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The presence of metals in aquatic environments has increased worldwide. Environmental assessments of metals in freshwater ecosystems presume that toxicity is mainly caused by aqueous exposure, but dietborne exposure (contaminated food) in zooplankton may occur because microalgae carry metal ions through adsorption/absorption of dissolved metal species, resulting in toxic effects once ingested by the animals. However, official regulations for ecotoxicological assays in most countries do not consider the toxic effects caused by dietborne exposure. Here, we provide life history parameters and secondary production of Simocephalus serrulatus (Koch 1841) (Cladocera: Daphniidae) fed with cadmium (Cd) contaminated algae during a 21-day bioassay. The microalgae Chlorophyceae Scenedesmus quadricauda was exposed for 96 h to dissolved Cd concentrations of 0.03; 5.87; 12.27 and 22.27 µg Cd l(-1) (equivalent to 1.6 × 10(-10); 3.2 × 10(-8); 6.7 × 10(-8); 1.2 × 10(-7) mol l(-1)) that resulted in algae internal Cd burdens of 0.004; 0.032; 0.270 and 0.280 pg Cd cell(-1), respectively. Significant toxic effects on life history parameters of S. serrulatus were observed. Time of embryonic development, generation time and age at first reproduction (primipara) showed significant delay. Length at first reproduction, number of eggs and clutches produced per female, hatching percentage, body length, survival and feeding rates were significantly reduced. Secondary production, that is, accumulated biomass for growth and reproduction, decreased significantly with dietborne Cd concentrations. Our results emphasize that food can be an important source of metals to zooplankton in aquatic ecosystems. Environmental regulations should consider the diet in ecotoxicological assessments. Furthermore, secondary production may be considered as a suitable endpoint in ecotoxicity tests.

Cylindrospermopsis raciborskii is a cosmopolitan and potentially toxic planktonic Cyanobacteria that produces and exudes copious amounts of dissolved organic materials. This organism dominates the eutrophic reservoir Barra Bonita (Brazil), where it normally blooms throughout the year. This investigation focused on the characterization of such exudates analyzing their capacity to complex copper, zinc, lead and cadmium through the determination of ligand concentration (CL) and conditional stability constant (logK’ML), as well as elemental composition (C, H, N and S), the content of carbohydrates, proteins, lipids and dissolved organic carbon (DOC). The dissolved organic material was fractionated into 3 molecular weights (>30 kDa; 30–10 kDa; 10–3 kDa) and each fraction was analyzed. The results showed that in the >30 kDa and 30–10 kDa fractions carbohydrates dominate over proteins and lipids. Different CL and logK'ML were obtained for the different molecular weight fractions of the excreted organic materials, suggesting high diversity of ligands. In the >30 kDa, there were more complexing sites (CL) for Cu, but higher affinity (K′) for Zn. In the 30–10 kDa fraction, the higher CL was for Cd, but the greatest affinities were for Cu and Zn. In the 10–3 kDa fraction, higher CL was obtained for Cd and Zn, while Cu and Cd had the highest strengths of association. In the environment, such diversity of ligands and strengths of association can result in a displacement of metals weakly bound to the EOM, and increase metal buffering capacity of the environment, supporting higher metal inputs before toxic effects are detected in the biota.

Copper and Cd are natural constituents of freshwater ecosystems, both cycling influenced by microbial communities. The present research examined the impacts of environmentally relevant concentrations of Cu and Cd on the growth, viability, cell size, chlorophyll a (Chl a) content and photochemical efficiency of the tropical freshwater phytoplankton Chlorolobion braunii. Cell growth was significantly impaired by Cu and Cd, with EC50 occurring at 33.6 and 1.6µM, respectively. At sublethal levels (< EC50), cell death was already induced at 5µM Cu and 1µMCd. Average cell volume significantly increased as metal concentrations increased, as did the Chl a content per cell, although the Chl a content per unit volume decreased. Copper did not affect both the photosystem II (PSII) maximum quantum yield (ΦM) or the operational quantum yield (ΦE), while Cd significantly impacted ΦE, with EC50 occurring at 18.4µM. Different responses for Cu and Cd were obtained whether the photochemical fluorescence quenching (Qp) or non-photochemical quenching (Qn) were considered. Qp decreased after Cd addition, but was not altered after Cu addition. Qn values significantly increased after the addition of either metal. Non-photochemical quenching due to heat dissipation (NPQ) significantly increased in response to both metals, but it was more pronounced in the case of Cd. Overall, Cd was more toxic to C. braunii than Cu.

The impact of nanoparticles (NPs) in phytoplankton is understudied, particularly with respect to the organism’s physiology and environmentally relevant concentrations. In the present research, we investigated the effects of titanium dioxide nanoparticles (nano-TiO2) in the physiology of Scenedesmus bijugus, a freshwater cosmopolitan phytoplankter, exposed to concentrations ranging from 3.30 × 10−9 mol L−1 (log −8.48) to 3.70 × 10−7 mol L−1 (log −6.43), which includes environmentally relevant values. The nano-TiO2 concentrations in the medium and in the cells were determined in experiments that lasted 96 h. Controlled environmental conditions were used throughout and a variety of endpoints were monitored. These included cell density, cell viability, chlorophyll a concentration, growth rates, maximum quantum yield of photosystem II (ΦM), intracelular proteins and carbohydrates, and proteins:carbohydrates ratios. The results showed that cell viability was the most sensitive parameter for the detection of the nano-TiO2 effects, being followed by ΦM. At the concentration of 3.90 × 10−8 mol L−1 (log −7.40), there was an increase of nano-TiO2 injured cells, and at 3.70 × 10−7 mol L−1 (log −6.43) 24%, ΦM decrease in comparison with the controls was obtained. Different from several literature results, we showed that nano-TiO2 particles at environmentally relevant concentrations affected microalgae physiology, and this was dependent on the endpoint used to evaluate the effect.

PURPOSE: To compare the efficacy of two systems in cleaning used healing abutments (HAs). MATERIALS AND METHODS: A total of 60 used HAs were randomized into two groups: one treated with an automatic cleaning system, and the other with conventional decontamination procedures. After sterilization and staining, the HAs were microscopically analyzed and underwent a cellular adhesion in vitro assay. RESULTS: Contaminated areas were observed with different frequencies in the two groups (3.6% test; 78.2% control; P < .001). In vitro assay showed a uniform cell distribution in test HAs, while areas of debris without adhering cells were a common finding in the control HAs. CONCLUSION: Further studies investigating the chemical composition and clinical influence of biologic remnants are necessary before considering reusing HAs.

