The importance of calcium in improving resistance of Daphnia to Microcystis

Changing environmental calcium (Ca) and rising cyanobacterial blooms in lake habitats could strongly reduce Daphnia growth and survival. Here, we assessed the effects of maternal Ca in Daphnia on transfer of resistance to their offspring against Microcystis aeruginosa PCC7806 (M. aeruginosa). Laboratory microcosm experiments were performed to examine effects in Daphnia carinata (D. carinata) and Daphnia pulex (D. pulex), and that how Ca induce responses in their offspring. The results showed that growth and survival were increased in offspring from exposed Daphnia as compared to unexposed, when raised in high Ca and increasing M. aeruginosa concentration. Among exposed Daphnia, offspring from high Ca mothers, produced more neonates with large size and higher survival as compared to offspring from low maternal Ca. Exposed D. carinata and D. pulex offspring, when reared in Ca deficient medium and increasing M. aeruginosa concentration, time to first brood increased, size become large and total offspring decreased subsequently in three alternative broods in offspring from low maternal Ca. In contrast, growth and reproduction in offspring from high Ca exposed mothers were consistent in three alternative broods. Despite species specific responses in growth, survival and variant life history traits in two Daphnia species, our results not only show maternal induction in Daphnia but also highlight that offspring response to M. aeruginosa varies with maternal Ca. This study demonstrates that Ca have role in Daphnia maternal induction against Microcystis, and recent Ca decline and increasing Microcystis concentration in lakes may decrease Daphnia growth and survival. Our data provide insights into the interactive effect of maternal Ca and Microcystis exposure on Daphnia and their outcome on offspring life history traits and survival.

TiO2-based photocatalytic disinfection of microbes in aqueous media: A review

The TiO₂ based photocatalyst has great potential for the disinfection/inactivation of harmful pathogens (such as E.coli in aqueous media) along with its well-known usefulness on various chemical pollutants. The disinfection property of TiO₂ is primarily attributed to surface generation of reactive oxygen species (ROS) as well as free metal ions formation. Furthermore, its disinfection capacity and overall performance can be significantly improved through modifications of the TiO₂ material. In this review, we provide a brief survey on the effect of various TiO₂ materials in the disinfection of a wide range of environmentally harmful microbial pathogens (e.g., bacteria, fungi, algae, and viruses) in aqueous media. The influencing factors (such as reactor design, water chemistry, and TiO₂ modifications) of such processes are discussed along with the mechanisms of such disinfection. It is believed that the combined application of disinfection and decontamination will greatly enhance the utilization of TiO₂ photocatalyst as a potential alternative to conventional methods of water purification.

Limnothrix sp. KO05: A newly characterized cyanobacterial biosorbent for cadmium removal: the enzymatic and non-enzymatic antioxidant reactions to cadmium toxicity

In this study, we isolated five indigenous cyanobacterial strains from different aqueous environments, with heavy metals contamination, in East Azerbaijan Province (northwest portion of Iran). A strain was identified by morphological and 16S rRNA sequence analysis as Limnothrix sp. KO05 and selected for further studies as having the greatest potential for cadmium uptake. Scanning electron microscopy (SEM) demonstrated cyanobacterium Limnothrix sp. KO05 forms filamentous structures and is straight or curved to some extent. The utmost biosorption capacity was found to be 82.18±1.22mgg^-1 at a Cd (II) concentration level of 150mgL^-1. Langmuir adsorption isotherm indicated a better fit to the experimental data. Response surface methodology (RSM) on the basis of four independent variables and the predicted maximum biosorption efficiency was 98.7% under the optimum condition. FT-IR spectroscopy profile of the Cd treated sample as demonstrated in confirmation of the benefits of various functional groups of proteins and polysaccharides of cyanobacterial biomass, involved in surface binding of Cd. The determination of catalase (CAT) activity in strain KO05 exposed to Cd (II) concentrations of 2, 5 and 10mgL^-1 showed an increase in enzyme activity after 24h exposure compared to unexposed cells. Correspondingly, CAT activity showed a significant decrease after 48h of treatment with Cd (II) concentrations of 5 and 10mgL^-1. CAT activity was decreased significantly at all concentrations within 72h after exposure to Cd. On the contrary, while ascorbate peroxidase (APX) gave the expected lower activity compared to the CAT within 24h after Cd treatment, its activity lasted up to 72h. Limnothrix sp. KO05 cells treated with 5 and 10mgL^-1 Cd (II) over 72h exposure showed a reduction in chlorophyll a contents compared to the controls. However, following exposure to Cd, chlorophyll a and carotenoid contents is reduced and after overcoming stress and deployment of an adaptation mechanism, the amounts of these pigments is gradually increased in the cells. The reduction was slower for chlorophyll a pigment compared to carotenoids that may be an indication of the physiological importance of chlorophyll pigment for the phtosynthetic cells. Results related to lipid peroxidation in Limnothrix sp. KO05 represent a significant increase of MDA in the first 24h after exposure to the different concentrations of Cd (2, 5 and 10mgL^-1). However, the MDA levels were decreased over time and no significant difference attained after 72h exposure to Cd concentrations of 2 and 10mgL^-1 compared to control.

