Bioremediation has been arising as a successful wastewater treatment concerning contamination events. Olive oil mill wastewaters (OOMW) are amongst the most concerning industrial wastewaters in the ...Mediterranean region mainly due to its seasonally intense production volumes, leading to numerous problems in recipient freshwater systems and soils. Bivalves present one of the most attractive solutions to integrate remediation strategies owing to their notable filtration capabilities and often their extensive tolerance to several chemical contaminants. The aim of this study was to explore the potential of Corbicula fluminea, a freshwater invasive bivalve, as a bioremediation agent towards OOMW. In this way, C. fluminea was exposed to a sample of this wastewater, and untreated and biotreated fractions were compared in terms of (i) their chemical composition; (ii) bioaccumulation in bivalve soft tissues and shells; and, finally, (iii) ecotoxicity, using standard organisms (bacteria, microalgae, macrophytes and cladocerans). The clam operated significant removal from OOMW of compounds holding OH and NH groups (e.g. phenols and amides) or CO, CC and CN groups (e.g. protein contents), as well as aliphatic compounds by more than half of the initial levels, as read by FTIR analysis. Corresponding transference into clams’ soft tissues can be suggested especially regarding proteins and phosphate groups, with metabolic transformation possibly explaining inconsistencies to some extent; the clam shells were also enriched in compounds bearing carboxyl, hydroxyl and phenol groups, to a lower extent in aliphatic compounds, proteins and polysaccharides, supporting that soft tissues and shells are proper recipients for the olive oil contaminants. Consistently, COD content was reduced by 89% and OOMW toxicity was generally reduced with the biotreatment, remarkably in tests with Lemna minor, where growth rate inhibition decreased from 100% to 60%. Overall, this study presents the first approach linking OOMW with C. fluminea as a potential bioremediation agent, with promising results regarding the use of this bivalve in remediation strategies.
•The Asian clam can assist the remediation of olive oil mill wastewaters (OOMW).•The chemical burden of OOMW was reduced through a 7-day filtration period by the clam.•Clam’s soft tissues and shells accumulated chemicals corresponding to OOMW losses.•Biofiltration promoted the decrease of OOMW ecotoxicity.
•Filter-feeding behaviour of Asian clam was sensitive to an array of contaminants.•Overall, feeding depression (2 h) was a protective surrogate for acute toxicity (96 h).•Dichlorvos was able to ...bypass the avoidance (valve closure) response of the clams.•The avoidance response mechanism and its potential as a screening tool are discussed.•The test can also support the improvement of control methods targeted at the biofoulers.
Bivalves are commonly used in biomonitoring programs to track pollutants. Several features, including its filter-feeding abilities, cumulatively argue in favour of the use of the Asian clam (Corbicula fluminea) as a biosentinel and an ecotoxicological model. Filtration in bivalves is very sensitive to external stimuli and its control is dictated by regulation of the opening/closure of the valves, which may be used as an avoidance defence against contaminants. Here, we investigate the filter-feeding behaviour of the Asian clam as an endpoint for assessing exposure to pollutants, driven by two complementary goals: (i) to generate relevant and sensitive toxicological information based on the ability of C. fluminea to clear an algal suspension, using the invasive species as a surrogate for native bivalves; (ii) to gain insight on the potential of exploring this integrative response in the refinement of chemical control methods for this pest. Clearance rates and proportion of algae removed were measured using a simple and reproducible protocol. Despite some variation across individuals and size classes, 50–90% of food particles were generally removed within 60–120 min by clams larger than 20 mm. Removal of algae was sensitive to an array of model contaminants with biocide potential, including fertilizers, pesticides, metals and salts: eight out of nine tested substances were detected at the μg l−1 or mg l−1 range and triggered valve closure, decreasing filter-feeding in a concentration-dependent manner. For most toxicants, a good agreement between mortality (96 h − LC50 within the range 0.4–5500 mg l−1) and feeding (2 h − IC50 within the range 0.005–2317 mg l−1) was observed, demonstrating that a 120-min assay can be used as a protective surrogate of acute toxicity. However, copper sulphate was very strongly avoided by the clams (IC50 = 5.3 μg l−1); on the contrary, dichlorvos (an organophosphate insecticide) did not cause feeding depression, either by being undetected by the clams’ chemosensors and/or by interfering with the valve closure mechanism. Such an assay has a large potential as a simple screening tool for industry, environmental agencies and managers. The ability of dichlorvos to bypass the Asian clam’s avoidance strategy puts it in the spotlight as a potential agent to be used alone or combined with others in eradication programs of this biofouler in closed or semi-closed industrial settings.