Early marginal bone loss (MBL) is a non-infective remodeling process of variable entity occurring within the first year after implant placement. It has a multifactorial etiology, being influenced by both surgical and prosthetic factors. Their impact remains a matter of debate, and controversial information is available, particularly regarding implants placed subcrestally. The present multicenter prospective clinical study aimed to correlate marginal bone loss around platform-switched implants with conical connection inserted subcrestally to general and local factors. Fifty-five patients were enrolled according to strict inclusion/exclusion criteria by four clinical centers. Single or multiple implants (AnyRidge, MegaGen, South Korea) were inserted in the posterior mandible with a one-stage protocol. Impressions were taken after two months of healing (T1), screwed metal-ceramic restorations were delivered three months after implant insertion (T2), and patients were recalled after six months (T3) and twelve months (T4) of prosthetic loading. Periapical radiographs were acquired at each time point. Bone levels were measured at each time point on both mesial and distal aspects of implants. Linear mixed models were fitted to the data to identify predictors associated with MBL. Fifty patients (25 male, 25 female, mean age 58.0 &plusmn, 12.8) with a total of 83 implants were included in the final analysis. The mean subcrestal position of the implant shoulder at baseline was 1.24 &plusmn, 0.57 mm, while at T4, it was 0.46 &plusmn, 0.59 mm under the bone level. Early marginal bone remodeling was significantly influenced by implant insertion depth and factors related to biological width establishment (vertical mucosal thickness, healing, and prosthetic abutment height). Deep implant insertion, thin peri-implant mucosa, and short abutments were associated with greater marginal bone loss up to six months after prosthetic loading. Peri-implant bone levels tended to stabilize after this time, and no further marginal bone resorption was recorded at twelve months after implant loading.

The objective of this proof-of-principle multicenter case series was to examine the bone regenerative potential of a newly introduced equine-derived bone mineral matrix (Equimatrix) to provide human sinus augmentation for the purpose of implant placement in the posterior maxilla. There were 10 patients requiring 12 maxillary sinus augmentations enrolled in this study. Histologic results at 6 months demonstrated abundant amounts of vital new bone in intimate contact with residual graft particles. Active bridging between residual graft particles with newly regenerated bone was routinely observed in intact core specimens. A mean value of 23.4% vital bone formation was observed at 6 months. This compared favorably with previous results using xenografts to produce bone in the maxillary sinus for the purpose of dental implant placement. Both the qualitative and quantitative results of this case series suggest comparable bone regenerative results at 6 months to bovine-derived xenografts.

Investigations were carried out to evaluate lipid class and fatty acid composition of Chlorella vulgaris in relation to several combinations of cadmium (2 × 10−8; 10−7 M Cd) and nitrogen (2.9 × 10−6 to 1.1 × 10−3 M N) concentrations. Triacylglycerols (TAG), acetone mobile polar lipids (AMPL) and phospholipids (PL) were the major lipid classes of C. vulgaris under all the tested conditions. TAG was the lipid class accumulated in the highest amount in N-limited C. vulgaris. The AMPL lipid class was lowest at the lowest N and highest Cd treatment. High proportions of saturated fatty acids (SAFA) and monounsaturated fatty acids (MUFA) in the total lipid extracts were recorded under N limitation in the presence of Cd. 16:1(n-11) was an exception among the MUFA as its levels decreased at low N. Total polyunsaturated FA (PUFA), ω3 PUFA levels, and PUFA:SAFA ratios increased with increasing N concentrations, but when exposed to Cd, their levels were significantly reduced. Unlike the other PUFA, 18:2(n-6) increase...

Objectives The purpose of this review was to evaluate whether history of periodontitis and smoking habits could represent a risk factor for peri-implantitis and implant loss. Material and Methods This systematic review followed PRISMA guidelines and was registered at the PROSPERO database [registration numbers CRD42016034160 (effect of history of periodontitis) and CRD42016033676 (effect of smoking)]. Broad electronic (MEDLINE) and manual searches were conducted among articles published from January 1st 1990 up to December 31st 2015, resulting in 49332 records for history of periodontitis and 3199 for smoking habits. Selection criteria included prospective studies comparing two cohorts of patients, with and without the investigated risk factor, with a minimum follow-up period of three years, and reporting data on peri-implantitis and implant loss occurrence. Considering that only prospective studies were included, dichotomous data were expressed as risk ratios and 95% confidence intervals. Results Three studies evaluating history of periodontitis (on which quantitative analysis was performed) and one study on smoking effect were included. Both implant and patient-based meta-analyses revealed a significantly higher risk of developing peri-implantitis in patients with a history of periodontitis compared with periodontally healthy subjects, but not a statistically significant increased risk for implant loss. Conclusions The outcomes of this systematic review indicate history of periodontitis as a possible risk factor for peri-implantitis, while insufficient data are present in literature to evaluate the role of smoking. However, available evidence is still weak and immature, and sound epidemiological studies are needed to analyse the specific contribution of these potential risk factors.

Introduction The task of Group 1 was to review and update the existing data concerning aetiology, risk factors and pathogenesis of peri-implantitis. Previous history of periodontitis, poor oral hygiene, smoking and presence of general diseases have been considered among the aetiological risk factors for the onset of peri-implant pathologies, while late dental implant failures are commonly associated with peri-implantitis and/or with the application of incorrect biomechanical forces. Special interest was paid to the bone cells dynamics as part of the pathogenesis of peri-implantitis. Material and Methods The main areas indagated by this group were as follows: influence of smoking, history of periodontitis and general diseases on peri-implantitis development, bio-mechanics of implant loading and its influence on peri-implant bone and cellular dynamics related to the pathogenesis of peri-implantitis. The systematic reviews and/or meta-analyses were registered in PROSPERO, an international prospective register of systematic reviews: http://www.crd.york.ac.uk/PROSPERO/. The literature in the corresponding areas of interest was screened and reported following the PRISMA (Preferred Reporting Item for Systematic Review and Meta-Analysis) Statement: http://www.prisma-statement.org/. Method of preparation of the systematic reviews, based on comprehensive search strategies, was discussed and standardized. The summary of the materials and methods employed by the authors in preparing the systematic reviews and/or meta-analyses is presented in Preface chapter. Results The results and conclusions of the review process are presented in the respective papers. One systematic review with meta-analysis, three systematic reviews and one theoretical analysis were performed. The group′s general commentaries, consensus statements, clinical recommendations and implications for research are presented in this article.

