Green Alga Selenastrum Capricornutum Research Articles

Composition and some biological activities of the essential oil of Callicarpa americana (L.).

The essential oil profile of Callicarpa americana was examined. Samples were collected from Lafayette county in north central Mississippi, and GC-MS data and retention indices were used to identify 67 oil components. Humulene epoxide II (13.9%), alpha-humulene (10.0%), 7-epi-alpha-eudesmol (9.4%), beta-pinene (8.8%), and 1-octen-3-ol (8.5%) were the major components of the steam-distilled oil. The oil was selectively toxic toward the cyanobacterium Oscillatoria perornata compared to Oscillatoria agardhii and the green alga Selenastrum capricornutum, with complete growth inhibition at 28.5 microgram/mL. The oil was only mildly phytotoxic and antifungal.

CADMIUM AND ZINC BIOAVAILABILITY TO SELENASTRUM CAPRICORNUTUM (CHLOROPHYCEAE): ACCIDENTAL METAL UPTAKE AND TOXICITY IN THE PRESENCE OF CITRATE.

Toxicities of cadmium (Cd) and zinc (Zn) to the green alga Selenastrum capricornutum Printz were determined over 72 h in defined synthetic media buffered by citrate (FRAQCIT ; [citrate] = 100 μM or 5 μM) or nitrilotriacetate (FRAQNTA ; [NTA] = 5 μM). Algal sensitivity to free Cd2 + or free Zn2 + in FRAQCIT was much higher than in FRAQNTA . In parallel experiments, short-term intracellular uptake of radiolabeled 109 Cd was measured as a function of time (0-30 min) in FRAQCIT and FRAQNTA ; for a given free Cd2 + concentration (8, 250, or 610 nM), intracellular accumulation of Cd was consistently higher in FRAQCIT than in FRAQNTA . Under the same conditions, the alga accumulated 14 C-labeled citrate almost linearly over a 2-h period. Loss of 109 Cd from algal cells that had been prelabeled with the radionuclide occurred slowly, and the loss rate was insensitive to the presence or absence of citrate, indicating that the overall permeability of the algal membrane to Cd was unaffected by citrate. The enhanced bioavailability of Cd in the presence of citrate could be explained by membrane transport of a charged Cd-citrate complex, presumably by accidental transport.

A higher tier flow-through toxicity test with the green alga Selenastrum capricornutum

A flow-through test system for the assessment of the toxicity of substances to the green alga Selenastrum capricornutum was developed. The dosing of a test substance commenced, once the growth of the algae was in a steady state, i.e. when the dilution rate was equal to the growth rate. The growth rate and hence the effect of the test substance was determined indirectly by the estimation of cell number under consideration of inflow volume over time. The ease of manipulation of the exposure regime via digitally controlled pumps makes this flow-through system also suitable for testing substances under realistic exposure conditions or in combination with their metabolites. In this study the degradation of a herbicide and its metabolites was simulated. The substance with an ErC50 (72 h) of 1.3 μg/l under static conditions ( OECD, 1984) was tested in the developed flow-through system. The simulated degradation at an initial dose of 3 μg/l of the herbicide had no effect on algal growth, whereas under static test conditions, an NOErC of 0.28 μg/l was determined. The lowest concentration at which effects were observed was a continuous dose of 6 μg/l.

Dihydrophenanthrene and Phenanthrene Mimics of Natural Compounds—Synthesis and Antialgal Activity

9,10-Dihydrophenanthrenes and phenanthrenes, mimics of natural compounds with strong antialgal activity, have been synthesized through cross-coupling of 1-(2-iodo-5-methoxy)-phenylethanol with variously substituted iodobenzenes. The synthetic compounds, bearing a hydroxyl or a methoxyl group at C-2 and a methyl in the C ring, were tested against the green alga Selenastrum capricornutum. All compounds, except 2-methoxy-7-methylphenanthrene, caused inhibition of algal growth by more than 70% at 10−4 M, and many of them retained this strong activity at 10−5 M.

