Evaluation of Lethality and Genotoxicity in the Freshwater Mussel Utterbackia imbecillis (Bivalvia: Unionidae) Exposed Singly and in Combination to Chemicals Used in Lawn Care

Abstract

Many chemicals, including fertilizers, herbicides, and insecticides, are routinely applied to turf in the care and maintenance of lawns. These chemicals have the potential to leach into nearby surface waters and adversely affect aquatic biota. In this study, we evaluated the lethal and genotoxic effects of chemicals used in lawn care on an early life stage of freshwater mussels (Utterbackia imbecillis). The chemicals tested were copper and commercial formulations of atrazine, glyphosate, carbaryl, and diazinon. Mussel glochidia were exposed to chemicals singly or in combination (equitoxic and environmentally realistic mixtures) for 24 h and toxic interactions were evaluated with Marking's additive index. Genotoxicity was quantified with the alkaline single-cell gel electrophoresis assay (Comet assay). In acute tests, copper was the most toxic of all chemicals evaluated (LC50 = 37.4 microg/L) and carbaryl was the most toxic of all pesticides evaluated (LC50 = 7.9 mg/L). In comparison to other aquatic organisms commonly used in toxicity tests (e.g., amphipods, cladocerans, and chironomids), mussel glochidia were as or more sensitive to the chemicals evaluated with the exception of diazinon, where mussels were observed to be less sensitive. The combined toxicity of equitoxic and environmentally realistic mixtures to mussels was additive. Genotoxic responses were observed in mussels exposed to copper, atrazine and diazinon at levels below their respective no-observed-effect concentrations. Together, these data indicate that freshwater mussels are among the most sensitive aquatic organisms tested for some chemicals commonly used in lawn care and that DNA damage may be useful as a screening tool to evaluate potential sublethal effects of lawn care products on non-target aquatic organisms.

Re-registration Challenges of Glyphosate in the European Union

“…Roundup R was found to disrupt 17β-estradiol and reduce glutathione concentration in the liver of the endangered fish species delta smelt (Hypomesus transpacificus) upon 6 h of exposure at levels corresponding to 78 µg/l glyphosate concentrations and above (Jin et al, 2018). As described earlier, effects of glyphosate and its formulated products on amphibians and mollusks (Conners and Black, 2004;Mann et al, 2009;Relyea and Jones, 2009;Paganelli et al, 2010;Carrasco, 2013;Meza-Joya et al, 2013;Wagner et al, 2013;Henao Muñoz et al, 2015;Baier et al, 2016a,b) received particular attention due to their known hormonal sensitivity. Differential toxicity of glyphosate and its formulated PPPs have been also considered in the official scientific opinion by EFSA on pesticide risk assessment for amphibians and reptiles (Ockleford et al, 2018).…”

“…Formulated glyphosate-based herbicides, Touchdown R and Roundup R caused neurotoxicity (McVey et al, 2016) as well as locomotion and fertility inhibition (García-Espiñeira et al, 2018) on the nematode Caenorhabditis elegans. Following the results of the late Andrés Carrasco and his research group (Paganelli et al, 2010;Carrasco, 2013), recent findings in environmental toxicology of glyphosate and its formulated products include its revealed toxicity on amphibian species (Mann et al, 2009;Relyea and Jones, 2009;Meza-Joya et al, 2013;Wagner et al, 2013;Henao Muñoz et al, 2015;Baier et al, 2016a,b), on mollusks (Conners and Black, 2004) and on earthworms (Zaller et al, 2014;Gaupp-Berghausen et al, 2015). It affected hemocyte parameters and acetylcholinesterase (AChE) activity, but not antioxidant enzyme activities in mussel Mytilus galloprovincialis (Matozzo et al, 2018) with disruption of key biological processes including energy metabolism, Ca 2+ homeostasis and endoplasmic reticulum stress response, as well as cell signaling identified by transcriptome analysis (Milan et al, 2018).…”

Sensitivity of freshwater molluscs to hydrilla-targeting herbicides: providing context for invasive aquatic weed control in diverse ecosystems

“…Similarly, of the 703 freshwater gastropod species in USA and Canada, 278 (40%) are federally listed as endangered and >74% are considered imperilled (Johnson et al 2013). Moreover, non-pulmonate snails and the early life stages of freshwater mussels are among the most sensitive aquatic organisms to several contaminants (e.g., atrazine, carbaryl (Conners & Black 2004); copper, ammonia (Besser et al 2009)), and glyphosate-based chemicals which are among the most widely used herbicides (Bringolf et al 2007). Potential risks of specific aquatic herbicides to freshwater molluscs should be assessed and balanced appropriately against the significant biological threat posed by invasive aquatic weeds like hydrilla.…”

Repeated and multiple stress (exposure to pesticides) on aquatic organisms

“…Zidan et al (2002) cites a paper by El-Fiki and Mohamed, (1978) that identifies the important role that copper ions play in the molluscicidal action of copper sulphate. Conners and Black (2004) looked at the combined effects of chemicals used in lawn care on the survival of glochidia (larval stage) of Freshwater Mussel Utterbackia imbecillis after 24 hours exposure. Pesticides used were copper sulphate, the herbicides atrazine and glyphosate and the insecticides carbaryl and diazinon.…”