Lethal and behavioral effects of semi-purified microcystins, Micropeptin and apolar compounds from cyanobacteria on freshwater microcrustacean Thamnocephalus platyurus.

The mass proliferation of cyanobacteria, episodes known as blooms, is a concern worldwide. One of the most critical aspects during these blooms is the production of toxic secondary metabolites that are not limited to the four cyanotoxins recognized by the World Health Organization. These metabolites comprise a wide range of structurally diverse compounds that possess bioactive functions. Potential human and ecosystem health risks posed by these metabolites and co-produced mixtures remain largely unknown. We studied acute lethal and sublethal effects measured as impaired mobility on the freshwater microcrustaceans Thamnocephalus platyurus for metabolite mixtures from two cyanobacterial strains, a microcystin (MC) producer and a non-MC producer. Both cyanobacterial extracts, from the MC-producer and non-MC-producer, caused acute toxicity with LC50 (24 h) values of 0.50 and 2.55 mgdw_biomass/mL, respectively, and decreased locomotor activity. Evaluating the contribution of different cyanopeptides revealed that the Micropeptin-K139-dominated fraction from the MC-producer extract contributed significantly to mortality and locomotor impairment of the microcrustaceans, with potential mixture effect with other cyanopeptolins present in this fraction. In the non-MC-producer extract, compounds present in the apolar fraction contributed mainly to mortality, locomotor impairment, and morphological changes in the antennae of the microcrustacean. No lethal or sublethal effects were observed in the fractions dominated by other cyanopetides (Cyanopeptolin 959, Nostoginin BN741). Our findings contribute to the growing body of research indicating that cyanobacterial metabolites beyond traditional cyanotoxins cause detrimental effects. This underscores the importance of toxicological assessments of such compounds, also at sublethal levels.

Physicochemical and Toxicological Assay of Leachate from Malt Spent Rootlets Biochar.

The aim of this study was to characterize the leachate derived from biochar produced from malt spent rootlets (MSR) and to evaluate the required washing level in order to provide water free from inorganic substances. MSR biochar was placed in a column and subjected to six serial washes with distilled water, and the leachate was analysed for main anions and heavy metals. The 1st wash aliquot contained increased levels of mainly phosphates (980 mg/L) and chlorides (760 mg/L), and lower levels of nitrates, sulfates, fluoride and bromide, which were decreased over washes. Zero concentrations were observed after three washes for most anions. The increased levels of Zn, Be, Cs, Mn, V and Se determined in the 1st wash aliquot were eliminated in the successive washes. The toxic potency of each wash aliquot, determined by the use of the fairy shrimp Thamnocephalus platyurus showed that the 1st and 2nd MSR biochar leachates were toxic with 4.52 and 1.46 toxic units (TU), respectively, followed by a significant elimination of toxicity after further washes.

Influence of nanoplastic surface charge on eco-corona formation, aggregation and toxicity to freshwater zooplankton.

Concerns about possible environmental implications of nano- and micro-plastics are continuously raising. Hence, comprehensive understanding of their behaviour, bioaccumulation and toxicity potential is required. Nevertheless, systematic studies on their fate and possible effects in freshwaters, as well as the influence of particle-specific and environmental factors on their behaviour and impacts are still missing. The aims of the present study are thus two-fold: (i) to examine the role of the surface charge on nanoplastic stability and acute effects to freshwater zooplankton; (ii) to decipher the influence of the refractory natural organic matter (NOM) on the nanoplastic fate and effects. Amidine and carboxyl-stabilized polystyrene (PS) spheres of 200 nm diameter characterized by opposite primary surface charges and neutral buoyancy were selected as model nanoplastics. The results demonstrated that the surface functionalization of the polystyrene nanoplastics controls their aggregation behaviour. Alginate or Suwannee River humic acid (SRHA) modified significantly the surface charge of positively-charged amidine PS nanoplastic and the aggregation state, while had no significant influence on the negatively-charged carboxyl PS nanoplastic. Both amidine and carboxyl PS nanoplastics were ingested by the zooplankton and concentrated mainly in the gut of water flea Daphnia magna and larvae Thamnocephalus platyurus, and the stomach of rotifer Brachionus calyciflorus. Amidine PS nanoplastic was more toxic than carboxyl one. The toxicity decreased in the order D. magna (48 h -immobilization) > B. calyciflorus (24 h - lethality) > T. platyurus (24 h - lethality). Alginate or SRHA reduced significantly the toxicity of both amidine and carboxyl PS nanoplastics to the studied zooplankton representatives. The implications of this laboratory study findings to natural environment were discussed.

