Toxicity of PAMAM-coated gold nanoparticles in different unicellular models.

Polyamidoamine (PAMAM) dendrimers are used for many pharmaceutical and biomedical applications. However, the toxicological risks of several PAMAM-based compounds are still not fully evaluated, despite evidences of PAMAM deleterious effects on biological membranes, leading to toxicity. In this report, we investigated the toxicity of generation 0 PAMAM-coated gold nanoparticles (AuG0 NPs) in four different models to determine how different cellular systems are affected by PAMAM-coated NPs. Toxicity was evaluated in two mammalian cell lines, Neuro 2A and Vero, in the green alga Chlamydomonas reinhardtii and the bacteria Vibrio fischeri. AuG0 NP treatments reduced cell metabolic activity in algal and bacterial cells, measured by esterase enzymatic activity (C. reinhardtii) and luminescence emission (V. fischeri). EC50 value after 30 min of treatment was similar in both organisms, with 0.114 and 0.167 mg mL(-1) for C. reinhardtii and V. fischeri, respectively. On the other hand, AuG0 NPs induced no change of mitochondrial activity in mammalian cells after 24 h of treatment to up to 0.4 mg mL(-1) AuG0 NPs. Change in the absorption spectra of AuG0 NP in the mammalian cell culture media may indicate an alteration of NP properties that contributed to the low toxicity of AuG0 NPs in mammalian cells. For a safe development of PAMAM-based nanomaterials, the difference of sensitivity between mammalian and microbial cells, as well as the modulation of NPs toxicity by medium properties, should be taken into account when designing PAMAM NPs for applications that may lead to their introduction in the environment.

Inhibitory effects of silver nanoparticles in two green algae, Chlorella vulgaris and Dunaliella tertiolecta.

Freshwater microalga Chlorella vulgaris and marine microalga Dunaliella tertiolecta were used to investigate toxic effects induced by 50 nm silver nanoparticles (AgNPs). To induce AgNPs effect, we exposed Chlorella vulgaris and Dunaliella tertiolecta for 24h to 0-10 mg/L. We showed that growth media had different effects in AgNPs agglomerates' formation. Cellular viability, reactive oxygen species (ROS) formation and lipids peroxidation were employed to assess the toxic effects of AgNPs. AgNPs were able to interact directly with the Chlorella vulgaris cells surface and large aggregates were observed. AgNPs have a negative effect on Chlorella vulgaris and Dunaliella tertiolecta, as manifested by a strong decrease in chlorophyll content, viable algal cells, increased ROS formation and lipids peroxidation. The variability in sensitivity of both algae towards AgNPs was observed. We conclude that AgNPs have a negative effect on aquatic algae and these alterations might have serious consequences on structure and function of aquatic plant communities.

Effect of cadmium on photosystem II activity in Chlamydomonas reinhardtii: alteration of O-J-I-P fluorescence transients indicating the change of apparent activation energies within photosystem II.

In this study, we evaluated how cadmium inhibitory effect on photosystem II and I electron transport may affect light energy conversion into electron transport by photosystem II. To induce cadmium effect on the photosynthetic apparatus, we exposed Chlamydomonas reinhardtii 24 h to 0-4.62 µM Cd(2+). By evaluating the half time of fluorescence transients O-J-I-P at different temperatures (20-30°C), we were able to determine the photosystem II apparent activation energies for different reduction steps of photosystem II, indicated by the O-J-I-P fluorescence transients. The decrease of the apparent activation energies for PSII electron transport was found to be strongly related to the cadmium-induced inhibition of photosynthetic electron transport. We found a strong correlation between the photosystem II apparent activation energies and photosystem II oxygen evolution rate and photosystem I activity. Different levels of cadmium inhibition at photosystem II water-splitting system and photosystem I activity showed that photosystem II apparent activation energies are strongly dependent to photosystem II donor and acceptor sides. Therefore, the oxido-reduction state of whole photosystem II and I electron transport chain affects the conversion of light energy from antenna complex to photosystem II electron transport.

Investigation of animal and algal bioassays for reliable saxitoxin ecotoxicity and cytotoxicity risk evaluation.