Severe atrophy of the anterior maxilla represents a major challenge for the clinician when planning an implant-supported rehabilitation. Several surgical options are available for augmenting bone volume in this area, including onlay or interpositional bone grafts, guided bone regeneration, distraction osteogenesis, and nasal floor augmentation. This case report describes a novel approach to nasal floor elevation using ultrasonic instruments to prepare the implant sites followed by transcrestal hydrodynamic nasal mucosa elevation and grafting with a collagenized xenogeneic biomaterial. This minimally invasive technique allowed for vertical augmentation of the atrophic anterior maxilla together with implant placement in a single-stage surgery.

Laurell-Gottlow suture modified by Sentineri for tight closure of a wound with a single line of sutures

The increasing contamination of aquatic environments motivates studies on the interactions among natural dissolved organic matter, metals, and the biota. This investigation focused on the organic exudates of the toxic cyanobacteria Cylindrospermopsis raciborskii as a Cu carrier through a three-level aquatic trophic chain (bacteria, protozoa, and copepod).The effects of bacteria activity and growth on the metal-organic complexes were evaluated through changes in free Cu(2+) ions, total dissolved, and total particulate Cu. To be sure that the added copper would be complexed to the exudates, its complexing properties were previously determined. The cyanobacteria exudate-Cu complexes were furnished to bacteria that were further used as a food source to the protozoan Paramercium caudatum. This was then furnished as food to the copepod Mesocyclops sp. The results showed that, in general, the cyanobacterial exudates decreased Cu bioavailability and toxicity to the first trophic level (bacteria), but because the heterotrophic bacteria accumulated Cu, they were responsible for the transference for the otherwise low availability metal form. Both the bacteria and protozoan organisms accumulated Cu, but no metal accumulation was detected in the copepods.

The acute toxicity of metals to Daphnia similis was determined and compared to other daphnid species to evaluate the suitability of this organism in ecotoxicology bioassays. To verify the performance D. similis in toxicity tests, we also investigated the effect of Pseudokirchneriella subcapitata at 1 x 10(5) and 1 x 10(6) cells ml(-1) on Cd and Cr acute toxicity to the cladoceran. Daphnid neonates were exposed to a range of chromium and cadmium concentrations in the absence and presence of the algal cells. Metal speciation calculations using MINEQL(+) showed that total dissolved metal concentrations in zooplankton culture corresponded to 96.2% free Cd and 100% free Cr concentrations. Initial total dissolved metal concentrations were used for 48 h-LC(50) determination. LC(50) for D. similis was 5.15 x 10(-7) mol l(-1) dissolved Cd without algal cells, whereas with 1 x 10(5) cells ml(-1), it was significantly higher (7.15 x 10(-7) mol l(-1) dissolved Cd). For Cr, the 48 h-LC(50) value of 9.17 x 10(-7) mol l(-1) obtained for the cladoceran in tests with 1 x 10(6) cells ml(-1) of P. subcapitata was also significantly higher than that obtained in tests without algal cells (5.28 x 10(-7) mol l(-1) dissolved Cr). The presence of algal cells reduced the toxicity of metals to D. similis, as observed in other studies that investigated the effects of food on metal toxicity to standard cladocerans. Comparing our results to those of literature, we observed that D. similis is as sensitive to metals as other standardized Daphnia species and may serve as a potential test species in ecotoxicological evaluations.

The original version of this article unfortunately contained a mistake. The name of the corresponding author was given as “Eduardo Caffagni de Camargo”. The correct name should be “Eduardo Caffagni Camargo”.

The present study aimed to investigate the response of several life history parameters (body length and age of primipara, duration of embryonic development, maximum body length, reproduction and survival) of the zooplankton Ceriodaphnia silvestrii while exposed to copper contaminated algae Pseudokirchneriella subcapitata. In order to evaluate chronic exposure on the animal's life history, long-term experimental design was used. Cladocerans were fed with a dietary copper concentration ranging from 3 to 68 fg Cu cell−1. Low waterborne copper exposure (around 10−10 mol L−1 free Cu2+ ions) was kept in the experiments. The results showed that by exposure of cladocerans during 7 days to contaminated food with 68 fg Cu cell−1, a significant reduction in neonate production, survival and body size were obtained. Inhibition on egg production of zooplankton at 38 fg Cu cell−1 were observed in 36 days chronic dietary copper exposure. The importance of entire life cycle study to better evaluate cladoceran responses to chronic dietary metal exposure was demonstrated.

Many studies have shown the reduction of metal toxicity in the presence of dissolved organic matter in natural waters; however, possible roles of metal-edible dissolved organic matter complexes as a vehicle of metal entrance into trophic chains have been poorly investigated. In this study copper uptake and toxicity to Ceriodaphnia cornuta Sars in the presence and absence of exudates produced by Anabaena spiroides Klebahn were investigated. Groups of 30 adult C. cornuta individuals were exposed to a range of copper concentration (10 28 –1 0 26 mol L 21 ) during a 24 h period. The “Trimmed Spearmen Karber” method was used to calculate EC50. Copper toxicity was almost 4-fold lower in the presence of 30 mg L 21 of cyanobacterial exudates; without exudates, EC50 was 8.1 � 10 28 mol L 21 , while with exudates it was 3.2 � 10 27 mol L 21 . Total copper concentration in the animals was determined using differential pulse anodic stripping voltammetry and the results showed that, for both treatments, metal accumulated by the organisms was not significantly different from the negative control, except for immobile individuals. The present results suggest that the animals were able to regulate their body copper content.