Canadian water quality guidelines for glycols-An ecotoxicological review of glycols and associated aircraft anti-icing and deicing fluids

This paper reviews the environmental fate, chemistry and toxicology of ethylene, propylene, and diethylene glycol, and their associated aircraft deicing/anti-icing fluids. Ethylene glycol is currently the most prevalent glycol in Canada with high volume production and primary uses in deicing fluid and antifreeze mixtures and minor uses in polyester manufacturing. Propylene glycol use in Canada is concentrated in resin and polyester production whereas diethylene glycol is primarily used as a dehydrator in the natural gas industry. Glycols are miscible in water, and have very low log Kow, and log Koc values, which make these substances highly mobile. Aerobic biodegradation is the most important environmental fate process affecting glycols in waters and soils with available information demonstrating low persistence. Canadian monitoring data is limited to ethylene glycol where it has been routinely detected in stormwater runoff at airports. Glycols have relatively low aquatic toxicity, with algae being more sensitive than vertebrates or invertebrates. The most sensitive response recorded for ethylene glycol exposure was a 96-h LOEC of 1923.4 mg L−1 for the green alga Selenastrum capricornutum. Aircraft deicing/anti-icing fluids were more toxic than pure glycols. The most sensitive recorded response was a 96-h LC50 of 18 mg L−1 for the fathead minnow Pimephales promelas, following exposure to a propylene glycol based anti-icing fluid. The review details the development and derivation of the Canadian Water Quality Guidelines for glycols, including numerical concentrations for the protection of aquatic life. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 481–522, 1999

Algal Toxicity of Antibacterial Agents Applied in Danish Fish Farming

Algal toxicity of antibacterial agents applied in fish farming was investigated. The growth-inhibiting effects of amoxicillin (A), flumequine (F), oxolinic acid (OA), oxytetracycline hydrochloride (OT), sarafloxacin hydrochloride (SF), sulfadiazine (SD), and trimethoprim (T) were investigated by a modified test procedure based on the procedure described in the ISO 8692 (1989) protocol on three algal species: the freshwater cyanobacteria Microcystis aeruginosa, the freshwater green alga Selenastrum capricornutum, and the marine cryptophycean Rhodomonas salina. Algal growth was measured as increased 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. M. aeruginosa showed higher sensitivity compared to both R. salina and S. capricornutum, whereas the results for the latter two were more or less identical. The toxicity (EC50 value, mg/L) in decreasing order were A (0.0037), SF (0.015), SD (0.135), F (0.159), OA (0.180), OT (0.207), and T (112) for M. aeruginosa; OT (1.6), OA (10), T (16), F (18), SF (24), SD (403), and A (3108) for R. salina; and OT (4.5), F (5.0), SD (7.8), OA (16), SF (16), T (130), and A (NOEC > 250) for S. capricornutum. Applying this test procedure the toxicity of antibacterial agents, being mono- or polyprotic compounds, may be underestimated because of partitioning between ionized and unionized forms.

Molecular structure and biochemical toxicity of four halogeno-benzenes on the unicellular green alga Selenastrum capricornutum

Comparative toxicity of hexachlorobenzene, 1,2,3-trichlorobenzene, bromobenzene, and chlorobenzene on the growth, protein concentration, ATP content and relevant enzyme activities of the unicellular green alga Selenastrum capricornutum was studied. Five typical molecular descriptive parameters: E homo, 1 χ v, K ow, E s, π x of these organic chemicals were selected to study the structure and bio-activities of the four halogeno-benzenes. The results indicated that the protein concentration, activities of G6PDH and AP, and ATP content were more sensitive to halogeno-benzenes than dry weight. Among the four halogeno-benzenes, the order of toxicity on the alga was: hexachlorobenzene>1,2,3-trichlorobenzene>bromobenzene>chlorobenzene. There was a good correlation between the molecular structure of halogeno-benzenes and their biochemical toxicity.

