Sensitized photooxygenation of the fungicide furalaxyl

BACKGROUND: The photolysis of pesticides is of high current interest since light is one of the most important abiotic factors which are responsible for the environmental fate of these substances and may induce their conversion into noxious products. The action of light can also be mediated by oxygen and synthetic or naturally occurring substances which act as sensitizers. Our objective in this study was to investigate the photochemical behaviour of the systemic fungicide furalaxyl in the presence of oxygen and various sensitizers, and to compare the toxicity of the main photoproduct(s) to that of the parent compound. Previous reports on the direct photolysis of the pesticide demonstrated a very slow degradation and the only identified photoproducts were N-2,6-xylyl-D,L-alaninare and 2,6-dimethylaniline. METHODS: Solutions of furalaxyl in CH3CN were photooxygenate using a 500W high-pressure mercury lamp (through a Pyrex glass filter, lambda>300 nm) or a 650W halogen lamp or sunlight and the proper sensitizer. When sunlight was used, aqueous solutions were employed. The photodegradation was checked by NMR and/or GC-MS. The photoproducts were spectroscopically evidenced and, when possible, isolated chromatographically. Acute toxicity tests were performed on the rotifer Brachionus calyciflorus, the crustacean cladoceran Daphnia magna and the anostracan Thamnocephalus platyurus, while chronic toxicity tests (sublethal endpoints) comprised a producer, the alga Pseudokirchneriella subcapitata and the crustacean Ceriodaphnia dubia, as a consumer. RESULTS AND DISCUSSION: In the presence of both oxygen and sensitizer, furalaxyl underwent rapid photochemical transformations mainly to N-disubstituted formamide, maleic anhydride and a 2(5H)-furanone derivative. The formation of these products was rationalized in terms of a furan endoperoxide intermediate derived from the reaction of furalaxyl with active dioxygenated species (singlet oxygen, superoxide anion or ground state oxygen). The 2(5H)-furanone exhibited a higher toxicity than the parent compound. CONCLUSION: This work reports the first data on the photosensitized oxygenation of furalaxyl with evidence of the high tendency of the pesticide to undergo photodegradation under these conditions leading, among other things, to a 2(5H)-furanone, which is more toxic than the starting furalaxyl towards aquatic organisms. RECOMMENDATIONS AND OUTLOOK: Investigation highlights that the photolytic fate of a pesticide, although quite stable to direct photoreaction due to its low absorption of solar radiation at ground level, can be significantly influenced in the environment by the presence of substances with energy or electron-transfer properties as natural dyes, e.g. chlorophyll, or synthetic pollutants, e.g. polycyclic aromatic hydrocarbons (PAH).     

Phototransformation products of tamoxifen by sunlight in water. Toxicity of the drug and its derivatives on aquatic organisms

Transformation of tamoxifen has been observed in water by prolonged sunlight irradiation. The main photoproducts, isolated by chromatographic techniques, have been identified by spectroscopic means. Photoisomerization, photocyclization and, to a lesser extent, photooxygenation appear to be involved in the degradation of the drug. The acute and chronic toxicity of the parent drug and its photoproducts were tested on non-target aquatic organisms (Brachionus calyciflorus, Thamnocephalus platyurus, Daphnia magna and Ceriodaphnia dubia). Exposure to all the compounds induced mainly chronic effects without significant differences among the parental and derivative compounds.     

Toxicity on crustaceans and endocrine disrupting activity on Saccharomyces cerevisiae of eight alkylphenols

In the last few years many concerns have been raised regarding the environmental safety of alkylphenol polyethoxylate surfactants (APnEOs).They are widely used in detergents, paints, herbicides and many other formulated products. It has been estimated that 60% of APnEOs end up in the aquatic environment; they are biodegradable and transformed into alkylphenols, such as nonylphenol and octylphenol that are hydrophobic and tend to accumulate. In the present study, acute and chronic aquatic toxicity and the estrogenic activity of the following eight alkylphenols were assessed: 4-nonylphenol, 4-octylphenol, 4-nonylphenol-10-ethoxylate, 4-tert-octylphenol, POE (1 to 2)-nonylphenol, POE (6)-nonylphenol, POE (3)-tert-octylphenol and POE (9 to 10)-tert-octylphenol. The toxic potential was measured on the crustaceans Daphnia magna and Ceriodaphnia dubia, while the estrogenic activity was determined by using the YES-test with the strain Saccharomyces cerevisiae RMY326. The results showed that the exposure of crustaceans to the eight xenoestrogens investigated caused both acute and chronic effects. The EC50 values found for C. dubia at 48 h were compared to D. magna at 24h and, gave a first indication about the toxic activity of the compounds investigated, that is better expressed in the long-term. In fact, chronic data showed a strong increase in toxicity with EC50 values one or two orders of magnitude lower than the acute values. The results of the YES-test showed that nonylphenol, octylphenol and 4-tert-octylphenol were the most estrogenic and the bioassay was able to detect their estrogenicity at very low concentrations (ng-microg/l).     

