Comparative toxicity of ten organic chemicals to ten common aquatic species

The susceptibilities of 10 aquatic organisms to 10 organic chemicals were determined using lethality tests. The species included six fishes, two crustaceans, a chironomid and an amphibian. The chemicals were selected to span the toxicity range from 26 g l⁻¹ to 1 μg l⁻¹ and include chemicals which were lethal by four modes of toxic action. There was no consistent relative susceptibility among the test species because the sensitivity to specific modes of toxic action varied among the chemicals. Nonetheless, the toxicities of the chemicals to any given species were highly correlated to the toxicities to other species, particularly among fishes. The 96-h median lethal concentration (LC₅₀) of the chemicals to rainbow trout (Salmo gairdneri) could be estimated from the 96-h LC₅₀ with fathead minnows (Pimephales promelas) with a correlation coefficient greater than 0.99. Equations for estimating the lethal concentration of chemicals with each species from the 96-h LC₅₀ for fathead minnows are presented.     

Comparison of chlorine and chlorine dioxide toxicity to fathead minnows and bluegill

The comparative toxicity of total residual chlorine (TRC) and chlorine dioxide (ClO₂) was evaluated by conducting 96 h flow-through bioassays with three types of fish. The fish were subjected to an intermittent exposure regime in which biocide residuals were present for approx. 2-h periods beginning at 0, 24, 48 and 72 h into the tests. These conditions simulated the antifouling procedure (1 h day⁻¹ biocide addition) used to control biofouling of nuclear reactor heat exchangers at the Savannah River Plant near Aiken, South Carolina. LC₅₀ values showed that ClO₂ was approx. 2–4 times more toxic than TRC to: (1) juvenile and 1-year-old fathead minnows (Pimphales promelas); and (2) young-of-the-year bluegill (Lepomis macrochirus).The TRC mean 96-h LC₅₀ values were: 0.08 mg l⁻¹ for juvenile fathead minnows, 0.35 mg l⁻¹ for adult fathead minnows and 0.44 mg l⁻¹ for young-of-the-year bluegills. The ClO₂ mean LC₅₀ values were: 0.02 mg l⁻¹ for juvenile fathead minnows, 0.17 mg l⁻¹ for adult fathead minnows and 0.15 mg l⁻¹ for young-of-the-year bluegills.     

Influence of potassium permanganate on chronic toxicity of cadmium to common carp,Cyprinus carpio,and aquatic ecosystem

Common carp Cyprinus carpio was chronically exposed to cadmium (2.5 mgL^‐1) and combined treatment of cadmium and KMnO₄ (1 mgL^‐1) for 90d in outdoor artificial enclosures. Although total and filtrable (dissolved) cadmium of water gradually decreased during the experiment whole body concentration of cadmium in common carp progressively increased in both treatments. Combination of KMnO₄ with cadmium marginally reduced the accumulation of cadmium during the initial periods (30 d) but failed to produce any impact on accumulation at the end of experiment (90 d). Cadmium treatment alone did not reduce the length and weight of fish, but there was abnormality in the length weight relationship. KMnO₄ alone and in combination with cadmium significantly reduced the length, weight and yield of fish. Limnological parameters were not affected by KMnO₄ alone, but combined treatment of Cd and KMnO₄ reduced the zooplankton and phytoplankton population, primary productivity of water and NPP/CR ratio. Judicious use of KMnO₄ in aquaculture to avoid toxic interaction with cadmium has been recommended.     

The reactions of chlorine dioxide with aquatic organic materials and their health effects

This review describes the main reactions that have been studied in water between chlorine dioxide and various groups of organic compounds. Although the reactions of ClO₂ with some model organic compounds have also been summarised, special emphasis has been given to the reaction products that were found in actual water plants treated with ClO₂ or under conditions closely related to these.Some conclusions were drawn with respect to the mechanism by which ClO₂ reacts with aquatic organic materials. As a result of the proposed reaction mechanisms a prediction was made as to which main organic products will be formed and which health effects may be expected.The last section of the review deals with the impact of ClO₂ on some kinds of organic micropollutants, such as pesticides and polycyclic aromatic hydrocarbons (PAH) which are often found in surface water sources and thus may also be found in drinking water.     

