Algal toxicity of antibacterial agents used in intensive farming

The growth inhibiting effects of eight antibiotics used either therapeutically or as growth promoters in intensive farming on two species of micro algae, Microcystis aeruginosa (freshwater cyanobacteria) and Selenastrum capricornutum (green algae) were investigated. The effects of the antibiotics benzylpenicillin (penicillin G) (BP), chlortetracycline (CTC), olaquindox (O), spiramycin (SP), streptomycin (ST), tetracycline (TC), tiamulin (TI) and tylosin (TY) were tested in accordance with the ISO 8692 (1989) standard protocol. Algal growth was measured as increase in chlorophyll concentration by extraction with ethanol followed by measurement of fluorescence. Results were quantified in terms of growth rates using the Weibull equation to describe the concentration response relationship. The toxicity (EC50 value, mg/l) in alphabetic order were BP (0.006); CTC (0.05); O (5.1); SP (0.005); ST (0.007); TC (0.09); TI (0.003) and TY (0.034) for M. aeruginosa. BP (NOEC = 100); CTC (3.1); O (40); SP (2.3); ST (0.133); TC (2.2); TI (0.165) and TY (1.38) for S. capricornutum. In this investigation M. aeruginosa is found to be about two orders of magnitude more sensitive than S. capricornutum. It was observed that most of the compounds were unstable during the test period due to hydrolysis and photolysis.     

Effects of pulp mill chlorate on Baltic Sea algae

The long-term effects of pulp mill chlorate on different algal species of the Baltic Sea were studied in land-based model ecosystems simulating the littoral zone. Brown algae (Phaeophyta) exhibited an extraordinarily high sensitivity to chlorate and pulp mill effluents containing chlorate. All brown algal species ceased growth or showed major signs of toxicity at all concentrations tested, down to microgram per litre levels. EC50 levels for growth of Fucus vesiculosus were about 80-100 microg ClO3- litre(-1). Blue-green algae (Cyanophyta) were not deleteriously affected nor were green algae (Chlorophyta). The perennial and annual species of red algae (Rhodophyta) were also unaffected by the effluents. Diatoms did not show any sensitivity and phytoplankton (fresh- and brackish water) were particularly insensitive. A phanerogam, Zostera marina was also unaffected by the treatments.     

On the uptake and release of zinc (65Zn) in the growing alga Selenastrum capricornutum Printz

A Zn- and pH-buffered medium was used to study the accumulation of Zn in batch-cultured algae (Selenastrum capricornutum Printz.). All experiments were carried out using (65)Zn radiotracers, which were measured by gamma-ray spectrometry. Zinc was applied in the presence of nitrilotriacetic acid (NTA), leading to free Zn(2+) concentrations ranging from 4.2 x 10(-11) to 1.6 x 10(-7) mol litre(-1). During the 75-h experiments, the rates of Zn influx and efflux were determined, the latter with full consideration for algal growth rates. Algal growth stopped completely at a free Zn(2+) concentration of 1.6 x 10(-8) mol litre(-1). Initial Zn binding was determined and, based on free Zn(2+) concentrations, presented by the apparent dissociation constant K(diss) and capacity C as 4.6 x 10(-9) mol litre(-1) and 19.8 x 10(6) mol gDW(-1), respectively. The rate constant of Zn efflux could be calculated as a constant 0.021 +/- 0.003 h(-1), irrespective of the Zn concentrations applied. The rates of Zn influx were expressed by the V(max) and K(M) values as 3.3 x 10(-10) mol gDW(-1) s(-1) and 6.3 x 10(-9) mol litre(-1), respectively. These values, which are based on applied free Zn(2+) concentrations, are compatible with the operation of a high-affinity low-concentration carrier mechanism. The results suggest that, under the conditions applied, free Zn(2+) may be the most relevant Zn species for Zn uptake; furthermore, relative growth rate may be regarded as a relatively sensitive signal for Zn stress circumstances.     

Zinc acclimation and its effect on the zinc tolerance of Raphidocelis subcapitata and Chlorella vulgaris in laboratory experiments.

