Alga Pseudokirchneriella Subcapitata Research Articles

Integrated water quality assessment of two Rivers Basins from a semiarid region of Argentina.

The Tunuyán and Mendoza River Basins (Province of Mendoza, Argentina) have been selected as a representative semiarid region to test the applicability of an integrated water quality evaluation. To detect spatio-temporal variations of anthropic contamination, physicochemical and bacteriological parameters, as well as three ecotoxicological assays, were assessed in reference sites for 3years. Bioassays based on the nematode Caenorhabditis elegans, the vascular plant Lactuca sativa, and the algae Pseudokirchneriella subcapitata were performed and toxicological categories were established. Our results showed that water quality, as well as water toxicity, deteriorates as both river systems run through urban areas. Interestingly, monitoring sites with good physicochemical and bacteriological qualities but with toxicity were identified, illustrating that traditional water quality studies do not predict potential toxic effects on living organisms. In addition, a multivariate statistical analysis was performed to detect clusters of monitoring sites according to the water quality status. In the context of climate change, this study provides information to support that integrated water monitoring is an essential tool to ensure sustainable water management and to guarantee economic growth, human health, food security, and environmental protection.

Computational modeling (in silico) methods combined with ecotoxicological experiments (in vivo) to predict the environmental risks of an antihistamine drug (loratadine)

This study employed computational modeling (in silico) methods, combined with ecotoxicological experiments (in vivo) to predict the persistence/biodegradability, bioaccumulation, mobility, and ecological risks of an antihistamine drug (Loratadine: LOR) in the aquatic compartment. To achieve these goals, four endpoints of the LOR were obtained from different open-source computational tools, namely: (i) “STP total removal”; (ii) Predicted ready biodegradability; (iii) Octanol-water partition coefficient (KOW); and (iv) Soil organic adsorption coefficient (KOC). Moreover, acute and chronic, ecotoxicological assays using non-target freshwater organisms of different trophic levels (namely, algae Pseudokirchneriella subcapitata; microcrustaceans Daphnia similis and Ceriodaphnia dubia; and fish Danio rerio), were used to predict the ecological risks of LOR. The main results showed that LOR: (i) is considered persistent (after a weight-of-evidence assessment) and highly resistant to biodegradation; (ii) is hydrophobic (LOG KOW = 5.20), immobile (LOG KOC = 5.63), and thus, it can potentially bioaccumulate and/or can cause numerous deleterious effects in aquatic species; and (iii) after ecotoxicological evaluation is considered “toxic” and/or “highly toxic” to the three trophic levels tested. Moreover, both the ecotoxicological assays and risk assessment (RQ), showed that LOR is more harmful for the crustaceans (RQcrustaceans = moderate to high risks) than for algae and fish. Ultimately, this study reinforces the ecological concern due to the indiscriminate disposal of this antihistamine drug in worldwide aquatic ecosystems.

Evaluation of Apical and Molecular Effects of Algae Pseudokirchneriella subcapitata to Cerium Oxide Nanoparticles.

Cerium oxide engineered nanoparticles (nCeO2) are widely used in various applications and are, also, increasingly being detected in different environmental matrixes. However, their impacts on the aquatic environment remain poorly quantified. Hence, there is a need to investigate their effects on non-target aquatic organisms. Here, we evaluated the cytotoxic and genotoxic effects of <25 nm uncoated-nCeO2 on algae Pseudokirchneriella subcapitata. Apical (growth and chlorophyll a (Chl a) content) and genotoxic effects were investigated at 62.5-1000 µg/L after 72 and 168 h. Results demonstrated that nCeO2 induced significant growth inhibition after 72 h and promotion post 96-168 h. Conversely, nCeO2 induced enhanced Chl a content post 72 h, but no significant changes were observed between nCeO2-exposed and control samples after 168 h. Hence, the results indicate P. subcapitata photosynthetic system recovery ability to nCeO2 effects under chronic-exposure conditions. RAPD-PCR profiles showed the appearance and/or disappearance of normal bands relative to controls; indicative of DNA damage and/or DNA mutation. Unlike cell recovery observed post 96 h, DNA damage persisted over 168 h. Thus, sub-lethal nCeO2-induced toxicological effects may pose a more serious threat to algae than at present anticipated.

