The Development of Marine Toxicity Identification Evaluation (TIE) Procedures Using the Unicellular Alga Nitzschia closterium

Unicellular algae are highly sensitive to a wide range of toxicants and have been used extensively in ecotoxicological testing. This, along with their ability to grow in very small test volumes over short test durations, make them ideal test organisms for use in Toxicity Identification Evaluations (TIEs). Despite this, microalgae have not previously been used in marine TIE studies. In this study, the marine diatom Nitzschia closterium was shown to be a highly suitable test organism after modification of the standard test protocol to reduce test volumes to 6 mL and test duration to 48 h. The alga was tolerant to the chemicals used in phase I of the standard USEPA TIE protocol, and physical TIE manipulations had no effect on algal growth. The cation exchange procedure, however, inhibited algal growth, while the anion exchange procedure stimulated growth, making these two procedures unsuitable for use with this species. Of the buffers trialed for the graduated pH procedure, 0.01 M PIPES buffer was found to be suitable for buffering at pH 7 because it maintained the required pH over the duration of the test and did not affect the growth or sensitivity of the algae to one reference toxicant (copper). A trial TIE on a secondary-treated sewage effluent for discharge into coastal waters showed that the developed protocols could successfully be used to identify ammonia as the major toxicant in the effluent.     

The Effect of pH on the Uptake and Toxicity of Copper and Zinc in a Tropical Freshwater Alga (Chlorella sp.)

Copper and zinc toxicity to the freshwater alga Chlorella sp. was determined at a range of pH values (5.5–8.0) in a synthetic softwater (hardness 40–48 mg CaCO₃/L). The effects of the metals on algal growth (cell division) rate were determined after 48-h exposure at pH 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. The toxicity of both metals was pH dependent. As pH decreased from 8.0 to 5.5, the copper concentration required to inhibit the algal growth rate by 50% (IC50) increased from 1.0 to 19 μg/L. For zinc, the IC50 increased from 52 to 2700 μg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu²⁺ and Zn²⁺ concentrations decreased with increasing pH, whereas toxicity was observed to increase. Measurements of extracellular (cell-bound) metal concentrations support the biotic ligand model (BLM) theory of competition between protons (H⁺) and metals for binding sites at the algal cell surface. Higher extracellular metal concentrations were observed at high pH, indicating reduced competition. Independent of pH, both extracellular and intracellular copper were directly related to growth inhibition in Chlorella sp., whereas zinc toxicity was related to cell-bound zinc only. These findings suggest that the algal cell surface may be considered as the biotic ligand in further development of a chronic BLM with microalgae. Conditional binding constants (log K) were determined experimentally (using measured intracellular metal concentrations) and theoretically (using concentration-response curves) for copper and zinc for Chlorella sp. at selected pH values. Excellent agreement was found indicating the possibility of using concentration-response data to estimate conditional metal-cell binding constants.     

Effects of Environmental Factors on the Uptake Rates of Dissolved Nitrogen by a Salt-water Green Alga (<Emphasis Type="Italic">Oocystis borgei</Emphasis> Snow)

Uptake rates for dissolved nitrogen (DN) by a marine alga (Oocystis borgei) were examined in a ¹⁵N tracer experiment. Maximal uptake rates for all forms of DN were observed at temperatures between 25 and 30°C and at algal concentrations between 3.22 × 10⁸ and 4.78 × 10⁸ cell L⁻¹. Light intensity required to achieve the maximal uptake rate was 45 μmol m⁻² s⁻¹ for dissolved inorganic nitrogen (DIN = NO₃ ⁻, NO₂ ⁻, NH₄ ⁺) and methionine, and 126 μmol m⁻² s⁻¹ for urea. Salinity required to achieve the maximal uptake rate was 12.85 ppt for DIN, 19.89 ppt for urea and 26.2 ppt for methionine.     

PAM Fluorometry in the Determination of the Sensitivity of Chlorella vulgaris, Selenastrum capricornutum, and Chlamydomonas reinhardtii to Copper

The pulse-amplitude-modulation (PAM) fluorometric method was used in the past as a sensitive and rapid method for assessing toxic effect of pollutants in plants. Here, we used the advantages of this method to evaluate the difference in sensitivity of Chlorella vulgaris, Selenastrum capricornutum, and Chlamydomonas reinhardtii to copper toxicity. We found by using the PAM-fluorescence parameters (φ_M, φ′_M, Q_P, and Q_N), that C. reinhardtii is the most sensitive species, followed by S. capricornutum and C. vulgaris. Indeed, the copper 5-, 48-, and 96-h EC₅₀ for φ_M, φ′_M, and Q_P vary between 11 and 34 μg/L for C. reinhardtii, while for S. capricornutum this value is between 25 and 50 μg/L. However, the same parameters obtained from C. vulgaris did not show susceptibility to copper, even at very high concentrations (100 μg/L). In this study, the estimated 5-h EC₅₀ for C. reinhardtii and S. capricornutum are lower than the 24-h EC₅₀ reported earlier for these species with other bioassays, indicating that the use of PAM fluorometry in copper bioassay provides a more sensitive method than the other biotests in aquatic toxicology. Received: 31 December 2000/Accepted: 5 August 2001     

A Comparison of the Relative Sensitivity of Structural and Functional Cellular Responses in the Alga Chlamydomonas eugametos Exposed to the Herbicide Paraquat

