Bioaccumulation of glyphosate and its formulation Roundup Ultra in Lumbriculus variegatus and its effects on biotransformation and antioxidant enzymes

https://doi.org/10.1016/j.envpol.2008.07.027Get rights and content

Abstract

The bioaccumulation potential of glyphosate and the formulation Roundup Ultra, as well as possible effects on biotransformation and antioxidant enzymes in Lumbriculus variegatus were compared by four days exposure to concentrations between 0.05 and 5 mg L−1 pure glyphosate and its formulation. Bioaccumulation was determined using 14C labeled glyphosate. The bioaccumulation factor (BCF) varied between 1.4 and 5.9 for the different concentrations, and was higher than estimated from log Pow. Glyphosate and its surfactant POEA caused elevation of biotransformation enzyme soluble glutathione S-transferase at non-toxic concentrations. Membrane bound glutathione S-transferase activity was significantly elevated in Roundup Ultra exposed worms, compared to treatment with equal glyphosate concentrations, but did not significantly differ from the control. Antioxidant enzyme superoxide dismutase was significantly increased by glyphosate but in particular by Roundup Ultra exposure indicating oxidative stress. The results show that the formulation Roundup Ultra is of more ecotoxicological relevance than the glyphosate itself.

Introduction

The non-selective, post-emergence herbicide glyphosate (N-(phosphonomethyl)glycine) is one of the most widely used pesticides. It is utilized for weed control, i.e. in agriculture, forestry, urban areas and even aquaculture. It is usually formulated as the isopropylamine salt and in case of the most common formulation Roundup Ultra combined with the surfactant polyoxyethylene amine (POEA) (Giesy et al., 2000). Due to cultivation of genetically modified glyphosate-resistant crops, the use of glyphosate clearly increased during the last years, raising again concerns regarding the potential environmental impact of this herbicide (Kolpin et al., 2006).

Due to its high adsorption tendency in soil (Kd values up to 900 L kg−1) and its fast degradation by microorganisms, glyphosate is generally regarded as having low potential to contaminate surface waters or groundwater (Borggaard and Gimsing, 2007, de Jonge et al., 2001, Vereecken, 2005). However, leaching of glyphosate and its degradation product AMPA (amino-methylphosphonic acid) up to 1 m depth has been observed in laboratory and field studies, suggesting a potential risk for the aquatic environment (Kjaer et al., 2005, Landry et al., 2005, Stadlbauer, 2005). Moreover, glyphosate and AMPA are present in surface waters worldwide in considerable concentrations, e.g. up to 2.2 μg L−1 in US rivers (Feng et al., 1990, Kolpin et al., 2006). The limit value for single pesticides in groundwater in Europe is 0.1 μg L−1 and for the sum of pesticides 0.5 μg L−1 (CEC, 1991). Because of the high water solubility of glyphosate (10 g L−1) and its increasing occurrence in the aquatic environment, the herbicide and its formulations have a growing relevance for aquatic ecotoxicology. The toxicity of technical-grade glyphosate to aquatic invertebrates is known to be only minor (LC50 values of >55 mg L−1 glyphosate, WHO, 1994). However, an increased toxicity of glyphosate formulations like Roundup Ultra has been reported and related to its surfactants, e.g. POEA (Bringolf et al., 2007, Giesy et al., 2000, Tsui and Chu, 2003, Tsui and Chu, 2004). Lower toxicity thresholds (LC/IC50 < 2 mg a.i. L−1) were determined for the amphipod Hyalella azteca, the copepod Acartia tonsa and the algae Sceletonema costatum, respectively (Tsui and Chu, 2003, Tsui and Chu, 2004).