Life and death of Pseudokirchneriella subcapitata: physiological changes during chronological aging.

The green alga Pseudokirchneriella subcapitata is widely used in ecotoxicity assays and has great biotechnological potential as feedstock. This work aims to characterize the physiology of this alga associated with the aging resulting from the incubation of cells for 21days, in the OECD medium, with continuous agitation and light exposure, in a batch mode. After inoculation, cells grow exponentially during 3days, and the culture presents a typical green color. In this phase, "young" algal cells present, predominantly, a lunate morphology with the chloroplast occupying a large part of the cell, maximum photosynthetic activity and pigments concentration, and produce starch as a reserve material. Between the 5th and the 12th days of incubation, cells are in the stationary phase. The culture becomes less green, and the cells stop dividing (≥ 99% have one nucleus) and start to age. "Old" algal cells present chloroplast shrinkage, an abrupt decline of chlorophylls content, and photosynthetic capacity (Fv/Fm and ɸPSII), accompanied by a degradation of starch and an increase of neutral lipids content. The onset of the death phase occurs after the 12th day and is characterized by the loss of cell membrane integrity of some algae (cell death). The culture stays, progressively, yellow, and the majority of the population (~93%) is composed of live cells, chronologically "old," with a significant drop in photosynthetic activity (decay > 75% of Fv/Fm and ɸPSII) and starch content. The information here achieved can be helpful when exploring the potential of this alga in toxicity studies or in biotechnological applications. KEY POINTS: • Physiological changes of P. subcapitata with chronological aging are shown • "Young" algae exhibit a semilunar shape, high photosynthetic activity, and accumulated starch • "Old"-live algae show reduced photosynthetic capacity and accumulated lipids.

The first plastic produced, but the latest studied in microplastics research: The assessment of leaching, ecotoxicity and bioadhesion of Bakelite microplastics

Bakelite, the first synthetic plastic, is a rather unexplored material in the field of ecotoxicology, despite its long production and use. The aim of this study was to investigate the ecotoxicity of Bakelite microplastics (before and after leaching) and its leachates on four aquatic organisms: the crustacean Daphnia magna, the plant Lemna minor, the bacterium Allivibrio fischeri and the alga Pseudokirchneriella subcapitata. Bakelite microplastics before and after leaching and leachates affected all organisms, but to varying degrees. Leachates showed increased ecotoxicity to Daphnia magna, while Pseudokirchneriella subcapitata was more affected by particles. For Lemna minor and Allivibrio fischeri, the effects of particles before leaching and leachate were comparable, while the negative effect of particles after leaching was minimal or not present. All leachates were analysed, and phenol and phenol-like compounds were the predominant organics found. In addition, bioadhesion of Bakelite microplastics to the surface of Daphnia magna and Lemna minor was confirmed, but the particles were mainly weakly adhered. Results of this study suggest that, in addition to the recently studied microplastics from consumer products (e.g. from polyethylene and polystyrene), microplastics from industrial plastics such as Bakelite may be of increasing concern, primarily due to leaching of toxic chemicals.

Ecological Impact of End-of-Life-Tire (ELT)-Derived Rubbers: Acute and Chronic Effects at Organism and Population Levels.

