Long-term persistence of seeded grass species: an unwanted side effect of ecological restoration

Spoil heaps are the visible footprint of hydropower production, particularly in vulnerable alpine environments. Speeding up vegetation development by seeding commercial grass species has been a common restoration practice for the last 50 years, but we lack information on whether seeded species decline and allow native plant cover to develop. We visually estimated cover of native vascular plants and five seeded grass species (Agrostis capillaris, Festuca ovina, Festuca rubra, Schedonorus pratensis and Phleum pratense) on eight spoil heaps at different elevations (boreal–alpine zone) in western Norway. Spoil heap vegetation was censused twice (9–20 and 24–36 years after spoil heap construction); the undisturbed surrounding vegetation was also censused on the second occasion. Total cover on the spoil heaps showed some increase, but remained far below that in surrounding areas. Cover of seeded grass species in the surroundings was low (but not negligible), indicating suboptimal establishment ability. Seeded species usually covered less than 20 % of the spoil heaps, and only F. rubra, F. ovina and A. capillaris contributed substantially. Proportional cover indicated better initial establishment by seeded species, but their cover decreased between the censuses on all but the highest located spoil heap. The persistence of seeded grass species is problematic, and despite the decrease in proportional cover, they are likely to persist for decades on spoil heaps, posing a risk of invasion of surrounding areas. We therefore recommend replacing the practice of seeding with more appropriate restoration measures.     

Sorption and desorption of glyphosate,MCPA and tetracycline and their mixtures in soil as influenced by phosphate

Phosphate fertilizers and herbicides such as glyphosate and MCPA are commonly applied to agricultural land, and antibiotics such as tetracycline have been detected in soils following the application of livestock manures and biosolids to agricultural land. Utilizing a range of batch equilibrium experiments, this research examined the competitive sorption interactions of these chemicals in soil. Soil samples (0-15 cm) collected from long-term experimental plots contained Olsen P concentrations in the typical (13 to 20 mg kg^?1) and elevated (81 to 99 mg kg^?1) range of build-up phosphate in agricultural soils. The elevated Olsen P concentrations in field soils significantly reduced glyphosate sorption up to 50%, but had no significant impact on MCPA and tetracycline sorption. Fresh phosphate additions in the laboratory, introduced to soil prior to, or at the same time with the other chemical applications, had a greater impact on reducing glyphosate sorption (up to 45%) than on reducing tetracycline (up to 13%) and MCPA (up to 8%) sorption. The impact of fresh phosphate additions on the desorption of these three chemicals was also statistically significant, but numerically very small namely < 1% for glyphosate and tetracycline and 3% for MCPA. The presence of MCPA significantly reduced sorption and increased desorption of glyphosate, but only when MCPA was present at concentrations much greater than environmentally relevant and there was no phosphate added to the MCPA solution. Tetracycline addition had no significant effect on glyphosate sorption and desorption in soil. For the four chemicals studied, we conclude that when mixtures of phosphate, herbicides and antibiotics are present in soil, the greatest influence of their competitive interactions is phosphate decreasing glyphosate sorption and the presence of phosphate in solution lessens the potential impact of MCPA on glyphosate sorption. The presence of chemical mixtures in soil solution has an overall greater impact on the sorption than desorption of individual organic chemicals in soil.     

Effects of sub-lethal glyphosate concentrations on growth and photosynthetic performance of non-target species Bolboschoenus maritimus

Glyphosate use has increased over the last decades for the control of invasive plant species in wetland ecosystems. Although glyphosate has been considered ‘environmentally’ safe, its repeated use could increase the toxicological risk derived from diffuse pollution of surface and groundwater on non-target vegetation. A glasshouse study was designed to determine the effect produced by the addition of different sub-lethal doses of glyphosate herbicides (5–30 mg L⁻¹) to the nutrient solution on the growth and photosynthetic apparatus of Bolboschoenus maritimus. Although B. maritimus plants were able to grow and survive after 20 d of exposure to glyphosate, the presence of this herbicide affected their growth, through a direct interaction with the root system. Particularly, at 30 mg L⁻¹ glyphosate, B. maritimus showed ca. 30% of biomass decrease. The reduction in B. maritimus growth was due to a decrease in net photosynthetic rate (A), which ranged between values ca. 11.5 and 5.5 μmol m⁻² s⁻¹ CO₂ for the control and the highest glyphosate treatment, respectively. The response of A to glyphosate could be largely accounted for by non-stomatal limitations, since stomatal conductance was similar in all glyphosate treatments. Thus, A decrease was prompted by the negative impact of herbicide on photochemical (PSII) apparatus, the reduction in the absorption of essential nutrients, the reduction of photosynthetic pigments and possibly the reduction in Rubisco carboxilation capacity. Moreover, glyphosate excess caused photoinhibitory damage. In conclusion, in this study we have shown that herbicide water pollution could be a source of indirect phytotoxicity for B. maritimus.     