The effect of zinc acclimation of Raphidocelis subcapitata (syn. Selenastrum capricornutum) and Chlorella vulgaris on their sensitivity towards this metal was examined in a series of laboratory experiments. These two commonly used algal species were acclimated to 65 microg Zn/l and changes in zinc tolerance were monitored using standard growth inhibition tests. The chemically defined ISO medium was used as a control culture medium. Both species demonstrated a maximum increase in zinc tolerance of a factor of 3 after 100 days of acclimation. Shifts in the shape of the concentration-response curve due to acclimation were observed for R. subcapitata. Compared to non-acclimated algae, acclimated R. subcapitata exhibited higher growth rates in all zinc treatments as well as in the controls. This suggests that the use of ISO-medium results in sub-optimal growth due to zinc deficiency. These effects could not be demonstrated for C. vulgaris. The zinc tolerance of both species decreased significantly one week after returning the acclimated algae to control (ISO) medium. 72hEC50 values based on growth rate were two to four times higher than those calculated using biomass measurements. Algal toxicity test results, particularly if used for metal risk assessments, must not be conducted using nutrient deficient media.     

Surfactant (Genapol OX-80) toxicity to Selenastrum capricornutum

A non-ionic surfactant (Genapol OX-80) was proposed as a means of reducing destructive crayfish activity in rice. In order to study the toxicity of this product on algae, a test in accordance to the ISO 8692 protocol (1989) was performed. The growth inhibiting effect of the pure formulation of Genapol OX-80 was studied on Selenastrum capricornutum in the concentration range of 0.01-1.0 mg/l. The result indicated a 72 h EC50-value of 0.5 mg/l. The suggested field concentration of approximately 50 mg/l is therefore two orders of magnitude above the algal EC50-value. From our findings it is expected that the impact on the rice field algae will not be negligible.     

The impact of aluminium on green algae isolated from two hydrochemically different headwater streams, Bavaria, Germany

Two strains of green algae (Scenedesmus sp. and Chlorella sp.) have been isolated from two headwater streams differing in stream chemistry (Eger river: acidic, low alkalinity; Püttlach river: slightly alkaline, high alkalinity). In this study the growth response of these indigenous algae to increased concentrations of aluminium (Al) is investigated. A semi-continuous culture technique was used for Al-toxicity studies. Algal response was determined by calculating growth rates from turbidity and cell counts. Those Al-species which are well known to be toxic were estimated by equilibrium calculations using the WATEQ computer program (Truesdall & Jones, 1973). The pH-value of the culture media was usually pH=5, except for one of the test series. Tested concentrations ranged from c=4 to 220 micromol litre(-1). The isolated strains of green algae were highly sensitive to increased Al-concentrations. The strain isolated from the Püttlach river was more sensitive than the Eger river algae. A total growth inhibition occurs at Al-concentrations of c=4 micromol litre(-1) if the whole Al was added at once. If Al was added gradually into the growth media the response of the algae was delayed. This is due to Al-enrichment in cells. In our long term toxicity studies, growth inhibition occurs even at nearly neutral pH-conditions (pH=6.5) although Al toxicity is expected at pH-values less than pH=5.5. This new result confirms the need of long-term studies in continuous cultures under simulated natural conditions. This might be the only way to achieve valid conclusions about the fate and the toxicity of environmental pollutants.     

A multiple testing approach for hazard evaluation of complex mixtures in the aquatic environment: the use of diesel oil as a model