Contamination of water bodies by saxitoxin can result in various toxic effects in aquatic organisms. Saxitoxin contamination has also been shown to be a threat to human health in several reported cases, even resulting in death. In this study, we evaluated the sensitivity of animal (Neuro-2A) and algal (Chlamydomonas reinhardtii) bioassays to saxitoxin effect. Neuro-2A cells were found to be sensitive to saxitoxin, as shown by a 24 h EC50 value of 1.5 nM, which was obtained using a cell viability assay. Conversely, no saxitoxin effect was found in any of the algal biomarkers evaluated, for the concentration range tested (2-128 nM). These results indicate that saxitoxin may induce toxic effects in animal and human populations at concentrations where phytoplankton communities are not affected. Therefore, when evaluating STX risk of toxicity, algal bioassays do not appear to be reliable indicators and should always be conducted in combination with animal bioassays.

Effect of aluminum on cellular division and photosynthetic electron transport in Euglena gracilis and Chlamydomonas acidophila.

The present study investigated aluminum's effect on cellular division and the photosynthetic processes in Euglena gracilis and Chlamydomonas acidophila at pH 3.0, at which Al is present mostly as Al(3+), AlSO(4) (+), and Al(SO(4))(2) (-). These algal species were exposed to 100, 188, and 740 microM Al, and after 24 h cell-bound Al was significantly different from control only for the highest concentration tested. However, very different effects of Al on algal cellular division, biomass per cell, and photosynthetic activity were found. Aluminum stimulated cell division but decreased at some level biomass per cell in C. acidophila. Primary photochemistry of photosynthesis, as Photosystem II quantum yield, and energy dissipation via nonphotochemical activity were slightly affected. However, for E. gracilis, under the same conditions, Al did not show a stimulating effect on cellular division or photosynthetic activity. Primary photochemical activity was diminished, and energy dissipation via nonphotochemical pathways was strongly increased. Therefore, when Al is highly available in aquatic ecosystems, these effects may indicate very different response mechanisms that are dependent on algal species.

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus.

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R2>or=0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (PhiM'), photochemical quenching (qP) and relative photochemical quenching (qP(rel)) values. The cells density was also linearly dependent (R2=0.838) on the relative unquenched fluorescence parameter (UQF(rel)). Non-linear correlation was found (R2=0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF(rel)>PhiM'>qP>qP(rel)>ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants.

Effect of chromium oxide (III) nanoparticles on the production of reactive oxygen species and photosystem II activity in the green alga Chlamydomonas reinhardtii.

With the growth of nanotechnology and widespread use of nanomaterials, there is an increasing risk of environmental contamination by nanomaterials. However, the potential implications of such environmental contamination are hard to evaluate since the toxicity of nanomaterials if often not well characterized. The objective of this study was to evaluate the toxicity of a chromium-based nanoparticle, Cr2O3-NP, used in a wide diversity of industrial processes and commercial products, on the unicellular green alga Chlamydomonas reinhardtii. The deleterious impacts of Cr2O3-NP were characterized using cell density measurements, production of reactive oxygen species (ROS), esterase enzymes activity, and photosystem II electron transport as indicators of toxicity. Cr2O3-NP exposure inhibited culture growth and significantly lowered cellular Chlorophyll a content. From cell density measurements, EC50 values of 2.05±0.20 and 1.35±0.06gL(-1) Cr2O3-NP were obtained after 24 and 72h of exposure, respectively. In addition, ROS levels were increased to 160.24±2.47% and 59.91±0.15% of the control value after 24 and 72h of exposition to 10gL(-1) Cr2O3-NP. At 24h of exposure, the esterase activity increased to 160.24% of control value, revealing a modification of the short-term metabolic response of algae to Cr2O3-NP exposure. In conclusion, the metabolism of C. reinhardtii was the most sensitive to Cr2O3-NP after 24h of treatment.

Resolution of the Photosystem I and Photosystem II contributions to chlorophyll fluorescence of intact leaves at room temperature.