Considering the large amount of tires that reach the end of life every year, the aim of this study was the evaluation of both acute and chronic effects of end-of-life-tire (ELT)-derived rubber granules (ELT-dg) and powder (ELT-dp) on a freshwater trophic chain represented by the green alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the teleost Danio rerio (zebrafish). Adverse effects were evaluated at the organism and population levels through the classical ecotoxicological tests. Acute tests on D. magna and D. rerio revealed a 50% effect concentration (EC50) > 100.0 mg/L for both ELT-dg and ELT-dp. Chronic exposures had a lowest observed effect concentration (LOEC) of 100.0 mg/L for both ELT-dg and ELT-dp on P. subcapitata grow rate and yield. LOEC decreased in the other model organisms, with a value of 9.8 mg/L for D. magna, referring to the number of living offspring, exposed to ELT-dg suspension. Similarly, in D. rerio, the main results highlighted a LOEC of 10.0 mg/L regarding the survival and juvenile weight parameters for ELT-dg and a LOEC of 10.0 mg/L concerning the survival and abnormal behavior in specimens exposed to ELT-dp. Tested materials exhibited a threshold of toxicity of 9.8 mg/L, probably a non-environmental concentration, although further investigations are needed to clarify the potential ecological impact of these emerging contaminants.

Drinking water quality evaluation of hand pumping wells using water quality index and standard algal toxicity testing in Mansoura and Talkha cities, Egypt

Six house-hold Abyssinian pumps distributed in different villages of Mansoura (Mans-I, Mans-II and Mans-III) and Talkha (Talk-I, Talk-II and Talk-III) cities, Egypt, have been selected for regular seasonal water quality assessment during 2017. Water samples have been collected within the mid-periods of four seasons Standard assessment tools were employed for the integrated water quality assessment including Water Quality Index (WQI) and ISO standard algal toxicity test. WQI displayed remarkable local and seasonal variations with excellent (≥ 90) and good (70 - 89) only recorded for water samples collected from Mans-I pump located in sparsely populated area and far 50 meters only from the eastern (Damietta) branch of Nile River. WQI of other pumps located in densely populated areas and far kilometers from the Nile branch indicated either medium (50-69) or bad (25-49) quality depending on sampling season and sampling site location. All water samples collected from the pump Mans-I were non toxic without any inhibitory effects on the growth of the standard test alga Pseudokirchneriella subcapitata. Water samples from all other pumps, however, showed obvious toxic effects on test algae growth with varying EC50 values ranged between15.8% and 83%, depending on water sample and the sampling season. Concisely, all water samples collected from Mans-I pump were health safe with acceptable drinking water guidelines while samples collected from other pumps can impose great human health risks if used for drinking

Effects of Sodium Chloride on Algae and Crustaceans—The Neighbouring Links of the Water Trophic Chain

Salinity limits the habitable living environment for aquatic organisms. Algae and crustaceans are widely used as bioindicators in freshwater environmental risk assessments. This study aimed to use biotests (Algaltoxkit and Daphtoxkit) to determine the effect of sodium chloride (NaCl) on algae Pseudokirchneriella subcapitata and crustaceans Daphnia magna. Standard biotests were extended to include NaCl effects on algal chlorophyll fluorescence and crustaceans swimming and heart rate. It was found that after 7 days, a 0.24 M of NaCl reduced the growth rate of the algae by 50% (EC50). A NaCl of 0.27 M inhibited the minimum (Fo), maximum (Fm) and variable (Fv) fluorescence by 50%, on average. The crustaceans also responded to NaCl. Those exposed to 0.19 M NaCl during 15 min swam slower by 50% and a 0.27 M immobilised three organisms (EC50). The crustacean immobilisation was less modified by NaCl than swimming. To determine the lethal effect in non-swimming organisms, the heart rate was examined. At 0.35 M of NaCl, all organisms were dead after 30 min, as their hearts did not beat. These studies suggest that physiological and behavioural features are sensitive indicators of the toxic effects of NaCl in algae and crustaceans, before morphological changes are observed.

Cytotoxicity and genotoxicity of coated-gold nanoparticles on freshwater algae Pseudokirchneriella subcapitata.