The influence of Anabaena spiroides exopolysaccharides (EPS) on copper speciation (total dissolved, particulate and free Cu2+ ions) and bioavailability in aquatic organisms was investigated. Bacteria were used as the first trophic level, Paramecium caudatum (protozoan) as the second and the copepod cyclopoid Metacyclops mendocinus as the third level. The organisms were obtained from a freshwater reservoir and held under continuous laboratory controlled conditions. Freshwater media containing EPS excreted by A. spiroides (10 mg L−1) and copper (1.0 × 10−6 mol L−1) were used for bacteria growth. Contamined bacteria were used as food source to protozoan, which was further furnished to copepods. The results showed a reduction of EPS concentration during bacteria growth and also a smaller copper accumulation by microorganisms in the presence of EPS. We concluded that A. spiroides exopolysaccharides have reduced copper entrance into the experimental aquatic microbial food chain.

This study aimed to investigate the influence of natural dissolved organic materials (DOM) on copper speciation (total dissolved, particulate, and free Cu2+ ions) and bioavailability during a two-level experimental microbial food chain. Bacteria were used as the first trophic level, and Paramecium caudatum (protozoan) as the second. The organisms were obtained from a freshwater reservoir and kept under controlled laboratory conditions. Three experimental treatments were performed: exposure of the organisms to copper in the absence of DOM, exposure to DOM in the absence of copper, and exposure to both copper and DOM. Freshwater medium containing natural DOM and copper at a total dissolved concentration of 1.8 x 10(-6) mol L(-1) was furnished to bacteria, which was further used as food to the protozoan. The results showed that after bacterial growth, DOM concentration decreased as quantified by total organic carbon determinations. At the same time, free Cu2+ ions concentration increased in the medium. A lower copper concentration was detected in both microorganisms in the presence of DOM. We conclude that natural DOM reduced copper accumulation in the organisms on the first and second trophic levels, thus reducing the entrance of copper into the aquatic microbial food chain.

The highest density of aggregates (1.4 3 103 L21) in the hypereutrophic Barra Bonita Reservoir (mean depth of 10.2 m) coincided with the peak population density of the diatom Aulacoseira granulata (2.3 3 106 chains L21), which was present in 94% of the aggregates for 22 consecutive months. To investigate why this diatom, which produces very small amounts of free extracellular polysaccharide (EPS) and transparent exopolymer particles (TEP), occurs so frequently in natural aggregates, we carried out aggregation experiments with cultures of A. granulata with and without its free EPS and TEP. Stickiness (a) was higher in exponential than stationary growth, either with or without EPS, but the highest value was obtained in cultures without EPS (0.37). During the stationary growth phase, a decreased, both with and without EPS. Replacement of natural polymer carbohydrates by A. granulata free EPS (.14 kiloDalton [kD] , 0.4 mm), or adding cultured diatom to reservoir water, produced aggregates larger than the natural ones. The role of EPS in these aggregation characteristics was investigated by analyzing its monosaccharide composition. The proportion of terminal monosaccharides significant in the aggregation was 74.5%, 56.1% of them consisting of hydrophobic deoxy-sugars fucose and rhamnose which increase the stickiness. Early in the growth, only hydrophobic-adhering films are responsible for fast aggregation by chain-to-chain collision. With aging cells, aggregation was mainly by the trapping effect of free EPS and TEP, both formed by released adherent films. We hypothesize that aggregates have an important role in seeding A. granulata in environments with significant advective transport, such as reservoirs.

A major question in the field of ecotoxicology is how DOM affects copper accumulation and toxicity in planktonic organisms; copper acute toxicity and bioaccumulation in Ceriodaphnia silvestrii were investigated in the presence and absence of humic substances (HS) under controlled laboratory conditions. Copper was determined as free Cu2+ ions in the media and total copper in the animals; metal ion buffers were used for ion selective electrode calibration, extending the lower detection limit to 10(-11) mol l(-1). Groups of 20 adult females of similar sizes were exposed (24 h) to a range of nominal copper concentrations. Based on total added copper, LC50 was 4.4 x 10(-8) mol l(-1) without HS, whereas with 20 mg l(-1) HS, it was 25 times higher (1.1 x 10(-6) mol l(-1)). Based on free Cu2+ ions LC50 was statistically similar either with (2.8 x 10(-8) mol l(-1)) or without HS (3.3 x 10(-8 )mol l(-1)). The present results showed that natural DOM reduced copper toxicity and that free Cu2+ ions correlates to the bioavailable fraction to zooplankton. Nevertheless, copper bioaccumulation by C. silvestrii was similar either in the presence or absence of humic substances, suggesting that C. silvestrii regulates its body copper content up to 3.0 x 10(-8) mol l(-1) free Cu2+ ions in the media. The organisms were not able to deal with higher free Cu2+ ions concentrations in the media.

A.T. Lombardi, T.M.R. Hidalgo, A.A.H. Vieira and A.L. Sartori. 2007. Toxicity of ionic copper to the freshwater microalga Scenedesmus acuminatus (Chlorophyceae, Chlorococcales). Phycologia 46: 74–7...

The objective of the present investigation was to verify if Anabaena spiroides exopolysaccharides sustains growth and reproduction of Ceriodaphnia cornuta. The animals were raised in controlled laboratory conditions and fed exclusively on A. spiroides exopolysaccharides, which were obtained from filtered stationary growth phase A. spiroides cultures. A molecular weight cut-off of 12-14 kDa was used to separate the exopolysaccharides from low molecular weight materials. The lyophilized exopolysaccharides were dissolved in filtered and autoclaved reservoir water at a concentration of 15 mgL -1 (0.22 ± 0.01 mg C animal -1 day -1 ). These results were compared with animals fed on seston at natural concentration obtained by filtering (68 μm) Barra Bonica Reservoir water (0.23 ± 0.01 mg C animal -1 day -1 ). Several life history parameters (duration of embryonic development, generation time, reproductive performance, age-specific length, primipara age and length) were obtained during 15-day experiments. Growth rate (GR) and weight-specific secondary production were also quantified. Exopolysaccharide-fed organisms had better growth and reproductive performance (0.091± 0.004 GR; 51 ± 4.59 eggs produced per female) than seston-fed individuals (0.078 ± 0.010 GR; 30.90 ± 7.25 eggs produced per female). These results show that such macromolecules are a potential food source, fulfilling nutritional requirements to sustain growth and reproduction of C. cornuta and supports trophic relationships in aquatic ecosystems.

