Comparative Sensitivity of Freshwater Algae to Atrazine

No abstract available.     

Toxicity of Chlorate and Chlorite to Selected Species of Algae, Bacteria, and Fungi

The present study confirms that chlorate is toxic only to brown algae and not to species of other ecologically relevant taxa. The brown algaEctocarpus variabilisexhibited a LOEC of 0.005 mM (0.4 mg ClO⁻₃/liter) and an LC₅₀of 0.012 mM, when cultured with nitrate as a sole source of nitrogen. The toxicity to species other than brown algae as measured in growth inhibition tests ranged from 0.75 mM (96-h NOEC) forSelenastrum capricornutumto ≥7.48 mM (48-h NOEC) for the fungusTrichoderma hamatum. The nitrogen source, nitrate or ammonium, did not significantly influence the toxicity to the nonsensitive species. The tests on brown algae found that as compared with ammonium, the toxicity to nitrate-grown cultures is higher by a factor of about 10. This confirms the hypothesis that nitrate reductase is involved in the toxic effects of chlorate on brown algae. Chlorite, tested as a potential toxic metabolite of chlorate, demonstrated high toxicity to many of the taxa tested and only low toxicity toE. variabilis. It may be concluded that brown algae are exceptionally sensitive to chlorate. It may also be concluded that various nitrogen sources could not induce toxicity in nonsensitive species. From these experiments no conclusions could be drawn as to the potential role of chlorite in chlorate toxicity. Furthermore it may be concluded thatE. variabilisis a suitable laboratory test species for further investigations into the mechanism of chlorate toxicity to brown algae.     

Acute Toxicity of Hexavalent Chromium to European Freshwater Fish

No abstract available.     

Long-Term Toxicity of Gadolinium to the Freshwater Crustacean Daphnia magna

The lanthanides are considered emerging contaminants but information on their long-term toxicity to aquatic species under environmentally relevant conditions is scarce. We aimed to fill this gap by evaluating the long-term adverse effects of gadolinium on the freshwater model—crustacean Daphnia magna. The exposure of D. magna for up to 39 days to 0.1 mg Gd/L (a 21-days chronic toxicity NOEC value derived by us formerly) in the lake water had no negative effect (p?>?0.05) on vitality, size and reproduction of parent animals as well as their offspring. Thus, assumingly the current Gd contamination levels of surface waters pose no hazard to aquatic crustaceans that in general are very sensitive to various pollutants. Moreover, presence of 0.1 mg Gd/L in the lake water even mitigated the long-term toxic effect of 0.2 mg Ni/L (studied as a model co-contaminant) to D. magna’s vitality and productivity.

     

Chronic Toxicity of Ammonia to the Freshwater Bivalve Sphaerium novaezelandiae

The chronic toxicity of total ammonium and unionized ammonia (NH₃) to the native New Zealand freshwater fingernail clam Sphaerium novaezelandiae was assessed in soft water under laboratory conditions. Control survival after 60 days was high (93%) and concentration-response relationships showed the sensitivity of S. novaezelandiae survival was markedly greater to both total and unionized ammonia (6.4× and 4.6×) after 60 days compared with the 30-day exposure at 20°C. Chronic mortality and number moribund (inability to rebury) showed similar sensitivities, but reproduction was a more sensitive endpoint based on a concentration-response analysis. The survival LC50 values for total and unionized ammonia were 3.8 mg (N)/L (pH 7.5) and 0.037 mg (NH₃-N)/L, and reproductive values 0.80 mg (N)/L (pH 7.5) and 0.013 mg (NH₃-N)/L at 60 days. No observed effect concentration (NOEC) values for both survival and reproduction were 0.97 mg (N)/L and 0.011 mg (NH₃-N)/L, and the lowest observed effect concentration (LOEC) values were 5.4 mg (N)/L and 0.046 mg (NH₃-N)/L for survival after 60 days, giving a calculated threshold effect concentration (TEC) of 2.3 mg (N)/L and 0.022 mg (NH₃-N)/L. Comparison of the S. novaezelandiae chronic ammonia sensitivity data with the US EPA criteria showed the survival and reproduction TEC values for total ammonia were 1.9× higher than the chronic criterion, and the lethality value 1.4× above the unionized ammonia criterion. The findings suggest that use of the US EPA criteria would provide minimal protection for S. novaezelandiae for chronic ammonia exposure, and that development of site-specific criteria, covering a wide range of environmental conditions, may be required to adequately protect all life stages of this species. Received: 23 September 1996/Accepted: 27 July 1998     

Short-Term Toxicity and Binding of Platinum to Freshwater Periphyton Communities

The release of platinum (Pt) from automobiles equipped with exhaust catalysts has resulted in increasing concentrations of this normally rare metal in the urban and roadside environment. Although concentrations are increasing, little is known about the environmental effects of Pt and its potential toxicity. This study was an investigation of Pt toxicity to naturally grown periphyton communities. Periphyton communities were exposed to Pt(II) and Pt(IV) in reference and stream waters. Uptake increased linearly with Pt concentration for both reference- and stream-water exposure. However, decreased photosynthetic activity was observed only for reference-water exposure. This difference was related to uptake by biotic components in reference water and binding to abiotic components in stream water.     