Hormetic effect of glyphosate on Urochloa decumbens plants

Abstract

Urochloa decumbens plants may be reached by herbicide drift from applications of glyphosate from neighboring areas or by variations during applications. Considering the different phenological stages and size of plants in these areas, the amount of active ingredient that reaches the plants probably varies. The objective of this study was to evaluate the effects of the application of different doses of glyphosate on U. decumbens plants. Two greenhouse experiments were conducted with two replications at different times. The first experiment evaluated the biological response of U. decumbens plants to glyphosate doses (0, 2.81, 5.63, 11.25, 22.5, 45, 90, 180, 360, 720, and 1,440?g a.e. ha^?1), with six replications. The second experiment evaluated the response of U. decumbens plants to the application of a selected low dose of 11.25?g a.e. ha^?1. Evaluations of injury were performed at 0, 7, 14, and 21?days after application, and dry weight of plants was determined for each evaluation period. U. decumbens plants increased in dry weight when using the glyphosate dose of 11.25?g a.e. ha^?1. However, plants had different responses to the application of this low dose. It can promote both stimulation and inhibition of plant growth.     

Effects of glyphosate on the non-target leaf beetle Cerotoma arcuata (Coleoptera: Chrysomelidae) in field and laboratory conditions

This study aimed to assess the glyphosate application effects on the Cerotoma arcuata Oliver (Coleoptera: Chrysomelidae) population in glyphosate-resistant soybean crops. Field studies were conducted with glyphosate and the insecticide endosulfan to observe the effects of these pesticides on C. arcuata, on its damages in the crop and on the populations of natural enemies in glyphosate-resistant soybean crops. Moreover, the lethal and behavioral sublethal response of C. arcuata to glyphosate and endosulfan was conducted in the laboratory. The results of the field and laboratory experiments showed that glyphosate caused moderate toxicity and high irritability in C. arcuata and that endosulfan caused high toxicity and irritability. Therefore, the direct effect of glyphosate on C. arcuata was negative and does not explain the population increases of this pest in glyphosate-resistant soybean. However, the glyphosate also decreased the density of predators. Thus, the negative effect of glyphosate on the predators may be related to population increases of C. arcuata in glyphosate-resistant soybean crops, however, more studies are needed to better evidence this relationship. This study suggests that glyphosate can impact other non-target organisms, such as herbivorous insects and natural enemies and that the use of this herbicide will need to be carefully stewarded to prevent potential disturbances in beneficial insect communities in agricultural systems.     

Coupled pot and lysimeter experiments assessing plant performance in microbially assisted phytoremediation

We performed an experiment at pot scale to assess the effect of plant growth-promoting bacteria (PGPB) on the development of five plant species grown on a tailing dam substrate. None of the species even germinated on inoculated unamended tailing material, prompting use of compost amendment. The effect of inoculation on the amended material was to increase soil respiration, and promote elements immobilisation at plant root surface. This was associated with a decrease in the concentrations of elements in the leaching water and an increase of plant biomass, statistically significant in the case of two species: Agrostis capillaris and Festuca rubra. The experiment was repeated at lysimeter scale with the species showing the best development at pot scale, A. capillaris, and the significant total biomass increase as a result of inoculation was confirmed. The patterns of element distribution in plants also changed (the concentrations of metals in the roots of A. capillaris and F. rubra significantly decreased in inoculated treatments, while phosphorus concentration significantly increased in roots of A. capillaris in inoculated treatment at lysimeter scale). Measured variables for plant oxidative stress did not change after inoculations. There were differences of A. capillaris plant–soil system response between experimental scales as a result of different substrate column structure and plant age at the sampling moment. Soil respiration was significantly larger at lysimeter scale than at pot scale. Leachate concentrations of As, Mn and Ni had significantly larger concentrations at lysimeter scale than at pot scale, while Zn concentrations were significantly smaller. Concentrations of several metals were significantly smaller in A. capillaris at lysimeter scale than at pot scale. From an applied perspective, a system A. capillaris—compost—PGPB selected from the rhizosphere of the tailing dam native plants can be an option for the phytostabilisation of tailing dams. Results should be confirmed by investigation at field plot scale.     