Gold engineered nanoparticles (nAu) are increasingly detected in ecosystems, and this raises the need to establish their potential effects on aquatic organisms. Herein, cytotoxic and genotoxic effects of branched polyethylenimine (BPEI)- and citrate (cit)-coated nAu (5, 20, and 40 nm) on algae Pseudokirchneriella subcapitata were evaluated. The apical biological endpoints: growth inhibition and chlorophyll a (Chl a) content were investigated at 62.5-1000 µg/L over 168 h. In addition, the apurinic/apyrimidinic (AP) sites, randomly amplified polymorphic deoxyribonucleic acid (RAPD) profiles, and genomic template stability (GTS) were assessed to determine the genotoxic effects of nAu. The results show algal growth inhibition at 5 nm BPEI-nAu up to 96 h, and thereafter cell recovery except at the highest concentration of 1000 µg/L. Insignificant growth reduction for cit-nAu (all sizes), as well as 20 and 40 nm BPEI-nAu, was observed over 96 h, but growth promotion was apparent at all exposures thereafter except for 40 nm BPEI-nAu at 250 µg/L. A decrease in Chl a content following exposure to 5 nm BPEI-nAu at 1000 µg/L corresponded to significant algal growth reduction. In genotoxicity studies, a significant increase in AP sites content was observed relative to the control - an indication of nAu ability to induce genotoxic effects irrespective of their size and coating type. For 5 nm- and 20 nm-sized nAu for both coating types and exposure concentrations no differences in AP sites content were observed after 72 and 168 h. However, a significant reduction in AP sites was observed following algae exposure to 40 nm-sized nAu (irrespective of coating type and exposure concentration) at 168 h compared to 72 h. Thus, AP sites results at 40 nm-size suggest likely DNA damage recovery over a longer exposure period. The findings on AP sites content showed a good correlation with an increase in genome template stability and growth promotion observed after 168 h. In addition, RAPD profiles demonstrated that nAu can induce DNA damage and/or DNA mutation to P. subcapitata as evidenced by the appearance and/or disappearance of normal bands compared to the controls. Therefore, genotoxicity results revealed significant toxicity of nAu to algae at the molecular level although no apparent effects were detectable at the morphological level. Overall, findings herein indicate that long-term exposure of P. subcapitata to low concentrations of nAu may cause undesirable sub-lethal ecological effects.

Evaluation of the environmental impact of magnetic nanostructured materials at different trophic levels

Safety on the use of magnetic nanomaterials (MNMs) has become an active topic of research given all the recent applications of these materials in various fields. It is known that the toxicity of MNMs depends on size, shape, and surface functionalization. In this study, we evaluate the biocompatibility with different aquatic organisms of engineered MNMs-CIT with excellent aqueous dispersion and long-term colloidal stability. Primary producers (the alga Pseudokirchneriella subcapitata), primary consumers (the rotifer Lecane papuana), and predators (the fish, Danio rerio) interacted with these materials in acute and sub-chronic toxicity tests. Our results indicate that P. subcaptita was the most sensitive taxon to MNMs-CIT. Inhibition of their population growth (IC50 = 22.84 mg L−1) elicited cell malformations and increased the content of photosynthetic pigments, likely due to inhibition of cell division (as demonstrated in AFM analysis). For L. papuana, the acute exposure to MNMs shows no significant mortality. However, adverse effects such as decreased rate of population and altered swimming patterns arise after chronic interaction with MNMs. For D. rerio organisms on early life stages, their exposure to MNMs results in delayed hatching of eggs, diminished survival of larvae, altered energy resources allocation (measured as the content of total carbohydrates, lipids, and protein), and increased glucose demand. As to our knowledge, this is the first study that includes three different trophic levels to assess the effect of MNMs in aquatic organisms; furthermore, we demonstrated that these MNMs pose hazards on aquatic food webs at low concentrations (few mgL−1).