Effects of the parasiticide ivermectin on the cladoceran Daphnia magna and the green alga Pseudokirchneriella subcapitata

Although widely used for the treatment of endo- and ectoparasites in livestock and pets, very few data on chronic effects on aquatic organisms are available for the parasiticide ivermectin. In the present study, toxicity of ivermectin to two freshwater organisms, the cladoceran Daphnia magna and the green alga Pseudokirchneriella subcapitata was investigated. For D. magna, a mean LC(50) 48 h of 5.7 ngl(-1) was derived from 10 acute tests. Chronic toxicity of ivermectin to D. magna was extremely high: with 0.001 and 0.0003 ngl(-1), respectively, nominal LOEC and NOEC based on growth and reproduction were far below the analytical limit of detection for this compound. P. subcapitata was considerably less sensitive to ivermectin than D. magna. For both growth rate and yield, EC(50) was >4,000 microgl(-1), LOEC was 1,250 microgl(-1) and NOEC 391microgl(-1). In view of the high toxicity to D. magna, the use of ivermectin might pose a risk to local aquatic ecosystems. Further studies should be carried out to investigate the effects of ivermectin and its degradation products on pelagic and benthic freshwater invertebrates.     

Transformation and Ecotoxicity of Carbamic Pesticides in Water (5 pp)

Background N-methylcarbamate insecticides are widely used chemicals for crop protection. This study examines the hydrolytic and photolytic cleavage of benfuracarb, carbosulfan and carbofuran under natural conditions. Their toxicity and that of the corresponding main degradation products toward aquatic organisms were evaluated. Methods Suspensions of benfuracarb, carbosulfan and carbofuran in water were exposed to sunlight, with one set of dark controls, for 6 days, and analyzed by 1H-NMR and HPLC. Acute toxicity tests were performed on Brachionus calyciflorus, Daphnia magna, and Thamnocefalus platyurus. Chronic tests were performed on Pseudokirchneriella subcapitata, and Ceriodaphnia dubia. Results and Discussion Under sunlight irradiation, benfuracarb and carbosulfan gave off carbofuran and carbofuran-phenol, while only carbofuran was detected in the dark experiments. The latter was degraded to phenol by exposure to sunlight. Effects of pH, humic acid and KNO3 were evaluated by kinetics on dilute solutions in the dark and by UV irradiation, which evidenced the lability of the pesticide at pH 9. All three pesticides and phenol exhibited acute and higher chronic toxicity towards the aquatic organisms tested. Conclusion Investigation on the hydrolysis and photolysis of benfuracarb and carbosulfan under natural conditions provides evidence concerning the selective decay to carbofuran and/or phenol. Carbofuran is found to be more persistent and toxic. Recommendations and Outlook The decay of benfuracarb and carbosulfan to carbofuran and the relative stability of this latter pesticide account for many papers that report the detection of carbofuran in water, fruits and vegetables.     

Hardness corrections for copper are inappropriate for protecting sensitive freshwater biota

Toxicity testing using a freshwater alga (Chlorella sp.), a bacterium (Erwinnia sp.) and a cladoceran (Ceriodaphnia cf. dubia) exposed to copper in synthetic and natural freshwaters of varying hardness (44-375 mg CaCO3/l), with constant alkalinity, pH and dissolved organic carbon concentration, demonstrated negligible hardness effects in the pH range 6.1-7.8. Therefore, the use of a generic hardness-correction algorithm, developed as part of national water quality guidelines for protecting freshwater biota, is not recommended for assessing the toxicity of copper to these, and other, sensitive freshwater species. Use of the algorithm for these sensitive species will be underprotective because the calculated concentrations of copper in water that cause a toxic effect will be higher.     