Effects of the sulfonylurea herbicide metsulfuron methyl on growth and macromolecular synthesis in the green alga Selenastrum capricornutum

The sulfonylureas (SU), are highly phytotoxic due to the inhibition of the enzyme acetolactate synthase (ALS), the key enzyme in the synthesis of branched-chain amino acids. In order to find a short-term algal test to be used as an indicator of the environmental toxicity of SU, the effects of the sulfonylurea metsulfuron methyl (MSM) in the green alga Selenastrum capricornutum were studied. As a comparison of long-term and short-term effects of MSM in Selenastrum, effects on growth were compared to short-term inhibition of protein synthesis and the synthesis of nucleic acids. The EC:50 for inhibition of growth of S. capricornutum by MSM was determined to be 4.1 μmol/l and the No Effect Concentration (NEC) to be between 0.1 and 0.2 μmol/l. The inhibition of growth could be substantially reduced by the addition of the branched chain amino acids and valine was especially important to restore growth. Protein synthesis measured as incorporation of [ 3H]methionine was, in spite of the shortage of amino acids, not inhibited by MSM in a short-term test. In contrast, the incorporation of [ 3H]adenine into cold-TCA-insoluble macromolecules, was inhibited by MSM, although maximal inhibition was restricted to about 50%. The No Effect Concentration for inhibition of adenine incorporation was 0.3 μmol/l, similar to the NEC value for growth inhibition. If alkaline hydrolysis was used to specifically hydrolyse RNA prior to the precipitation with cold TCA, a greater portion of the adenine incorporation could be inhibited by MSM. Adenine incorporation into nucleic acids seems to be appropriate for a short-term test of effects of SU on natural microbial communities, since adenine incorporation is quickly inhibited at concentrations of SU known to inhibit growth.

Toxic cell concentrations of three polychlorinated biphenyl congeners in the green algaSelenastrum capricornutum

Algal growth inhibition tests were performed with the unicellular green alga Selenastrum capricornutum and three 14C-labeled polychlorinated biphenyl (PCB) congeners. Toxicity was related to external aqueous concentrations and additionally to internal algal bound PCB concentrations. Estimates of the concentrations at 50% effectiveness (EC50s) for the three PCB congeners ranged within a factor of 17 (14–241 nmol/L) when based on measured aqueous concentrations. When based on internal toxicant concentrations (toxic cell concentrations, TCC50) the corresponding range was 6.7 to 14.3 mmol/kg wet weight. Thus, changing the basis from external to internal concentrations reduced the range by almost one order of magnitude. Additional toxic cell concentrations of five monoaromatic compounds and S. capricornutum were calculated from literature data to be in the same order of magnitude as the experimental toxic cell concentrations for the PCBs, whereas EC50 values for all substances ranged by more than four orders of magnitude. The experimental and calculated data indicate that observed differences in the estimated EC50 values were mainly due to differences in bioconcentration behavior rather than to different intrinsic toxicities. These findings are in agreement with the concept of baseline toxicity, meaning that a number of hydrophobic organics exerts their acute toxicity by one relatively nonspecific mode of action.

Influence of growth conditions on the results obtained in algal toxicity tests

AbstractThe influence of test conditions on results from algal growth inhibition tests was investigated for the toxicants atrazine, 3,4‐dichloroaniline, 3,5‐dichlorophenol, and potassium dichromate. Emphasis was put on the following four main factors: light, temperature, nitrogen source, and pH. The green alga Selenastrum capricornutum was grown in batch cultures, and the toxic response was measured as reduction in average growth rate, relative to controls. Multifactor experiments were carried out to investigate the effects of the above four factors as well as the interactions between them: light intensity (44 and 198 μE/m2/s), temperature (16 and 26°C), nitrogen source (NH and NO), and pH of the medium (7.5 and 8.6). Within the data set generated, the highest and lowest median effective concentration estimate differed by a factor of 3.8. The sensitivity of the test system to 3,4‐dichloroaniline, potassium dichromate, and 3,5‐dichlorophenol was less under light limitation than under light saturation. Conversely, with the photosynthetic inhibitor atrazine a reduced sensitivity was found at high light intensity, which, however, was high enough to cause slight photoinhibition. The inhibitory response to the weak organic acid 3,5‐dichlorophenol was less at the high than at the low pH level, which stems from the fact that neutral species of ionizable compounds are usually more toxic than charged species. No effect of the nitrogen source on inhibitory responses could be ascertained, and temperature influenced the results only indirectly by interacting with light (the saturation intensity increases with temperature). It is concluded that the light intensity in standardized algal toxicity tests could preferably be increased to achieve light‐saturated photosynthesis as this may potentially reduce test result variability.