Acute Toxicity of Synthetic Pyrethroid Cypermethrin to Some Freshwater Organisms

Ninety-six hours static bioassays were made in the laboratory to determine acute toxicity of cypermethrin to five non-target freshwater organisms belonging to different taxa and niche. Susceptibility of the organisms to cypermethrin was in the order: the crustacean Diaptomus forbesi > the aquatic insect Ranatra filiformis > the freshwater carp Cyprinus carpio > the tadpole larva of the toad Bufo melanostictus > the oligochaet worm Branchiura sowerbyi. Ninety-six hours LC50 values of aqueous cypermethrin ranged from 0.03 μg/L for the crustacean to 9.0 μg/L for the tadpole larva. The value was very high (71.12 μg/L) for the oligochaet worm. LC50 values changed with hours of exposure till 72 h after which cypermethrin became inactive in both aqueous and acetone solution. Acetone solution of cypermethrin was more toxic to B. sowerbyi, C. carpio and the tadpole larva. There was no significant difference in susceptibility of any other test organism between aqueous and acetone solution of cypermethrin.     

Experimental Factors That May Affect Toxicity of Cadmium to Freshwater Organisms

The effects of exposure duration, test organism, and test endpoint on the toxicity of cadmium to a variety of freshwater species were evaluated. Toxicity of cadmium was assessed by monitoring the survival and reproduction of Ceriodaphnia dubia Richard; the survival of Daphnia magna Straus; and the survival and growth of Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque. Organisms were exposed in static systems for 48 h, 96 h, 7 d, 10 d, and 14 d to determine acute and chronic toxicity. Relative sensitivities of test organisms exposed to aqueous cadmium varied with test duration and test endpoint. In general, H. azteca was the most sensitive organism tested, followed in decreasing sensitivity by P. promelas, C. dubia, D. magna, and C. tentans. Mortality of C. dubia and D. magna was consistent up to 7 d, after which little additional mortality occurred. Effects of test duration on cadmium toxicity were most pronounced for H. azteca and C. tentans, with mortality and growth becoming increasingly sensitive with increasing test duration. Received: 10 August 1996/Revised: 24 February 1997     

Cadmium Toxicity and Bioaccumulation in Freshwater Biofilms

A microcosm study was undertaken to examine the effects of dissolved cadmium at various concentrations (0, 10, and 100 μg · L⁻¹) on biofilm accumulation and diatom assemblages. A natural biofilm sampled from the Riou-Mort River (Southwest France) was inoculated into three experimental systems, where biofilm settled on glass slides. Samples collected after 1, 2, 4, and 6 weeks of colonization were analyzed for metal accumulation (total metal content and intracellular metal content in the biofilm), biomass (as measured through dry weight and ash-free dry matter), and quantitative as well as qualitative analysis of diatom assemblages. There was a positive correlation between cadmium accumulation and dissolved cadmium concentrations and duration of exposure: a linear relationship was found between concentration factors (CFs) of growing biofilms and time (CFs/day = 0.25 and 0.38 under contaminations of 10 and 100 μgCd · L⁻¹, respectively). Biofilm settlement, more than photosynthetic activity, was affected by high cadmium concentrations: we observed for all stages of settlement a drastic and significant (p < 0.05) reduction in biofilm biomass and in diatom densities in the highest cadmium contamination, compared to control and low cadmium concentration units.     

Mercury Toxicity to Freshwater Organisms: Extrapolation Using Species Sensitivity Distribution

Mercury toxicity to aquatic organisms was evaluated in different taxonomic groups showing the following species sensitivity gradient: Daphnia magna > Daphnia longispina > Pseudokirchneriella subcapitata > Chlorella vulgaris > Lemna minor > Chironomus riparius. Toxicity values ranged from 3.49 μg/L (48 h-EC₅₀ of D. magna) to 1.58 mg/L (48 h-EC₅₀ of C. riparius). A species sensitivity distribution was used to estimate hazardous mercury concentration at 5 % level (HC5) and the predicted no effect concentration (PNEC). The HC5 was 3.18 μg Hg/L and the PNEC varied between 0.636 and 3.18 μg Hg/L, suggesting no risk of acute toxicity to algae, plants, crustaceans and insects in most freshwaters.     

