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Natasha M Franklin - One of the best experts on this subject based on the ideXlab platform.
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comparative toxicity of nanoparticulate zno bulk zno and zncl2 to a Freshwater microAlga pseudokirchneriella subcapitata the importance of particle solubility
Environmental Science & Technology, 2007Co-Authors: Natasha M Franklin, Simon C. Apte, Nicola J Rogers, Graeme E Batley, Gerald E Gadd, Philip S CaseyAbstract:Metal oxide nanoparticles are finding increasing application in various commercial products, leading to concerns for their environmental fate and potential toxicity. It is generally assumed that nanoparticles will persist as small particles in aquatic systems and that their bioavailability could be significantly greater than that of larger particles. The current study using nanoparticulate ZnO (ca. 30 nm) has shown that this is not always so. Particle characterization using transmission electron microscopy and dynamic light scattering techniques showed that particle aggregation is significant in a Freshwater system, resulting in flocs ranging from several hundred nanometers to several microns. Chemical investigations using equilibrium dialysis demonstrated rapid dissolution of ZnO nanoparticles in a Freshwater medium (pH 7.6), with a saturation solubility in the milligram per liter range, similar to that of bulk ZnO. Toxicity experiments using the Freshwater Alga Pseudokirchneriella subcapitata revealed c...
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the effect of ph on the uptake and toxicity of copper and zinc in a tropical Freshwater Alga chlorella sp
Archives of Environmental Contamination and Toxicology, 2006Co-Authors: Karyn L Wilde, Scott J. Markich, Jennifer L. Stauber, Natasha M Franklin, Paul L BrownAbstract: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 CaCO(3)/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 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) 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.
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toxicity of metal mixtures to a tropical Freshwater Alga chlorella sp the effect of interactions between copper cadmium and zinc on metal cell binding and uptake
Environmental Toxicology and Chemistry, 2002Co-Authors: Jennifer L. Stauber, Natasha M Franklin, Richard P Lim, Peter PetoczAbstract:The individual and combined effects of copper, cadmium, and zinc on the cell division rate of the tropical Freshwater Alga Chlorella sp. were determined over 48 to 72 h. Metal mixtures were prepared based on multiples of their single-metal median effective concentration (EC50) values, i.e., toxic units (TU) using a triangular mixture design with five toxicant levels (0, 0.75, 1.0, 1.25, and 1.5 TU). Single-metal EC50 values after a 72-h exposure were 0.11, 0.85, and 1.4 μM for copper, cadmium, and zinc, respectively. Significant interactions were observed for all metal combinations after 48 and 72 h. An equitoxic mixture of Cu 1 Cd was more than concentration additive (synergistic) to the growth of Chlorella sp., while combinations of Cu + Zn, Cd + Zn, and Cu + Cd + Zn were all less than concentration additive or were antagonistic. To determine the effect of each metal on the uptake of the other, extracellular (membrane-bound) and intracellular metal concentrations, both alone and in mixtures, were compared. The increased growth inhibition observed for mixtures of Cu + Cd was due to higher concentrations of cell-bound and intracellular copper in the presence of cadmium compared with copper alone (i.e., cadmium-enhanced copper uptake). In contrast, both extra- and intracellular cadmium concentrations were reduced in the presence of copper. In mixtures of Cu + Zn, copper also inhibited the binding and cellular uptake of zinc, which resulted in decreased toxicity. Zinc had no appreciable effect on the uptake of copper by Chlorella sp. Our results suggest that all three metals share some common uptake and transport sites on Chlorella cells and that copper out competes both cadmium and zinc for cell binding. Determination of metal cell distribution coefficients (Kd) confirmed that Kd values for cadmium and zinc in single-metal exposures decreased in the presence of copper.