Acute ecotoxicity bioassay using Dendrocephalus brasiliensis: alternative test species for monitoring of contaminants in tropical and subtropical freshwaters.

In International guidelines for standard ecotoxicological bioassays, Daphnia magna is the most applied microcrustacea for assessing toxicity of different pollutants. However, in research realized in tropical and subtropical areas, autochthonous species must be prioritized because they are adapted to the specificities of ecosystems. In this sense, the present study aimed to assess and compare (with D. magna) the sensitivity of the tropical species Dendrocephalus brasiliensis as alternative test species for monitoring of contaminants in tropical and subtropical freshwaters, by carrying out acute toxicity tests with different pollutants. According results, D. brasiliensis presented EC50-48 h values lower than D. magna for all substances tested, indicating higher sensitivity of the tropical organism in relation to the temperate organism. Furthermore, comparing the results obtained with data from other studies, D. brasiliensis is more sensitive to the chemicals tested than D. magna and has similar sensitivity to Pseudosida ramosa and Ceriodaphnia dubia, common species in tropical areas. In view of this, we suggest that D. brasiliensis can be used as alternative test species for monitoring of contaminants in tropical and subtropical freshwaters.

Toxic potential of the emerging contaminant nicotine to the aquatic ecosystem.

Nicotine is a "life-style compound" widely consumed by human populations and, consequently, often found in surface waters. This fact presents a concern for possible effects in the aquatic ecosystems. The objective of this study was to assess the potential lethal and sublethal toxicity of nicotine in aquatic organisms from different trophic levels (Vibrio fischeri, Pseudokirchneriella subcapitata, Thamnocephalus platyurus, and Daphnia magna). The bioassays were performed by exposing the organisms to concentrations of nicotine in a range of 0.5-1000 µg/L. Results showed that nicotine, at tested concentration, was not acutely toxic to V. fischeri and T. platyurus. On the contrary, this substance exhibited toxicity to P. subcapitata and Daphnia magna. Thus, concentrations of nicotine of 100 and 200 µg/L promoted an inhibition in the growth of P. subcapitata. In addition, a concentration of 100 µg/L nicotine acted on the reproduction of the crustacean D. magna, by decreasing the number of juveniles produced by female. On the other hand, the results showed that concentrations equal to or greater than 10 µg/L induced the production of daphnids male offspring, which may indicate that nicotine is a weak juvenoid compound of the D. magna endocrine system. Furthermore, the result showed that concentrations tested of this chemical have the capacity to revert the effect of fenoxycarb, a strong juvenoid chemical insecticide. The results of the study revealed that nicotine can induce several changes in some of the most important key groups of the aquatic compartment, which can compromise, in a short time, the balance of aquatic ecosystem. Finally, a preliminary environmental risk assessment of this stimulant was performed from the highest measured concentration in surface water and the no observable effect concentration value in the most sensitive species, i.e., D. magna. This process revealed that nicotine can produce an important risk to aquatic organisms.

Chemometrics Expertise in the Links Between Ecotoxicity and Physicochemical Features of Silver Nanoparticles: Environmental Aspects.