Microalgae need a variety of nutrients for optimal growth and health. However, this rarely occurs in nature, and if nutrient proportions vary, biochemical changes can occur in phytoplankton community. This may result in modifications of zooplankton food quality, affecting aquatic food chains. Our aim was to investigate the toxicity of copper (Cu) to Selenastrum gracile, a common freshwater Chlorophyceae, at different physiological status induced by varying phosphorus (P) concentration in culture medium. Phosphorus was investigated at 2.3×10(-4), 1.1×10(-4), 2.3×10(-5), 4.6×10(-6) and 2.3×10(-6) mol L(-1) and Cu at six concentrations, ranging from 6.9×10(-9) mol L(-1) to 1.0×10(-7) mol L(-1) free Cu(2+) ions. To guarantee the cells would be in a physiological status that reflected the external P concentration, they were previously acclimated up to constant growth rate at each P concentration. Phosphorus acclimated cells were then exposed to Cu and toxicity was evaluated through population density, growth rates and chlorophyll a content. Free Cu(2+) ions concentrations were calculated through the chemical equilibrium model MINEQL(+). The results showed that higher Cu toxicity was obtained in P-limited than in P-replete cells, and that chlorophyll a/cell was higher in P-limited cells and excess Cu than in P-replete cells. This confirms the importance of microalgae nutritional status to withstand the negative effects of the trace metal.

The aim of this study was to assess the feasibility of a 180 L photobioreactor in which a submerged ultrafiltration system was used to maintain continuous nutrient inflow without biomass loss from the culture. After exponential growth, approximately 15% of the total volume was removed and replaced with a modified medium to induce algal physiological responses as a biochemical manipulation procedure. In this system, Chlorella sorokiniana was kept under healthy conditions, according to protein: carbohydrate ratio. C. sorokiniana was grown exponentially for 4 days up to 8.9x106 cells mL-1. The culture medium used for biochemical manipulation (72 h exposure) consisted of LC Oligo medium without nitrates or phosphates, and with 7x10-7 molL-1 total copper. The results confirmed the effectiveness of the submerged membrane and showed that algae exposure to a stressing medium resulted in intracellular carbohydrate increase, thus protein: carbohydrate (P:C) ratios, and affected lipid class composition. This novel photobioreactor configuration has the potential to improve microalgal yields and/or specific intracellular constituents, inasmuch as biochemical manipulation of the biomass is facilitated and the continuous system is operated without biomass loss.

Universidade Federal do Parana (UFPF), Ctr Estudos Mar, BR-83255000 Pontaldo Parand, Parana, Brazil

Metals have interactive effects on the uptake and metabolism of nutrients in microalgae. However, the effect of trace metal toxicity on amino acid composition of Chlorella vulgaris as a function of varying nitrogen concentrations is not known. In this research, C. vulgaris was used to investigate the influence of cadmium (10 −7 and 2.0 × 10 −8 mol L −1 Cd) under varying nitrogen (2.9 × 10 −6 , 1.1 × 10 −5 and 1.1 × 10 −3 mol L −1 N) concentrations on its growth rate, biomass and biochemical composition. Total carbohydrates, total proteins, total lipids, as well as individual amino acid proportions were determined. The combination of Cd stress and N limitation significantly inhibited growth rate and cell density of C. vulgaris. However, increasing N limitation and Cd stress stimulated higher dry weight and chlorophyll a production per cell. Furthermore, biomolecules like total proteins, carbohydrates and lipids increased with increasing N limitation and Cd stress. Ketogenic and glucogenic amino acids were accumulated under the stress conditions investigated in the present study. Amino acids involved in metal chelation like proline, histidine and glutamine were significantly increased after exposure to combined Cd stress and N limitation. We conclude that N limitation and Cd stress affects the physiology of C. vulgaris by not only decreasing its growth but also stimulating biomolecule production.

Summary 1. This work investigated the consumption of a microalgal (Anabaena spiroides) exopolysaccharide by the cladoceran Simocephalus serrulatus (Cladocera, Daphnidae) and its effect on copper toxicity. 2. Total organic carbon concentration was used to quantify the microalgal exopolysaccharide. Both copper-complexed exopolysaccharides and copper-free exopolysaccharides were taken up by S. serrulatus. 3. A reduction of free copper ions was obtained in the presence of A. spiroides exopolysaccharide. Copper toxicity (EC50) and zooplankton concentrations were inversely correlated to exopolysaccharide concentration in experimental media. 4. An increase of free copper ions in experimental media was obtained after exopolysaccharide consumption, suggesting that S. serrulatus excreted copper to the surrounding environment.

Dissolved organic materials released by the freshwater microalgae Scenedesmus acuminatus were fractionated into low- and high-molecular weight materials, which were investigated for their capacity to bind copper. The high-molecular weight material was also investigated for its monosaccharide composition and is further discussed in relation to the copper binding property. S. acuminatus was grown in batch cultures under laboratory controlled conditions and harvested at the beginning of stationary growth phase when exuded organic materials were obtained. Copper-complexing property of the total exuded organic materials and exopolysaccharides before and after freeze-drying was evaluated by complexometric titrations and Scatchard Plot Analysis of the titration data. The results revealed the presence of two copper-complexing ligands in the total exuded material, but only one in the exopolysaccharide. Stronger copper-complexing ligands are associated to low molecular weight compounds (LogK'1=7.3, LogCL1=-5.6; LogK'2=6.3, LogCL2=-5.1), whereas weaker ligands to the high molecular weight fraction (LogK'2=6.4, LogCL2=-5.6). Although freeze-drying the polymeric organic material (exopolysaccharide) may result in conformational changes of the molecule, no effect on copper-complexing properties was detected. Gas chromatography was used to evaluate the monosaccharide composition of the microalgal exopolysaccharide, which detected high content of mannose and 12% of acid monosaccharides.

In response to the government's strategic intentions for nursing outlined in Making a Difference (DoH 1999), the University of Brighton has used national vocational qualification (NVQ) standards to facilitate assessment of practice during the common foundation year of the pre-registration diploma in nursing. The aim of this initiative is to provide 'step on' and 'step off' points using a nationally recognised qualification to meet government requirements for a more flexible approach to nurse education.