Interspecies correlations of toxicity to eight aquatic organisms: Theoretical considerations

Interspecies correlations allow the prediction of toxicity to a number of other species. However, little attention has been paid to the theoretical considerations of the interspecies relationship based on the differences of bio-uptake and toxic mechanism between species. This study examines the interspecies correlations of toxicity between species of Vibrio fischeri, river bacteria, algae, Daphnia magna, carp, Tetrahymena pyriformis, fathead minnow and guppy based on the theoretical background. The results show that there are good interspecies correlations between marine bacterium and fresh water bacteria or fish and fish. It is suggested that compounds share the same bio-uptake and toxic mechanism of action between the species. On the other hand, poor interspecies relationships were found between toxicities to algae and T. pyriformis or D. magna. It is suggested that compounds have different toxic mechanisms of action between these species. Interspecies relationships can be improved by inclusion of the octanol/water partition coefficient or the energy of the lowest unoccupied molecular orbital. They reflect the difference of bio-uptake or toxic mechanism of action between species for organic compounds. Benzoic acids show very different toxicity contributions to the three species, V. fischeri, D. magna and carp. They can be easily absorbed into the unicellular bacteria, V. fischeri. On the contrary, the skin and lipid content of multicellular organisms, such as D. magna and fish, can strongly inhibit the bio-uptake for ionizable compounds, which results in the different toxic effect between V. fischeri and D. magna or carp. Good correlation coefficients were observed between toxicities to V. fischeri and D. magna or fishes by inclusion of hydrophobic and ionization parameters. V. fischeri or D. magna can serve as a surrogate of fish toxicity for hydrophobic and ionizable compounds studied. Toxic mechanisms of action are discussed based on the theoretical background of the interspecies correlation.     

Acute toxicity of selected hydrazines to the common guppy

Hydrazine, unsymmetrical dimethylhydrazine (UDMH), Aerozine-50 and monomethylhydrazine were evaluated, respectively, in three or four static bioassays each using hard and soft water. Hydrazine was the most toxic compound and UDMH the least toxic to common guppies. Hydrazine was significantly more toxic in soft water than hard water, whereas UDMH was the opposite. The results of bioassays in which survival times of fish pre-exposed to these compounds were compared to those previously unexposed, along with other observations, indicate that the toxic effects of the hydrazines are cumulative. The effects of chemical differences in these compounds, of water quality characteristics and of other factors on acute toxicity are discussed.     

Effects of lead toxicity on the total chlorophyll content and growth changes of the aquatic plant Ceratophyllum demersum L.

This paper reports results of a laboratory-scale experiment conducted to determine the effects of different initial concentrations of a toxic heavy trace metal (lead) on the total chlorophyll (a + b) content of aquatic plant tissues Ceratophyllum demersum L., and also to monitor the visible growth changes during the experiment under different lead concentrations (2, 4 and 6 mg/L), as well as in control plants (without any addition of lead nitrate solution). Lead concentrations in water and plant samples were determined using AAS, where the total chlorophyll content in plant leaf tissues was measured every 15 days during the experimental period using a UV/VIS Spectrophotometer, Model 160A, Shimadzu, with wavelengths of 665 and 649 nm. The results showed that the content of total chlorophyll decreased noticeably, with increasing initial concentrations of lead throughout the exposure time. Decreases in total chlorophyll content in the tissues of C. demersum over the period of the experiment were accompanied by different morphological changes in the plants, depending on the initial lead concentration and exposure duration. These changes in morphology and growth affected the number and length of branches, the number of leaves and the number of leaflets.     