Studies of the ecotoxicological aspects of nanomaterials in aquatic environments are scarce. Given the growing variety of nanoparticles (NPs), along with the diversity of aquatic species and environments, the key to promoting sound risk assessment in nanoecotoxicology is understanding the mechanisms that govern the fate of NPs in aquatic environments and their behavior at the NP-biota interface. In this paper, data collected from the literature on ecotoxicological effects observed in aquatic species is discussed and analyzed using multivariate statistics techniques. We expand the knowledge of the environmental impact of silver NPs (AgNPs) by testing the acute toxicity of 47 AgNPs on crustacean eukaryotic organisms (Daphnia magna, Thamnocephalus platyurus, and D. galeata). Physicochemical properties, stabilization agents, toxicological end points, and test media were monitored as adding-outcome factors for the evaluation of environmental effects due to exposure to NPs. The chemometrics expertise performed by the use of hierarchical and nonhierarchical cluster analysis and principal component analysis revealed specific links between the ecotoxicology and the physicochemical features of NPs and helped in creating specific patterns of NPs discriminated by ecotoxicity levels and physicochemical parameters.

Acute sensitivity of the vernal pool fairy shrimp, Branchinecta lynchi (Anostraca; Branchinectidae), and surrogate species to 10 chemicals.

Vernal pool fairy shrimp, Branchinecta lynchi, (Branchiopoda; Anostraca) and other fairy shrimp species have been listed as threatened or endangered under the US Endangered Species Act. Because few data exist about the sensitivity of Branchinecta spp. to toxic effects of contaminants, it is difficult to determine whether they are adequately protected by water quality criteria. A series of acute (24-h) lethality/immobilization tests was conducted with 3 species of fairy shrimp (B. lynchi, Branchinecta lindahli, and Thamnocephalus platyurus) and 10 chemicals with varying modes of toxic action: ammonia, potassium, chloride, sulfate, chromium(VI), copper, nickel, zinc, alachlor, and metolachlor. The same chemicals were tested in 48-h tests with other branchiopods (the cladocerans Daphnia magna and Ceriodaphnia dubia) and an amphipod (Hyalella azteca), and in 96-h tests with snails (Physa gyrina and Lymnaea stagnalis). Median effect concentrations (EC50s) for B. lynchi were strongly correlated (r2 = 0.975) with EC50s for the commercially available fairy shrimp species T. platyurus for most chemicals tested. Comparison of EC50s for fairy shrimp and EC50s for invertebrate taxa tested concurrently and with other published toxicity data indicated that fairy shrimp were relatively sensitive to potassium and several trace metals compared with other invertebrate taxa, although cladocerans, amphipods, and mussels had similar broad toxicant sensitivity. Interspecies correlation estimation models for predicting toxicity to fairy shrimp from surrogate species indicated that models with cladocerans and freshwater mussels as surrogates produced the best predictions of the sensitivity of fairy shrimp to contaminants. The results of these studies indicate that fairy shrimp are relatively sensitive to a range of toxicants, but Endangered Species Act-listed fairy shrimp of the genus Branchinecta were not consistently more sensitive than other fairy shrimp taxa. Environ Toxicol Chem 2017;36:797-806. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Investigating the Toxicity of the Aeruginosin Chlorosulfopeptides by Chemical Synthesis.

Harmful algal blooms are becoming more prevalent all over the world, and identification and mechanism-of-action studies of the responsible toxins serve to protect ecosystems, livestock, and humans alike. In this study, the chlorosulfopeptide aeruginosin 828A, which rivals the well-known toxin microcystin LR in terms of crustacean toxicity, has been synthesized for the first time. Furthermore, three congeners with different permutations of the chloride and sulfate groups were prepared, thereby enabling toxicity studies without the risk of contamination by other natural toxins. Toxicity assays with the sensitive crustacean Thamnocephalus platyurus demonstrated that the introduction of a sulfate group leads to pronounced toxicity, and NMR spectroscopic evidence suggests that the chloride substituent modulates the conformation, which in turn might influence protease inhibition.

Investigation of olive mill wastewater (OMW) ozonation efficiency with the use of a battery of selected ecotoxicity and human toxicity assays.