Toxicity of surfactants to green microalgae Pseudokirchneriella subcapitata and Scenedesmus subspicatus and to marine diatoms Phaeodactylum tricornutum and Skeletonema costatum

Ecotoxicity of different commercial surfactants (six anionic, two amphoteric and one nonionic), essential constituents of cleansing hair products (shampoos), as well as ecotoxicity of eight shampoos containing different combinations of these surfactants, were tested in order to evaluate their possible toxic effects on microalgae. Specific objective of this research was to compare the sensitivity of selected freshwater and marine microalgae to these widely used surfactants and well-known pollutants in surface waters. Internationally validated methods (ISO standards) for the determination of toxic effects on the growth of planktonic freshwater green algae Pseudokirchneriella subcapitata and Scenedesmus subspicatus and marine diatoms Skeletonema costatum and Phaeodactylum tricornutum, were used. The obtained results showed that the concentrations of tested surfactants and shampoos, which resulted in 50% growth reduction of planktonic freshwater green algae, when compared to the controls without test substances (EC50), were in the range from 0.32 to 4.4 mg l(-1) for surfactants and from 2.1 to 8.5 mg l(-1) for shampoos expressed as active substance. Marine diatoms were significantly more sensitive to the tested surfactants than freshwater green algae (EC50 0.14-1.7 mg l(-1) for surfactants and 0.35-1.25 mg l(-1) for shampoos). According to the classification on the basis of environmental effects, the obtained results suggested that all tested surfactants can be classified as having toxic effects on freshwater green alga Pseudokirchneriella subcapitata. Some of them indicated that they have a very toxic effect on Scenedesmus subspicatus and marine diatoms Skeletonema costatum and Phaeodactylum tricornutum.     

Influence of UV irradiation on the toxicity of phenylurea herbicides using Microtox test

Halogenated phenylurea herbicides are not very toxic by themselves to animals, but their exposure to UV light may significantly increase the toxicity of their solutions. Absorption of light may indeed induce a phototransformation of the herbicide with a possible formation of more toxic intermediate photoproducts. Fortunately in environmental conditions photolysis is usually slow and photoproducts do not accumulate appreciably. Microtox was used for the evaluation of the toxicity of the crude irradiated solutions of some phenylurea herbicides. The sharp initial increase of toxicity shown by metobromuron solutions is mainly due to intermediate photoproducts which rapidly disappear. In the case of diuron and metoxuron toxicity is due to minor photoproducts and it does not disappear so rapidly. Hence the decrease of herbicide concentration is not necessarily associated to a lower toxicity of the solution.     

Population-level toxicity of the insecticide, spinosad and the nonylphenol polyethoxylate, R-11, to the cladoceran species Ceriodaphnia dubia Richard

The effects of the natural insecticide, spinosad, and the agricultural adjuvant, R-11, were evaluated on populations of the water flea, Ceriodaphnia dubia after chronic 8-day exposures. The number of individuals used to start the chronic exposure studies (founders) and the number of offspring/surviving female were significantly reduced after exposure to spinosad concentrations ≥ 2.5 μg/L. The final number of individuals was significantly reduced after exposure to spinosad concentrations ≥ 1.0 μg/L. Population growth rate was significantly reduced after exposure to spinosad concentrations ≥ 1 μg/L. Extinction occurred (defined as negative population growth rate) after exposure to spinosad concentrations of 10 μg/L. Therefore, negative effects were observed in C. dubia after exposure to spinosad at a concentration near the chronic expected environmental concentration (EEC) of 2.3 μg/L. R-11 was much less toxic to C. dubia than spinosad. The number of founders was not significantly reduced until C. dubia were exposed to 12,000 μg/L. The number of offspring/surviving female, final number of individuals, and population growth rate were significantly reduced after exposure to R-11 concentrations ≥ 5,000 μg/L. Extinction occurred after exposure to R-11 concentrations of 12,000 μg/L which was above the EEC of 790 μg/L. These results indicate that spinosad and R-11 both have lethal and sublethal effects on C. dubia. However, spinosad appears to affect C. dubia at or near the EEC while R-11 does not negatively affect this species until concentrations are much higher than the EEC.     