The chemical fractionation and bioleaching of Mn, Al, Zn, Cu and Ti in municipal sewage sludge were investigated using Thiobacillus ferrooxidans as leaching microorganism. As a result of the bacterial activity, ORP increase and pH reduction were observed. Metal solubilization was accomplished only in experimental systems supplemented with energy source (Fe(II)). The solubilization efficiency approached approximately 80% for Mn and Zn, 24% for Cu, 10% for Al and 0.2% for Ti. The chemical fractionation of Mn, Al, Zn, Cu and Ti was investigated using a five-step sequential extraction procedure employing KNO3, KF, Na4P2O7, EDTA and HNO3. The results show that the bioleaching process affected the partitioning of Mn and Zn, increasing its percentage of elution in the KNO3 fraction while reducing it in the KF, Na4P2O7 and EDTA fractions. No significant effect was detected on the partitioning of Cu and Al. However, quantitatively the metals Mn, Zn, Cu and Al were extracted with higher efficiency after the bacterial activity. Titanium was unaffected by the bioleaching process in both qualitative and quantitative aspects.

The purpose of the present investigation was to evaluate possible ecological and physiological functions of mucilaginous capsules produced by the freshwater algae Kirchneriella aperta Teiling (Chlorococcales) as related to copper ions. All experiments were performed using synthetic media under laboratory-controlled conditions. Copper interactions were investigated by distinguishing between adsorption onto the mucilaginous material present at the surface of the cells, intracellular uptake, and differentiation between total dissolved copper and free copper ions in the culture medium. Kirchneriella aperta is sensitive to copper, as revealed by a 96-h EC 5 0 value of 10 - 9 . 2 2 M Cu 2 + . We demonstrated that the mucilaginous capsules were able to sequester copper ions from the medium through a passive mechanism, thus providing the cell with a mechanism able to postpone the toxic effects of copper. The organic material that diffuses into the test medium as well as the mucilaginous capsules produced by K. aperta both effectively complex copper; thus, toxicity must be related to free copper ions and not the total dissolved copper concentration in the medium.

Cadmium (Cd) is an important industrial and toxic metal. Its fate and toxicity in the environment may be mediated by association with dissolved organic materials excreted by phytoplankton. The aim of the present study was to investigate the trophodynamics and toxicity of Cd complexed with Cylindrospermopsis raciborskii exudates in a plankton food chain. The microbial loop involves heterotrophic bacteria as the primary consumer, which is supplemented with a Cd–exudate complex. The secondary consumer (protozoan Paramecium caudatum) was fed on the bacteria, and the tertiary consumer (copepod Mesocyclops longisetus) on the protozoa. The Cd complexing properties of the exudate were determined before the experiments, to ensure that all Cd was furnished to the organisms as the organic complex alone. The results showed that free Cd2+ ions caused the highest observed toxicity to bacteria, while Cd complexed to the cyanobacterial exudate was less toxic, but could be bioavailable and transferred through the food web. This study is a contribution to aquatic ecosystem management and to current knowledge of Cd dynamics, bioavailability and interaction with aquatic planktonic organisms.

The effects of municipal sewage sludge solids concentration, leaching microorganisms (Thiobacillus thiooxidans or Thiobacillus ferrooxidans) and the addition of energy source (S0 or Fe(II)) on the bioleaching of metals from sewage sludge has been investigated under laboratory conditions using shake flasks. The results show that metal solubilization was better accomplished if additional energy source is supplemented to the microorganisms and that T. thiooxidans furnishes, in general, more adequate conditions for the bioleaching than T. ferrooxidans. At a total solids concentration of 70 g L-1 (originally present in the sludge) pH drop and ORP increase are attenuated, so metal solubilization is negatively affected. It was also demonstrated that if lead (Pb) solubilization is to be achieved, than a special combination of microorganism/energy source must be applied.

Nitrogen and phosphorus present in sewage can be used for microalgae growth, possibiliting cost reduction in the production of microalgae at the same time that it decreases the eutrophication potential of the effluent. This research aimed at monitoring the native community of microalgae and coliform bacteria in a secondary effluent from anaerobic municipal sewage treatment. Two treatments (aerated and non-aerated) were performed to grow microalgae under semi-controlled conditions in semi-closed photobioreactors in a greenhouse. The results showed no significant pH and coliforms (total and Escherichia coli ) variation between treatments. Nutrient concentrations were reduced supporting microalgae growth up to 10 (7) cells.mL (-1) independent of aeration. Exponential growth was obtained from the first day for the non-aerated, but a 5 day lag phase of growth was obtained for the aerated. Chlorella vulgaris was the dominant microalgae (99.9%) in both treatments. In the aerated, 5 algae classes were detected (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae), with 12 taxa, whereas in the non-aerated, 2 classes were identified (Chlorophyceae and Cyanophyceae), with 5 taxa. We concluded that effluent is viable for microalgae growth, especially Chlorella vulgaris, at the same time that the eutrophication potential and coliforms are decreased, contributing for better quality of the final effluent.

The need for clean and low-cost algae production demands for investigations on algal physiological response under different growth conditions. In this research, we investigated the growth, biomass production and biochemical composition of Chlorella vulgaris using semi-continuous cultures employing three growth media (LC Oligo, Chu 10 and WC media). The highest cell density was obtained in LC Oligo, while the lowest in Chu medium. Chlorophyll a, carbohydrate and protein concentrations and yield were highest in Chu and LC Oligo media. Lipid class analysis showed that hydrocarbons (HC), sterol esthers (SE), free fatty acids (FFA), aliphatic alcohols (ALC), acetone mobile polar lipids (AMPL) and phospholipids (PL) concentrations and yields were highest in the Chu medium. Triglyceride (TAG) and sterol (ST) concentrations were highest in the LC Oligo medium. The results suggested that for cost effective cultivation, LC Oligo medium is the best choice among those studied, as it saved the cost of buying vitamins and EDTA associated with the other growth media, while at the same time resulted in the best growth performance and biomass production. A necessidade de algas limpas e custo de produção baixo demanda as investigações sobre a resposta fisiologica das algas sob condições diferentes de crescimento. Nesta pesquisa, investigamos o crescimento, produção biomassa e composição bioquímica de Chlorella vulgaris cultivada em três meios de crescimento (LC Oligo, Chu 10 e WC). A maior densidade celular foi obtida em LC Oligo, enquanto mais baixo em meio Chu 10. Concentrações e rendimentos de clorofila a, carboidratos e proteínas foram mais altas em meios de Chu e Oligo. Análise de classe lipidicas mostrou que as concentrações e rendimentos dos hidrocarbonetos (HC), ésteres de esterol (SE), ácidos graxos livres (FFA), álcoois alifáticos (ALC), lipídios polares móveis em acetona (AMPL) e fosfolipídios (PL) foram maiores no meio Chu. Triglicerídeos (TAG) e esterol livre (ST) foram maiores no meio LC Oligo. Os resultados sugerem que pra o cultivo rentável, LC Oligo é a melhor escolha entres os meios estudados, como ele salvou o custo de comprar as vitaminas e EDTA associados com os outros meios, enquanto, ao mesmo tempo resultou no melhor desempenho de crescimento e produção biomassa.