Toxicological effects induced by the biocide triclosan on Pseudokirchneriella subcapitata

Triclosan, a widely used biocide broadly found in aquatic environments, is cause of concern due to its unknown effects on non-targets organisms. In this study, a multi biomarker approach was used in order to evaluate the 72 h-effect of triclosan on the freshwater alga Pseudokirchneriella subcapitata (Raphidocelis subcapitata). Triclosan, at environmental relevant concentrations (27 and 37 μg L−1), caused a decrease of proliferative capacity, which was accompanied by an increase of cell size and a profound alteration of algae shape. It was found that triclosan promoted the intracellular accumulation of reactive oxygen species, the depletion of non-enzymatic antioxidant defenses (reduced glutathione and carotenoids) and a decrease of cell metabolic activity. A reduction of photosynthetic pigments (chlorophyll a and b) was also observed. For the highest concentration tested (37 μg L−1), a decrease of photosynthetic efficiency was detected along with a diminution of the relative transport rate of electrons on the photosynthetic chain. In conclusion, triclosan presents a deep impact on the microalga P. subcapitata morphology and physiology translated by multiple target sites instead of a specific point (cellular membrane) observed in the target organism (bacteria). Additionally, this study contributes to clarify the toxicity mechanisms of triclosan, in green algae, showing the existence of distinct modes of action of the biocide depending on the microalga.

Effects of Three Commonly Used Pharmaceutical products on Biochemical parameters of the Micro-alga Pseudokirchneriella subcapitata (Under Laboratory Conditions)

Despite the great importance of pharmaceutical products in our daily life, they have negative effects on the environment; where it may threatens many non-target organisms. The present study provides an integrated framework of contribution to understanding the toxicity of three commonly used pharmaceutical products (amoxicillin, naproxen and tramadol) on the micro-green alga Pseudokirchneriella subcapitata. The impact of pharmaceutical pollution on aquatic organisms can be evaluated by assessing its physiological response. The alga was exposed to sub-lethal concentrations (LC10, LC25 and LC50) of each tested pharmaceutical to determine its impact on growth behavior, pigments, total lipids, protein and carbohydrate content. The obtained results clarified that, exposure to the pharmaceuticals by their sub-lethal concentrations mostly resulted in a decrease in cell density up to 66.25% by amoxicillin and 37.24% by tramadol within LC50, although exposure to low naproxen concentration promoted cell density (up to 21.7%) after 24h. Amoxicillin (67.74 - 97.44%) followed by tramadol (59.67- 93.55%) significantly reduced the content of the pigment after 96h but in a different manner, however except within LC50, naproxen induced both carotenoids (4.55- 11.61%) and chlorophyll-a (1.54 - 9.23%) during the first 24h. The tested pharmaceuticals also reducing protein, carbohydrates and total lipid content of P.subcapitata at the end of the experiment by ratios up to 96.7, 86.2 and 74.9% respectively. Due to the dramatic effects of pharmaceuticals on the aquatic non-target organisms all new pharmaceutical products must undergo an environmental risk assessment test during and after the development of the product to obtain marketing approval.

Exposure of the alga Pseudokirchneriella subcapitata to environmentally relevant concentrations of the herbicide metolachlor: Impact on the redox homeostasis

This study investigated the effect of the herbicide metolachlor (MET) on the redox homeostasis of the freshwater green alga Pseudokirchneriella subcapitata. At low MET concentrations (≤40 μg L−1), no effects on algal cells were detected. The exposure of P. subcapitata to 45–235 μg L−1 MET induced a significant increase of reactive oxygen species (ROS). The intracellular levels of ROS were particularly increased at high (115 and 235 μg L−1) but environmentally relevant MET concentrations. The exposure of algal cells to 115 and 235 μg L−1 MET originated a decrease in the levels of antioxidants molecules (reduced glutathione and carotenoids) as well as a reduction of the activity of scavenging enzymes (superoxide dismutase and catalase). These results suggest that antioxidant (non-enzymatic and enzymatic) defenses were affected by the excess of MET. As consequence of this imbalance (ROS overproduction and decline of the antioxidant system), ROS inflicted oxidative injury with lipid peroxidation and damage of cell membrane integrity. The results provide further insights about the toxic modes of action of MET on a non-target organism and emphasize the relevance of toxicological studies in the assessment of the impact of herbicides in freshwater environments.