Green leaves illuminated with photosynthetically active light emit red fluorescence, whose time-dependent intensity variations reflect photosynthetic electron transport (the Kautsky effect). Usually, fluorescence variations are discussed by considering only the contribution of PSII-associated chlorophyll a, although it is known that the fluorescence of PSI-associated chlorophyll a also contributes to the total fluorescence [Aust. J. Plant Physiol. 22 (1995) 131]. Because the fluorescence emitted by each photosystem cannot be measured separately by selecting the emission wavelength in in vivo conditions, the contribution of PSI to total fluorescence at room temperature is still in ambiguity. By using a diode array detector, we measured fluorescence emission spectra corresponding to the minimal (F(O)) and maximal (F(M)) fluorescence states. We showed that the different shapes of these spectra were mainly due to a higher contribution of PSI chlorophylls in the F(O) spectrum. By exciting PSI preferentially, we recorded a reference PSI emission spectrum in the near far-red region. From the F(O) and F(M) spectra and from this PSI reference spectrum, we derived specific PSI and PSII emission spectra in both the F(O) and F(M) states. This enables to estimate true value of the relative variable fluorescence of PSII, which was underestimated in previous works. Accurate separation of PSI-PSII fluorescence emission spectra will also enable further investigations of the distribution of excitation energy between PSI and PSII under in vivo conditions.

Changes in the room-temperature emission spectrum of chlorophyll during fast and slow phases of the Kautsky effect in intact leaves.

Changes in the room-temperature emission spectrum of chlorophyll (Chl) were analyzed using fast diode-array recordings during the Kautsky effect in mature and in greening barley leaves. In mature leaves, the comparison of F(O) (basal level of fluorescence yield at transient O) and F(M) (maximum level of fluorescence yield at transient M) spectra showed that the relative amplitude of total variable fluorescence was maximal for the 684 nm Photosystem II (PSII) band and minimal for the 725 nm Photosystem I band. During the increase from F(O) to F(M), a progressive redshift of the spectrum of variable fluorescence occurred. This shift reflected the different fluorescence rise kinetics of different layers of chloroplasts inside the leaf. This was verified by simulating the effect of screening on the emission spectrum of isolated chloroplasts and by experiments on greening leaves with low Chl content. In addition, experiments performed at different greening stages showed that the presence of uncoupled Chl at early-greening stages and light-harvesting complex II (LHCII) at later stages have detectable but minor effects on the shape of room-temperature emission spectra. When strong actinic light was applied to mature green leaves, the slow fluorescence yield, which declined from F(M) to F(T) (steady-state level of fluorescence yield at transient T), was accompanied by a slight redshift of the 684 nm PSII band because of nonphotochemical quenching of short-wavelength-emitting Chl ascribed to LHCII.

Determination of photosynthetic and enzymatic biomarkers sensitivity used to evaluate toxic effects of copper and fludioxonil in alga Scenedesmus obliquus.

Modulated PAM fluorometry and Plant Efficiency Analyser methods were used to investigate photosynthetic fluorescence parameters of alga Scenedesmus obliquus exposed to inhibitory effect of fungicides copper sulphate and fludioxonil (N-(4-nitrophenyl)-N'-propyl-uree). The change of those parameters were studied when alga S. obliquus have been exposed during 48 h to different concentrations of fungicides (1, 2 and 3 mgl(-1)). Under the same condition, enzymatic activities of catalase, ascorbate peroxidase, glutathione reductase and glutathione S-transferase were investigated to evaluate antioxidative response to fungicides effects. The change of sensitivity of those parameters was dependent to the mode of fungicide action, their concentration and time of exposure. For copper effects, the most indicative photosynthetic biomarkers were parameters Q(N) as non-photochemical fluorescence quenching, Q(Emax) as the proton induced fluorescence quenching and ABS/RC as the antenna size per photosystem II reaction center. Copper induced oxidative stress was indicated by increased activity of catalase serving as the most sensitive and valuable enzymatic biomarker. On the other hand, fludioxonil effect on photosynthetic parameters was very negligible and consequently not very useful as biomarkers. However, fludioxonil induced strong antioxidative activities associated with cytosol enzymes, as we found for catalase, ascorbate peroxidase and glutathione S-transferase activities. By obtained results, we may suggest for the activation of those enzymes to be sensitive and valuable biomarkers of oxidative stress induced by fludioxonil. Determination of biomarkers sensitivity may offer advantages in providing real criteria to use them for ecotoxicological diagnostic studies.