The blackworm Lumbriculus variegatus (Muller), a typical sediment dwelling invertebrate, was selected to study the impact of glyphosate and Roundup Ultra. The oligochaete L. variegatus, native to European and North American river and lake sediments, feeds on decomposing plant material and microorganisms. It shows moderate sensitivity to xenobiotics (Drewes, 1997). Scientific studies conducted with L. variegatus focused on the bioaccumulation and depuration of organic substances and metals in the worm, as well as on the biological impact of the xenobiotics, using acute toxicity, the locomotor and burial behavior or the feeding rate as toxicological endpoints (Landrum et al., 2004, Leppanen and Kukkonen, 2004, Maenpaa and Kukkonen, 2006). Only few studies have been conducted to gain more insight in the enzymatic and physiological response of the organism when exposed to anthropogenic pollutants. Activity of the cytochrome P-450 enzymes seems to be limited (Ankley and Collyard, 1995). Enzymes as delta-aminolevulinic acid dehydratase (ALA-D) or inhibition of cholinesterase (ChE) activity, as biomarker of lead or organophosphorous pesticides exposure, respectively, have been recognised to be useful (Aisemberg et al., 2005, Kristoff et al., 2006). Also glutathione S-transferase (GST) and catalase (CAT) reacted to an exposure of the organism to the herbicide paraquat or to dissolved organic matter (Wiegand et al., 2007), as well as to atrazine and contaminated sediments (Contardo-Jara and Wiegand, 2008). Physiological endpoints proved to be reliable indicators for exposure and for negative sub-lethal impact of pollutants on the organism, especially activity changes of the biotransformation system enzymes, modifying chemical substances, or the enzymes involved in the defence against oxidative stress, preventing cell damage of proteins, lipids, and DNA. To our knowledge, this is among the first studies assessing superoxide dismutase (SOD) activity in L. variegatus as biomarker for oxidative stress.

The aim of this study was to investigate if a sediment living organism, such as L. variegatus is negatively influenced by an exposition to pure glyphosate and the formulation Roundup Ultra in surface waters. Therefore we studied (1) the bioaccumulation in the worm tissue and (2) the activity changes of the biotransformation enzymes soluble GST (sGST) and membrane bound GST (mGST), as well as of the antioxidant enzymes SOD and CAT in response to increasing concentrations of glyphosate and Roundup Ultra in water.

Section snippets

Rearing of the organisms

The culture of L. variegatus, originating from NOAA/Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan, USA, reproduces exclusively asexual through fragmentation (Lesiuk and Drewes, 1999) ensuring a genetically homogenous worm population. The worms were reared according to Leppanen and Kukkonen (1998) in 5 L glass tanks containing artificial tank water reconstituted from Milli-Q-grade water (100 mg L−1 Instant Ocean sea salt, 200 mg L−1 CaCl2, 103 mg L−1 NaHCO3) at 20 ± 1 °C and a

Bioaccumulation study

An average dry weight (dw) of 12.6 ± 0.5% and a lipid content of 1.6 ± 0.3% of fresh weight were determined for L. variegatus.

The glyphosate concentration in the test medium was constant over the 4-day test period. The degradation product AMPA (amino-methylphosphonic acid) was not detectable.

With increasing glyphosate concentrations, the total amount of glyphosate accumulated in L. variegatus per gram fresh body mass increased, in both, the pure glyphosate and the Roundup Ultra treatments (Fig. 2).

Discussion

In this work we studied the bioaccumulation potential and physiological effect of pure glyphosate and the formulation Roundup Ultra in an oligochaete. L. variegatus was shown to be suitable for determination of both parameters, the bioaccumulation in animal tissue and changed enzyme activity of the biotransformation system, e.g. GST and of the antioxidant defense, e.g. SOD and CAT.

Conclusion

This study shows that glyphosate accumulates in L. variegatus, despite the hydrophilic character of the herbicide. The accumulated amounts of glyphosate and the added surfactants in Roundup Ultra cause an elevation of the biotransformation enzyme sGST at non-toxic concentrations. The accumulation and the enzymatic response of the worms were clearly higher in the animals exposed to Roundup Ultra, indicating that the formulation Roundup Ultra is of more ecotoxicological relevance than the

Acknowledgements

We would like to thank the German Research Foundation (Deutsche Forschungsgemeinschaft – DFG) for providing a PhD grant for V. Contardo-Jara and E. Klingelmann within the graduate school 780/II “Perspectives on Urban Ecology II”. We are indebted to the Federal Research Centre for Cultivated Plants, Institute for Ecological Chemistry (JKI), for providing laboratory facilities enable to the handling of 14C. The authors thank S. Chakrabati and J. Krüger for helpful technical assistance and S.