Acute toxicity of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol alone and in combination using a battery of bioassays.

Acute toxicity of chlorpyrifos (CP) and its principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) alone and in combination have been evaluated using a test battery comprising aquatic organisms from different trophic levels: luminescent marine bacteria Aliivibrio fischeri, freshwater unicellular alga Pseudokirchneriella subcapitata, and cladoceran Daphnia magna. As expected, D. magna was the more sensitive organism to the compounds tested, being CP more toxic than its metabolite. On the contrary, TCP was found to be more toxic than its parental compound to A. fischeri and P. subcapitata. In all cases, the mixture of CP and its metabolite was more toxic than the compounds tested separately, multiplying between 5 and 200 times CP toxicity level and up to 15 times TCP toxicity level. These results indicate that the co-existence of parent chemical and its degradation product in the environment can result in a synergic interaction involving high risk to the aquatic ecosystems. Graphical abstract.

Chronic exposure of the freshwater alga Pseudokirchneriella subcapitata to five oxide nanoparticles: Hazard assessment and cytotoxicity mechanisms

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.

Novel use of the alga Pseudokirchneriella subcapitata, as an early-warning indicator to identify climate change ambiguity in aquatic environments using freshwater finfish farming as a case study.

Aquaculture is one of the fastest growing food producing industries in the world. This dramatic increase in growth has raised many environmental concerns. Evaluation of fish farm effluent is frequently assessed by physicochemical parameters. This approach indicates potential degradation caused by the effluent and not cumulative effects on aquatic ecosystems. This study investigated relationships between physicochemical parameters (temperature, pH, conductivity, nitrogen, phosphorus, oxygen and suspended solids), typically used to assess water quality with the Pseudokirchneriella subcapitata algal bioassay, which evaluated the potential ecotoxicological effects that freshwater fish farm effluent has on its receiving ecosystems and organisms. Influent and effluent samples were collected from a freshwater farm facility every two weeks from April 2018 to October 2018 in the Republic of Ireland. This monitoring period coincided with one of the warmest and driest periods recorded by meteorological stations in the Republic of Ireland. Physicochemical analyses were found to be similar to those in other farm studies. After exposure of algae to the effluent, stimulation of algal growth rates increased by >50%. This stimulation was observed during periods of increased temperatures which were as a result of heat wave and drought conditions experienced during monitoring. Correlation studies identified a moderately strong relationship between algal stimulation and temperature (r = -0.619). This study discovered that removal of Lemna minor (aquatic plant), impacted strongly on the freshwater farm pond-process to cope with nitrates. The constructed wetland system was unable to efficiently treat nitrates and phosphates during conditions of drought. These findings indicate that standard water quality parameters may not be applicable to inform appropriate suitability of fish farm effluent for discharge to receiving water. The research conducted in this study has suggested a potential toolbox that includes P. subcapitata may provide an early warning system for adverse effects as a result of climate change.

Ecotoxic effects of loratadine and its metabolic and light-induced derivatives

Loratadine and desloratadine are second-generation antihistaminic drugs. Because of human administration, they are continuously released via excreta into wastewater treatment plants and occur in surface waters as residues and transformation products (TPs).Loratadine and desloratadine residues have been found at very low concentrations (ng/L) in the aquatic environment but their toxic effects are still not well known. Both drugs are light-sensitive even under environmentally simulated conditions and some of the photoproducts have been isolated and characterized. The aim of the present study was to investigate the acute and chronic ecotoxicity of loratadine, desloratadine and their light-induced transformation products in organisms of the aquatic trophic chain. Bioassays were performed in the alga Pseudokirchneriella subcapitata, the rotifer Brachionus calyciflorus and in two crustaceans, Thamnocephalus platyurus and Ceriodaphnia dubia. Loratadine exerted its acute and chronic toxicity especially on Ceriodaphnia dubia (LC50: 600 µg/L, EC50: 28.14 µg/L) while desloratadine showed similar acute toxicity among the organisms tested and it was the most chronically effective compound in Ceriodaphnia dubia and Pseudokirchneriella subcapitata. Generally, transformation products were less active in both acute and chronic assays.