Relationship between the structural and functional changes of the photosynthetic apparatus during chloroplast-chromoplast transition in flower bud of Lilium longiflorum.

The relationship between the structural and functional changes of the photosynthetic apparatus in the flower bud of Lilium longiflorum during chloroplast-chromoplast transition was examined. Compared with green petals, there was a five-fold increase of the carotenoid content in yellow petals, whereas the chlorophyll content decreased five-fold. Absorption and emission fluorescence spectra of chromoplasts indicated that newly synthesized carotenoids were not associated with photosystem II (PSII) photochemistry. The maximum quantum yield in the remaining PSII reaction centers remained constant during the chromoplast formation, whereas the photosynthetic electron transport beyond PSII became inhibited, as indicated by a marked decrease of the O2 evolution capacity, of the photochemical quenching of chlorophyll-alpha fluorescence and of the operational quantum yield of photosynthetic electron transport. Deconvoluted fluorescence emission spectra indicated a more rapid degradation of photosystem I (PSI) complexes than of PSII during chromoplast formation. Compared with green petals, the spillover between PSII and PSI decreased by approximately 40% in yellow petals. Our results indicate that during chloroplast-chromoplast transition in the flower bud of L. longiflorum, PSII integrity was preserved longer than the rest of the photosynthetic apparatus.

Effects of methanol on photosynthetic processes and growth of Lemna gibba.

Effects of methanol on growth and photosynthetic activity of Lemna gibba exposed under continuous illumination were examined. As a higher plant, L. gibba appeared to be much more sensitive to methanol inhibitory effect compared with some algae (Theodoridou et al. [2002] Biochim. Biophys. Acta, 1573, 189-198). We found that stimulatory or inhibitory effects were strongly dependent on the methanol concentration and the time of exposure. When the exposure was up to 0.2% methanol, the growth rate of biomass was improved by 50%. However, stimulatory effect of methanol appeared to be smaller when plants were exposed for 48 h compared with 24 h. Increase in biomass induced by methanol was not based on the increase in primary photosynthetic process but rather on accommodation of energy dissipation during photosynthesis. Inhibitory effect on the growth of L. gibba already observed for 0.5% methanol was strongly associated with the increase in the nonphotochemical energy dissipation. The ratio between biomass and methanol concentration appeared to determine the stimulatory or the inhibitory effect. Suggested explanations for the stimulatory and the inhibitory effects are presented.

Early reactions of light-induced protochlorophyllide and chlorophyllide transformations analyzed in vivo at room temperature with a diode array spectrofluorometer.

The steps of protochlorophyllide (Pchlide) photoreduction and subsequent chlorophyllide (Chlide) transformations which occur in the seconds to minutes time-scale were studied using a diode array spectrofluorometer in dark-grown barley leaves. The intensity of the excitation light was varied between 3 and 2,500 micromol m(-2) s(-1) and a series of fluorescence spectra were recorded at room temperature in the seconds and minutes time scales. In certain experiments, 77-K emission spectra were measured with the same equipment. The high quality of the spectra allowed us to run spectral resolution studies which proved the occurrence, at room temperature, of multiple Pchlide and Chlide forms found previously in 77-K spectra. The comparison of the 77-K and room-temperature spectra showed that the fluorescence yields of the nonphotoactive 633-nm Pchlide form and of the Chlide product emitting at 678 nm were temperature independent. The fluorescence intensity of aggregated NADPH-pigment-POR complexes (photoactive 656-nm Pchlide and 693-nm Chlide forms) were strongly increased at 77 K, while that of the NADP(+)-Chlide-POR (684-686-nm Chlide form) was much less affected by temperature. Information was obtained also about the dynamics of the transformation of pigment forms in the light at different photon densities. At low light intensities, the phototransformation of the 642-644-nm Pchlide form was faster than that of the 654-656-nm form. The relative amplitudes of Gaussian components related to different Chlide forms found after exposure to a constant amount of photons strongly depended on the light intensity used. Strong quenching of all Chlide components occurred upon prolonged exposure to high intensity light. These effects are discussed by considering the interconversion processes between different forms of the pigment-protein complexes, their relative fluorescence yields and energy migration processes.

Protochlorophyllide phototransformation in the bundle sheath cells of Zea mays.