Review of selenium toxicity in the aquatic food chain

In many environmental contaminant situations selenium has become the primary element of concern because of its bioaccumulative nature in food webs. Initial concerns about selenium were related to fish kills at Belews Lake, NC, Martin Lake, TX, and Kesterson Reservoir, CA, and to bird deformities at Kesterson Reservoir. Additional concerns were identified under the National Irrigation Water Quality Program at Salton Sea, CA, Kendrick, WY, Stewart Lake, UT, and Grand Valley and Uncompahgre Valley, CO. Recent studies have raised concerns about selenium impacts on aquatic resources in Southeastern Idaho and British Columbia. The growing discomfort among the scientific community with a waterborne criterion has lead the US Environment Protection Agency to consider a tissue-based criterion for selenium. Some aquatic ecosystems have been slow to recover from selenium contamination episodes. In recent years, non-governmental researchers have been proposing relatively high selenium thresholds in diet and tissue relative to those proposed by governmental researchers. This difference in opinions is due in part to the selection of datasets and caveats in selecting scientific literature. In spite of the growing selenium literature, there are needs for additional research on neglected organisms. This review also discusses the interaction of selenium with other elements, inconsistent effects of selenium on survival and growth of fish, and differences in depuration rates and sensitivity among species.     

A toxicity testing system for exposing small invertebrates and fish to short square-wave concentrations of chlorine

We describe a flow-through toxicity testing system which can be manipulated to deliver a “square-wave” chlorine concentration curve for short exposure times to small invertebrates and fish. The system consists of a series of test containers, each with dual input delivery lines (dilution water alone or toxicant plus dilution water), a syringe pump for addition of toxicant to one of the two delivery lines, a constant head tank, and reservoir tanks. Control of valves on the delivery lines and on the test chamber drains caused chlorine concentration to rise to the target value in 1 min and to fall below detection limits (0.01 mg 1⁻¹) in 2 min at the beginning and end of the exposure period, respectively. Using this system, we determined the toxicity of 30- and 60-min exposures of total residual chlorine (85–95% free residual to Daphnia magna and Gambusia affinis. The 30- and 60-min LC 50 values were 0.097 and 0.063 mg 1⁻¹, respectively, for Daphnia and 1.59 and 0.84 mg 1⁻¹, respectively, for Gambusia. Use of this (or a similar) system can provide the readily comparable data base which is important for developing chlorine criteria for power plants.     

Effects of dissolved humic materials on acute toxicity of some organic chemicals to aquatic organisms

The influence of dissolved humic materials (DHM) on the acute toxicity of diazinon, tetrabromobisphenol-A (TBP), 4-chloroanilin (4-CA) and pentachlorophenol (PCP) was evaluated using the zebrafish (Brachydanio rerio Hamilton-Buchanan) and waterflea (Daphnia magna Straus). The 96-h LC₅₀ (zebrafish) and 48-h EC₅₀ values for four chemicals were determined in the presence of 0, 0.5, 5.0 and 50 TOC mg/l. The effects of DHM on the toxicity of four test chemicals to B. rerio were not observed in all of the DHM treatments. In the daphnid toxicity test, DHM significantly reduced the toxicity of diazinon and 4-CA, while no reduction of the toxicity of TBP and PCP was observed. These results indicate that the interaction between DHM and chemicals can alter the toxicity of some chemicals to D. magna.     