Traditional single species toxicity tests and multiple component laboratory-scaled microcosm assays were combined to assess the toxicological hazard of diesel oil, a model complex mixture, to a model aquatic environment. The immediate impact of diesel oil dosed on a freshwater community was studied in a model pond microcosm over 14 days: a 7-day dosage and a 7-day recovery period. A multicomponent laboratory microcosm was designed to monitor the biological effects of diesel oil (1.0 mg litre(-1)) on four components: water, sediment (soil + microbiota), plants (aquatic macrophytes and algae), and animals (zooplanktonic and zoobenthic invertebrates). To determine the sensitivity of each part of the community to diesel oil contamination and how this model community recovered when the oil dissipated, limnological, toxicological, and microbiological variables were considered. Our model revealed these significant occurrences during the spill period: first, a community production and respiration perturbation, characterized in the water column by a decrease in dissolved oxygen and redox potential and a concomitant increase in alkalinity and conductivity; second, marked changes in microbiota of sediments that included bacterial heterotrophic dominance and a high heterotrophic index (0.6), increased bacterial productivity, and the marked increases in numbers of saprophytic bacteria (10 x) and bacterial oil degraders (1000 x); and third, column water acutely toxic (100% mortality) to two model taxa: Selenastrum capricornutum and Daphnia magna. Following the simulated clean-up procedure to remove the oil slick, the recovery period of this freshwater microcosm was characterized by a return to control values. This experimental design emphasized monitoring toxicological responses in aquatic microcosm; hence, we proposed the term 'toxicosm' to describe this approach to aquatic toxicological hazard evaluation. The toxicosm as a valuable toxicological tool for screening aquatic contaminants was demonstrated using diesel oil as a model complex mixture.     

Acute toxicity of chlorophenols to earthworms using a simple paper contact method and comparison with toxicities to fresh water organisms

An acute toxicity test of chlorophenols on earthworms (Eisenia fetida) was performed using a simple paper contact method proposed by OECD testing guideline no. 207, that were applied as an earthworm toxicity test. The median lethal concentration, EC50, had significant correlation with logP(ow) (1-octanol/water partition coefficient) of the chemicals. The toxicity of chlorophenols on E. fetida was compared with toxicities for other species: an algae (Selenostrum capricornutum), a crustacean (Daphnia magna), and a fish (Oryzias latipes). It was found that the toxicity of chlorophenols was almost same for E. fetida and for fresh water organisms. These results suggest the possibility of drawing correlations between the effects of pollutants on living things in different environments, fresh water and soil.     

The impact of atrazine on lake periphyton communities, including carbon uptake dynamics using track autoradiography

Chlorophyll a, freshweight biomass, ash-free dry weight, cell numbers, species richness, community carbon uptake and species-specific carbon uptake were used to monitor the impact of atrazine (2 chloro-4-ethylamino-6-isopropylamino-s-triazine) on an in situ, enclosed periphyton community. Atrazine concentrations ranging from 0.08 to 1.56 mg litre(-1) were used during the 2 years of study. In both 1982 and 1983, there was a shift from a chlorophyte- to a diatom-dominated community. In 1982 the cyanobacterium Cylindrospermum stagnale and the chlorophyte Tetraspora cylindrica developed isolated colonies in the 1.56 mg litre(-1) treatment, indicating resistance to atrazine at this concentration. After atrazine exposure, community productivity was reduced by 21% to 82% in the low to high exposures, respectively. After day 21 productivity returned to control levels. It was shown, using track autoradiography, that the productivities of the larger algae Mougeotia sp., Oedogonium sp., Tolypothrix limbata and Epithemia turgida were the most affected, with reductions of 74.3% to 93.1% that of the controls. All the biotic measures indicated reduced growth after herbicide exposure.     

Effects of herbicides on two submersed aquatic macrophytes, Potamogeton pectinatus L. and Myriophyllum sibiricum Komarov, in a prairie wetland

Clopyralid, picloram, 2,4-D and a mixture of 2,4-D plus picloram, (Tordon 202C) were added to the water of 1 m square enclosures in a prairie wetland in Saskatchewan, Canada to produce concentrations of 0.01 and 0.1 mg active ingredient litre(-1). Effects on the submersed macrophytes, Potamogeton pectinatus and Myriophyllum sibiricum, were monitored by taking repeated measurements of plant weight, flower and tuber production and inspecting for injuries at 30 and 60 days after application. Clopyralid did not inhibit weight gain (growth) in either species, but stimulated growth and flowering by M. sibiricum at 0.01 mg litre(-1) and tuber production by P. pectinatus at both rates. The low rate of 2,4-D stimulated flowering by M. sibiricum and tuber production by P. pectinatus, whereas the high rate inhibited growth of M. sibiricum and injured both species. Picloram did not affect growth of either species, but injured M. sibiricum at both concentrations and inhibited flowering at 0.1 mg litre(-1). Tordon 202C at 0.1 mg litre(-1) caused reduced growth and flowering in M. sibiricum and injured both species; 0.01 mg litre(-1) also injured M. sibiricum. Mortality resulted only from Tordon 202C and 2,4-D. Field data are lacking to assess the extent to which submerged macrophytes in prairie ponds are exposed to harmful concentrations of herbicide from aerial spraying, drift from ground application, runoff or wind erosion of soil.     