Compounds with selective toxicity towards the off-flavor metabolite-producing cyanobacterium Oscillatoria cf. chalybea

Oscillatoria cf. chalybea produces the musty, off-flavor compound 2-methylisoborneol, which can taint the flesh of channel catfish and render them unmarketable. Green algae are preferred over cyanobacteria in aquaculture ponds since they do not produce 2-methylisoborneol and because they are better in maintaining the primary productivity in pond ecosystems. The discovery of compounds exhibiting selective toxicity towards cyanobacteria is the first step in the development of a cyanobacterial algicide that would benefit the channel catfish industry. Herbicides and other synthetic compounds were screened using a microplate bioassay to determine their toxicity towards the cyanobacterium O. cf. chalybea and the green alga Selenastrum capricornutum. Diquat, paraquat, and diuron were most inhibitory to the growth of O. cf. chalybea (0.1, 0.1, and 1.0 μM, respectively) but only diquat and paraquat were selectively toxic towards O. cf. chalybea. Bromoxynil, cinmethylin, diclofop, isoxaben, and sodium carbonate peroxyhydrate were selective, with complete growth inhibition towards O. cf. chalybea. Of these compounds, sodium carbonate peroxyhydrate appears to be the most environmentally and toxicologically safe for use in aquaculture. Sodium carbonate peroxyhydrate may not be selectively toxic against all species of cyanobacteria, as evidenced by our additional screening of the compound using another cyanobacterium, Anabaena sp.

Bioavailability of phosphorus in purified municipal wastewaters

The phosphorus (P) load from municipalities to surface waters can be markedly reduced using current wastewater treatment technology. However, the choice of optimal treatment method and assessment of the eutrophication caused by wastewaters are confounded by the unknown bioavailability of various P forms in the effluents. We estimated the potential bioavailability of total phosphorus (TP) and of three P fractions in 20 purified wastewater samples from five municipal treatment plants in Finland. All the plants had an activated sludge process and simultaneous P precipitation. In addition, two plants had a post precipitation unit and the others nitrified wastewater. On average 36% (0–67%) of TP in effluents was utilized by the green alga Selenastrum capricornutum Printz in bioassays lasting 2–4 weeks. If P became available according to first-order kinetics, the amount of P converted into an available form during an extended time frame was usually negligible. Dissolved reactive phosphorus (DRP) appeared to be entirely bioavailable, whereas only an average of 22% (0–74%) of dissolved unreactive phosphorus (DUP) and 25% (0–54%) of particulate phosphorus (PP) was utilized by algae. Higher relative and absolute amounts of P were generally available in the effluents from the nitrifying plants than from the post precipitation plants. In addition, when the capacity of a plant was exceeded, the concentration of bioavailable P in effluents appeared to increase. Our results suggest that TP alone is not a satisfactory criterion for use in eutrophication control measures of municipal P loading.

Influence of a low molecular weight metabolite (citrate) on the toxicity of cadmium and zinc to the unicellular green alga Selenastrum Capricornutum: An exception to the free-ion model