Pesticides impact on Clavibacter michiganensis ssp. sepedonicus biofilm formation

The effect of various pesticides on the biofilm formation by the phytopathogenic bacterium Clavibacter michiganensis ssp. sepedonicus (Cms), the potato ring rot causative agent, was explored for the first time. Systemic herbicides: 2,4-D, diuron, glyphosate, clopyralid, fluorodifen, as well as the commercial preparations “Lazurite,” “Ridomil Gold,” and the mitochondria inhibiting pesticides analog, sodium monoiodoacetate, were studied. These pesticides' effect on the Cms biofilm formation was shown to be distinct and dependent on the agent under question. Cms biofilm formation was reduced when exposed to sodium monoiodoacetate, as well as “Lazurite” preparation, that could be due to the bactericidal effect of these agents. 2,4-D and “Ridomil Gold” preparation stimulated the biofilm formation. Systemic herbicides diuron, glyphosate, clopyralid, fluorodifen did not exert appreciable influence on the process of bacterial biofilm formation.     

Effects of glyphosate and foliar amendments on activity of microorganisms in the soybean rhizosphere

A field study was conducted to determine the effects of glyphosate on microbial activity in the rhizosphere of glyphosate-resistant (GR) soybean and to evaluate interactions with foliar amendments. Glyphosate at 0.84 kg ae ha^{? 1} was applied GR soybean at the V4–V5 development stages. Check treatments included a conventional herbicide tank mix (2003 study only) and no herbicides (hand-weeded). Ten days after herbicide application, a commercially available biostimulant and a urea solution (21.0% N) were applied to soybean foliage at 33.5 mL ha^{? 1} and 9.2 kg ha^{? 1}, respectively. Soil and plant samples were taken 0, 5, 10, 15, 20 and 25 days after herbicide application then assayed for enzyme and respiration activities. Soil respiration and enzyme activity increased with glyphosate and foliar amendment applications during the 2002 growing season; however, similar increases were not observed in 2003. Contrasting cumulative rainfall between 2002 and 2003 likely accounted for differences in soil microbial activities. Increases in soil microbial activity in 2002 suggest that adequate soil water and glyphosate application acted together to increase microbial activity. Our study suggests that general soil microbial properties including those involving C and N transformations are not sensitive enough to detect effects of glyphosate on rhizosphere microbial activity. Measurements of soil-plant-microbe relationships including specific microbial groups (i.e., root-associated Fusarium spp.) are likely better indicators of impacts of glyphosate on soil microbial ecology.     

Evaluation of stem injection for managing giant reed (Arundo donax)

Giant reed is an emergent aquatic plant that may be weedy in riparian habitats. Two herbicides approved for controlling giant reed in the US are glyphosate (N-(phosphonomethyl) glycine) and imazapyr (2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid). Foliar applications of these herbicides may be restricted in some areas, such as those, which are within the range of threatened or endangered species. We conducted two field experiments at sites in northern and central California. The first experiment evaluated the effects of three aquatic herbicides (glyphosate, imazapyr, and triclopyr [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid) injected into all of the stems within a giant reed (5 mL stem^?1). In this experiment, leaf chlorophyll content, the proportion of living stems, and the number of new stems produced during the year after treatment declined (>80%) following injection of either full strength glyphosate or imazapyr. The effects of injecting full strength triclopyr were considerably less. In a second experiment, different proportions (0, 10%, 25%, or 100%) of the stems within a plant were injected with full strength glyphosate. Results indicated that it was necessary to inject all of the stems within a clump to achieve the greatest reduction in the plant growth characteristics measured. These results imply that giant reed may be successfully controlled by injecting full strength glyphosate (5 mL stem^?1) into all of the stems within a clump. While labor intensive and thus potentially more costly this method, offers a new method for managing giant reed in sensitive sites where foliar spray applications may be restricted.     

Is the growth stimulation by low doses of glyphosate sustained over time?

The herbicide, glyphosate, has been shown to stimulate growth in a range of species when applied at doses of 5-60 g a.e. ha⁻¹, corresponding to realistic spray drift events. This study investigates growth of shoot parameters over time to detect whether the glyphosate induced growth increase was sustained and had a final effect on reproduction. The results showed that an actual biomass growth rate increase took place within the first week after spraying with glyphosate doses <60 g a.e. ha⁻¹. This initial growth boost kept treated plants larger than untreated plants for up to six weeks, but at harvest there was no significant difference between control plants and treated plants. Possible effects of glyphosate hormesis on the competitive ability of spray drift affected plants are discussed.     