Biodegradability and toxicity of sulphonate-based surfactants in aerobic and anaerobic aquatic environments

Four types of commonly used sulphonate-based surfactants (alkane sulphonates, alpha-olefin sulphonates, sulphosuccinates and methyl ester sulphonates) were tested for their aerobic and anaerobic biodegradability as well as for their toxicity to Daphnia magna and Photobacterium phosphoreum to assess the effect of the surfactant structure on those properties. Aerobic biodegradation was evaluated by means of the CO₂ headspace test and anaerobic biodegradation was assessed by a method based on the ECETOC test. All the surfactants tested were readily biodegraded under aerobic conditions. No clear effect of the surfactant structures on the toxicity to the aquatic organisms tested was found. The most significant differences in the surfactants studied were observed in their behaviour under anaerobic conditions. Alkane sulphonates, alpha-olefin sulphonates and methyl ester sulphonates were not mineralized in lab anaerobic digesters despite the fact that the last one showed a certain degree of primary degradation. Nevertheless, these surfactants did not significantly inhibit methanogenic activity at concentrations up to 15 g surfactant/kg dry sludge, a concentration that is much higher than the expected concentrations of these surfactants in real anaerobic digesters. Sulphosuccinates showed a high level of primary biodegradation in anaerobic conditions. However, linear alkyl sulphosuccinates were completely mineralized whereas branched alkyl sulphosuccinates achieved percentages of ultimate biodegradation ≤50%.     

A two-species marine algal bioassay for detecting aquatic toxicity of chemical pollutants

A simple, rapid and sensitive two-species marine algal bioassay for determining the toxicity of chemical pollutants was developed. The bioassay employs the marine diatoms Phaeodactylum tricornutum (clone Phaeo) and Cyclotella cryptica (clone 03A), which were selected after screening 40 clones of 32 species for an optimum pair of organisms. These algae are easily grown in the laboratory, and the cells can be differentiated and counted with an electronic particle counter. Alteration of species ratio and/or total biomass were used to determine toxicity. Polychlorinated biphenyls (PCB, Aroclor 1254) at 10 parts per thousand million (10⁹; ptm) significantly altered species ratio in favor of Phaeo, and 10 ptm of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) and 20 ptm of dieldrin produced a significant species alteration opposite to that produced by PCB.     

Cyanobacteria diversity and toxicity in a wastewater treatment plant (Portugal)

Cyanobacteria are common in eutrophic natural waters. Being favoured by warm, stable and nutrient-enriched waters they may constitute an important part of the phytoplankton community in Wastewater Treatment Plants (WWTP). The phytoplankton communities of two ponds (facultative and maturation) of the WWTP of Esmoriz (North Portugal) were studied, with particular importance given to cyanobacteria. Mouse bioassays were performed with cyanobacteria samples during some of the blooms and ELISA assays specific for hepatotoxic microcystins were carried out. During the study period (January-July 1999) cyanobacteria were frequently dominant in the ponds ranging from 15.2 to 99.8% of the total phytoplankton density. The main species were Planktothrix mougeotii, Microcystis aeruginosa and Pseudanabaena mucicola. Mouse bioassays were performed during Oscillatoria bloom period but the results were negative, in spite of the high cyanobacteria biomass. ELISA assays were performed for both ponds but only in the maturation pond positive values were found. Microcystin concentrations (as MCYST-LR equivalents) varied from 2.3 to 56.0 micrograms/l on the margin of the pond and between 1.7 and 4.6 micrograms/l in the outflow of this pond. These values indicate that WWTP may be a source of contamination of water bodies with cyanobacteria toxins.     

An evaluation of mathematical models for the effects of pH and temperature on ammonia toxicity to aquatic organisms

Available data on the pH and temperature dependence of ammonia toxicity to aquatic organisms were examined and their agreement with various models was evaluated. A model which considers alteration of the relative concentration of un-ionized ammonia at the gill surface failed to adequately describe either pH or temperature dependence. A model that assumes that un-ionized ammonia and ammonium ion are jointly toxic was strongly supported by the data on pH dependence, but could not explain observed temperature dependence. Temperature dependence can be described empirically by a simple log-linear model. The effects of pH and temperature were generally found to be qualitatively and quantitatively similar among fish species.     