The effects of olive mill wastewater (OMW) on a battery of biological assays, before and during the ozonation process, were investigated in order to assess ozone's efficiency in removing phenolic compounds from OMW and decreasing the concomitant OMW toxicity. Specifically, ozonated-OMW held for 0, 60, 120, 300, 420, 540min in a glass bubble reactor, showed a drastic reduction of OMW total phenols (almost 50%) after 300min of ozonation with a concomitant decrease of OMW toxicity. In particular, the acute toxicity test primarily performed in the fairy shrimp Thamnocephalus platyurus (Thamnotoxkit F™ screening toxicity test) showed a significant attenuation of OMW-induced toxic effects, after ozonation for a period of 120 and in a lesser extent 300min, while further treatment resulted in a significant enhancement of ozonated-OMW toxic effects. Furthermore, ozonated-OMW-treated mussel hemocytes showed a significant attenuation of the ability of OMW to cause cytotoxic (obtained by the use of NRRT assay) effects already after an ozonation period of 120 and to a lesser extent 300min. In accordance with the latter, OMW-mediated oxidative (enhanced levels of superoxide anions and lipid peroxidation by-products) and genotoxic (induction of DNA damage) effects were diminished after OMW ozonation for the aforementioned periods of time. The latter was also revealed by the use of cytokinesis block micronucleus (CBMN) assay in human lymphocytes exposed to different concentrations of both raw- and ozonated-OMW for 60, 120 and 300min. Those findings revealed for a first time the existence of a critical time point during the OMW ozonation process that could be fundamentally used for evaluating OMW ozonation as a pretreatment method of OMW.

LETHAL EFFECTS OF PESTICIDES ON THE NAUPLII FAIRY SHRIMP, BRANCHINELLA THAILANDENSIS.

During agricultural activities, large amounts of insecticides and herbicides are used for controlling pests. The overspraying of pesticides may contaminate freshwater bodies, as well as having a significant effect on aquatic animals. To determine the potential risk of pesticides, the acute toxicity of insecticides and herbicides on the nauplii fairy shrimp, Branchinella thailandensis were evaluated. The organisms were exposed to different concentrations of insecticides (chlorpyrifos and carbaryl), and herbicides (paraquat and 2,4-D) for 24 h, after which the LC50 values were compared. The acute toxicity tests determined that the LC50 values of chlorpyrifos and carbaryl after 24 h were 0.00186 mg/L and 0.21 mg/L, respectively. For herbicides, paraquat and 2,4-D, the LC50 values were 0.11 mg/L and 27.91 mg/L. Therefore, chlorpyrifos insecticides were found to be more toxic than herbicides (2,4-D and paraquat) with regard to the nauplii fairy shrimp. The high toxicity of pesticides has a long-term, and potentially damaging effect on aquatic organisms in the application areas.

Chemical pollution and toxicity of water samples from stream receiving leachate from controlled municipal solid waste (MSW) landfill.

The present study was aimed to determine the impact of municipal waste landfill on the pollution level of surface waters, and to investigate whether the choice and number of physical and chemical parameters monitored are sufficient for determining the actual risk related to bioavailability and mobility of contaminants. In 2007-2012, water samples were collected from the stream flowing through the site at two sampling locations, i.e. before the stream׳s entry to the landfill, and at the stream outlet from the landfill. The impact of leachate on the quality of stream water was observed in all samples. In 2007-2010, high values of TOC and conductivity in samples collected down the stream from the landfill were observed; the toxicity of these samples was much greater than that of samples collected up the stream from the landfill. In 2010-2012, a significant decrease of conductivity and TOC was observed, which may be related to the modernization of the landfill. Three tests were used to evaluate the toxicity of sampled water. As a novelty the application of Phytotoxkit F™ for determining water toxicity should be considered. Microtox(®) showed the lowest sensitivity of evaluating the toxicity of water samples, while Phytotoxkit F™ showed the highest. High mortality rates of Thamnocephalus platyurus in Thamnotoxkit F™ test can be caused by high conductivity, high concentration of TOC or the presence of compounds which are not accounted for in the water quality monitoring program.

Environmental effects of soil contamination by shale fuel oils.