Combined effect of diuron and simazine on photosystem II photochemistry in a sandy soil and soil amended with solid olive-mill waste

Diuron (3-(3,4-dichlorophenyl)- = 1,1-dimethylurea) and simazine (6-chloro-N ², N ⁴-diethyl-1,3,5-triazine-2,4-diamine) are soil-applied herbicides used in olive crops. The objective of this study is to investigate the effect of these herbicides on Photosystem II photochemistry of Olea europaea L., and whether the amendment of soil with an organic waste (OW) from olive oil production industry modifies this effect. For this purpose, herbicide soil adsorption studies, with unamended and OW-amended soil, and chlorophyll fluorescence measurements in adult olive leaves, after one, two and three weeks of soil herbicide treatment and/or OW amendment, were performed. Soil application of these herbicides reduced the efficiency of Photosystem II photochemistry of olive trees due to chronic photoinhibition, and this effect is counterbalanced by the addition of OW to the soil. OW reduces herbicide uptake by the plant due to an increase in herbicide adsorption.     

Microbially assisted phytoremediation approaches for two multi-element contaminated sites

Phytoremediation is an environmental friendly, cost-effective technology for a soft restoration of abandoned mine sites. The grasses Agrostis capillaris, Deschampsia flexuosa and Festuca rubra, and the annual herb Helianthus annuus were combined with microbial consortia in pot experiments on multi-metal polluted substrates collected at a former uranium mine near Ronneburg, Germany, and a historic copper mine in Kopparberg, Sweden, to test for phytoextraction versus phytostabilization abilities. Metal uptake into plant biomass was evaluated to identify optimal plant–microbe combinations for each substrate. Metal bioavailability was found to be plant species and element specific, and influenced by the applied bacterial consortia of 10 strains, each isolated from the same soil to which it was applied. H. annuus showed high extraction capacity for several metals on the German soil independent of inoculation. Our study could also show a significant enhancement of extraction for F. rubra and A. capillaris when combined with the bacterial consortium, although usually grasses are considered metal excluder species. On the Swedish mixed substrate, due to its toxicity, with 30 % bark compost, A. capillaris inoculated with the respective consortium was able to extract multi-metal contaminants.     

Evaluation of the cytotoxic effects of glyphosate herbicides in human liver,lung, and nerve

Glyphosate-based herbicides are broad-spectrum pesticides widely used in the world, which is considered a highly safe pesticide due to their target specificity, but recently, there has been an ongoing controversy regarding their carcinogenicity and possible side effects of glyphosate on human health. Commercial glyphosate-based herbicides (GBHs) consist of declared active ingredient (glyphosate salts) and a number of formulants such as ethoxylated formulants (4130®, 3780^®, and A-178^®). The aim of our study is to investigate whether the toxicity of GBHs is related to formulants. The effects of GBHs on human health were studied at the cellular level based on their toxicity to liver, lungs and nerve tissue. The inhibitory toxicity to cell viability by GBHs was examined with cell-based systems using three human cell lines: HepG2, A549, and SH-SY5Y. Data obtained showed that all tested ethoxylated formulants and their mixtures with declared active ingredient glyphosate isopropylamine salt (GP) have significant inhibitory effect on cell proliferation, while the declared active ingredient has no significant toxicity. Our study demonstrates that the toxic effect of GBH is primarily due to the use of formulants. This result suggests that GP is relatively safe and a new approach for the assessment of toxicity should be made.     

Isolation of culturable mycobiota from agricultural soils and determination of tolerance to glyphosate of nontoxigenic Aspergillus section Flavi strains

Glyphosate-based herbicides are extensively used in Argentina's agricultural system to control undesirable weeds. This study was conducted to evaluate the culturable mycobiota [colony forming units (CFU) g^?1 and frequency of fungal genera or species] from an agricultural field exposed to pesticides. In addition, we evaluated the tolerance of A. oryzae and nontoxigenic A. flavus strains to high concentrations (100 to 500 mM – 17,000 to 84,500 ppm) of a glyphosate commercial formulation. The analysis of the mycobiota showed that the frequency of the main fungal genera varied according to the analyzed sampling period. Aspergillus spp. or Aspergillus section Flavi strains were isolated from 20 to 100% of the soil samples. Sterilia spp. were also observed throughout the sampling (50 to 100%). Aspergillus section Flavi tolerance assays showed that all of the tested strains were able to develop at the highest glyphosate concentration tested regardless of the water availability conditions. In general, significant reductions in growth rates were observed with increasing concentrations of the herbicide. However, a complete inhibition of fungal growth was not observed with the concentrations assayed. This study contributes to the knowledge of culturable mycobiota from agricultural soils exposed to pesticides and provides evidence on the effective growth ability of A. oryzae and nontoxigenic A. flavus strains exposed to high glyphosate concentrations in vitro.     