Preliminary ecotoxicological characterization of a new energetic substance, CL-20

A new energetic substance hexanitrohexaazaisowurtzitane (or CL-20) was tested for its toxicities to various ecological receptors. CL-20 (epsilon-polymorph) was amended to soil or deionized water to construct concentration gradients. Results of Microtox (15-min contact) and 96-h algae growth inhibition tests indicate that CL-20 showed no adverse effects on the bioluminescence of marine bacteria Vibrio fischeri and the cell density of freshwater green algae Selenastrum capricornutum respectively, up to its water solubility (ca. 3.6 mg l(-1)). CL-20 and its possible biotransformation products did not inhibit seed germination and early seedling (16-19 d) growth of alfalfa (Medicago sativa) and perennial ryegrass (Lolium perenne) up to 10,000 mg kg(-1) in a Sassafras sandy loam soil (SSL). Indigenous soil microorganisms in SSL and a garden soil were exposed to CL-20 for one or two weeks before dehydrogenase activity (DHA) or potential nitrification activity (PNA) were assayed. Results indicate that up to 10,000 mg kg(-1) soil of CL-20 had no statistically significant effects on microbial communities measured as DHA or on the ammonium oxidizing bacteria determined as PNA in both soils. Data indicates that CL-20 was not acutely toxic to the species or microbial communities tested and that further studies are required to address the potential long-term environmental impact of CL-20 and its possible degradation products.     

TNT and 4-amino-2,6-dinitrotoluene influence on germination and early seedling development of tall fescue

Cost-effective and environmentally acceptable methods are needed to remediate munitions-contaminated soil. Some perennial grass species are tolerant of soil contaminants and may promote remediation because of their high water use and extensive fibrous root systems. The effects of 2,4,6-trinitrotoluene (TNT) and its reduction product, 4-amino-2,6-dinitrotoluene (4ADNT), on germination and early seedling development of tall fescue (Festuca arundinacea Schreb.) were determined. Tall fescue seeds were germinated in nutrient-free agar containing 0-60 mg TNT litre(-1) or 0-15 mg 4ADNT litre(-1). Germination decreased linearly as TNT concentration increased but was not significantly affected by 4ADNT at these concentrations. Concentrations less than 30 mg TNT litre(-1) or 7.5 mg 4ADNT litre(-1) had little effect on seedling growth and development. Higher TNT or 4ADNT concentrations substantially delayed seedling development, caused abnormal radicle tissue development, and reduced secondary root and shoot growth. Seedling respiration rates decreased linearly with increasing TNT concentration. Experiments indicate that tall fescue may be grown in soils that maintain soil solution concentrations of 30 mg TNT litre(-1) or less.     

Interactions between algae (Selenastrum capricornutum) and pesticides: implications for managing constructed wetlands for pesticide removal

This laboratory study examined the interactions between an algal species found in wetlands (Selenastrum capricornutum) and two agricultural pesticides (atrazine and lindane). Pesticide additions had a positive effect on the chlorophyll a concentrations of the treatments. The presence of algae decreased the aqueous persistence of both pesticides. It is speculated that the algae either provided sites for pesticide sorption or facilitated pesticide degradation.     

Effects of ammonia on periphytic communities

Laboratory tests were conducted to evaluate the chronic effects of ammonia on periphytic communities. Species richness of the protozoan component of these communities was affected at un-ionized ammonia concentrations of 相似文献   

Lethal and sublethal toxicity of 4-nonylphenol to the common mussel (Mytilus edulis L.)

