Effects of sediment-spiked lufenuron on benthic macroinvertebrates in outdoor microcosms and single-species toxicity tests

Non-conventional endpoints show higher sulfoxaflor toxicity to Chironomus riparius than conventional endpoints in a multistress environment

Evidence grows that standard toxicity testing might underestimate the environmental risk of neurotoxic insecticides. Behavioural endpoints such as locomotion and mobility have been suggested as sensitive and ecologically relevant additions to the standard tested endpoints. Possible interactive effects of chemicals and additional stressors are typically overlooked in standardised testing. Therefore, we aimed to investigate how concurrent exposure to environmental stressors (increased temperature and predation cues) and a nicotinic acetylcholine receptor (nAChR)-modulating insecticide ('sulfoxaflor') impact Chironomus riparius across a range of conventional and non-conventional endpoints. We used a multifactorial experimental design encompassing three stressors, sulfoxaflor (2.0-110 µg/L), predation risk (presence/absence of predatory cues), and elevated temperature (20 °C and 23 °C), yielding a total of 24 distinct treatment conditions. Additional stressors did not change the sensitivity of C. riparius to sulfoxaflor. To assess potential additive effects, we applied an Independent Action (IA) model to predict the impact on eight endpoints, including conventional endpoints (growth, survival, total emergence, and emergence time) and less conventional endpoints (the size of the adults, swimming abilities and exploration behaviour). For the conventional endpoints, observed effects were either lower than expected or well-predicted by the IA model. In contrast, we found greater than predicted effects of predation cues and temperature in combination with sulfoxaflor on adult size, larval exploration, and swimming behaviour. However, in contrast to the non-conventional endpoints, no conventional endpoints detected interactive effects of the neurotoxic insecticide and the environmental stressors. Acknowledging these interactions, increasing ecological context of ecotoxicological test systems may, therefore, advance environmental risk analysis and interpretation as the safe environmental concentrations of neurotoxic insecticides depend on the context of both the test organism and its environment.

Spiking organic chemicals onto sediments for ecotoxicological analyses: an overview of methods and procedures

Laboratory testing with spiked sediments with organic contaminants is a valuable tool for ecotoxicologists to study specific processes such as effects of known concentrations of toxicants, interactions of the toxicants with sediment and biota, and uptake kinetics. Since spiking of the sediment may be performed by using different strategies, a plethora of procedures was proposed in the literature for spiking organic chemicals onto sediments to perform ecotoxicological analyses. In this paper, we reviewed the scientific literature intending to characterise the kind of substrates that were used for spiking (i.e. artificial or field-collected sediment), how the substrates were handled before spiking and amended with the organic chemical, how the spiked sediment was mixed to allow the homogenisation of the chemical on the substrate and finally how long the spiked sediment was allowed to equilibrate before testing. What emerged from this review is that the choice of the test species, the testing procedures and the physicochemical properties of the organic contaminant are the primary driving factors affecting the selection of substrate type, sediment handling procedures, solvent carrier and mixing method. Finally, we provide recommendations concerning storage and characterization of the substrate, equilibrium times and verification of both equilibration and homogeneity.

Species Sensitivity Distributions of Benthic Macroinvertebrates in Fludioxonil-Spiked Sediment Toxicity Tests

The fungicide fludioxonil, given its physicochemical properties, potentially accumulates and persists in sediments. Fludioxonil has a widespread agricultural use to control various fungal diseases. Its residues may cause toxic effects to benthic aquatic fauna, thereby impacting ecosystem service functions of aquatic ecosystems. To assess the potential environmental effects of fludioxonil in the sediment compartment of edge-of-field surface waters, sediment-spiked single-species toxicity tests with benthic macroinvertebrates were performed. In all experiments artificial sediment was used with an organic carbon content of 2.43% on dry weight basis. The single-species tests were conducted with 8 benthic macroinvertebrates covering different taxonomic groups typical for the Yangtze River Delta, China. The 28d-EC₁₀ and 28-LC₁₀ values thus obtained were used to construct species sensitivity distributions (SSDs). In addition, our dataset was supplemented with 28d-EC₁₀ and 28-LC₁₀ values for 8 different benthic invertebrates from a study in the Netherlands that used field-collected sediment. Based on SSDs constructed with 28d-EC₁₀ or 28d-LC₁₀ values hazardous concentrations to 5% of the species tested (HC₅'s) were obtained. The HC₅ values based on the toxicity tests from China were lower than those from the Netherlands, although 95% confidence bands overlapped. The HC₅ values derived from the separate datasets from China and the Netherlands, as well as from the combined dataset, were compared to the Tier-3 Regulatory Acceptable Concentrations (RAC) for fludioxonil and the benthic invertebrate community derived from a sediment-spiked outdoor microcosm experiment conducted in the Netherlands. The HC₅ values obtained appeared to be lower than this Tier-3 RAC when expressed in terms of total sediment concentration, but not always when expressed in terms of pore water concentrations.