Estonia is currently one of the leading producers of shale oils in the world. Increased production, transportation and use of shale oils entail risks of environmental contamination. This paper studies the behaviour of two shale fuel oils (SFOs)--'VKG D' and 'VKG sweet'--in different soil matrices under natural climatic conditions. Dynamics of SFOs' hydrocarbons (C10-C40), 16 PAHs, and a number of soil heterotrophic bacteria in oil-spiked soils was investigated during the long-term (1 year) outdoor experiment. In parallel, toxicity of aqueous leachates of oil-spiked soils to aquatic organisms (crustaceans Daphnia magna and Thamnocephalus platyurus and marine bacteria Vibrio fischeri) and terrestrial plants (Sinapis alba and Hordeum vulgare) was evaluated. Our data showed that in temperate climate conditions, the degradation of SFOs in the oil-contaminated soils was very slow: after 1 year of treatment, the decrease of total hydrocarbons' content in the soil did not exceed 25 %. In spite of the comparable chemical composition of the two studied SFOs, the VKG sweet posed higher hazard to the environment than the heavier fraction (VKG D) due to its higher mobility in the soil as well as higher toxicity to aquatic and terrestrial species. Our study demonstrated that the correlation between chemical parameters (such as total hydrocarbons or total PAHs) widely used for the evaluation of the soil pollution levels and corresponding toxicity to aquatic and terrestrial organisms was weak.

The ecotoxicological evaluation of Cylindrospermopsis raciborskii from Lake Balaton (Hungary) employing a battery of bioassays and chemical screening.

Ecotoxicity of four Cylindrospermopsis raciborskii strains (ACT 9502, ACT 9503, ACT 9504, ACT 9505) isolated from Lake Balaton (Hungary) was evaluated in four aquatic bioassays including the Thamnocephalus platyurus acute lethality test; Daphnia magna acute immobilization assay; D. magna feeding inhibition assay and Danio rerio embryo developmental toxicity assay, assisted by chemical screening for known toxins by HPLC-MS. For reference, we analyzed in parallel the toxin content and toxic effects of two previously characterized toxin-producing strains: the Australian cylindrospermopsin producer AQS C. raciborskii and the anatoxins producer Oscillatoria sp. PCC 6506. Bioassays were used to evaluate the overall toxicity of the hydrophilic bioactive metabolites pool synthesized by the selected cyanobacteria. Chemical screening has proven that the ACT C. raciborskii extracts investigated did not contained cylindrospermopsins and anatoxins. The relative toxicity of the ACT C. raciborskii aqueous extracts observed in each bioassay was comparable to the effects recorded for the anatoxins producer PCC 6506 strain while toxicity values (EC50/LC50) calculated for the AQS extract were in general one order of magnitude lower. Concerning sublethal effects of ACT C. raciborskii extracts to the D. rerio embryogenesis, the general morphological abnormality observed was a significant retardation of development. Overall, our results suggest that C. raciborskii populating Lake Balaton produce metabolites with significant bioactive potencies. Therefore, continued investigation of these unknown compounds is required.

Toxicity of two types of silver nanoparticles to aquatic crustaceans Daphnia magna and Thamnocephalus platyurus.

Although silver nanoparticles (NPs) are increasingly used in various consumer products and produced in industrial scale, information on harmful effects of nanosilver to environmentally relevant organisms is still scarce. This paper studies the adverse effects of silver NPs to two aquatic crustaceans, Daphnia magna and Thamnocephalus platyurus. For that, silver NPs were synthesized where Ag is covalently attached to poly(vinylpyrrolidone) (PVP). In parallel, the toxicity of collargol (protein-coated nanosilver) and AgNO3 was analyzed. Both types of silver NPs were highly toxic to both crustaceans: the EC50 values in artificial freshwater were 15-17 ppb for D. magna and 20-27 ppb for T. platyurus. The natural water (five different waters with dissolved organic carbon from 5 to 35 mg C/L were studied) mitigated the toxic effect of studied silver compounds up to 8-fold compared with artificial freshwater. The toxicity of silver NPs in all test media was up to 10-fold lower than that of soluble silver salt, AgNO3. The pattern of the toxic response of both crustacean species to the silver compounds was almost similar in artificial freshwater and in natural waters. The chronic 21-day toxicity of silver NPs to D. magna in natural water was at the part-per-billion level, and adult mortality was more sensitive toxicity test endpoint than the reproduction (the number of offspring per adult).