A method to measure total antioxidant capacity against peroxyl radicals in aquatic organisms: Application to evaluate microcystins toxicity

Determination of total antioxidant capacity, instead of the measurements of limited number of antioxidants, is very important for the understanding of how antioxidants interact with reactive oxygen species (ROS). Several techniques already exist with this propose, although some of them are extremely time-consuming. A new methodology is proposed, based on the detection of ROS by fluorometry (ex/em: 485/520 nm) employing 2′,7′-dichlorofluorescein diacetate (H₂DCF-DA) as substrate. Supernatant of homogenized samples from different organs (gill, muscle, liver, and brain) of the teleost fish Jenynsia multidentata (Anaplebidae) were exposed to peroxyl radicals generated by thermal (35 °C) decomposition of 2,2′-azobis (2 methylpropionamidine) dihydrochloride (ABAP, 4 mM). Different protein concentrations (0.5, 1, 2 and 8 mg/ml) were assayed to get the best signal and curve fitting of fluorescence data over time (30 min). Total antioxidant capacity against peroxyl radicals was estimated as the difference in ROS area with and without ABAP, relative to the fluorescence registered without ABAP. For application of this methodology, J. multidentata specimens were exposed for 24 h to microcystins, cyanotoxins known to induce oxidative stress. Almost all organs showed a lower antioxidant capacity (p < 0.05) in samples with 8 mg proteins/ml, when compared to protein content of 1-2 mg/ml. In liver samples, higher (p < 0.05) free iron content was determined in samples with 8 mg proteins/ml. Sensitivity test employing GSH spiked in homogenized samples showed the protocol efficiency in detecting total antioxidant capacity. In the test with microcystins a dose-dependent decrease (p < 0.05) of antioxidant competence in gills and brain and an inverse result with liver samples were observed. The use of antioxidant defenses was efficient in avoiding oxidative damage, as the content of oxidized proteins was not altered. Data obtained show the potential of this new methodology to be used in ecotoxicological studies.     

Reduction of aquatic toxicity of linear alkylbenzene sulfonate (LAS) by biodegradation

Partial biodegradation of LAS is shown to significantly reduce the specific toxicity (i.e. per unit weight) of the remaining LAS to Daphnia magna (water fleas) and Pimephales promelas (fathead minnows). This results from the fact that the longer homologs and more terminal isomers, which are the more toxic, are also the more rapidly degraded under bacterial action. The acute aquatic LC₅₀ of LAS may range from 0.5 to 50 mg/l depending mainly upon the chain length of the particular homolog. A high molecular weight commercial type LAS with LC₅₀ around 2 mg/l before biodegradation may show Daphnia LC₅₀'s of 30–40 mg/l. for the LAS remaining after 80–85% degradation.A further contribution to this toxicity reduction may occur if the methylene blue analytical method is used to determine the amount of LAS remaining, since some of the biodegradation intermediates show methylene blue activity but no significant toxicity. For example, sulfophenylundecanoate, a model of early intermediates, shows Daphnia and fathead lc₅₀'s 200 and 75 mg/l., respectively. Sulfophenylbutyrate, modeling somewhat later intermediates, gives lc₅₀ values around 5000–10,000 mg/l. Dialkyl tetralin/indane sulfonates (the major non-linear components in commercial LAS) exhibit 1/2–1/10 the toxicity of the corresponding LAS homologs.These results re-emphasize that analysis simply for methylene blue active substances (MBAS) gives no basis for predicting the aquatic toxicity of an environmental sample. And furthermore, that meaningful water quality criteria and standards cannot be established in terms of MBAS content while based on toxicity studies on intact, undegraded LAS.     