Toxicities of Cd and Zn to the chlorophyte Selenastrum capricornutum were determined in synthetic media buffered by 100 μmol·l −1 of NTA (FRAQ NTA or citrate (FRAQ CIT), or in unbuffered FRAQUIL medium (FRAQ). Metal speciation in these exposure media was adjusted so as to maintain constant free concentrations of Ca 2+, Mg 2+ and Me z+ even while the free Zn 2+ or Cd 2+ concentrations were varied. The growth response of the algae to variations in free Zn 2+ and free Cd 2+ was similar in FRAQ and FRAQ NTA media, but algal sensitivity to free Zn 2+ or free Cd 2+ increased markedly in FRAQ CIT medium. Addition of Zn to FRAQ, FRAQ NTA or FRAQ CIT media (0.02–2 μmol·l −1 free Zn 2+) caused a decrease in the algal growth rate, but the algae remained in exponential growth just as long as in the control (72 h). Similar results were obtained for exposures to Cd in FRAQ or FRAQ NTA media (0.01–0.9 μmol·1 −1) free Cd 2+), but additions of Cd to FRAQ CIT yielded anomalous growth curves (heightened sensitivity to Cd 2+ at low Cd levels; shortened period of exponential growth at high Cd levels). Short-term (6 min) intracellular uptake of radiolabelled 109Cd was measured in the three media containing the same free Cd 2+ concentration (0.25 μmol·l −1). Uptake of cadmium was more than 2-fold higher in FRAQ CIT than in the other two media. Under the same conditions, the algae could be shown to accumulate citrate; the measured uptake rate (83 pmol citrate·m −2·s −1) was about 4 times greater than that of Cd in the presence of citrate (21 pmol Cd·m −2·s −1)—the citrate transporter would only have to be fooled once every four transport events to account for the enhanced cadmium uptake in the presence of citrate. Our results clearly show that the bioavailability of Cd and Zn diverges from the predictions of the Free-Ion Model in the presence of a low molecular weight metabolite such as citrate—accidental or piggy-back uptake of the metal-ligand complex across the biological membrane is a plausible explanation for this enhanced availability.

Minor Bioactive Dihydrophenanthrenes from Juncus effusus

Seven new minor dihydrophenanthrenes have been isolated from Juncus effusus L. Structures have been defined by spectroscopic means. An antialgal assay, using the green alga Selenastrum capricornutum, showed good activity for six of them. The presence of both polar and nonpolar substituents in these molecules seems to be important for the bioactivity.

The effects of ultraviolet radiation on respiration and photosynthesis in two species of microalgae

The effects of ultraviolet (UV) radiation (310-400 nm) on respiratory activity and photosynthetic carbon assimilation of the cyanobacterium Aphanizomenon flos-aquae and the green alga Selenastrum capricornutum were examined. When exposed for 2 h to 100 or 550 µmol · m-2 · s-1 photosynthetically active radiation (PAR) supplemented with UV-A + UV-B radiation, the two organisms differed in their responses. Photosynthetic rates were depressed by 33-81% in A. flos-aquae but never by more than 25% in S. capricornutum. Rates of oxygen uptake by A. flos-aquae following UV exposure were similar to or less than rates achieved without UV treatment. In contrast,S. capricornutum exhibited a stimulation of oxygen consumption immediately after exposure to UV + high PAR compared with treatment with PAR alone. In A. flos-aquae, dark carbon losses were completely eliminated after the cells had been exposed to UV (irrespective of the levels of PAR). This effect was less marked in S. capricornutum. Respiratory electron transport chain activity in A. flos-aquae was initially stimulated following UV + PAR exposure but was slightly impaired in S. capricornutum. The results indicate that there is considerable interspecific variation in the response of autotrophic organisms to UV radiation and that these responses are modulated by the level of concomitant exposure to PAR.

増殖阻害試験に用いる供試藻類の栄養条件がモノクロラミンの毒性評価に及ぼす影響

The toxicity of monochloramine (NH2Cl), which is the main by-product of sewage effluent chlorination, was evaluated from growth inhibition in different condition of nutrients by a green alga Selenastrum capricornutum. The effect of NH2C1 on algal growth was depended on the nutrients condition, and nutrients limited algal cells were more sensitive than the non-limited cells. When using the nutrient-limited algal cells for the test organisms, lowest-observed-effect concentration (LOEC) and 50% effective concentration (EC50) after 96 hours exposed period were 0.001 and 0.002 mg-Cl2·l-1, respectively.The obtained LOEC and EC50 were lower than the water quality criteria for residual oxidants and the detection limit of oxidant determination. It is clear that chemical analysis is insufficient to monitor the various effluents. From these results, an algal growth test using the nutrient-limited algal cells is very sensitive and useful for the toxicity evaluation of disinfected effluents.

Identification of a copper-sensitive ascorbate peroxidase in the unicellular green alga Selenastrum capricornutum.