Surface metal adsorption on zooplankton carapaces: implications for exposure and effects in consumer organisms

The current study aimed to determine the potential of two important aquatic invertebrate crustacean species, Daphnia magna and Ceriodaphnia dubia, to adsorb cadmium on to their carapaces from aqueous solution. Using the Langmuir equation to model data outputs, it was shown that cadmium readily became associated with the carapace surfaces of both species, with uptake being dependent on exposure time and concentration. Maximum carapace-adsorption potential was found to be directly related to surface area, so that at predicted carapace saturation, D. magna neonates bound approximately five times more cadmium than the smaller C. dubia neonates. However, adsorption per unit surface area was found to be similar under the same exposure conditions. Results of surface metal adsorption studies in C. dubia suggested that short term exposures to high concentrations of aqueous cadmium would lead to similar levels of adsorption as obtained with long-term exposures to low concentrations. The study illustrates that contaminants adsorbed to prey surfaces may be an important mechanism of exposure to predators, and highlights some potential problems of feeding organisms during long-term toxicity tests.     

Waterborne and sediment toxicity of fluoxetine to select organisms

Ecological risk assessments of pharmaceuticals are currently difficult because little-to-no aquatic hazard and exposure information exists in the peer-reviewed literature for most therapeutics. Recently several studies have identified fluoxetine, a widely prescribed antidepressant, in municipal effluents. To evaluate the potential aquatic toxicity of fluoxetine, single species laboratory toxicity tests were performed to assess hazard to aquatic biota. Average LC(50) values for Ceriodaphnia dubia, Daphnia magna, and Pimephales promelas were 0.756 (234 microg/l), 2.65 (820 microg/l), and 2.28 microM (705 microg/l), respectively. Pseudokirchneriella subcapitata growth and C. dubia fecundity were decreased by 0.044 (14 microg/l) and 0.72 microM (223 microg/l) fluoxetine treatments, respectively. Oryias latipes survival was not affected by fluoxteine exposure up to a concentration of 28.9 microM (8.9 mg/l). An LC(50) of 15.2 mg/kg was estimated for Chironomus tentans. Hyalella azteca survival was not affected up to 43 mg/kg fluoxetine sediment exposure. Growth lowest observed effect concentrations for C. tentans and H. azteca were 1.3 and 5.6 mg/kg, respectively. Our findings indicate that lowest measured fluoxetine effect levels are an order of magnitude higher than highest reported municipal effluent concentrations.     

The joint effects of sulfonamides and their potentiator on Photobacterium phosphoreum: differences between the acute and chronic mixture toxicity mechanisms

Organisms are typically exposed to mixtures of chemicals over long periods of time; thus, chronic mixture toxicity analysis is the best way to perform risk assessment in regards to organisms. However, most studies focus on the acute mixture toxicity. To investigate the difference between chronic mixture toxicity and acute mixture toxicity, Photobacterium phosphoreum were exposed to chronic (24 h exposure) and acute (15 min exposure) toxicity of single sulfonamide (SA) and their potentiator (trimethoprim, TMP), both individually and mixtures (SA with TMP). A comparison of chronic vs. acute mixture toxicity revealed the presence of an interesting phenomenon, that is, that the joint effects vary with the duration of exposure; the acute mixture toxicity was antagonistic, whereas the chronic mixture toxicity was synergistic. Based on the approach of Quantitative Structure Activity Relationships (QSARs) and molecular docking, this phenomenon was proved to be caused by the presence of two points of dissimilarity between the acute and chronic mixture toxicity mechanism: (1) the receptor protein of SAs in acute toxicity was Luc, while in chronic toxicity it was Dhps, and (2) there is a difference between actual concentration of binding-Luc in acute toxicity and individual binding-Dhps in chronic toxicity. This deep insight into the difference between chronic and acute mixture toxicity will benefit environmental science, medical science, and other disciplines. The existence of these differences poses a challenge for the assessment of routine combinations in medicine, risk assessment, and mixture pollutant control, in which, previously, only a synergistic effect has been observed between SA and their potentiator.     

Comparative study on the susceptibility of freshwater species to copper-based pesticides