References (53)

  • D.W. Kolpin et al.

    Urban contributions of glyphosate and its degradate AMPA to streams in the United States

    Science of the Total Environment

    (2006)
  • G. Kristoff et al.

    Inhibition of cholinesterase activity by azinphos-methyl in two freshwater invertebrates: Biomphalaria glabrata and Lumbriculus variegatus

    Toxicology

    (2006)
  • D. Landry et al.

    Leaching of glyphosate and AMPA under two soil management practices in Burgundy vineyards (Vosne-Romane'e, 21-France)

    Environmental Pollution

    (2005)
  • V.C. Langiano et al.

    Toxicity and effects of a glyphosate-based herbicide on the Neotropical fish Prochilodus lineatus

    Comparative Biochemistry and Physiology, Part C

    (2008)
  • K.A. Maenpaa et al.

    Bioaccumulation and toxicity of 4-nonylphenol (4-NP) and 4-(2-dodecyl)-benzene sulfonate (LAS) in Lumbriculus variegatus (Oligochaeta) and Chironomus riparius (Insecta)

    Aquatic Toxicology

    (2006)
  • F. Morin et al.

    Glyphosate uptake in Catharanthus roseus cells: role of a phosphate transporter

    Pesticide Biochemistry and Physiology

    (1997)
  • F. Peixoto

    Comparative effects of the Roundup and glyphosate on mitochondrial oxidative phosphorylation

    Chemosphere

    (2005)
  • P.L. Peruzzo et al.

    Levels of glyphosate in surface waters, sediments and soils associated with direct sowing soybean cultivation in north pampasic region of Argentina

    Environmental Pollution

    (2008)
  • A.B. Soso et al.

    Chronic exposure to sub-lethal concentration of a glyphosate-based herbicide alters hormone profiles and affects reproduction of female Jundia (Rhamdia quelen)

    Environmental Toxicology and Pharmacology

    (2007)
  • M.T.K. Tsui et al.

    Aquatic toxicity of glyphosate-based formulations: comparison between different organisms and the effects of environmental factors

    Chemosphere

    (2003)
  • N. Wang et al.

    Influence of sediment on the fate and toxicity of a polyethoxylated tallowamine surfactant system (MON 0818) in aquatic microcosms

    Chemosphere

    (2005)
  • C. Wiegand et al.

    Bioaccumulation of paraquat by Lumbriculus variegatus in the presence of dissolved natural organic matter and impact on energy costs, biotransformation and antioxidative enzymes

    Chemosphere

    (2007)
  • N. Benachour et al.

    Time- and dose-dependent effects of roundup on human embryonic and placental cells

    Archives of Environmental Contamination and Toxicology

    (2007)
  • O.K. Borggaard et al.

    Fate of glyphosate in soil and the possibility of leaching to ground and surface waters: a review

    Pest Management Science

    (2007)
  • R.B. Bringolf et al.

    Acute and chronic toxicity of glyphosate compounds to glochidia and juveniles of Lampsilis siliquoidea (Unionidae)

    Environmental Toxicology and Chemistry

    (2007)
  • A. Claiborne

    Catalase activity

  • Cited by (130)

    • Pollutant load and ecotoxicological effects of sediment from stormwater retention basins to receiving surface water on Lumbriculus variegatus

      2023, Science of the Total Environment
      Citation Excerpt :

      However, due to the lack of strong correlations between these endpoints and the pollutant loads, this assumption could not be validated. At the sub-organism level, biomarker responses in L. variegatus have been recommended as a sensitive endpoint to pollutants and other stressors in their immediate environment (Contardo-Jara et al., 2009; Contardo-Jara and Wiegand, 2008; Wiegand et al., 2007). The lack of correlation between the biomarkers and the concentrations of xenobiotics in sediment was not in agreement with similar studies involving L. variegatus (Contardo-Jara and Wiegand, 2008; Wang et al., 2014).

    View all citing articles on Scopus
    1

    Both authors contributed equally to the experimental work and the manuscript.

    View full text