The protochlorophyllide transformation process was investigated by using comparative analysis of 77 K fluorescence spectral changes occurring in isolated bundle sheath (BS) cells of etiolated Zea mays leaves after being exposed to a 200 ms saturating flash. Deconvolution analysis of the fluorescence spectra showed essential differences in the ratio of protochlorophyll(ides) and chlorophyll(ides) spectral forms indicating for BS cells to have a characteristic pathway of protochlorophyllide transformation. Bundle sheath cells showed a high ratio between non-photoactive protochlorophyll(ide)-F632 and photoactive protochlorophyllide-F655. In those cells, the 200 ms flash triggered a preferential formation of chlorophyll(ide)-F675 which remained stable in the dark for at least 90 min. Isolated BS cells showed an accumulation of chlorophyll(ide)-F675 resulting in the formation of inactive photosystem II. However for mesophyll cells of intact leaves, it was found to have a high ratio between photoactive and non-photoactive protochlorophyll(ide), showing the succession of chlorophyll(ide) forms usually known in C(3) plants. Protochlorophyllide phototransformation pathway in BS cells related to early stages of plastid differentiation triggered by light may indicate specific conditions for PSII assembly process leading to inactive PSII forms.

Different toxicity mechanisms between bare and polymer-coated copper oxide nanoparticles in Lemna gibba.

In this report, we investigated how the presence of a polymer shell (poly(styrene-co-butyl acrylate) alters the toxicity of CuO NPs in Lemna gibba. Based on total Cu concentration, core-shell CuO NPs were 10 times more toxic than CuO NPs, inducing a 50% decrease of growth rate at 0.4 g l(-1) after 48-h of exposure while a concentration of 4.5 g l(-1) was required for CuO NPs for a similar effect. Toxicity of CuO NPs was mainly due to NPs solubilization in the media. Based on the accumulated copper content in the plants, core-shell CuO NPs induced 4 times more reactive oxygen species compared to CuO NPs and copper sulfate, indicating that the presence of the polymer shell changed the toxic effect induced in L. gibba. This effect could not be attributed to the polymer alone and reveals that surface modification may change the nature of NPs toxicity.

Alteration of chromium effect on photosystem II activity in Chlamydomonas reinhardtii cultures under different synchronized state of the cell cycle.

The inhibitory effect of chromium (Cr) on photosystem II (PSII) activity was investigated in the green alga Chlamydomonas reinhardtii during different phases of the cell cycle. Algae were cultivated in continuous light or a light/dark cycle (16:8 h) to obtain a synchronously dividing cell culture. The cell division phases were determined with the DNA-specific fluorescent probe SYBR green using flow cytometry. The effect of Cr on PSII activity was investigated after a 24-h treatment with algal cultures having different proportions of newly divided cells (G(0)/G(1)), dividing cells at the DNA replication phase (S), and dividing cells at the mitosis phase (G(2)/M). Using chlorophyll a fluorescence parameters based on PSII electron transport capacity in dark- (Φ(M)II) and light-adapted (Φ'(M)II) equilibrium state, we found that the effect of Cr differs depending on the stage of the cell cycle. When algal cultures had a high proportion of cells actively dividing (M phase), the toxic effect of Cr on PSII activity appeared to be much higher and PSII quantum yield was decreased by 80 % compared to algal cultures mainly in the G(0)/G(1) phase. Therefore, the inhibitory effect of Cr on photosynthesis appears to be different according to the cell cycle state of the algal population.

Alleviation of silver toxicity by calcium chloride (CaCl2) in Lemna gibba L.

The toxicity effects of silver (Ag) and the protective role of calcium chloride (CaCl2) was studied in Lemna gibba L. (L. gibba) plants. Silver speciation showed that silver toxicity in L. gibba culture medium can be attributed to free ionic Ag(+) concentration. Frond abscission, intracellular reactive oxygen species (ROS) formation and intracellular uptake of Ag(+) were investigated when L. gibba plants were exposed to AgNO3 concentrations (0.5, 1, 5, and 10 µM) supplemented or not by 10 µM CaCl2. An increase in frond abscission, intracellular ROS and intracellular uptake of Ag(+) were detected in L. gibba plants for all tested concentrations of AgNO3 after 24 h treatment. However, addition of 10 µM CaCl2 to the L. gibba culture medium reduced the toxic effects of Ag by decreasing silver uptake into the plant and intracellular ROS formation. The results suggest that Ag-induced toxicity was attributed to Ag(+) accumulation and chloride was able to protect L. gibba plants against Ag toxicity by formation of complexes with Ag and then alleviation of the metal induced oxidative stress.

