The Air Pollution Tolerance index (APTI) of six plants located within Ikpoba Okha gas flaring site in Oredo Local Government Area of Edo State, Nigeria during wet and dry seasons were assessed. Plant samples for this research work were randomly collected from the vicinity of the flaring site. Six (6) sample of each plant was used for laboratory analysis. The plant parameters assessed include relative water content (RWC), the ascorbic acid content (AAC), total leaf chlorophyll (TLC) and pH extract of the leaves and were used to compute the Air pollution tolerance indices (APTI). Based on the analyzed result, the RWC in Drypetes leonensis, Ficus exasperata Vahl, Chromolaena odorata (Linn) and Gmelina arborea Roxb. ex Smith   species in dry season were higher than those in wet season. Icacina tricantha showed a relatively high level of acidity when compared to others. A. boonei De Wild has the highest ascorbic acid content in the leaves in both seasons. The highest level of chlorophyll contents was recorded in the dry season with Drypetes leonensis having the highest, followed by Icacina trichantha. There was no statistically significant difference in pH and total chlorophyll contents between samples collected in wet and dry season; however, there were significant difference observed in ascorbic acid and RWC in both seasons. APTI in wet and dry season showed a statistically significant difference. This study recommends planting of tolerant species that can acts as bio-indicators especially in gas flaring stations in Nigeria.

International audience | Copper (Cu) concentration in agricultural soils often exceeds toxicological limits due to application of Cu-based fungicides. The potential of weeds for their use as functional cover plants in vineyard management and phytoremediation practices is little explored. We identified five weed species widely present in vineyards and assessed their Cu accumulation from eleven Mediterranean vineyards (soil Cu: 60-327 mu g g(-1)) and two adjacent control sites (soil Cu: 15-30 mu g g(-1)). Soils and plants were characterized by their physico-chemical properties and nutrient content. We applied multivariate techniques to analyze relationships between soil properties and leaf nutrient composition. Copper tolerance and accumulation traits were further tested in hydroponics using a series of CuSO4 concentrations (0.1-16 mu M).Under field conditions, the highest Cu concentration in both roots and leaves were found in Lolium perenne (221 and 461 mu g g(-1), respectively), followed by Plantago lanceolata, Rumex obtusifolius and Taraxacum officinale (>100 mu g g(-1) Cu in leaves). Only one species, Trifolium repens, did not accumulate remarkable Cu concentrations. Overall, and as revealed by the multivariate analyses, leaf Cu concentration was driven by soil Cu content, soil texture, organic matter, nitrogen, and Cu uptake into roots. However, functional regression analysis and controlled experiments suggested that Cu might be additionally absorbed from the deposits on the leaf surface related to the Cu-fungicide treatments and soil dust. Our study highlights the importance of intra-specific variability in Cu accumulation among weed species in Cu-contaminated agricultural soils. Further validation of these findings under controlled conditions could provide essential insights for optimizing management and remediation strategies.

International audience | Copper (Cu) concentration in agricultural soils often exceeds toxicological limits due to application of Cu-based fungicides. The potential of weeds for their use as functional cover plants in vineyard management and phytoremediation practices is little explored. We identified five weed species widely present in vineyards and assessed their Cu accumulation from eleven Mediterranean vineyards (soil Cu: 60-327 mu g g(-1)) and two adjacent control sites (soil Cu: 15-30 mu g g(-1)). Soils and plants were characterized by their physico-chemical properties and nutrient content. We applied multivariate techniques to analyze relationships between soil properties and leaf nutrient composition. Copper tolerance and accumulation traits were further tested in hydroponics using a series of CuSO4 concentrations (0.1-16 mu M).Under field conditions, the highest Cu concentration in both roots and leaves were found in Lolium perenne (221 and 461 mu g g(-1), respectively), followed by Plantago lanceolata, Rumex obtusifolius and Taraxacum officinale (>100 mu g g(-1) Cu in leaves). Only one species, Trifolium repens, did not accumulate remarkable Cu concentrations. Overall, and as revealed by the multivariate analyses, leaf Cu concentration was driven by soil Cu content, soil texture, organic matter, nitrogen, and Cu uptake into roots. However, functional regression analysis and controlled experiments suggested that Cu might be additionally absorbed from the deposits on the leaf surface related to the Cu-fungicide treatments and soil dust. Our study highlights the importance of intra-specific variability in Cu accumulation among weed species in Cu-contaminated agricultural soils. Further validation of these findings under controlled conditions could provide essential insights for optimizing management and remediation strategies.