Extracts from the unicellular green alga Selenastrum capricornutum exhibit high superoxide dismutase activity, but only traces of catalase activity. The excess hydrogen peroxide (H2O2) generated by the superoxide dismutase in S. capricornutum may be degraded by a unique peroxidase. This peroxidase has a high specificity for ascorbate as its electron donor. The enzyme has an optimum pH at 8, is insensitive to cyanide and is inhibited by oxine. Addition of low concentrations of copper to algal cultures stimulates the peroxidase activity threefold. This enzymatic system could be used as a sensitive bioindicator for copper in fresh water.

Algal toxicity tests with volatile and hazardous compounds in air-tight test flasks with CO 2 enriched headspace

The application of an air-tight test flasks with a CO 2 enriched head space has been found useful for toxicity testing of volatile and hazardous chemicals with algae. The procedure has been demonstrated to perform well with the green algae Selenastrum capricornutum in tests of one or two days duration for a pH range of 7.0 – 8.5. The procedure makes it possible to maintain a constant pH as well as a constant and well defined concentration of test compound during the entire test. To ensure a sufficient carbon supply for exponential growth of the algae through the whole test period and to avoid pH increase due to bicarbonate utilization, the headspace of the test flask is enriched with I % or 2% CO 2 depending on the test duration, the algal growth rate and the inoculated algal density. The test medium is buffered with HCO 3 which is added to a (precalculated) concentration in equilibrium with the partial pressure of CO 2 in the head space at the end of the test, at the desired test pH. With 1 % CO 2, approximately 12.5 mM of [HCO 3 − (which is high) must be added to obtain the pH of 8.1 prescribed in the ISO 8692 standard procedure. Therefore it is suggested to perform the closed test at pH of 7. Results with the method are shown for phenanthrene, a moderate volatile PAH compound (H = 3.6·10 −5 atm·m 3/mole). The obtained EC10 and EC50 values were 10 times lower than those obtained with open test systems.

Action of antialgal compounds fromJuncus effusus L. onSelenastrum capricornutum

Twenty-nine free and glucosylated dihydrophenanthrenes and tetrahydropyrenes isolated fromJuncus effusus have been tested against the unicellular green algaSelenastrum capricornutum. The free compounds showed a strong inhibitory activity, while the glucosides were inactive or had a slight stimulating effect on growth. Tetrahydropyrene33, obtained by hydrolysis of the naturalβ-glucosides29 and30 or by hemisynthesis from1, is the most active compound, causing 90% inhibition of the growth at 2.5 × 10(-5) M concentration. Synthetic α-glucosides28, 31, and32 showed comparable activity to those of29 and30.

Comparative study of the effects of MCPA, butylate, atrazine, and cyanazine on Selenastrum capricornutum

The herbicides MCPA, butylate, atrazine and cyanazine are extensively used in Canadian agriculture and information regarding their effects on indigenous biota is scarce. Phytotoxicity assessments were conducted in the laboratory on the common green alga Selenastrum capricornutum using both the active ingredient of the herbicides and their formulated products (for MCPA and butylate). Endpoints determined after the 96 h exposure included algal population growth inhibition (IC 50—cell counts), percent lethality (LC 50—flow cytometry derived) and photosynthetic electron transport inhibition (EC 50—fluorescence induction). Pesticide formulations had greater toxic effects than the active ingredient alone. The 96 h IC 50 (50% Inhibition Concentration) and LOEC (Lowest Observable Effects Concentration) using cell counts of S. capricornutum were 18.4 and 8.9 mg l −1 respectively for MCPA-active ingredient and for MCPA-formulated, these were 0.62 and 0.0062 mg l −1 respectively. Those for butylateactive ingredient were 61.0 and 8.3 mg l −1 and for butylate-formulated 1.46 and 0.17 mg l −1, respectively. The triazines active ingredient, which are photosynthetic inhibitors, had greater effects than either the MCPA or butylate. The IC 50 for cyanazine and atrazine were 0.059 and 0.026 mg l −1, respectively. By comparing the IC 50 and LC 50 values for the tested active ingredients, it was found that the effects of atrazine were algicidal, whereas those of cyanazine, butylate and MCPA were algistatic.