Potentiation of antifungal effect of a mixture of two antifungal fractions obtained from Baccharis glutinosa and Jacquinia macrocarpa plants

The aim of the present work was to evaluate the effect of mixtures of antifungal fractions extracted from Baccharis glutinosa and Jacquinia macrocarpa plants on the development of the filamentous fungi Aspergillus flavus and Fusarium verticillioides. The minimal inhibitory concentration that inhibited 50% of growth (MIC₅₀) of each plant antifungal fraction was determined from the percentage radial growth inhibition of both fungi. Binomial mixtures made with both plant fractions were used at their MIC₅₀ to determine the Fractional Inhibitory Concentration index (FIC index) for each fungus in order to evaluate their synergistic effect. Each synergistic mixture was analyzed in their effect on spore germination, spore size, spore viability, mitotic divisions, hyphal diameter and length, and number of septa per hypha. Some antifungal mixtures, even at low concentrations, showed higher antifungal effect than those of the individual antifungal fraction. The FIC indices of mixtures that showed the highest antifungal activity against A. flavus and F. verticillioides were 0.5272 and 0.4577, respectively, indicating a synergistic effect against both fungi. Only 12% and 8% of the spores of A. flavus and F. verticillioides, respectively, treated with the synergistic mixtures, were able to germinate, although their viability was not affected. An increase in the number of septa per hypha of both fungi was observed. The results indicated that the synergistic mixtures strongly affected the fungal growth even at lower concentrations than those of the individual plant fractions.     

Conditioning sulfidic mine waste for growth of Agrostis capillaris—impact on solution chemistry

Contamination of the environment due to mining and mineral processing is an urgent problem worldwide. It is often desirable to establish a grass cover on old mine waste since it significantly decreases the production of leachates. To obtain sustainable growth, it is often necessary to improve several properties of the waste such as water-holding capacity, nutrient status, and toxicity. This can be done by addition of organic materials such as wood residues, e.g., compost. In this study, we focus on the solution chemistry of the leachates when a substrate containing historic sulfidic mine waste mixed with 30 % (volume) bark compost is overgrown by Agrostis capillaris. The pot experiments also included other growth-promoting additives (alkaline material, mycorrhiza, and metabolizable carbon) to examine whether a more sustainable growth could be obtained. Significant changes in the plant growth and in the leachates composition were observed during 8 weeks of growth. It was concluded that in this time span, the growth of A. capillaris did not affect the composition of the leachates from the pots. Instead, the composition of the leachates was determined by interactions between the bark compost and the mine waste. Best growth of A. capillaris was obtained when alkaline material and mycorrhiza or metabolizable carbon was added to the substrate.     

Effects of glyphosate and foliar amendments on activity of microorganisms in the soybean rhizosphere

A field study was conducted to determine the effects of glyphosate on microbial activity in the rhizosphere of glyphosate-resistant (GR) soybean and to evaluate interactions with foliar amendments. Glyphosate at 0.84 kg ae ha(-1) was applied GR soybean at the V4-V5 development stages. Check treatments included a conventional herbicide tank mix (2003 study only) and no herbicides (hand-weeded). Ten days after herbicide application, a commercially available biostimulant and a urea solution (21.0% N) were applied to soybean foliage at 33.5 mL ha(-1) and 9.2 kg ha(-1), respectively. Soil and plant samples were taken 0, 5, 10, 15, 20 and 25 days after herbicide application then assayed for enzyme and respiration activities. Soil respiration and enzyme activity increased with glyphosate and foliar amendment applications during the 2002 growing season; however, similar increases were not observed in 2003. Contrasting cumulative rainfall between 2002 and 2003 likely accounted for differences in soil microbial activities. Increases in soil microbial activity in 2002 suggest that adequate soil water and glyphosate application acted together to increase microbial activity. Our study suggests that general soil microbial properties including those involving C and N transformations are not sensitive enough to detect effects of glyphosate on rhizosphere microbial activity. Measurements of soil-plant-microbe relationships including specific microbial groups (i.e., root-associated Fusarium spp.) are likely better indicators of impacts of glyphosate on soil microbial ecology.     