What is the spatial-temporal behavior of a low, medium and high adsorptive compound in two contrasting natural sediments in OECD 218/219 test systems?

Artificial sediment used in studies according to OECD 218/219 (Sediment Water Chironomid Toxicity Test Using Spiked Sediment/Water) does not necessarily mirror the characteristics of natural sediments. To investigate the influence of sediment characteristics on the spatial-temporal behaviors of bixafen (KfOM = 2244 mL/g), fluopyram (KfOM = 162 mL/g) and N,N-dimethylsulfamide (KfOM ≈ 0 mL/g), experiments according to OECD 218/219 with two contrasting natural sediments were conducted. The silt loam sediment provided a high content of organic matter (OM) (13.1%), while the OM (0.45%) of the sandy sediment was low. Diffusion into (OECD 219) or out (OECD 218) of the sediment was dependent on the extent of adsorption, which is linked to the model compounds ́ adsorption affinities and the sediments ́ OM. Consequently, N,N-dimethylsulfamide showed unhindered mobility in each experimental set up, while the high adsorption affinities of fluopyram and bixafen limited the diffusion in the respective sediments. Therefore, in experiments with the silt loam sediment, both compounds revealed a limited mobility and either accumulated in the top 5 mm of the sediment (OECD 219) or remained homogenously distributed over the sediment depth (OECD 218). A greater mobility was observed within the sandy sediment.The influence of OM as found in a study using artificial sediment could be confirmed. Moreover, the applicability of a TOXSWA model was reassured to predict the measured concentrations at different sediment depths. TOXSWA is used in the regulatory exposure assessment to simulate the behavior of pesticides in surface waters. Calibration of three driving input parameters by inverse modelling (diffusion-, adsorption coefficient and OM) revealed no potential for improvement. The core sampling technique used and the model may contribute to a more realistic determination of concentration to which the Chironomid larvae are exposed to. This applies to water sediment test systems where the test organisms do not evenly inhabit the sediment.

Assessing the ecological risk of active principles used currently by freshwater fish farms

The global aquaculture industry has grown exponentially in recent years using to control of infections and diseases, a variety of veterinary drugs (VMP) are used, including antibiotics, antifungals and antiparasitics, which have different routes of emission, environmental persistence and side effects to aquatic organisms, becoming one of the main concerns in its use of veterinary drugs (VMP) and its potential toxicological impact on the environment, in this context, Chile is considered one of the main salmon producers. Ecological risk assessment of active principles used infreshwater fish farms worldwide and in Chile were investigated. We recollect a physical - chemical properties of active principles used by fish farms and we could estimate the relative hazard a priori. Later active principles grouped as antibiotics (n = 6), antiparasitics (n = 5), anesthetics (n = 3), and disinfectants (n = 7) were assessed using a mass balance model based on fugacity was developed for each active principle under treatments via immersion and food administration in fish, while a volumetric model for disinfectants and sodium chloride was used for estimating the predicted environmental concentration (PEC), under a real smolt farming scenario in fish farms. Ecotoxicological data were collected from open literature to predict the no-effect concentration (PNEC). The ecological risk assessment was characterized using a risk quotient (RQ = PEC/PNEC) based in two assessment tiers. Results revealed that 12 active ingredients showed a high risk (RQ ≥ 1), thus indicating that adverse effects could occur and further investigation with measured concentrations in the field are required to reduce exposure in surface waters.

Periodic density as an endpoint of customized plankton community responses to petroleum hydrocarbons: A level of toxic effect should be matched with a suitable time scale

As an endpoint of community response to contaminants, average periodic density of populations (APDP) has been introduced to model species interactions in a community with 4 planktonic species. An ecological model for the community was developed by means of interspecific relationship including competition and predation to calculate the APDP. As a case study, we reported here the ecotoxicological effects of petroleum hydrocarbons (PHC) collected from Bohai oil field on densities of two algae, Platymonas subcordiformis and Isochrysis galbana, a rotifer, Brachionus plicatilis, and of a cladocera, Penilia avirostris, in single species and a microcosm experiment. Time scales expressing toxic effect increased with increasing levels of toxic effect from molecule to community. Remarkable periodic changes in densities were found during the tests in microcosm experiment, revealing a strong species reaction. The minimum time scale characterizing toxic effect at a community level should be the common cycle of population densities of the microcosm. In addition, the cycles of plankton densities shortened in general with increasing PHC, showing an evident toxic effect on the microcosm. Using APDP as the endpoint, a threshold concentration for the modeled microcosm was calculated to be 0.404 mg-PHC L^-1. The APDP was found to be more sensitive and reliable than the standing crops of populations as the endpoint. This indicated that the APDP, an endpoint at the community level, could be quantitatively related to the endpoints at the population level, and led to the quantitative concentration-toxic effect relationship at the community level.