Impact of Atrazine on Chlorpyrifos Toxicity in Four Aquatic Vertebrates

Atrazine has been shown previously to potentiate chlorpyrifos toxicity in selected invertebrates. This study examined interactions of atrazine and chlorpyrifos in four aquatic vertebrates. Organisms were exposed to binary mixtures of atrazine and chlorpyrifos during toxicity bioassays. Inhibition of cholinesterase (ChE) enzyme activity and chlorpyrifos uptake kinetics were also examined with and without atrazine exposure. Atrazine alone did not affect organisms at concentrations up to 5000 μg/L; however, the presence of atrazine at 1000 μg/L did result in a significant increase in the acute toxicity of chlorpyrifos in Xenopus laevis. Mixed results were encountered with Pimephales promelas; some bioassays showed greater than additive toxicity, while others showed an additive response. No effect of atrazine on chlorpyrifos toxicity was observed for Lepomis macrochirus and Rana clamitans. Atrazine did not affect ChE activity or chlorpyrifos uptake rates, indicating that these toxicodynamic and toxicokinetic parameters may not be related to the mechanism of atrazine potentiation of chlorpyrifos toxicity. Based on the results of this study, it does not appear that a mixture toxicity of atrazine and chlorpyrifos at environmentally relevant concentrations presents a risk to the vertebrate organisms examined in this study.     

Acute Toxicity and Effects Analysis of Endosulfan Sulfate to Freshwater Fish Species

Endosulfan sulfate is a persistent environmental metabolite of endosulfan, an organochlorine insecticide–acaricide presently registered by the United States Environmental Protection Agency. There is, however, limited acute fish toxicity data for endosulfan sulfate. This study determines the acute toxicity (LC₅₀s and LC₁₀s) of endosulfan sulfate to three inland Florida native fish species (mosquitofish [Gambusia affinis]; least killifish [Heterandria formosa]; and sailfin mollies [Poecilia latipinna]) as well as fathead minnows (Pimephales promelas). Ninety-six-h acute toxicity tests were conducted with each fish species under flow-through conditions. For all of the above-mentioned fish species, 96-h LC₅₀ estimates ranged from 2.1 to 3.5 μg/L endosulfan sulfate. The 96-h LC₁₀ estimates ranged from 0.8 to 2.1 μg/L endosulfan sulfate. Of all of the fish tested, the least killifish appeared to be the most sensitive to endosulfan sulfate exposure. The above-mentioned data were combined with previous acute toxicity data for endosulfan sulfate and freshwater fish for an effects analysis. The effects analysis estimated hazardous concentrations expected to exceed 5, 10, and 50% of the fish species’ acute LC₅₀ or LC₁₀ values (HC₅, HC₁₀, and HC₅₀). The endosulfan sulfate freshwater-fish acute tests were also compared with the available freshwater-fish acute toxicity data for technical endosulfan. Technical endosulfan is a mixture of α- and β-endosulfan. The LC₅₀s had a wider range for technical endosulfan, and their distribution produced a lower HC₁₀ than for endosulfan sulfate. The number of freshwater-fish LC₅₀s for endosulfan sulfate is much smaller than the number available for technical endosulfan, reflecting priorities in examining the toxicity of the parent compounds of pesticides. The toxicity test results and effects analyses provided acute effect values for endosulfan sulfate and freshwater fish that might be applied in future screening level ecologic risk assessments. The effects analyses also discussed several deficiencies in conventional methods for setting water-quality criteria and determining ecologic effects from acute toxicity tests.     

A Qualitative Meta-Analysis Reveals Consistent Effects of Atrazine on Freshwater Fish and Amphibians

Objective

The biological effects of the herbicide atrazine on freshwater vertebrates are highly controversial. In an effort to resolve the controversy, we conducted a qualitative meta-analysis on the effects of ecologically relevant atrazine concentrations on amphibian and fish survival, behavior, metamorphic traits, infections, and immune, endocrine, and reproductive systems.

Data sources

We used published, peer-reviewed research and applied strict quality criteria for inclusion of studies in the meta-analysis.

Data synthesis

We found little evidence that atrazine consistently caused direct mortality of fish or amphibians, but we found evidence that it can have indirect and sublethal effects. The relationship between atrazine concentration and timing of amphibian metamorphosis was regularly nonmonotonic, indicating that atrazine can both accelerate and delay metamorphosis. Atrazine reduced size at or near metamorphosis in 15 of 17 studies and 14 of 14 species. Atrazine elevated amphibian and fish activity in 12 of 13 studies, reduced antipredator behaviors in 6 of 7 studies, and reduced olfactory abilities for fish but not for amphibians. Atrazine was associated with a reduction in 33 of 43 immune function end points and with an increase in 13 of 16 infection end points. Atrazine altered at least one aspect of gonadal morphology in 7 of 10 studies and consistently affected gonadal function, altering spermatogenesis in 2 of 2 studies and sex hormone concentrations in 6 of 7 studies. Atrazine did not affect vitellogenin in 5 studies and increased aromatase in only 1 of 6 studies. Effects of atrazine on fish and amphibian reproductive success, sex ratios, gene frequencies, populations, and communities remain uncertain.

Conclusions

Although there is much left to learn about the effects of atrazine, we identified several consistent effects of atrazine that must be weighed against any of its benefits and the costs and benefits of alternatives to atrazine use.