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ph dependent toxicity of copper and uranium to a tropical Freshwater Alga chlorella sp
Aquatic Toxicology, 2000Co-Authors: Scott J. Markich, Jennifer L. Stauber, Natasha M Franklin, Richard P LimAbstract:Copper (Cu) and uranium (U) are of potential ecotoxicological concern to tropical Freshwater organisms in northern Australia as a result of mining activity. No local data on the toxicity of these metals to tropical Freshwater Algae are currently available. The aim of this study was to investigate the effect of pH (5.7 and 6.5) on the toxicity of Cu and U to the green Alga Chlorella sp. in a synthetic softwater representative of fresh surface waters in sandy-streams of tropical northern Australia. The effects of Cu and U on Algal growth (cell division) rate after a 72-h exposure were determined. Intracellular and extracellular (membrane-bound) metal concentrations at the two selected pH values were also compared. Based on the 72-h minimum detectable effect concentrations (MDEC), Chlorella sp. was approximately 20-fold more sensitive to Cu (0.7 and 1.4 µg l(-1) at pH 6.5 and 5.7, respectively) than U (13 and 34 µg l(-1) at pH 6.5 and 5.7, respectively), and more sensitive than other Australian tropical Freshwater organisms. The toxicity of Cu and U was highly pH-dependent. Copper concentrations required to inhibit growth (cell division) rate by 50% (72-h EC(50)) increased from 1.5 to 35 µg l(-1) as the pH decreased from 6.5 to 5.7. Similarly, the 72-h EC(50) values for U increased from 44 to 78 µg l(-1) over the same pH range. Calculation of Cu and U speciation using the geochemical model HARPHRQ, showed that differences in the concentrations of the free metal ions (Cu(2+) and UO(2)(2+)) were only minimal (<10%) between pH 5.7 and 6.5. The decreased toxicity at pH 5.7 was due to lower concentrations of cell-bound and intracellular Cu and U compared to those at pH 6.5. These results are explained in terms of the possible mechanism of competition between H(+) and the metal ion at the cell surface.
Eduardo V Soares - One of the best experts on this subject based on the ideXlab platform.
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chronic exposure of the Freshwater Alga pseudokirchneriella subcapitata to five oxide nanoparticles hazard assessment and cytotoxicity mechanisms
Aquatic Toxicology, 2019Co-Authors: Catia A Sousa, Helena M V M Soares, Eduardo V SoaresAbstract:Abstract The increasing use of nanoparticles (NPs) unavoidably enhances their unintended introduction into the aquatic systems, raising concerns about their nanosafety. This work aims to assess the toxicity of five oxide NPs (Al2O3, Mn3O4, In2O3, SiO2 and SnO2) using the Freshwater Alga Pseudokirchneriella subcapitata as a primary producer of ecological relevance. These NPs, in OECD medium, were poorly soluble and unstable (displayed low zeta potential values and presented the tendency to agglomerate). Using the Algal growth inhibition assay and taking into account the respective 72 h-EC50 values, it was possible to categorize the NPs as: toxic (Al2O3 and SnO2); harmful (Mn3O4 and SiO2) and non-toxic/non-classified (In2O3). The toxic effects were mainly due to the NPs, except for SnO2 which toxicity can mainly be attributed to the Sn ions leached from the NPs. A mechanistic study was undertaken using different physiological endpoints (cell membrane integrity, metabolic activity, photosynthetic efficiency and intracellular ROS accumulation). It was observed that Al2O3, Mn3O4 and SiO2 induced an algistatic effect (growth inhibition without loss of membrane integrity) most likely as a consequence of the cumulative effect of adverse outcomes: i) reduction of the photosynthetic efficiency of the photosystem II (ФPSII); ii) intracellular ROS accumulation and iii) loss of metabolic activity. SnO2 NPs also provoked an algistatic effect probably as a consequence of the reduction of ФPSII since no modification of intracellular ROS levels and metabolic activity were observed. Altogether, the results here presented allowed to categorize the toxicity of the five NPs and shed light on the mechanisms behind NPs toxicity in the green Alga P. subcapitata.