Copper compounds have been intentionally introduced into water bodies as aquatic plant herbicides, algicides and molluscicides. Copper-based fertilizers and fungicides have been widely used in agriculture as well. Despite the fact that copper is an essential element for all biota, elevated concentrations of this metal have been shown to affect a variety of aquatic organisms. Nonetheless, comparative studies on the susceptibility of different freshwater species to copper compounds have seldom been performed. This study was conducted to compare toxicity of copper-based pesticides (copper oxychloride, cuprous oxide and copper sulfate) to different freshwater target (Raphidocelis subcapitata, a planktonic alga and Biomphalaria glabrata, a snail) and non-target (Daphnia similis, a planktonic crustacean and Danio rerio, a fish) organisms. Test water parameters were as follows: pH = 7.4 +/- 0.1; hardness 44 +/- 1 mg/l as CaCO3; DO 8-9 mg/l at the beginning and > 4 mg/l at the end; temperature, fish and snails 25 +/- 1 degrees C, Daphnia 20 +/- 2 degrees C, algae 24 +/- 1 degrees C. D. similis (immobilization), 48-h EC50s (95% CLs) ranging from 0.013 (0.011-0.016) to 0.043 (0.033-0.057) mg Cu/l, and R. subcapitata (growth inhibition), 96-h IC50s from 0.071 (0.045-0.099) to 0.137 (0.090-0.174) mg Cu/l, were the most susceptible species. B. glabrata (lethality), 48-h LC50s from 0.179 (0.102-0.270) to 0.854 (0.553-1.457) mg Cu/l, and D. rerio (lethality), 48-h LC50s 0.063 (0.045-0.089), 0.192 (0.133-0.272) and 0.714 (0.494-1.016) mg Cu/l, were less susceptible than Daphnia to copper-based pesticides. Findings from the present study therefore suggest that increased levels of copper in water bodies is likely to adversely affect a variety of aquatic species.     

Reduction in labile copper in the 7-day Ceriodaphnia dubia toxicity test due to the interaction with zooplankton food

Due to the increased popularity of zooplankton toxicity tests, it is important to investigate potential confounding factors. Though zooplankton food has been studied extensively to meet the nutritional needs of the zooplankton, less research has been done on whether food addition reduces the toxicity of metals in the tested sample. This investigation combines toxicity tests and metal speciation analysis to determine whether the EPA recommended food of YCT (yeast, cerophyll, and trout chow) and Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum) reduces copper toxicity by decreasing the concentration of labile copper. Toxicity tests were performed with Ceriodaphnia dubia on culture water spiked with 0, 787, and 1574 nM copper with five different food levels. A Chelex-100 cation exchange resin and a graphite furnace-atomic absorption spectrophotometer were used in conjunction with the toxicity tests to measure the amount of labile copper in the culture water. At the EPA recommended food dosage, the C. dubia food has a chelating capacity of approximately 500 nM Cu. For both concentrations of spiked culture water, the toxicity to C. dubia was reduced with increasing food level, which seemed to be both from a decrease in labile copper concentration and an increase in the nutritional condition of the zooplankton.     

Growth assays with mixed cultures of cyanobacteria and algae assessed by in vivo fluorescence: One step closer to real ecosystems?

A growth toxicity assay with mixed cultures of cyanobacteria and algae using in vivo fluorescence is presented. Test organisms (the green alga Pseudokirchneriella subcapitata and the cyanobacterium Aphanothece clathrata) growing alone and in a mixture were exposed to selected chemicals. P. subcapitata featured a higher sensitivity to toxicants in the presence of A. clathrata compared to the single species assay. On the other hand, growth of a cyanobacterium was not affected by the presence or absence of the green alga. The proposed method seems to be suitable for pre-screening studies of toxicants (algistatic agents, herbicides) applied into the aquatic environment and for the assessment of their impact on natural phytoplankton communities.     

Toxicity of water and sediment in a small urban river (Store Vejleå, Denmark)

The urban stream Store Vejle? (Denmark), which receives discharges of urban runoff, was investigated using a combination of biological toxicity tests and chemical analysis. The urban stormwater and road runoff gave low, but statistically significant, effects on the reproduction of the alga Pseudokirchneriella subcapitata. In all pre-concentrated water samples toxic effects were found and differences in toxicity depending on time and location of sampling were identified. Undiluted pore water samples from sediments collected in the stream were all toxic towards the algae and dilutions from 4 to 14 times were needed compared to a pore water sample from an unpolluted stream where a dilution factor of only 1.6 was required. A qualitative correlation between the toxicity of the pore water and the degree of pollution as evidenced by the metal concentration was observed, but statistically significant correlations could not be established by ranking procedures of, e.g. metal content or PAH-concentrations versus the observed toxicity.     