International audience | Climate change and human activities induce an increased frequency and intensity of cyanobacterial blooms which could release toxins to aquatic ecosystems. Zooplankton communities belong to the first affected organisms, but in tropical freshwater ecosystems, this issue has yet been poorly investigated. We tested two questions (i) if the tropical Daphnia lumholtzi is capable to develop tolerance to an ecologically relevant concentration of purified microcystin-LR and microcystins from cyanobacterial extract transferable to F1 and F2 generations? And (ii) would F1 and F2 generations recover if reared in toxin-free medium? To answer these questions, we conducted two full factorial mutigenerational experiments, in which D. lumholtzi was exposed to MC-LR and cyanobacterial extract at the concentration of 1 μg L microcystin continuously for three generations. After each generation, each treatment was spit into two one reared in the control (toxin free) while the other continued in the respective exposure. Fitness-related traits including survival, maturity age, body length, and fecundity of each D. lumholtzi generation were quantified. Though there were only some weak negative effects of the toxins on the first generation (F0), we found strong direct, accumulated and carried-over impacts of the toxins on life history traits of D. lumholtzi on the F1 and F2, including reductions of survival, and reproduction. The maturity age and body length showed some inconsistent patterns between generations and need further investigations. The survival, maturity age (for extract), and body length (for MC-LR) were only recovered when offspring from toxin exposed mothers were raised in clean medium for two generations. Chronic exposure to long lasting blooms, even at low density, evidently reduces survival of D. lumholtzi in tropical lakes and reservoirs with ecological consequences.

Frequent drought events and particulate matter pollution from vehicular exhaust seriously affect urban plant growth and provisioning of ecological services. Yet, how plants respond physiologically and morphologically to these two combined stressors remains unknown. Here, we assessed particle retention dynamics and plant morphology and physiology of Euonymus japonicus Thunb. var. aurea-marginatus Hort. under continuous drought with severe exhaust exposure. Our results showed that continuous drought insignificantly lowered particle retention in each of three size fractions by 1.02 μg·cm⁻² on average in the first 28 days, but significantly lowered total particle retention by 35.75 μg·cm⁻² on the 35th day. We observed evident changes in morphology, leaf mass per area (LMA), pigments, gas exchange in all stressed plants. Compared with single stress, combined drought and pollution caused earlier yellowing and shedding of old leaves, significantly lowered LMA by 1.21 mg·cm⁻², caused a greater decline in pigments and net photosynthetic rate (Pₙ). Large particles may mainly explain pigment reduction, lower weekly LMA increases, and stomatal restriction, while coarse particles may be the main drivers of the decline in Pₙ. Continuous drought mediated the influence of all three particle sizes on some parameters, such as weakening the impact of total particles on LMA, strengthening the impact of fine particles on photosynthesis. Our findings suggest that drought accelerates the physiological responses of plants to exhaust pollution. Under controlled severe exhaust pollution conditions, the optimal time to maintain high particle retention during continuous drought without decline in physiological conditions for E. japonicus var. aurea-marginatus was 14 days. Some additional interventions after 14 days (it could be postponed appropriately under field conditions) may help ensure healthy growth of plants and retention of particulate matter.

How to evaluate the ecological risk of transgenic technology is a focus of scientists because of the safety concerns raised by genetically modified (GM) organisms. Nevertheless, most studies are based on individual chemicals and always analyze the GM organism as a type of toxicant. In this study, we changed the approach and used GM organisms as the test objects with normal chemical exposure. Three types of chemicals (two substituted phenols, 4-chlorophenol and 4-nitrophenol; two ionic liquids, 1-butylpyridinium chloride and 1-butylpyridinium bromide; two pesticides, dichlorvos and glyphosate) were used to construct a six-component mixture system. The lethality to wild-type (N2) and sod-3::GFP (SOD-3) Caenorhabditis elegans was determined when they were exposed to the same mixture system after 12 and 24 h. The results showed that the pEC50 values of all of the single chemicals on SOD-3 were greater than those on N2 at 24 h. The toxicities of the single chemicals and nine mixture rays on the two strains increased with time. Notably, we discovered a significant difference between the two strains; time-dependent synergism occurred in mixtures on N2, but time-dependent antagonism occurred in mixtures on SOD-3. Finally, the strength of the synergism or antagonism turned to additive action on the two strains as the exposure time increased. These findings illustrated that the GM factor of the nematode influenced the mixture toxicological interaction at some exposure times. Compared with N2, SOD-3 were more sensitive to stress or toxic reactions. Therefore, the influence of the GM factor on mixture toxicological interactions in environmental risk assessment must be considered.