Ecotoxicological assessment of silica and polystyrene nanoparticles assessed by a multitrophic test battery.

The acute ecotoxicity of different diameters of silica and polyethyleneimine polystyrene (PS-PEI) nanoparticles (NPs) was assessed on a test battery of aquatic organisms representing different trophic levels. Daphnia magna, Thamnocephalus platyurus, Pseudokirchneriella subcapitata and Vibrio fischeri, were employed in a series of standard acute ecotoxicity tests and work was complemented with two cytotoxicological end points on a rainbow trout gonadal cell line (RTG-2). Physico-chemical characterization of the NPs was performed in the different test media employed, using dynamic light scattering (DLS) and zeta potentiometry. In contrast to silica NPs exposure, for which no effect was observed for concentrations up to 1000 µg ml(-1) for all in vivo aquatic organisms tested, significant toxicity was detected after exposure to PS-PEI NPs at concentrations from 0.40 µg ml(-1) to 416.5 µg ml(-1). Differing sensitivities for each NP diameter for the different organisms were observed as: P. subcapitata≥D. magna>T. platyurus>V. fischeri. The effects observed were dependent in some cases on the NP size, a higher effect being observed for the larger NPs. Finally, cytotoxicity studies showed an effect at the highest concentrations for both sets of NPs which was greater in the case of the PS-PEI NPs. However, as agglomeration and sedimentation of the nanoparticles was observed at these concentrations, the cytotoxicity studies were found not to be a reliable ecotoxicity test model.

Seasonal alterations of landfill leachate composition and toxic potency in semi-arid regions.

The present study investigates seasonal variations of leachate composition and its toxic potency on different species, such as the brine shrimp Artemia franciscana (formerly Artemia salina), the fairy shrimp Thamnocephalus platyurus, the estuarine rotifer Brachionus plicatilis and the microalgal flagellate Dunaliella tertiolecta. In specific, leachate regularly collected from the municipal landfill site of Aigeira (Peloponissos, Greece) during the year 2011, showed significant alterations of almost all its physicochemical parameters with time. Further analysis showed that seasonal alterations of leachate composition are related with the amount of rainfall obtained throughout the year. In fact, rainfall-related parameters, such as conductivity (Cond), nitrates (NO(3)(-)), total nitrogen (TN), ammonium (NH(4)-N), total dissolved solids (TDS) and the BOD(5)/NH(4)-N ratio could merely reflect the leachate strength and toxicity, as verified by the significant correlations occurred among each of them with the toxic endpoints, 24 h LC(50) and/or 72 h IC(50), obtained in all species tested. According to the result of the present study, it could be suggested that the aforementioned leachate parameters could be used independently, or in combination as a low-cost effective tools for estimating leachate strength and toxic potency, at least in the case of semi-arid areas such as the most of the Mediterranean countries.

Landfill leachate toxicity removal in combined treatment with municipal wastewater.

Combined treatment of landfill leachate and municipal wastewater was performed in order to investigate the changes of leachate toxicity during biological treatment. Three laboratory A2O lab-scale reactors were operating under the same parameters (Q-8.5-10 L/d; HRT-1.4-1.6 d; MLSS 1.6-2.5 g/L) except for the influent characteristic and load. The influent of reactor I consisted of municipal wastewater amended with leachate from postclosure landfill; influent of reactor II consisted of leachate collected from transient landfill and municipal wastewater; reactor III served as a control and its influent consisted of municipal wastewater only. Toxicity of raw and treated wastewater was determinted by four acute toxicity tests with Daphnia magna, Thamnocephalus platyurus, Vibrio fischeri, and Raphidocelis subcapitata. Landfill leachate increased initial toxicity of wastewater. During biological treatment, significant decline of acute toxicity was observed, but still mixture of leachate and wastewater was harmful to all tested organisms.

Toxicity of copper oxide nanoparticle suspensions to aquatic biota.