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toxic effects of nickel oxide nio nanoparticles on the Freshwater Alga pseudokirchneriella subcapitata
Aquatic Toxicology, 2018Co-Authors: Catia A Sousa, Helena M V M Soares, Eduardo V SoaresAbstract:Abstract Over the last decade, concerns have been raised regarding the potential health and environmental effects associated with the release of metal oxide nanoparticles (NPs) into ecosystems. In the present work, the potential hazards of nickel oxide (NiO) NPs were investigated using the ecologically relevant Freshwater Alga Pseudokirchneriella subcapitata. NiO NP suspensions in Algal OECD medium were characterized with regard to their physicochemical properties: agglomeration, surface charge, stability (dissolution of the NPs) and abiotic reactive oxygen species (ROS) production. NiO NPs formed loose agglomerates and released Ni2+. NiO NPs presented a 72 h-EC50 of 1.6 mg L−1, which was evaluated using the Algal growth inhibition assay and allowed this NP to be classified as toxic. NiO NPs caused the loss of esterase activity (metabolic activity), the bleaching of photosynthetic pigments and the intracellular accumulation of reactive oxygen species (ROS) in the absence of the disruption of plasma membrane integrity. NiO NPs also disturbed the photosynthetic process. A reduction in the photosynthetic efficiency (ΦPSII) accompanied by a decrease in the flow rate of electrons through the photosynthetic chain was also observed. The leakage of electrons from the photosynthetic chain may be the origin of the ROS found in the Algal cells. The exposure to NiO NPs led to the arrest of the cell cycle prior to the first cell division (primary mitosis), an increase in cell volume and the presence of aberrant morphology in the Algal cells. In this work, the use of different approaches allowed new clues related to the toxicity mechanisms of NiO NPs to be obtained. This work also contributes to the characterization of the environmental and toxicological hazards of NiO NPs and provides information on the possible adverse effects of these NPs on aquatic systems.
Paul L Brown - One of the best experts on this subject based on the ideXlab platform.
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the effect of ph on the uptake and toxicity of copper and zinc in a tropical Freshwater Alga chlorella sp
Archives of Environmental Contamination and Toxicology, 2006Co-Authors: Karyn L Wilde, Scott J. Markich, Jennifer L. Stauber, Natasha M Franklin, Paul L BrownAbstract: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 CaCO(3)/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 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) 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.
Jennifer L. Stauber - One of the best experts on this subject based on the ideXlab platform.
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the effect of ph on the uptake and toxicity of copper and zinc in a tropical Freshwater Alga chlorella sp
Archives of Environmental Contamination and Toxicology, 2006Co-Authors: Karyn L Wilde, Scott J. Markich, Jennifer L. Stauber, Natasha M Franklin, Paul L BrownAbstract: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 CaCO(3)/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 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) 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.
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toxicity of metal mixtures to a tropical Freshwater Alga chlorella sp the effect of interactions between copper cadmium and zinc on metal cell binding and uptake
Environmental Toxicology and Chemistry, 2002Co-Authors: Jennifer L. Stauber, Natasha M Franklin, Richard P Lim, Peter PetoczAbstract:The individual and combined effects of copper, cadmium, and zinc on the cell division rate of the tropical Freshwater Alga Chlorella sp. were determined over 48 to 72 h. Metal mixtures were prepared based on multiples of their single-metal median effective concentration (EC50) values, i.e., toxic units (TU) using a triangular mixture design with five toxicant levels (0, 0.75, 1.0, 1.25, and 1.5 TU). Single-metal EC50 values after a 72-h exposure were 0.11, 0.85, and 1.4 μM for copper, cadmium, and zinc, respectively. Significant interactions were observed for all metal combinations after 48 and 72 h. An equitoxic mixture of Cu 1 Cd was more than concentration additive (synergistic) to the growth of Chlorella sp., while combinations of Cu + Zn, Cd + Zn, and Cu + Cd + Zn were all less than concentration additive or were antagonistic. To determine the effect of each metal on the uptake of the other, extracellular (membrane-bound) and intracellular metal concentrations, both alone and in mixtures, were compared. The increased growth inhibition observed for mixtures of Cu + Cd was due to higher concentrations of cell-bound and intracellular copper in the presence of cadmium compared with copper alone (i.e., cadmium-enhanced copper uptake). In contrast, both extra- and intracellular cadmium concentrations were reduced in the presence of copper. In mixtures of Cu + Zn, copper also inhibited the binding and cellular uptake of zinc, which resulted in decreased toxicity. Zinc had no appreciable effect on the uptake of copper by Chlorella sp. Our results suggest that all three metals share some common uptake and transport sites on Chlorella cells and that copper out competes both cadmium and zinc for cell binding. Determination of metal cell distribution coefficients (Kd) confirmed that Kd values for cadmium and zinc in single-metal exposures decreased in the presence of copper.