Evaluation of toxicity and oxidative stress induced by copper oxide nanoparticles in the green alga Chlamydomonas reinhardtii.

Copper oxide nanoparticles (CuO NP) are frequently employed for their antimicrobial properties in antifouling paints. Their extensive use can contaminate aquatic ecosystems. However, the toxicological effects of this NP in the environment are poorly known. In this study, we evaluated the toxicity and oxidative stress induced by CuO NP on Chlamydomonas reinhardtii using several toxicological assays. CuO NP was found to induce growth inhibition and a significant decrease in carotenoids levels. From data on cells density after 72 h of CuO NP exposure in light, the EC50 value was calculated to be 150.45±1.17 mg L(-1) and the NOEC≤100 mg L(-1). Evaluation of esterase activity demonstrates a decrease in cell metabolism activity with the increase of CuO NP concentration. The CuO NP induced an increase of reactive species level (190±0.45% at 1000 mg L(-1) after 72 h of exposition, compared to control) and lipid peroxidation of cellular membranes (73±2% at 1000 mg L(-1) of CuO NP in 72 h of exposition, compared to control). Investigation of CuO NP uptake showed the presence of NP into C. reinhardtii cells in different sites of the cell and, biomarkers of enzymatic antioxidants showed a change of activity after CuO NP exposition. In conclusion, C. reinhardtii was shown to be sensitive to the presence of CuO NP in their environment and CuO NP treatments induced a toxic response from 0.1 mg L(-1) after 72 h of treatment.

Interactive effects of temperature and copper on photosystem II photochemistry in Chlorella vulgaris.

In natural aquatic ecosystems, temperature conditions may undergo changes depending on the depth of the water column or micro-environmental conditions. In this study, copper effect on the photosynthetic performance of Chlorella vulgaris was investigated at different temperatures by using chlorophyll a fluorescence transients and fluorescence imaging parameters. Copper as a pollutant is known to be an inhibitor of photosystem II (PSII) photochemistry; therefore it was important to know how the change of temperature may alter this effect. PSII photochemistry was investigated when C. vulgaris, affected by different copper concentrations, was exposed to 24, 28 and 31 °C. Increase of temperature induced higher alterating effects to PSII quantum yield, primary photosynthetic electron transport from water splitting system and consequently higher decrease of total photosynthetic performance if compared to copper effect alone. Additional temperature effect to copper inhibition increased energy dissipation via non-photochemical pathway. In this study we indicated that, when C. vulgaris changes temperature conditions, inhibitory effect of copper also undergoes changes. For natural aquatic system we may suppose, when algae are distributed at different depths of water column, that toxicity effect will be dependent to the temperature conditions of the site.

Temperature influence on silver nanoparticles inhibitory effect on photosystem II photochemistry in two green algae, Chlorella vulgaris and Dunaliella tertiolecta.

PURPOSE: In this study, the effect of silver nanoparticles (AgNPs) on the photosynthetic performance of two green algae, Chlorella vulgaris and Dunaliella tertiolecta, was investigated at 25°C and 31°C. METHODS: To induce AgNPs effect, algal cells were exposed for 24 h to concentrations varying from 0 to 10 mg/L. The polyphasic OJIP fluorescence transient was used to evaluate photosystem II (PSII). RESULTS: We show that growth media and temperature had different effects in AgNPs agglomerates formation and Zeta potential. When temperature conditions change, inhibitory effect of AgNPs also undergoes changes. Increase of temperature induced higher altering effects to PSII quantum yield, primary photosynthetic electron transport, and consequently higher decrease of total photosynthetic performance if compared to AgNPs effect alone. AgNPs has a negative effect on D. tertiolecta compared to C. vulgaris. CONCLUSION: We conclude that temperature tends to enhance the toxic effects on aquatic alga and these alterations might have serious consequences on ecosystem equilibrium and aquatic plant communities.