Low-methylesterified homogalacturonans have been suggested to play a role in the binding and immobilization of Pb in CW. Using root apices of hybrid aspen, a plant with a high phytoremediation potential, as a model, we demonstrated that the in situ distribution pattern of low-methylesterified homogalacturonan, pectin epitope (JIM5-P), reflects the pattern of Pb occurrence. The region which indicated high JIM5-P level corresponded with “Pb accumulation zone”. Moreover, JIM5-P was especially abundant in cell junctions, CWs lining the intercellular spaces and the corners of intercellular spaces indicating the highest accumulation of Pb. Furthermore, JIM5-P and Pb commonly co-localized.The observations indicate that low-methylesterified homogalacturonan is the CW polymer that determines the capacity of CW for Pb sequestration. Our results suggest a promising directions for CW modification for enhancing the efficiency of plant roots in Pb accumulation, an important aspect in the phytoremediation of soils contaminated with trace metals.

Climate change and human activities induce an increased frequency and intensity of cyanobacterial blooms which could release toxins to aquatic ecosystems. Zooplankton communities belong to the first affected organisms, but in tropical freshwater ecosystems, this issue has yet been poorly investigated. We tested two questions (i) if the tropical Daphnia lumholtzi is capable to develop tolerance to an ecologically relevant concentration of purified microcystin-LR and microcystins from cyanobacterial extract transferable to F1 and F2 generations? And (ii) would F1 and F2 generations recover if reared in toxin-free medium? To answer these questions, we conducted two full factorial mutigenerational experiments, in which D. lumholtzi was exposed to MC-LR and cyanobacterial extract at the concentration of 1 μg L⁻¹ microcystin continuously for three generations. After each generation, each treatment was spit into two: one reared in the control (toxin free) while the other continued in the respective exposure. Fitness-related traits including survival, maturity age, body length, and fecundity of each D. lumholtzi generation were quantified. Though there were only some weak negative effects of the toxins on the first generation (F0), we found strong direct, accumulated and carried-over impacts of the toxins on life history traits of D. lumholtzi on the F1 and F2, including reductions of survival, and reproduction. The maturity age and body length showed some inconsistent patterns between generations and need further investigations. The survival, maturity age (for extract), and body length (for MC-LR) were only recovered when offspring from toxin exposed mothers were raised in clean medium for two generations. Chronic exposure to long lasting blooms, even at low density, evidently reduces survival of D. lumholtzi in tropical lakes and reservoirs with ecological consequences.

Generally, ecotoxicologists rely on short-term tests that assume populations to be static. Conversely, natural populations may be exposed to the same stressors for many generations, which can alter tolerance to the same (or other) stressors. The objective of this study was to improve our understanding of how multigenerational stressors alter life history traits and stressor tolerance. After continuously exposing Daphnia magna to cadmium for 120 days, we assessed life history traits and conducted a challenge at higher temperature and cadmium concentrations. Predictably, individuals exposed to cadmium showed an overall decrease in reproductive output compared to controls. Interestingly, control D. magna were the most cadmium tolerant to novel cadmium, followed by those exposed to high cadmium. Our data suggest that long-term exposure to cadmium alter tolerance traits in a non-monotonic way. Because we observed effects after one-generation removal from cadmium, transgenerational effects may be possible as a result of multigenerational exposure.

Environmental contaminants are implicated in the global decline of amphibian populations. Copper (Cu) is a widespread contaminant that can be toxic at concentrations just above the normal physiological range. In the present study we examined the effects of chronic Cu aqueous exposure on embryos and larvae of southern toads, Anaxyrus (Bufo) terrestris. Measurable levels of Cu were found in larvae, with tissue concentrations up to 27.5 μg Cu/g dry mass. Aqueous concentrations of Cu as low as 10 μg/L significantly reduced survival to the free-swimming stage and no larvae reached metamorphosis at concentrations above 15 μg/L. Clutches from populations with prior Cu exposure had the lowest survivorship. Among several populations there was significant variation in survivorship at different levels of Cu. More data are needed to understand the underlying causes of within- and among-population resilience to anthropogenic stressors.