Release of copper from sintered tungsten-bronze shot under different pH conditions and its potential toxicity to aquatic organisms

Sintered tungsten-bronze is a new substitute for lead shot, and is about to be deposited in and around the wetlands of North America. This material contains copper in the alloyed form of bronze. This in vitro study was performed according to U.S. Fish and Wildlife Service criteria to determine the dissolution rate of copper from the shot, and to assess the toxic risk that it may present to aquatic organisms. The dissolution of copper from tungsten-bronze shot, pure copper shot, and glass beads was measured in a buffered, moderately hard, synthetic water of pH 5.5, 6.6, and 7.8 over a 28-day period. The dissolution of copper from both the control copper shot and the tungsten-bronze shot was affected significantly by the pH of the water and the duration of dissolution (all p values<0.000). The rate of copper release from tungsten bronze shot was 30 to 50 times lower than that from the copper shot, depending on pH (p<0.0000). The observed expected environmental concentration of copper released from tungsten-bronze shot after 28 days was 0.02 microg/L at pH 7.8, and 0.4 microg/L at pH 5.6, using a loading and exposure scenario specific in a U.S. Fish and Wildlife Service protocol. Ratio Quotient values derived from the highest EEC observed in this study (0.4 microg/L), and the copper toxic effect levels for all aquatic species listed in the U.S. Environmental Protection Agency ambient water quality criteria database, were all far less than the 0.1 criterion value. Given the conditions stipulated by the U.S. Fish and Wildlife Service and the U.S. Environmental Protection Agency, heavy loading from discharged tungsten-bronze shot would not pose a toxic risk to potable water, or to soil. Consequently, it would appear that no toxic risks to aquatic organisms will attend the use of tungsten-bronze shot of the approved composition. Given the likelihood that sintered tungsten-bronze of the same formula will be used for fishing weights, bullets, and wheel balance weights, it is expected that the use of this new material in these applications will not be associated with toxic risks to aquatic life.     

A simple continuous-flow toxicity test system for microscopic life stages of aquatic organisms

This paper describes a flow-through toxicity testing system utilizing a new exposure chamber designed for microscopic organisms. Typically, flow-through testing is conducted with either a serial or proportional diluting system. While generally relying on gravity to drive water flow, as different amounts of toxicant and diluent are combined in glass or plexiglass mixing cells, they are almost always open to the surrounding atmosphere. In contrast, the system described here is based on a simple exposure design utilizing premixed stocks representing each exposure concentration. While the system is entirely closed to the surrounding atmosphere, for testing of volatile organic mixtures in addition to nonvolatile inorganic toxicants, the delivery manifold may be aerated for toxicants of low volatility and high BOD. The system incorporates flexible Teflon gas sampling bags for stock preparation and storage (thus avoiding need for a headspace), and digital unified-drive peristaltic pumps for controlled toxicant delivery. To reduce surface partitioning of toxicants, all system components are constructed of chemically inert materials (Teflon, glass and silicone).     

The toxicity of aniline to rainbow trout

The acute lethal toxicity of aniline to rainbow trout was assessed, the fish being exposed for a maximum period of 1 week. The 7-day median lethal concentration was 8.2 mg l^?1 and the concentration/survival time relation was rectilinear over the period. A limited investigation into the physiological fate of the aniline is described; the amine moiety is detached and excreted as ammonia.The mammalian toxicology of aniline and mutagenic and teratogenic effects on fish ova, are reviewed.     

The fate of chlorine in sea-water

The consumption of hypohalite (or chlorine demand) in sea-water seems to occur in two phases. Residual chlorine concentration decreased rapidly within the first hour and noticeably slower afterwards. Total consumption of up to 3.3 ppm chlorine was observed within 30 h. The chlorine demand increased with increasing initial hypohalite concentrations and increasing time of contact. No limit of chlorine demand was observed. Data from ultra-violet spectroscopy suggest that the hypochlorite reacts with bromide ion to form hypobromite. The reaction is fast and seems to reach completion within 2.5 min. Hypobromite is thus the major species measured as residual chlorine which is consumed in sea-water. One of the products can liberate iodine from iodide at low pH (pH 1.4). This species, however, is not bromate and it decomposes with time. Further studies on the chemistry and toxicity of bromine containing species in chlorinated sea-water will be necessary in order to realize fully the environmental impact of the chlorination of sea-water.