Evidence for behavioral preference toward environmental concentrations of urban-use herbicides in a model adult fish

Abstract

Fish live in waters of contaminant flux. In three urban, fish-bearing waterways of British Columbia, Canada, we found the active ingredients of WeedEx, KillEx, and Roundup herbicide formulations (2,4-D, dicamba, glyphosate, and mecoprop) at low to high ng/L concentrations (0.26 to 309 ng/L) in routine conditions, i.e., no rain for at least one week. Following rain, these concentrations increased by an average of eightfold, suggesting runoff as a major route of herbicide introduction in these waterways. To determine whether fish might be able to limit point-source exposures through sensory-driven behaviors, we introduced pulses of representative herbicide mixtures to individual adult zebrafish (a model species) in flow-through tanks. Fish did the opposite of limit exposure; they chose to spend more time in pulses of herbicide mixtures representative of those that may occur with rain events. This attraction response was not altered by a previous 4-d exposure to lower concentrations of the mixtures, suggesting fish will not learn from previous exposures. However, previous exposures did alter an attraction response to an amino acid prevalent in food (L-alanine). The present study demonstrates that fish living within urban waterways may elect to place themselves in herbicide-contaminated environments and that these exposures may alter their behavioral responses to cues necessary for survival.

Ecological relevance of biomarkers in monitoring studies of macro-invertebrates and fish in Mediterranean rivers

“…Further, some pollutants can induce alterations in hormone levels that may impair migration, for instance thyroid hormones appear to play a key role in the colonization of river habitats by elves of the European eel (A. anguilla) (Imbert et al, 2008). In contrast, environmental levels of urban-use pesticides appear to attract salmons (Oncorhynchus kisutch) although these impair their response to food stimuli (Tierney et al, 2011). Alterations of feeding behaviour are also used as biomarker in ecotoxicology (see energy metabolism section).…”

Impact of glyphosate and glyphosate‐based herbicides on the freshwater environment

“…Fish behaviour and the effects of glyphosate‐based herbicides have been assessed using a variety of sensitive endpoints, including reproductive displays and preference/avoidance response. Adult zebrafish ( Danio rerio ) were tested as either naïve or pre‐exposed to herbicide mixtures containing pure glyphosate, at concentrations equivalent to those detected in the natural environment (0.26–309 ng l –1 ), to determine if fish would avoid the herbicide and if exposure would alter attraction to L‐alanine, a proxy for the presence of food (Tierney et al ., ). Zebrafish was found to spend more time in the regions of herbicide pulse addition and this response was independent of previous experience.…”

Macondo crude oil from the Deepwater Horizon oil spill disrupts specific developmental processes during zebrafish embryogenesis

“…The small adult fish size, large embryo clutches, ex utero development, and transparent embryo and larval stages of zebrafish enable cost effective maintenance of many fish, reproducible sample sizes, simple application of toxin treatments, and easy evaluation of end-point toxicity [14-18]. The use of zebrafish to assay drug and pollutant toxicity has already provided insights into the developmental and molecular mechanistic roles of metals [19,20], dioxins [21-24], pesticides [25,26], endocrine disruptors [27,28], alcohols [29-31], chemotherapies [32-34] and specific pharmaceutical compounds many of which were assessed via high-throughput screening [35]. …”