Glyphosate input modifies microbial community structure in clear and turbid freshwater systems

Since it was commercially introduced in 1974, glyphosate has been one of the most commonly used herbicides in agriculture worldwide, and there is growing concern about its adverse effects on the environment. Assuming that glyphosate may increase the organic turbidity of water bodies, we evaluated the effect of a single application of 2.4?±?0.1 mg l^?1 of glyphosate (technical grade) on freshwater bacterioplankton and phytoplankton (pico, micro, and nanophytoplankton) and on the physical and chemical properties of the water. We used outdoor experimental mesocosms under clear and oligotrophic (phytoplanktonic chlorophyll a?=?2.04 μg l^?1; turbidity?=?2.0 NTU) and organic turbid and eutrophic (phytoplanktonic chlorophyll a?=?50.3 μg l^?1; turbidity?=?16.0 NTU) scenarios. Samplings were conducted at the beginning of the experiment and at 1, 8, 19, and 33 days after glyphosate addition. For both typologies, the herbicide affected the abiotic water properties (with a marked increase in total phosphorus), but it did not affect the structure of micro and nanophytoplankton. In clear waters, glyphosate treatment induced a trend toward higher bacteria and picoeukaryotes abundances, while there was a 2 to 2.5-fold increase in picocyanobacteria number. In turbid waters, without picoeukaryotes at the beginning of the experiment, glyphosate decreased bacteria abundance but increased the number of picocyanobacteria, suggesting a direct favorable effect. Moreover, our results show that the impact of the herbicide was observed in microorganisms from both oligo and eutrophic conditions, indicating that the impact would be independent of the trophic status of the water body.     

Assessment of the effects of herbicide spray drift on a range of plant species of conservation interest

With increasing use of herbicides there has been growing concern that spray drift from treated land will affect vegetation on adjacent nature reserves and other areas of high conservation interest. A preliminary attempt was made to assess this risk by placing a range of native plant species at different distances downwind from standardised drift events and assessing lethal effects and sublethal damage. Five herbicides were tested: asulam, 'Finesse' (chlorsulfuron + metsulfuron-methyl), glyphosate, MCPA and mecoprop. Applications were made at the appropriate time of years for each herbicide (autumn, spring and summer), and at both low and high wind speeds. The maximum safe distance at which no lethal effects were found was 6 m from the sprayer, but for most herbicides the distance was 2 m or less. Generally, damage symptoms were found at greater distances than lethal effects, but in most cases there was rapid recovery by the end of the growing season. These observations are consistent with drift-deposition models, in which the fallout of herbicide droplets has been measured. It is suggested that buffer zones surrounding nature reserves should be in the order of 5-10 m for ground sprayers to minimise the risk of herbicide impacts on these habitats.     

Dissipation of glyphosate and aminomethylphosphonic acid in water and sediment of two Canadian prairie wetlands

Glyphosate [N-(phosphonomethyl)glycine] is the active ingredient of several herbicide products first registered for use in 1974 under the tradename Roundup. The use of glyphosate-based herbicides has increased dramatically over the last two decades particularly in association with the adoption of glyphosate-tolerant crops. Glyphosate has been detected in a range of surface waters but this is the first study to monitor its fate in prairie wetlands situated in agricultural fields. An ephemeral wetland (E) and a semi-permanent wetland (SP) were each divided into halves using a polyvinyl curtain. One half of each wetland was fortified with glyphosate with the added mass simulating an accidental direct overspray. Glyphosate dissipated rapidly in the water column of the two prairie wetlands studied (DT₅₀ values of 1.3 and 4.8 d) which may effectively reduce the impact of exposure of aquatic biota to the herbicide. Degradation of glyphosate to its major metabolite aminomethylphosphonic acid (AMPA) and sorption of the herbicide to bottom sediment were more important pathways for the dissipation of glyphosate from the water column than movement of the herbicide with infiltrating water. Presently, we are not aware of any Canadian guidelines for glyphosate residues in sediment of aquatic ecosystems. Since a substantial portion of glyphosate entering prairie wetlands will become associated with bottom sediments, particularly in ephemeral wetlands, guidelines would need to be developed to assess the protection of organisms that spend all or part of their lifecycle in sediment.