Sediment toxicity of the fungicide fludioxonil to benthic macroinvertebrates -evaluation of the tiered effect assessment procedure

28-Day sediment-spiked laboratory toxicity tests with eight benthic macroinvertebrates and the lipophilic fungicide fludioxonil were conducted to verify the proposed tiered sediment effect assessment procedure as recommended by the European Food Safety Authority (EFSA). The test species were the oligochaetes Lumbriculus variegatus and Tubifex tubifex, the insects Chironomus riparius and Caenis horaria, the crustaceans Hyalella azteca and Asellus aquaticus and the bivalves Corbicula fluminalis and Pisidium amnicum. Toxicity estimates were expressed in terms of total concentration of dry sediment as well as in pore water concentration. Field-collected sediment, also used in a previously performed sediment-spiked microcosm experiment, was used in tests with all species. L. variegatus and C. riparius had similar lowest 28d-L(E)C₁₀ values when expressed in terms of total sediment concentration, but in terms of pore water concentration L. variegatus was more sensitive. Three of the six additional benthic test species (A. aquaticus, C. horaria, C. fluminalis) had 28d-EC₁₀ values a factor of 2-6 lower than that of L. variegatus. Comparing different effect assessment tiers for sediment organisms, i.e. Tier-0 (Modified Equilibrium Partitioning approach), Tier-1 (Standard Test Species approach), Tier-2 (Species Sensitivity Distribution (SSD) approach) and Tier-3 (Model Ecosystem approach), it is concluded that the tiers based on sediment-spiked laboratory toxicity tests provide sufficient protection when compared with the Tier-3 Regulatory Acceptable Concentration (RAC). Differences between Tier-1 and Tier-2 RACs, however, appear to be relatively small and not always consistent, irrespective of expressing the RAC in terms of total sediment or pore water concentration. Derivation of RACs by means of the SSD approach may be a challenge, because it is difficult obtaining a sufficient number of valid chronic EC₁₀ values with appropriate 95% confidence bands for sediment-dwelling macroinvertebrates. Therefore, this paper proposes a Tier-2 Weight-of-Evidence approach to be used in case an insufficient number of valid additional toxicity data is made available. Similar studies with pesticides that differ in fate properties and toxic mode-of-action are necessary for further validation of the tiered effect assessment approach for sediment organisms.

Response of a nematode community to the fungicide fludioxonil in sediments of outdoor freshwater microcosms compared to a single species toxicity test

When entering aquatic ecosystems, hydrophobic organic chemicals like the fungicide fludioxonil partition to the sediment compartment where they pose potential risks to benthic invertebrates. To assess the ecological risk for sediment-dwelling invertebrates, nematodes are a suitable organism group, as they are abundantly present and possess key positions in the benthic food web. Therefore, the toxicity of the fungicide fludioxonil to nematodes was assessed in a standardized sediment toxicity test with Caenorhabditis elegans (ISO 10872), as well as in an outdoor sediment-spiked microcosm test system. In the microcosms, effects on the nematode species composition were studied, while exposure concentrations of fludioxonil were monitored in total sediment and pore water. Toxic effects on nematodes were better predicted using concentrations in pore water than total sediment concentrations. In laboratory single species tests, fludioxonil showed considerably lower toxicity in spiked field-collected sediment, compared to artificial ISO-sediments. Applying an assessment factor of 10 to the C. elegans 96-h EC₁₀, a Tier-1 RAC_Nematode of 7.99 mg kg^-1 dry artificial sediment (corresponding to 69 μg l^-1 in pore water) appeared to be protective for nematode communities in microcosms that showed no response in total abundance and species composition up to 39.9 mg fludioxonil kg^-1 dry sediment (corresponding to 392 μg l^-1 in pore water).