As a consequence of the growing global dependence on groundwater resources, environmental risk assessments (ERA) for groundwater are increasingly required and, with that, ecotoxicological studies ...with groundwater fauna (stygofauna). However, the literature on the ecotoxicological studies with stygobiotic species (i.e. species that complete their life cycle exclusively in groundwater) has not expanded significantly since the first paper published in this field. The limitations regarding the use of stygobiotic species for ecotoxicological testing are clear and consistent across the globe; stygobiotic species are often 1) naturally present in low numbers, 2) difficult to collect, and 3) difficult to culture under laboratory conditions. This paper reviews the methods used in ecotoxicological studies performed with stygobiotic species, and provides ten recommendations for Good Laboratory Practice (GLP) for such tests. The recommendations focused on the following 10 points: 1) the taxonomic identification, the life stage/size and gender of the test organisms; 2) collection methodology of the organisms, including collection location, conditions and methods; 3) holding and acclimation conditions in the laboratory; 4) exposure conditions such as test set up and exposure time, number of replicates and densities of organisms in tests and in test vessels; 5) range-finding test set up and schedule; 6) final test design, including details of controls and treatments, and replication options; 7) incubation conditions, specifying temperature, pH and oxygenation levels throughout the test; 8) test duration; 9) observations and endpoints; 10) test validity criteria and compliance. The recommendations were developed for the purpose of supporting future short-term ecotoxicological testing with stygofauna through providing consistency in the protocols. A discussion of the potential implications for groundwater managers and decision-makers committed to ERA for groundwater is included.
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•There is a need for ERA procedures specifically formulated for the groundwater biota.•The use of stygobiotic species in ecotoxicological experiments presents difficulties.•The methods of available ecotoxicological studies with stygofauna are reviewed.•Ten recommendations for ecotoxicity assays with stygofauna are presented.•The recommendations pave the way towards improved ERA for groundwater.
This study was aimed at assessing the contribution of wastewater treatment effluents to the contamination profile of the sediments of receiving waterways. Three wastewater treatment plants (WWTP) ...were addressed, encompassing different population equivalent sizes, urbanization degrees and treatment methods translating differences in expected contamination patterns. Within each WWTP system, the assessment targeted the effluent and sediment samples collected upstream and downstream the effluent discharge point; contaminants belonging to several concerning chemical classes (metals and metalloids; pesticides; pharmaceuticals and personal care products, PPCPs; and polycyclic aromatic hydrocarbons, PAHs) were quantified both in effluent and sediment samples. Clear associations between contaminants present in the effluent and corresponding sediment samples were not always verified. In fact, a noticeable difference between the number or abundance of contaminants detected in effluents and in sediments, suggesting that effluents are not always the most likely source (e.g. PAHs). However, sediment contaminants that were likely sourced by the effluents were also identified (e.g. PPCPs). Sediment analysis offers an important historical view of contamination, especially in flowing recipient ecosystems where any characterization over the water matrix is ephemeral and linking exclusively to the moment of sampling. Hence, sediments should be considered for the establishment of WWTP operational benchmarks regulating the emission of contaminants, which is currently focused mostly on effluent composition thus potentially over/underestimating the longer-term impact of effluent discharge in the recipient waterways.
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•WWTP effluents aren't always a source of sediment contaminants in recipient waterways.•Sediment metals, pesticides and PAHs do not relate strongly to effluent inputs.•PPCP contaminants in sediments could be related to WWTP effluent inputs.•Effluent and sediment's load reflects PPCP consumption patterns by served populations.•Sediments provide a non-ephemeral view on effluent contributions to contamination.
Groundwater is an indispensable resource for humankind and sustainable biomes functioning. Anthropogenic disturbance threatens groundwater ecosystems globally, but to which extent groundwater ...organisms respond to stressors remains poorly understood. Groundwater animals are rare, with small populations, difficult to find and to breed in the lab, which poses a main challenge to the assessment of their responses to pollutants. Despite the difficulties, assessing the toxicity of a large spectrum of stressors to groundwater organisms is a priority to inform towards appropriate environmental protection of these ecosystems. We tested the sensitivity to CuSO4, diclofenac, and NaCl of a groundwater population of the copepod Diacyclops crassicaudis crassicaudis and compared its sensitivity with the model organism Daphnia magna. We ranked its sensitivity using a species sensitivity distribution (SSD) approach using the feasible data available for groundwater and surface crustaceans. Our results show that the most toxic compound was CuSO4 for which higher amount of data was recorded and wider variability in response was observed. It was followed by diclofenac, largely lacking data for groundwater-adapted organisms, and the least toxic compound was NaCl. The differential sensitivity between D. crassicaudis and D. magna was contaminant-dependent. As a general trend D. crassicaudis was always distributed in the upper part of the SSD curves together with other groundwater-adapted organisms. Our results highlight that the widespread groundwater populations of the D. crassicaudis species complex, which can be successfully breed in the lab, may provide a reasonable approach to assess the ecological effects of anthropogenic stressors in groundwater ecosystems.
