrestris avoided plant residues contaminated with glyphosate on the surface. As a consequence these earthworms might have lived in deeper soil horizons and avoided surface foraging and casting. This might also suggest the – albeit not significant – higher water infiltration in mesocosms with this species when exposed to the herbicides (see below). Overall, at the end of the experiment we retrieved 93.3 ± 6.6% and 86.7 ± 9.9% of introduced numbers of L. terrestris and 100.0 ± 0.1% and 100.0 ± 2.6% of introduced numbers of A. caliginosa in –H and +H treatments, respectively.

Bottom Line: However, our knowledge of potential side-effects on non-target soil organisms, even on such eminent ones as earthworms, is still very scarce.Reproduction of the soil dwellers was reduced by 56% within three months after herbicide application.These sizeable herbicide-induced impacts on agroecosystems are particularly worrisome because these herbicides have been globally used for decades.

View Article: PubMed Central - PubMed

Affiliation: Institute of Zoology, University of Natural Resources and Life Sciences Vienna, Gregor Mendel Straße 33, A-1180 Vienna, Austria.

ABSTRACT
Herbicide use is increasing worldwide both in agriculture and private gardens. However, our knowledge of potential side-effects on non-target soil organisms, even on such eminent ones as earthworms, is still very scarce. In a greenhouse experiment, we assessed the impact of the most widely used glyphosate-based herbicide Roundup on two earthworm species with different feeding strategies. We demonstrate, that the surface casting activity of vertically burrowing earthworms (Lumbricus terrestris) almost ceased three weeks after herbicide application, while the activity of soil dwelling earthworms (Aporrectodea caliginosa) was not affected. Reproduction of the soil dwellers was reduced by 56% within three months after herbicide application. Herbicide application led to increased soil concentrations of nitrate by 1592% and phosphate by 127%, pointing to potential risks for nutrient leaching into streams, lakes, or groundwater aquifers. These sizeable herbicide-induced impacts on agroecosystems are particularly worrisome because these herbicides have been globally used for decades.

No MeSH data available.