Effects of increased temperature, drought, and an insecticide on freshwater zooplankton communities

In the present study we performed a microcosm experiment to assess the effects of the insecticide lufenuron on zooplankton communities exposed to increased temperature and drought in (semi-)arid regions. The experiment consisted of 3 environmental scenarios, assessed in 2 parts. Firstly, we assessed how water temperature (20 and 28 °C) affects the sensitivity and resilience of the zooplankton community to lufenuron. Secondly, we investigated the influence of drought on the structure of the zooplankton community at a high water temperature (28 °C) and evaluated its possible interaction with lufenuron. The results show that the community exposed to lufenuron at 28 °C had a faster lufenuron-related response and recovery than the community at 20 °C. The combined effects of lufenuron and temperature resulted in a synergistic effect on some taxa (Daphnia sp., Cyclopoida, and Copepoda nauplii). The tested zooplankton community had a high resilience to drought, although some particular taxa were severely affected after desiccation (Calanoida). Interactions between drought and lufenuron were not statistically significant. However, rewetting after desiccation contributed to lufenuron remobilization from sediments and resulted in a slight Cyclopoida population decline at high exposure concentrations. The study shows how environmental conditions related to global change in (semi-)arid regions may influence chemical fate and the vulnerability of zooplankton communities to chemical stress. Environ Toxicol Chem 2019;38:396-411. © 2018 SETAC.

Hematological, physiological and genotoxicological effects of Match 5% EC insecticide on Biomphalaria alexandrina snails

Freshwater snails are used as brilliant biomarkers of aquatic ecosystem pollution by chemical compounds. The objective of this study is to highlight the ecotoxicological impacts of the insecticide Match 5%EC (its active ingredient is lufenuron 5% EC) on Biomphalaria alexandrina snails the intermediate host of Schistosoma mansoni in Egypt. The present investigation recorded a remarkable molluscicidal effect of lufenuron 5% EC on these snails and there was a decrease in total number of their hemocytes after exposure. Three morphologically distinct populations of circulating hemocytes were identified (round small cells, granulocytes and hyalinocytes) and results showed that some hyalinocytes had a shrunk nucleus and some were degenerated. Significant increase of transaminases (ALT and AST), while, a decrease of the total protein and albumin content in hemolymph was recorded. The results of alkaline comet assay in the present study demonstrated that lufenuron 5% EC has a genotoxic effect especially when its concentration increases. It can be concluded that Biomphalaria alexandrina snails can be used as bio monitor to screen the deleterious effects of lufenuron 5% EC insecticide as a cause of the environmental pollution, and this insecticide can be used in controlling schistosomiasis because of its molluscicidal effects on B. alexandrina snails.

Exposure and effects of sediment-spiked fludioxonil on macroinvertebrates and zooplankton in outdoor aquatic microcosms

Information from effects of pesticides in sediments at an ecosystem level, to validate current and proposed risk assessment procedures, is scarce. A sediment-spiked outdoor freshwater microcosm experiment was conducted with fludioxonil (lipophilic, non-systemic fungicide) to study exposure dynamics and treatment-related responses of benthic and pelagic macroinvertebrates and zooplankton. Besides blank control and solvent control systems the experiment had six different treatment levels (1.7-614mga.s./kg dry sediment) based around the reported 28-d No Observed Effect Concentration (NOEC) for Chironomus riparius (40mga.s./kg dry sediment). Twelve systems were available per treatment of which four were sacrificed on each of days 28, 56 and 84 after microcosm construction. Fludioxonil persisted in the sediment and mean measured concentrations were 53-82% of the initial concentration after 84days. The dissipation rate increased with the treatment level. Also exposure concentrations in overlying water were long-term, with highest concentrations 28days after initiation of the experiment. Sediment-dwelling Oligochaeta and pelagic Rotifera and Cladocera showed the most pronounced treatment-related declines. The most sensitive sediment-dwelling oligochaete was Dero digitata (population NOEC 14.2mga.s./kg dry sediment). The same NOEC was calculated for the sediment-dwelling macroinvertebrate community. The most sensitive zooplankton species was the cladoceran Diaphanosoma brachyurum (NOEC of 1.6μga.s./L in overlying water corresponding to 5.0mga.s./kg dry sediment). At the two highest treatments several rotifer taxa showed a pronounced decrease, while the zooplankton community-level NOEC was 5.6μga.s./L (corresponding to 14.2mga.s./kg dry sediment). Zooplankton taxa calanoid Copepoda and Daphnia gr. longispina showed a pronounced treatment-related increase (indirect effects). Consequently, an assessment factor of 10 to the chronic laboratory NOECs of Chironomus riparius (sediment) and Daphnia magna (water) results in a regulatory acceptable concentration that is sufficiently protective for both the sediment-dwelling and pelagic organisms in the microcosms.