Systematic Underestimation of Pesticide Burden for Invertebrates under Field Conditions: Comparing the Influence of Dietary Uptake and Aquatic Exposure Dynamics

Abstract

Pesticides used in agriculture can end up in nearby streams and can have a negative impact on nontarget organisms such as aquatic invertebrates. During registration, bioaccumulation potential is often investigated using laboratory tests only. Recent studies showed that the magnitude of bioaccumulation in the field substantially differs from laboratory conditions. To investigate this discrepancy, we conducted a field bioaccumulation study in a stream known to receive pollutant loadings from agriculture. Our work incorporates measurements of stream pesticide concentrations at high temporal resolution (every 20 min), as well as sediment, leaves, and caged gammarid analyses (every 2−24 h) over several weeks. Of 49 investigated pesticides, 14 were detected in gammarids with highly variable concentrations of up to 140 ± 28 ng/g ww . Toxicokinetic modeling using laboratory-derived uptake and depuration rate constants for azoxystrobin, cyprodinil, and fluopyram showed that despite the highly resolved water concentrations measured, the pesticide burden on gammarids remains underestimated by a factor of 1.9 ± 0.1 to 31 ± 3.0, with the highest underestimations occurring after rain events. Including dietary uptake from polluted detritus leaves and sediment in the model explained this underestimation only to a minor proportion. However, suspended solids analyzed during rain events had high pesticide concentrations, and uptake from them could partially explain the underestimation after rain events. Additional comparison between the measured and modeled data showed that the pesticide depuration in gammarids is slower in the field. This observation suggests that several unknown mechanisms may play a role, including lowered enzyme expression and mixture effects. Thus, it is important to conduct such retrospective risk assessments based on field investigations and adapt the registration accordingly.

Speed it up: How temperature drives toxicokinetics of organic contaminants in freshwater amphipods

“…For each of the two species, one bioconcentration experiment was performed at each of four different temperatures (6, 11, 16 and 21°C). The temperatures represent the range gammarids experience at their collection site (Baumgartner & Robinson, 2015) or in other streams during monitoring studies (Lauper et al, 2021).…”

“…wastewater treatment plant outflow) were modelled in order to compare the impact of temperature on the internal concentrations of amphipods. For this purpose, the python-based script established and described by Lauper et al (2021) was fed with the Arrhenius' parameters (parent model) determined in the present study. The differential equation (Equation 1) was solved numerically using Heun's method (Ascher & Petzold, 1998).…”

“…temperature, oxygen, salinity) than H. azteca (Cottin et al, 2012;Javidmehr et al, 2015;Maltby, 1995). Amphipods are well established for laboratory studies (McCahon & Pascoe, 1988;US EPA, 2000) but are recently also used for retrospective monitoring approaches (Berlioz-Barbier et al, 2014;Lauper et al, 2021;Miller et al, 2015;Munz et al, 2018).…”

“…The short-term exposure peak scenario used a realistic surface water concentration profile (fluopyram and cyprodinil) based on monitoring data inLauper et al (2021) with high temporal resolution. The tissue concentrations of G. pulex and H. azteca were modelled at the four tested temperatures for the same exposure event.In the DTF scenario, a constant exposure concentration of 50 μg L −1 (carbamazepine in H. azteca) was chosen and modelled withboth a constant temperature (16°C) as well as a daily fluctuating temperature profile (adapted from Verheyen & Stoks, 2019), which had the same average temperature, but ranged over 10°C from 11 to 21°C.…”

Aquatic‐Terrestrial Insecticide Fluxes: Midges as Neonicotinoid Vectors

“…These authors reported much lower 24‐h BCFs (between 20 and 70 for exposure at 0.1 µg/L) than the ones determined in the present study, but the authors reported an increasing BCF with increasing exposure time and a maximum value was not established. Underestimation of the bioconcentration potential of neonicotinoids in amphipods is also well established in the literature and may be attributed to binding of the insecticide to biomolecules and the exoskeleton of the organisms (Chen & Kuo, 2018; Lauper et al, 2022; H. Li et al, 2021). In the present study, the lower BCFs of indoxacarb and thiacloprid at the higher treatment level can result from the saturation of uptake mechanisms or changes in the physiological condition of the larvae which reduce uptake, for example reduced respiration rate and immobilization (Mackay & Fraser, 2000).…”