•Widespread groundwater copepod had differential sensitivity to the tested compounds.•Cu was the most toxic compound tested, followed by diclofenac and NaCl.•The sensitivity of Diacyclops crassicaudis and Daphnia magna was compound-specific.•Groundwater species are located at the top of the SSD curves, over surface species.•D. crassicaudis may be useful for assessing stressors in groundwater.
Climate change has been increasing the frequency and severity of drought periods. There is a need to understand how this water scarcity affects aquatic communities. The main aim of this work was to ...compare the macroinvertebrate communities and their bioindicator value (ecological status sensu the Water Framework Directive) in three Regions northeast (N), central (C) and south (S) of Portugal along a water availability and climate gradient, in two consecutive years that reflect hydrologically distinct scenarios (2018 versus 2019). The period prior to sampling (summer and autumn 2017) was extremely dry and hot, whereas climatic fluctuations in 2018–2019 (when the sampling occurred) were closer to the norm. A total of 28 sampling sites were surveyed in streams of Regions where water scarcity is differentially constitutive. The results showed a consistent environmental and ecological gradient in both years, despite the background differences. A coinciding mineralization, temperature, riparian cover and water availability gradient clearly separated Regions C (wettest) and S (driest), with Region N occupying an intermediate position. Region C had overall higher ecological quality (prevalence of sensitive organisms) in both years. Despite our a priori expectations that 2018 would represent a much more stressful condition, with larger differences across Regions (because of their constitutive background), the data suggest that macroinvertebrate communities may be resilient or adapted, to some degree, to hydrological fluctuations. Signs of more favourable conditions in 2019 were also observed (general improvement in ecological status). Studies across hydrological and climatic gradients (in time and space) are particularly important where water availability is becoming more challenging.
•ZnPT caused significant toxic effect on C. fluminea, namely oxidative stress.•ZnPT was not causative of cholinesterasic inhibition in exposed C. fluminea.•Levels of znPT required for toxic responses ...were above environmental concentrations.•ZnPT is not exempt of toxicity and can compromise key features of C. fluminea.
Zinc pyrithione (ZnPT) is an organometallic biocide with bactericide, algaecide, and fungicide activity. Considering this biological activity, ZnPT has been used in anti-fouling paints, and also in human therapeutics and cosmetics, in shampoos to treat dandruff and seborrhoea. Despite its potential uses and consequent presence in the aquatic environment, the ecotoxicological effects of ZnPT are poorly understood. This work aims to characterise the effects of ZnPT in biochemical parameters of the Asian clam, one of the most invasive bivalves known for its biofouling action in hydro-dependent industries, using a classical (LC50 determination) and a biomarker-based approach (quantification of the activities of catalase, GSTs, and acetylcholinesterase, and also the muscle glycogen content). The here determined LC50-96 h for zinc pyrithione was 2.17 mg/L. ZnPT caused significant increases in the activity of catalase and of cholinesterases. These findings evidence the pro-oxidative effects caused by the metabolism of ZnPT. Despite the absence of clear effects, it is important to stress that the presence of ZnPT in the wild is usually accompanied by other pyrithiones, whose co-existence can contribute to the exertion of considerable toxic effects.
•Wildfire runoffs induce physic-chemical changes in downhill river waters.•In-situ exposure to affected water inhibits the feeding rates of several species.•Wildfire effects are better discriminated ...by in-situ than laboratory bioassays.•Metals incoming with the runoff should play a role in noticed ecotoxic effects.