Several freshwater phytoplanktonic species (eukaryotic and prokaryotic) were grown in batch cultures up to stationary phase and quantified by chlorophyll a analysis. The complexation properties (co...

The freshwater planktonic alga Kirchneriella aperta was grown in batch cultures to stationary growth phase. Copper and lead complexation properties of the exudate from stationary and exponential gr...

Marine dissolved organic material (“marine DOM”, Mediterranean Sea) and a well characterized soil fulvic acid (“SFA”, Conway) were extracted using tC18 Sep-Pak cartridges. The extracts were characterized by fluorescence spectroscopy before and after reverse phase high performance liquid chromatographic fractionation (RP-HPLC). Based on soil fulvic acid, the tC18 Sep-Pak extraction procedure led to a loss of 65% of the fluorophores at λ ex 350 nm, and 34% of those at λ ex 450 nm, yet with no alteration in wavelength maxima; similar behavior was obtained for the marine DOM. Conventional fluorescence emission showed that the SFA fluorescence is 2.5 times higher than that of the marine DOM at λ ex / λ em 350/452 nm and 11 times higher at λ ex / λ em 450/522 nm. The higher fluorescence emission of the SFA in relation to the marine DOM can be attributed to compounds of high polarity. A blue shift was obtained when comparing the emission maximum of marine DOM ( λ em 437 nm) to that of SFA ( λ em 452 nm) at a fixed excitation of 350 nm, whereas no significant difference was obtained when excitation was fixed at 450 nm. Several distinct classes of fluorophores were detected in both marine DOM and SFA by the synchronous excitation technique: λ ex / λ em 317/335 nm and 486/504 nm are present in the SFA, and λ ex / λ em 352/370 nm and 566/584 nm in the marine DOM.

Carbon (14C) assimilation and the release of labeled dissolved organic carbon (DO14C) by Synura petersenii Korshikov (Chrysophyceae) were investigated at a range of irradiances (100–1260 μmol photons m−2 s−1) in axenic batch cultures. At up to 1260 μmol m−2 s−1, carbon assimilation was not saturated, although a 25% chlorophyll-a reduction in relation to the initial value at 1000 μmol m−2 s−1 and 28% at 1260 μmol m−2 s−1 was observed. The DO14C release was low at all irradiances investigated and dependent on carbon fixation; the highest release (4.8% of the total 14C assimilated) was observed at 1260 μmol m−2 s−1. In a second experiment, 14C assimilation by S. petersenii was measured at 130 μmol m−2 s−1. The subsequent loss of labeled particulate organic carbon (PO14C) and release of DO14C were determined during a 5-h period in which cells were incubated in nonlabeled medium at different irradiances. At 2000 μmol m−2 s−1 there was a 20.6% PO14C loss. The values of DO14C release were low for both 2...

The freshwater chrysophyte Synura sp. was grown in batch cultures up to stationary growth phase, harvested, and the dissolved organic material collected. Gas–liquid chromatographic analysis showed that mannose and xylose made up 50% of the total polysaccharide composition. Large amounts of protein were detected in the extracellular material by spectrophotometric assay. The complexation properties (conditional stability constant and total ligand concentration) presented by the polysaccharide were investigated using copper and lead ion selective electrodes for complexometric titrations. Scatchard plot analysis revealed that Synura sp. produces one major ligand characterized by high affinity for copper and moderate affinity for lead and another ligand with very low affinity for either metal.

Copper complexation parameters, e.g., conditional stability constant (K') and ligand concentration (CL), were obtained for marine DOM and soil fulvic acid (SFA). Complexometric titrations using Cu(II) as the titrant were monitored by fluorescence quenching and data treatment was performed using a two-binding site model. The marine DOM was isolated by partitioning onto tC18 Sep-Pak cartridges and followed by a reverse phase-high performance liquid chromatography fractionation. The SFA was investigated before and after receiving the same treatment as the marine sample. The results show that there is a loss of ligands with high affinity for copper as a result of the Sep-Pak treatment on the SFA. The Sep-Pak processed SFA ligands are associated with fluorophores with excitation wavelength at 350 nm. The more polar chromatographic fractions have higher values of CL/TOC, obeying a linear relation. A linear relation was also observed between total quenching (100-IML) and normalised CL values (CL/TOC).

The green algae D. tertiolecta, the flagellate I. galbana and the diatom C. gracilis were grown in batch cultures. The organisms were analysed for lipid class composition at the logarithmic and stationary growth phases using the Chromarod-Iatroscan thin layer chromatography with flame ionization detection (TLC-FID) system. There were major differences in lipid class production among the organisms investigated, but few differences in lipid class distribution between log phase and stationary phase cultures of D. tertiolecta and I. galbana. C. gracilis displayed the general trend exhibited in diatom metabolism, which can be characterized by an increase in triacylglycerol synthesis in situations of stress.

Extending the fluorescence quenching single-ligand model of Ryan-Weber, a multiligand model that does not require a direct measurement of the free metal ion concentration is proposed. It is shown that the problem of inconsistent negative ligand concentrations, commonly predicted by single-ligand models, may be overcome by using multiligand models. Finally, particular results concerning the conditional stability constants and ligand concentrations for one-, two and three- ligand cases are presented for soil fulvic acid, both before and after reverse phase HPLC fractionation.