Integrated assessment of the impacts of agricultural drainwater in the Salinas River (California,USA)

The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California. Large areas of this watershed are cultivated year-round in row crops and previous laboratory studies have demonstrated that acute toxicity of agricultural drainwater to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. In the current study, we used a combination of ecotoxicologic tools to investigate incidence of chemical contamination and toxicity in waters and sediments in the river downstream of a previously uncharacterized agricultural drainage creek system. Water column toxicity was investigated using a cladoceran C. dubia while sediment toxicity was investigated using an amphipod Hyalella azteca. Ecological impacts of drainwater were investigated using bioassessments of macroinvertebrate community structure. The results indicated that Salinas River water downstream of the agricultural drain is acutely toxic to Ceriodaphnia, and toxicity to this species was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to H. azteca, which is a resident genus. Macroinvertebrate community structure was moderately impacted downstream of the agricultural drain input. While the lowest macroinvertebrate abundances were measured at the station demonstrating the greatest water column and sediment toxicity and the highest concentrations of pesticides, macroinvertebrate metrics were more significantly correlated with bank vegetation cover than any other variable. Results of this study suggest that pesticide pollution is the likely cause of laboratory-measured toxicity in the Salinas River samples and that this factor may interact with other factors to impact the macroinvertebrate community in the system.     

Algal tests with soil suspensions and elutriates: a comparative evaluation for PAH-contaminated soils

An algal growth inhibition test procedure with soil suspensions is proposed and evaluated for PAH-contaminated soil. The growth rate reduction of the standard freshwater green alga Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) was used as the toxicity endpoint, and was quantified by measuring the fluorescence of solvent-extracted algal pigments. No growth rate reduction was detected for soil contents up to 20 g/l testing five non-contaminated Danish soils. Comparative testing with PAH-contaminated soil elutriates and soil suspensions showed that the suspensions had toxicity endpoints 2.5-3000 times lower than tests with the corresponding elutriates. Algal growth inhibition tests with soil suspensions are recommended for screening purposes as a supplement to elutriate testing. Experiments with a phenanthrene-spiked soil, showed that the sorbed compound did not contribute to the toxicity. However, the soil did act as a reservoir for phenanthrene, allowing desorption to occur continuously during the algal test which maintained higher concentrations of phenanthrene in the dissolved phase. Phenanthrene-spiked soil incubated for 90 days before algal testing, resulted in a reduction of the toxicity to P. subcapitata by a factor of 76 (from EC10 = 0.3 to 23.6 g soil/l). However, during this 90-day period the total concentration of phenanthrene in the soil decreased by 38% (from 322 to 199 mg/kg) indicating that phenanthrene in the aged soil had become less bioavailable.     

Influence of glyphosate and its formulation (Roundup) on the toxicity and bioavailability of metals to Ceriodaphnia dubia

This study examined the toxicological interaction between glyphosate (or its formulation, Roundup) and several heavy metals to a freshwater cladoceran, Ceriodaphnia dubia. We demonstrated that all binary combinations of Roundup and metals (Cd, Cu, Cr, Ni, Pb, Se and Zn) exhibited "less than additive" mixture toxicity, with 48-h LC50 toxic unit > 1. Addition of glyphosate alone could significantly reduce the acute toxicity of Ag, Cd, Cr, Cu, Ni, Pb and Zn (but not Hg and Se). The ratio between glyphosate and metal ions was important in determining the mitigation of metal toxicity by glyphosate. A bioaccumulation study showed that in the presence of glyphosate the uptake of some metals (e.g. Ag) was halted but that of others (e.g. Hg) was increased significantly. Therefore, our study strongly suggests that glyphosate and its commercial formulations can control the toxicity as well as the bioavailability of heavy metals in aquatic ecosystems where both groups of chemicals can co-occur.     

Review of recent ecotoxicological studies on cladocerans

Cladocerans have been widely used as the bioassay organisms in evaluating the impact of different toxic substances. Literature survey during the last 10 years revealed that cladoceran ecotoxicological research has been in an exponential phase constituting nearly 10% of publications on this group. Many studies have considered typically planktonic taxa such as Daphnia magna, D. pulex, Moina macrocopa, M. micrura and Ceriodaphania dubia. Experimental data on toxicity tests, to a lesser extent, are also available for littoral-benthic genera such as Simocephalus, Macrothrix and Alona. Most toxicity tests are limited to the derivation of median lethal concentrations of various durations but mostly at 24 or 48 h. Studies related to the evaluation of changes in the life history variables of cladocerans as a result of sublethal exposure to toxic substances are not many, but gaining importance. The common toxic substances used in the cladoceran toxicity tests appear to be heavy metals, pesticides and a few natural toxins such as cyanotoxins. We review here the effect of different toxic substances on cladocerans based on both the field and the laboratory studies from an ecotoxicology point of view. Suggestions for the future cladoceran ecotoxicology are also commented on.