Toxicity effects induced by nanosuspensions of CuO (<50 nm; Sigma-Aldrich) on macrophytic algae cells of Nitellopsis obtusa (96-h median lethal concentration [LC50]), microphytic algae Chlorella (30-min median inhibitory concentration [IC50]), shrimp Thamnocephalus platyurus (24-h LC50), and rotifer Brachionus calyciflorus (24-h LC50) were investigated. No substantial differences between the effects of nonsonicated and sonicated nCuO suspensions were observed. The particle size distribution analysis accomplished by the laser diffraction technique at suspension concentration from 3 to 100 mg/L revealed rapid (within 5 min) reagglomeration of the particles after the sonication. The observed adverse effects on N. obtusa cells may be attributed to nanoparticles per se, but not to ionic Cu, because neither chemical analysis nor biological testing (algae survival in the supernatants of suspensions) confirmed the presence of cupric ions in toxic amounts. Contrary to ionic Cu form, nCuO delayed the initial phase of N. obtusa cell membrane depolarization. Lethality tests with rewash demonstrated that the least used 5-min exposure in 100 mg/L nCuO sonicated suspension induced 70% mortality in charophyte cells after 8 d, whereas the rewash after a short exposure to a noticeably toxic concentration of Cu(2+) prevented cell mortality. The obtained data suggested the possible influence of a thick charophyte cell wall on the dynamics of nanotoxicity effects.

Acute toxicity of Roundup and carbosulfan to the Thai fairy shrimp, Branchinella thailandensis.

The potential risk of herbicides and insecticides sprayed near pools to non-target fairy shrimp has not been assessed in Thailand. The acute toxicity of Roundup (isopropylamine salt 48% w/v) herbicide and carbosulfan (2,3-dihydro-2,2-dimethylbenzofuran-7-yl (dibutylaminothio) methylcabamate 20% w/v) insecticide were evaluated in 6 hours, 12 hours, and 24 hours static bioassay using nauplii fairy shrimp, Branchinella thailandensis. Median lethal concentration (LC50) values were calculated after probit transformation of resulting data. Median 24 hours lethal concentrations were 0.319 and 0.702 ppm for Roundup and carbosulfan, respectively.

The effect of composition of different ecotoxicological test media on free and bioavailable copper from CuSO4 and CuO nanoparticles: comparative evidence from a Cu-selective electrode and a Cu-biosensor.

The analysis of (bio)available copper in complex environmental settings, including biological test media, is a challenging task. In this study, we demonstrated the potential of a recombinant Pseudomonas fluorescens-based biosensor for bioavailability analysis of CuSO4 and CuO nanoparticles (nano-CuO) in seventeen different ecotoxicological and microbiologial test media. In parallel, free Cu in these test media was analysed using Cu-ion selective electrode (Cu-ISE). In the case of CuSO4, both free and bioavailable Cu decreased greatly with increasing concentration of organics and phosphates in the tested media. A good correlation between free and bioavailable Cu was observed (r = 0.854, p < 0.01) indicating that the free Cu content in biological test media may be a reasonably good predictor for the toxicity of CuSO4. As a proof, it was demonstrated that when eleven EC50 values for CuSO4 from different organisms in different test media were normalized for the free Cu in these media, the difference in these EC50 values was decreased from 4 to 1.8 orders of magnitude. Thus, toxicity of CuSO4 to these organisms was attributed to the properties of the test media rather than to inherent differences in sensitivity between the test organisms. Differently from CuSO4, the amount of free and bioavailable Cu in nano-CuO spiked media was not significantly correlated with the concentration of organics in the test media. Thus, the speciation of nano-CuO in toxicological test systems was not only determined by the complexation of Cu ions but also by differential dissolution of nano-CuO in different test conditions leading to a new speciation equilibrium. In addition, a substantial fraction of nano-CuO that was not detectable by Cu-ISE (i.e., not present as free Cu-ions) was bioavailable to Cu-biosensor bacteria. Thus, in environmental hazard analysis of (nano) particulate materials, biosensor analysis may be more informative than other analytical techniques. Our results demonstrate that bacterial Cu-biosensors either in combination with other analytical/speciation techniques or on their own, may serve as a rapid (eco)toxicological screening method.