Fatty acids are the fundamental structural components of membrane lipids, and the degree of saturation of the long hydrocarbon chains in microalgae contributes to regulation of growth, biomass production and reproduction of aquatic consumers. This research aimed at evaluating the effects of cadmium (2×10(-8); 10(-7) mol L(-1) Cd) on lipid class and fatty acid composition of the microalga Chlorella vulgaris under varying phosphate (PO(4)(3-)) concentrations (6.0×10(-7) to 2.3×10(-4) mol L(-1)). Under PO(4)(3-) limitation and Cd stress, the storage lipid class triacylglycerol (TAG) was the most accumulated among the lipid classes. Fatty acid composition revealed that the degree of saturation increased with increasing Cd stress and PO(4)(3-) limitation. Decreasing PO(4)(3-) and increasing Cd concentrations resulted in higher saturated fatty acid (SAFA) and monounsaturated FA (MUFA) concentrations. Total polyunsaturated FA (PUFA) and ω3 PUFA, and PUFA:SAFA ratios were higher in the control (2.3×10(-4) mol L(-1) PO(4)(3-)) cells than in either PO(4)(3-) limitation or Cd stress, or in the combination of both stresses. Contrasting with all the other PUFAs, 18:2n - 6 increased as PO(4)(3-) limitation increased. A significant positive relationship of PUFAs, acetone mobile polar lipids (AMPL) and phospholipids (PL) with phosphate concentration in the culture media was obtained, while TAG concentrations had a positive association with total MUFA and SAFA. Total SAFA, 14:0, 18:1n - 9 and 18:2n - 6 were positively correlated with Cd and negatively with PO(4)(3-) concentrations. The microalga responded to combined PO(4)(3-) limitation and Cd exposure by increasing its total lipid production and significantly altering its lipid composition. The FA 18:2n - 6 may be considered a stress biomarker for PO(4)(3-) limitation and Cd stress in C. vulgaris.

The aim of this study was to investigate the dynamics of the fluorescent dissolved organic matter (FDOM) in Paranaguá Estuarine System (PES) as to infer about the contribution of allochthonous FDOM to the estuarine waters in relation to tidal condition and seasons. Fluorescence spectroscopy was used for such purpose and DOM characterization through fluorescence emission was performed using excitation wavelengths of λex 350 nm and λex 450 nm, the two main fluorescence groups known to be present in natural DOM. Relations between emission wavelength (λem) and environmental variables, and the relevance of these variables to the different tides and seasons were identified by principal component analysis. The results showed that the first class of fluorophores (λex 350 nm) changed from the river (freshwater) towards the estuary, whilst the second class (λex 450 nm) has a more conservative nature and does not change as significantly as the first. Allochthonous DOM contribution to the estuarine system is intensified during the rainy season, especially in spring tides, whereas in the dry season the ratio of autochthonous DOM to total DOM in PES waters increased. We concluded that the variation of maximum λem of the first class of fluorophores (λex 350 nm) is mainly related to allochthonous contribution, whilst the maximum of emission for the second class of fluorophores (λex 450 nm) is dependent on the contribution of the different sources of organic matter (freshwater and marine water DOM contribution).O objetivo deste estudo foi investigar a dinâmica da matéria orgânica fluorescente (FMOD) no Complexo Estuarino de Paranaguá (CEP) para inferir sobre a contribuição da FMOD alóctone nas águas estuarinas em relação à condição de maré e estações do ano (seca e chuvosa). Empregou-se a técnica de espectroscopia de fluorescência, através da utilização de dois comprimentos de onda de excitação, os quais correspondem a duas classes conhecidas de fluoróforos, λex 350 nm e λex 450 nm, para desta forma determinar o comprimento de onda de máxima emissão (λem) da fluorescência da MOD. Relações entre λem e variáveis ambientais e a relevância das relações nas diferentes condições de maré (sizígia e quadratura) e estações do ano (seca e chuvosa) foram identificadas com o uso de análise de componentes principais. Os resultados demonstraram que a primeira classe de fluoróforos (λex 350 nm) foi alterada durante a transição rio estuário, enquanto a segunda classe (λex 450 nm) apresentou um comportamento mais conservativo. A contribuição da MOD alóctone no estuário foi intensificada durante a estação chuvosa, especialmente durante as marés de sizígia, enquanto na estação seca a MOD autóctone é preponderante na composição da MOD total no CEP. Conclui-se que a variação nos λem da primeira classe de fluoróforos (λex 350 nm) é principalmente relacionada à contribuição alóctone, enquanto as diferenças nos λem da segunda classe (λex 450 nm) estão relacionadas com as flutuações nas contribuições das diferentes fontes de MOD no CEP.

Life-history parameters of Ceriodaphnia cornuta (Cladocera: Daphniidae) fed on Pseudokirchneriella subcapitata (Chlorophyceae) exposed to different copper concentrations were investigated. C. cornuta individuals were reared in four treatments: (a) reconstituted water and non-contaminated algae (RW); (b) reconstituted water and copper-contaminated algae with either 1.28 × 10(-13) (10(-7)Cu) or (c) 1.93 × 10(-13) g Cu cell(-1) (10(-6)Cu); and (d) natural water from a local reservoir and non-contaminated algae (NW). Copper content in C. cornuta individuals increased as diet-borne exposure increased (RW 10(-7)Cu NW 10(-6)Cu), except for NW individuals, which exhibited higher copper body burden than RW and 10(-7)Cu individuals, suggesting that some copper was available in the natural water. The results suggest that subacute levels of dietary copper stimulated C. cornuta's growth and reproduction, whereas organisms reared on reconstituted water showed nutritional deficiency. Depending on copper exposure concentration, either growth (lower Cu concentration) or reproduction (higher Cu concentration) was further stimulated, suggesting that an alteration of resource allocation is involved in diet-borne copper exposure. Because differences among treatments were only significantly different after day 12 of the experiment, our results reinforce that full life-cycle tests are more appropriate than the standard 7 day or three-brood chronic bioassays used to evaluate dietary copper effects at low, chronic copper inputs and that the use of standard test-organisms may not address site-specific situations for tropical environments.