Biological Assessment of Water Toxicity and Fertility of Wastewater Omer Bek Drain Discharging into Receiving Water of the River Nile in Egypt

Water toxicity and fertility of a drain wastewater discharging wastewater directly to theDamietta branch of the River Nile were seasonally investigated from winter to autumn,2016. Nutrient enrichment bioassays to define the algal growth limiting nutrients, theirbioavailability and heavy metal toxicity of the sampled water, were carried out with the ISOstandard test alga Pseudokirchneriella subcapitata. The algal growth potential (AGP) testexhibited a wide range of growth potential ranging from 0.4 mg.l-1 to 19.42 mg.l-1 algal dryweight. At drain, mixing and recovery stations the algal growth was mainly limited byheavy metals toxicity with inhibition percent at day 14 of growth (%I14) ranged between27.9 and 58.6 while at the upstream reference station, %I14 ranged between 20 and 37.Thealgal growth was also limited by N and P depending on site and season. In all seasons, butonly at drain station, the expected Chl. a was significantly higher than the observed Chl. a,however, the reverse was held true for other sampling stations during this study. Therelationships between the chemically analyzed nutrients (P and N) and their bioavailableconcentrations were greatly affected by heavy metal toxicity. The results indicated that theobserved chlorophyll a showed significant correlations with TDP(r=0.82), while theexpected chlorophyll a correlated significantly with NH4-N(r=0.73). The algal growthpotential test proved a sensitive and reliable mean to assess water fertility and toxicity ofpolluting drains and the receiving waters.

Toxic effects of nickel oxide (NiO) nanoparticles on the freshwater alga Pseudokirchneriella subcapitata

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.

Ecotoxicity of disinfectant benzalkonium chloride and its mixture with antineoplastic drug 5-fluorouracil towards alga Pseudokirchneriella subcapitata.

BackgroundBenzalkonium chloride (BAC) is one of the most common ingredients of the disinfectants. It is commonly detected in surface and wastewaters where it can interact with the residues of pharmaceuticals that are also common wastewater pollutants. Among the latter, the residues of antineoplastic drugs are of particular concern as recent studies showed that they can induce adverse effect in aquatic organisms at environmentally relevant concentrations.MethodsEcotoxicity of BAC as an individual compound and in a binary mixture with an antineoplastic drug 5-fluorouracil (5-FU) was determined towards alga Pseudokirchneriella subcapitata, a representative of primary producers. The toxicity of the BAC+5-FU binary mixture was predicted by the two basic models: concentration addition (CA) and independent action (IA), and compared to the experimentally determined toxicity. Additionally combination index (CI) was calculated to determine the type of interaction.ResultsAfter 72 h exposure to BAC a concentration dependent growth inhibition of P. subcapitata was observed with an EC50 0.255 mg/L. Comparing the predicted no effect concentration to the measured concentrations in the surface waters indicate that BAC at current applications and occurrence in aquatic environment may affect algal populations. The measured toxicity of the mixture was higher from the predicted and calculated CI confirmed synergistic effect on the inhibition of algal growth, at least at EC50 concentration. The observed synergism may have impact on the overall toxicity of wastewaters, whereas it is less likely for general environments because the concentrations of 5-FU are several orders of magnitude lower from its predicted no effect concentration.DiscussionThese results indicate that combined effects of mixtures of disinfectants and antineoplastic drugs should be considered in particular when dealing with environmental risk assessment as well as the management of municipal and hospital wastewaters.