The toxicity of nonylphenol to the common mussel (Mytilus edulis L.) has been determined in both semistatic and continuous flow test systems. The LC50 values obtained were for 96 h, 30 mg litre(-1); 360 h, 0.5 mg litre(-1); and 850 h, 0.14 mg litre(-1). Sublethal effects, manifested as decreased byssus strength and change of scope for growth, were obtained at a concentration as low as 0.056 mg litre(-1). Fertilization and early developmental success were not affected at the highest concentration tested (0.2 mg litre(-1)).     

The impact of inorganic tin on the planktonic cyanobacterium Synechocystis aquatilis: the effect of pH and humic acid

The influence of inorganic tin compounds on the unicellular cyanobacterium Synechocystis aquatilis was studied, and its dependence on changing pH of the surrounding medium and the presence of humic acid. Both Sn(II) and Sn(IV), used as chlorides (at the concentrations 1-10 mg litre(-1)), inhibit the growth and chlorophyll a content of the cyanobacterium cultures, but only under alkaline conditions. Generally, the observed tin toxicity increased with increase of metal concentration, time of exposure and pH value of the medium (in the range 7-9.8). Sn(II) seems to be more toxic than Sn(IV). At the lowest studied metal concentration (1 mg litre(-1)), Sn(II) caused a 36 and 40% decrease in growth and chl a content, respectively, after 96 h exposure at pH 9.8, while Sn(IV) caused even a slight increase of both physiological parameters (hormetic effect). Similar increases in growth and chl a content were also observed at a high Sn (II) and Sn(IV) concentration (10 mg litre(-1)), but only in cultures exposed to metal at pH 7. At high pH (9.8), 10 mg litre(-1) of Sn(II) and Sn(IV) significantly suppressed both the growth of the cyanobacterium (by 54.2 and 26.1%, respectively) and the chl a content in cultures (by 58.2 and 24%, respectively). Humic acid reduced the toxicity of tin towards the cyanobacterium. The observed effects of pH and complexing ligand on the inorganic tin toxicity are discussed in the context of changing, chemical metal speciation and bioavailability.     

Germination and seedling development of switchgrass and smooth bromegrass exposed to 2,4,6-trinitrotoluene

It is estimated that explosives contaminate approximately 0.82 million cubic metres of soil at former military installations throughout the US; major contaminants often include 2,4,6-trinitrotoluene (TNT) and its degradation products. At some sites, phytoremediation may be a viable option to incineration or other costly remediation treatments. Grasses may be particularly suited for remediation because of their growth habit and adaptability to a wide range of soil and climate conditions. We characterized the effects of TNT on germination and early seedling development of switchgrass and smooth bromegrass to evaluate their potential use on contaminated sites. Switchgrass and smooth bromegrass seeds were germinated in nutrient-free agar containing 0 to 60 mg TNT litre(-1). Smooth bromegrass germination decreased as TNT concentration increased, while switchgrass germination was unaffected by TNT. Concentrations up to 15 mg TNT litre(-1) did not affect switchgrass root growth rate, but bromegrass root growth was reduced at TNT concentrations above 7.5 mg litre(-1). At 7.5 mg TNT litre(-1), however, shoot growth rate was reduced in both species. Examination at 20-fold magnification revealed switchgrass radicles were unaffected by TNT, while smooth bromegrass radicles appeared slightly swollen. Results indicate switchgrass is more tolerant of TNT than smooth bromegrass, but the establishment of both species may be limited to soil containing less than 50 mg kg(-1) of extractable TNT.     