The effect of the herbicide paraquat on the freshwater microalga Chlamydomonas eugametos was studied in function of different parameters such as growth, elemental composition, total lipids, and photosynthetic pigments content and others assayed by flow cytometry (cell viability, cell volume, and granularity). The study reveals that paraquat concentrations above 0.15 μM are toxic for the microalga C. eugametos, inducing an inhibition of all the physiological parameters analyzed and strong structural changes. However, lower concentrations cause alterations in certain cellular components that are especially sensitive to the toxic action of the herbicide; so total lipids and photosynthetic pigments content are affected by concentrations such low as 0.037 μM. Taking into account these results, these parameters are better indicators of the cellular state than data on biomass or growth rate. Received: 29 May 1998/Accepted: 12 October 1998     

The NCI-N87 Cell Line as a Gastric Epithelial Model to Study Cellular Uptake,Trans-Epithelial Transport,and Gastric Anti-Inflammatory Properties of Anthocyanins

Abstract

Anthocyanins are ubiquitous plant pigments with reported antioxidant, anti-inflammatory, and anti-cancer activities. To better understand these benefits, metabolism of anthocyanins requires further evaluation, especially in the stomach. Mammalian cell cultures provide useful models for investigating compound metabolism and absorption, but they are generally maintained at physiological pH. The NCI-N87 cell line is an acid-stable model of the gastric epithelium used to study gastric drug metabolism. The objective of this work was to investigate the uptake, trans-epithelial transport, and anti-inflammatory activity of anthocyanins by the NCI-N87 cell line. The cells formed a coherent monolayer, stable ≤32?days post confluency. Minimal effects on monolayer integrity were observed when the pH of the apical chamber was adjusted to pH 3.0, 5.0, or 7.4. Anthocyanins were transported across the NCI-N87 cell monolayer at 37?°C, but not at 0?°C, suggesting a facilitated process. Chokeberry anthocyanins (0–1500?μM) were not cytotoxic. At apical pH 3.0, they had anti-inflammatory properties by significantly attenuating IL-8 secretion when added to medium before, during, and after incubation with IL-1β. These results suggest that the NCI-N87 cell line is a physiologically relevant model for in vitro studies of the transport, anti-inflammatory and potential anti-carcinogenic activities of anthocyanins in gastric tissue.     

Investigation of Concentrations of Paddy Herbicides and Their Transformation Products in the Sakura River, Japan, and Toxicity of the Compounds to a Diatom and a Green Alga

Four paddy herbicides and their transformation products (TPs) were monitored in the Sakura River, Japan, during the rice growing seasons of 2009 and 2010. Toxicity tests to an attached diatom, Mayamaea atomus, and a green alga, Pseudokirchneriella subcapitata, were also conducted. Clomeprop propionic acid, which forms from the degrading herbicide, was detected in the river water at much higher concentrations than the parent compound (the maximum concentration of the TP and the parent compound; 0.829–0.925 μg/L and 0.039–0.073 μg/L, respectively). The toxicity of the TPs to the diatom and green alga was relatively low; the 72-h median effective concentration (EC₅₀) value > 1,470 μg/L; for each compound, the maximum concentration in the river did not exceed the EC₅₀ value.     

Acute and Chronic Toxicity of Alcohol Ethoxylates to the Green Alga, Desmodesmus (=Scenedesmus) subspicatus, and the Subsequent Development of Structure Activity Relationships

No abstract available.     

The Hooded Crow (Corvus cornix) as an Environmental Bioindicator Species of Heavy Metal Contamination

This study aims to examine the possible presence of lead and cadmium in the liver and kidneys of hooded crows (Corvus cornix). Liver and kidneys of hooded crow carcasses were collected in Province of Cuneo (Piedmont, Italy) in order to detect lead and cadmium content. Significant differences were found in lead and cadmium levels between areas of intensive cultivation versus areas where meadows are prevalent. Moreover, age greatly influenced the burden of heavy metals, while sex did not seem to affect the level of contamination. The source of contamination may be phosphate fertilizers used for intensive cultivation in the study area.     

Metal accumulation in a biological indicator (Ulva rigida) from the lagoon of Venice (Italy)

Ulva rigida (C. Agardht) was collected from the Palude della Rosa (lagoon of Venice), a particular area characterized by a salinity gradient, from December 1991 to June 1993. Metal contents (Al, Mn, Fe, Cu, Zn, Cr, Co, Ni, Cd, and Pb) were determined by atomic absorption spectrophotometry and statistically analysed for differences between months and sampling sites. The mean seasonal variability is very significant (p<0.001) for all studied metals. Seasonal trends are comparable for groups of metals according to possible functional similarities. A significant positive correlation was calculated for the pairs Fe-Al and Fe-Pb. Mechanisms regulating metal uptake are discussed, particularly the role of Fe and its linear relationship with Al. Metal concentrations in relation to salinity also were studied. Larger amounts of Fe, Zn, and Cd accumulated in correspondence of lower salinity, may be owing to both higher metal activity and burden of bioavailable metals in freshwater flowing into the Palude. Calculation of concentration factor (CF) indicates that U. rigida specifically accumulates Fe. CF linearly correlates with dissolved metal concentrations, suggesting that U. rigida is a good bioindicator of metal bioavailability, although seasonal active accumulation occurs in some cases (Mn). Metal concentrations determined in this macroalga support the conclusion that the studied area is rich in bioavailable Fe and poor in toxic metals. In any case, a great affinity for Al in U. rigida may be proposed.