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The effect of water hardness on the toxicity of uranium to a tropical Freshwater Alga Chlorella sp.
Aquatic Toxicology, 2001Co-Authors: Amanda L. Charles, Scott J. Markich, Jennifer L. Stauber, Lou F De FilippisAbstract:Uranium (U) derived from mining activities is of potential ecotoxicological concern to Freshwater biota in tropical northern Australia. Few data are available on the effects of water hardness (Ca and/or Mg), which is elevated in U mine wastewaters, on the toxicity and bioavailability of U to Freshwater biota, particularly Algae. This study determined the effect of water hardness (8, 40, 100 and 400 mg CaCO3 l−1, added as calcium (Ca) and magnesium (Mg) sulphate) on the toxicity (72 h growth rate inhibition) of U to the unicellular green Alga, Chlorella sp., in synthetic Freshwater, at constant pH (7.0) and alkalinity (8 mg CaCO3 l−1), similar in chemical composition to sandy coastal streams in tropical northern Australia. A 50-fold increase in water hardness resulted in a 5-fold decrease (P≤0.05) in the toxicity of U to Chlorella sp. (i.e. the 72 h EC50 increased from 56 to 270 μg U l−1). Possible explanation for the ameliorative effect of water hardness includes: (i) competition between U and Ca and/or Mg for binding sites on the cell surface; and (ii) a change in U speciation, and hence, bioavailability. Results showed that extracellular (cell-surface) and intracellular U concentrations significantly (P 0.05) differences in the predicted speciation (% distribution) of U amongst the four water hardness levels. The reduction in U toxicity with increasing water hardness was most likely due to competition between U and Ca and/or Mg for binding sites on the Algal cell surface. The minimum detectable effect concentrations of U were approximately 3 and 24 times higher (at 8 and 400 mg CaCO3 l−1 hardness, respectively) than the national interim U guideline value (0.5 μg l−1) for protecting aquatic ecosystems. Overall, the results reinforce the need for a more flexible U guideline based on a hardness-dependent algorithm, which may allow environmental managers to relax the national guideline for U on a site-specific basis.
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ph dependent toxicity of copper and uranium to a tropical Freshwater Alga chlorella sp
Aquatic Toxicology, 2000Co-Authors: Scott J. Markich, Jennifer L. Stauber, Natasha M Franklin, Richard P LimAbstract:Copper (Cu) and uranium (U) are of potential ecotoxicological concern to tropical Freshwater organisms in northern Australia as a result of mining activity. No local data on the toxicity of these metals to tropical Freshwater Algae are currently available. The aim of this study was to investigate the effect of pH (5.7 and 6.5) on the toxicity of Cu and U to the green Alga Chlorella sp. in a synthetic softwater representative of fresh surface waters in sandy-streams of tropical northern Australia. The effects of Cu and U on Algal growth (cell division) rate after a 72-h exposure were determined. Intracellular and extracellular (membrane-bound) metal concentrations at the two selected pH values were also compared. Based on the 72-h minimum detectable effect concentrations (MDEC), Chlorella sp. was approximately 20-fold more sensitive to Cu (0.7 and 1.4 µg l(-1) at pH 6.5 and 5.7, respectively) than U (13 and 34 µg l(-1) at pH 6.5 and 5.7, respectively), and more sensitive than other Australian tropical Freshwater organisms. The toxicity of Cu and U was highly pH-dependent. Copper concentrations required to inhibit growth (cell division) rate by 50% (72-h EC(50)) increased from 1.5 to 35 µg l(-1) as the pH decreased from 6.5 to 5.7. Similarly, the 72-h EC(50) values for U increased from 44 to 78 µg l(-1) over the same pH range. Calculation of Cu and U speciation using the geochemical model HARPHRQ, showed that differences in the concentrations of the free metal ions (Cu(2+) and UO(2)(2+)) were only minimal (<10%) between pH 5.7 and 6.5. The decreased toxicity at pH 5.7 was due to lower concentrations of cell-bound and intracellular Cu and U compared to those at pH 6.5. These results are explained in terms of the possible mechanism of competition between H(+) and the metal ion at the cell surface.