Comparative toxicity of effluents processed by different treatments in V79 fibroblasts and the algae Selenastrum capricornutum

The efficacy of ozonation and of photocatalysis processing in the treatment of pulp mill ECF (elementary chlorine free) bleaching and textile effluents was evaluated by determining total organic carbon reduction (TOC) and the toxicity. The chronic toxicity of the effluents was evaluated by the ability to inhibit the growth of algae Selenastrum capricornutum. Cultured hamster V79 fibroblasts were used to assess the cytotoxicity of effluents submitted to different detoxification processes. Two endpoints were measured in V79 cells: 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) reduction and neutral red uptake (NRU). Both treatment processes were able to reduce the TOC, although ozonization was less effective for pulp mill ECF bleaching. The pulp mill ECF bleaching and textile effluents reduced the growth of S. capricornutum by 39% and 27%, respectively. However, at the highest concentration tested, the textile effluents treated by photochemical process for 60 min showed increased cytotoxicity in V79 cells compared to the untreated effluent when assessed by the NRU and MTT reduction assays (increases of 30% and 40%, respectively). Pulp mill ECF bleaching effluent treated by ozonization had a similar cytotoxicity to that of untreated effluent in the NRU assay. In contrast, the MTT reduction assay indicated that effluents treated with ozone were around 20% more cytotoxic than untreated effluents. These results show that cultured fibroblasts may be useful for studying cellular responses to pollutants and may be included in tests to monitor the efficiency of effluent detoxification processes.     

Acceleration of catalase and peroxidase activities in Lemna minor L. and Allium cepa L. in response to low levels of aquatic mercury

The purpose of this study was to assess certain physiological responses of Lemna minor L. (duckweed) and Allium cepa L. (onion) to aquatic mercury at low concentrations. Following a 96-h exposure of plants to nutrient medium contaminated with known levels of mercuric chloride (HgCl(2)), 0.001 to 4 mg litre(-1) (0.0007 to 2.95 mg Hg litre(-1)) or methyl mercuric chloride (MeHgCl(2)), 0.0001 to 0.1 mg litre(-1) (0.0007 to 0.07 mg Hg litre(-1)), the physiological endpoints measured were the growth of fronds (Lemna minor) or roots (Allium cepa), and catalase and peroxidase activities in both plant assays. The EC(50) for HgCl(2) on the basis of the growth curve of Lemna minor was found to be 2.1 mg litre(-1). HgCl(2) and MeHgCl(2) were lethal to L. minor at concentrations of 4 and 0.01 mg litre(-1), respectively. The range of low concentrations that accelerated growth as well as enzymic activities in L. minor was 0.004 to 0.04 mg litre(-1) for HgCl(2) and 0.001 mg litre(-1) for MeHgCl(2). HgCl(2) and MeHgCl(2) induced maximum enzymic activity in Lemna fronds at concentrations of 0.008 and 0.0005 mg litre(-1), respectively. In Allium roots, catalase activity was accelerated at all the concentrations of HgCl(2) (0.001-2 mg litre(-1)) and MeHgCl(2) (0.0001-0.1 mg litre(-1)) tested. The activity of peroxidase was, however, accelerated by HgCl(2) at concentration range 0.01-1.0 mg litre(-1), or by MeHgCl(2) at 0.001 mg litre(-1). The concentrations of HgCl(2) and MeHgCl(2) that induced the highest enzymic activity in Allium roots were 0.05 mg litre(-1) and 0.001 mg litre(-1), respectively.     

The acute toxicity of phenol and unionized ammonia, separately and together, to the ephemeropteran Baetis rhodani (Pictet)

The acute toxicity of phenol and ammonia, singly and in combination, to larvae of the ephemeropteran, Baetis rhodani, was examined using a computerized continuous flow system in the laboratory. The 24 h LC50 values (with 95% confidence intervals) were calculated to be 29.9 (17.3-51.5) mg phenol litre(-1) and 8.2 (2.0-33.0) mg un-ionized ammonia litre(-1). When phenol and ammonia were together in low concentration (< 20 mg litre(-1) and < 3 mg litre(-1) [un-ionized], respectively), they expressed their toxicity additively, but at higher concentrations they behaved in a greater-than-additive manner. When the 24 h LC50 values were used to predict the toxicity of a coking plant effluent, containing principally ammonia and phenol, it was found that the B. rhodani larvae died quicker than expected indicating the presence of other toxic chemicals. This exemplifies the value of using direct toxicity assessments to detect the presence of unknown toxicants.