Among the various environmental disturbances caused by wildfires, their impacts within burnt areas and on the downhill aquatic ecosystems has been receiving increased attention. Post-fire rainfalls and subsequent runoffs play an important role in transporting ash and soil to aquatic systems within the burnt areas. These runoffs can be a diffuse source of toxic substances such as metals. The present work aims at assessing the effects of ash-loaded runoff on feeding rates of three representative aquatic invertebrates (Daphnia magna, Corbicula fluminea and Atyaephyra desmarestii) and the mosquitofish, Gambusia holbrooki, through post-exposure feeding inhibition bioassays carried out in-situ and in the laboratory using water collected from the experimental field sites. Four sites were selected in a partially burnt basin for bioassay deployment and sample collection: one site upstream of the burnt area (RUS); three sites receiving runoff directly from the burnt area, one immediately downstream of the burnt area (RDS) and two in permanent tributary streams within the burnt area (BS1 and BS2). The in-situ exposure lasted four days and began following the first post-fire major rain events. At sites affected by the wildfire, post-exposure feeding rates for D. magna, A. desmarestii and G. holbrooki were lower, which is consistent with the highest levels of metals found at these sites compared to the unaffected site, although the individual concentrations of each metal were generally below corresponding ecological safety benchmarks. Thus, interactions between metals and/or between metals and other environmental parameters certainly played a role in modulating the ecotoxic effects of the runoffs; this was further supported by a Toxic Units Summation exercise. Even if direct causal links between the ecotoxicological effects observed in D. magna, A. desmarestii and G. holbrooki and the physicochemical parameters of the water samples could not be established, the results suggest an important role of major and trace elements in explaining post-exposure feeding rate variation.
The use of fungicides in agriculture has been playing a role in the enhancement of agricultural yields through the control of pathogens causing serious diseases in crops. Still, adverse environmental ...and human health effects resulting from its application have been reported. In this study, the possibility of readjusting the formulation of a commercial product combining azoxystrobin and tebuconazole (active ingredients – AIs; Custodia®) towards environmentally safer alternative(s) was investigated. Specifically, the sensitivity of non-target aquatic communities to each AI was first evaluated by applying the Species Sensitivity Distributions (SSDs) approach. Then, mixtures of these AIs were tested in a non-target organism (
Raphidocelis subcapitata
) denoting sensitivity to both AIs as assessed from SSDs. The resulting data supported the design of the last stage of this study, where mixtures of those AIs at equivalent
vs
. alternative ratios and rates as in the commercial formulation were tested against two target fungal species:
Pyrenophora teres
CBS 123929 and
Rhynchosporium secalis
CBS 110524. The comparison between the sensitivity of non-target aquatic species and the corresponding efficacy towards target fungi revealed that currently applied mixture and rates of these AIs are generally environmentally safe (antagonistic interaction; concentrations below the EC
1
for
R. subcapitata
and generally below the HC
5
for aquatic non-target communities), but ineffective against target organisms (maximum levels of inhibition of 70 and 50% in
P. teres
CBS 123929 and
R. secalis
CBS 110524, respectively). Results additionally suggest a potentiation of the effects of the AIs by the other formulants added to the commercial product at tested rates. Overall, this study corroborates that commercial products can be optimized during design stages based on a systematic ecotoxicological testing for ingredient interactions and actual efficacy against targets. This could be a valuable pathway to reduce environmental contamination during transition to a more sustainable agricultural production.
•The impacts of wildfires on the freshwater clam Corbicula fluminea were assessed.•Aqueous extracts of ash (AEA) were used to represent ash-loaded post-fire runoff.•The bio-concentration ability of ...the clam was assessed in a filtration experiment.•Post-fire loads (rich in metals and PAHs) can compromise clams survival.
Wildfires, increasingly frequent and severe in the Mediterranean countries, can cause serious impacts on ecosystems. As a diffuse source of contaminants – namely inorganic elements (metals, metalloids and non-metallic elements) and polycyclic aromatic hydrocarbons (PAHs) – post-fire runoff may cause toxic effects on the aquatic biota. Despite the recognition of these likely impacts, this issue has been still largely neglected. This study explores the impacts of ash from wildfires on the freshwater clam Corbicula fluminea and the ability of this filter feeder to concentrate the contaminants associated with ash in post-fire runoff. The bio-concentration potential of the clam was assessed in a 7-day filtration experiment, using aqueous extract of ashes (AEA) to represent post-fire runoff. Despite the noticeable mortality of the clams exposed to the AEA (∼30% higher in AEA than in control after 7 days of exposure), there was a clear reduction on the concentration of almost all pyrolytic substances in the water linked to bio-filtration and bio-concentration activity. Along 7 days the clams operated decreases of more than 70% for some chemicals (Cu, Mn and Zn) while others were no longer detected in the water at the end of the experiment (Cr, NAP and PHE). The removal from water was accompanied by contaminants’ accumulation in clams’ soft tissues and, less extensively, in shells. Lower pollutant loads of filtered AEA translated into decreased toxicity of the matrix towards standard aquatic species (microalgae, macrophytes and cladocerans) confirming an improvement as well in the biological quality of the water through bio-filtration. Although post-fire loads can compromise C. fluminea survival, this study evidenced the potential of this invasive species to contribute to water quality improvement.