Catia A Sousa - One of the best experts on this subject based on the ideXlab platform.
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chronic exposure of the Freshwater Alga pseudokirchneriella subcapitata to five oxide nanoparticles hazard assessment and cytotoxicity mechanisms
Aquatic Toxicology, 2019Co-Authors: Catia A Sousa, Helena M V M Soares, Eduardo V SoaresAbstract:Abstract The increasing use of nanoparticles (NPs) unavoidably enhances their unintended introduction into the aquatic systems, raising concerns about their nanosafety. This work aims to assess the toxicity of five oxide NPs (Al2O3, Mn3O4, In2O3, SiO2 and SnO2) using the Freshwater Alga Pseudokirchneriella subcapitata as a primary producer of ecological relevance. These NPs, in OECD medium, were poorly soluble and unstable (displayed low zeta potential values and presented the tendency to agglomerate). Using the Algal growth inhibition assay and taking into account the respective 72 h-EC50 values, it was possible to categorize the NPs as: toxic (Al2O3 and SnO2); harmful (Mn3O4 and SiO2) and non-toxic/non-classified (In2O3). The toxic effects were mainly due to the NPs, except for SnO2 which toxicity can mainly be attributed to the Sn ions leached from the NPs. A mechanistic study was undertaken using different physiological endpoints (cell membrane integrity, metabolic activity, photosynthetic efficiency and intracellular ROS accumulation). It was observed that Al2O3, Mn3O4 and SiO2 induced an algistatic effect (growth inhibition without loss of membrane integrity) most likely as a consequence of the cumulative effect of adverse outcomes: i) reduction of the photosynthetic efficiency of the photosystem II (ФPSII); ii) intracellular ROS accumulation and iii) loss of metabolic activity. SnO2 NPs also provoked an algistatic effect probably as a consequence of the reduction of ФPSII since no modification of intracellular ROS levels and metabolic activity were observed. Altogether, the results here presented allowed to categorize the toxicity of the five NPs and shed light on the mechanisms behind NPs toxicity in the green Alga P. subcapitata.
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toxic effects of nickel oxide nio nanoparticles on the Freshwater Alga pseudokirchneriella subcapitata
Aquatic Toxicology, 2018Co-Authors: Catia A Sousa, Helena M V M Soares, Eduardo V SoaresAbstract:Abstract Over the last decade, concerns have been raised regarding the potential health and environmental effects associated with the release of metal oxide nanoparticles (NPs) into ecosystems. In the present work, the potential hazards of nickel oxide (NiO) NPs were investigated using the ecologically relevant Freshwater Alga Pseudokirchneriella subcapitata. NiO NP suspensions in Algal OECD medium were characterized with regard to their physicochemical properties: agglomeration, surface charge, stability (dissolution of the NPs) and abiotic reactive oxygen species (ROS) production. NiO NPs formed loose agglomerates and released Ni2+. NiO NPs presented a 72 h-EC50 of 1.6 mg L−1, which was evaluated using the Algal growth inhibition assay and allowed this NP to be classified as toxic. NiO NPs caused the loss of esterase activity (metabolic activity), the bleaching of photosynthetic pigments and the intracellular accumulation of reactive oxygen species (ROS) in the absence of the disruption of plasma membrane integrity. NiO NPs also disturbed the photosynthetic process. A reduction in the photosynthetic efficiency (ΦPSII) accompanied by a decrease in the flow rate of electrons through the photosynthetic chain was also observed. The leakage of electrons from the photosynthetic chain may be the origin of the ROS found in the Algal cells. The exposure to NiO NPs led to the arrest of the cell cycle prior to the first cell division (primary mitosis), an increase in cell volume and the presence of aberrant morphology in the Algal cells. In this work, the use of different approaches allowed new clues related to the toxicity mechanisms of NiO NPs to be obtained. This work also contributes to the characterization of the environmental and toxicological hazards of NiO NPs and provides information on the possible adverse effects of these NPs on aquatic systems.