Molybdenum and phosphorus limitation of moss-associated nitrogen fixation in boreal ecosystems

Biological nitrogen fixation (BNF) performed by moss-associated cyanobacteria is one of the main sources of new nitrogen (N) input in pristine, high-latitude ecosystems. Yet, the nutrients that limit BNF remain elusive. Here, we tested whether this important ecosystem function is limited by the availability of molybdenum (Mo), phosphorus (P), or both. BNF in dominant mosses was measured with the acetylene reduction assay (ARA) at different time intervals following Mo and P additions, in both laboratory microcosms with mosses from a boreal spruce forest and field plots in subarctic tundra. We further used a ¹⁵ N₂ tracer technique to assess the ARA to N₂ fixation conversion ratios at our subarctic site. BNF was up to four-fold higher shortly after the addition of Mo, in both the laboratory and field experiments. A similar positive response to Mo was found in moss colonizing cyanobacterial biomass. As the growing season progressed, nitrogenase activity became progressively more P limited. The ARA : ¹⁵ N₂ ratios increased with increasing Mo additions. These findings show that N₂ fixation activity as well as cyanobacterial biomass in dominant feather mosses from boreal forests and subarctic tundra are limited by Mo availability.

Phytoestrogens and sterols in waters with cyanobacterial blooms - Analytical methods and estrogenic potencies

Compounds with estrogenic potencies and their adverse effects in surface waters have received much attention. Both anthropogenic and natural compounds contribute to overall estrogenic activity in freshwaters. Recently, estrogenic potencies were also found to be associated with cyanobacteria and their blooms in surface waters. The present study developed and compared the solid phase extraction and LC-MS/MS analytical approaches for determination of phytoestrogens (8 flavonoids - biochanin A, coumestrol, daidzein, equol, formononetin, genistein, naringenin, apigenin - and 5 sterols - ergosterol, β-sitosterol, stigmasterol, campesterol, brassicasterol) and cholesterol in water. The method was used for analyses of samples collected in stagnant water bodies dominated by different cyanobacterial species. Concentrations of individual flavonoids ranged from below the limit of detection to 3.58 ng/L. Sterols were present in higher amounts up to 2.25 μg/L. Biological potencies of these phytoestrogens in vitro were characterized using the hERα-HeLa-9903 cell line. The relative estrogenic potencies (compared to model estrogen - 17β-estradiol) of flavonoids ranged from 2.25E-05 to 1.26E-03 with coumestrol being the most potent. None of the sterols elicited estrogenic response in the used bioassay. Estrogenic activity was detected in collected field water samples (maximum effect corresponding to 2.07 ng/L of 17β-estradiol equivalents, transcriptional assay). At maximum phytoestrogens accounted for only 1.56 pg/L of 17β-estradiol equivalents, contributing maximally 8.5% of the total estrogenicity of the water samples. Other compounds therefore, most likely of anthropogenic origin such as steroid estrogens, are probably the major drivers of total estrogenic effects in these surface waters.

Treatment challenge of a cyanobacterium Romeria elegans bloom in a South Australian wastewater treatment plant - a case study

A bloom of the non-toxic cyanobacterium Romeria elegans in waste stabilisation ponds (WSPs) within Angaston waste water treatment plant (WWTP) has posed an unprecedented treatment challenge for the local water utility. The water from the WSPs is chlorinated for safety prior to reuse on nearby farmland. Cyanobacteria concentrations of approximately 1.2 × 106 cells mL^-1 increased the chlorine demand dramatically. Operators continuously increased the disinfectant dose up to 50 mg L^-1 to achieve operational guideline values for combined chlorine (0.5-1.0 mg L^-1) prior to reuse. Despite this, attempts to achieve targeted combined chlorine residual (CCR) failed. In this study, samples from the waste stabilisation pond at Angaston WWTP were chlorinated over a range of doses. Combined chlorine, disinfection by-product formation, cyanobacteria cell concentration, Escherichia coli inactivation, as well as dissolved organic carbon and free ammonia were monitored. This study shows that, in the occurrence of cyanobacterial blooms, CCR does not directly suggest pathogen removal efficiency and is therefore not an ideal parameter to evaluate the effectiveness of disinfection process in WWTP. Instead, E. coli removal is a more direct and practical parameter for the determination of the efficiency of the disinfection process.

Biological nitrogen fixation by alternative nitrogenases in boreal cyanolichens: importance of molybdenum availability and implications for current biological nitrogen fixation estimates

Cryptogamic species and their associated cyanobacteria have attracted the attention of biogeochemists because of their critical roles in the nitrogen cycle through symbiotic and asymbiotic biological fixation of nitrogen (BNF). BNF is mediated by the nitrogenase enzyme, which, in its most common form, requires molybdenum at its active site. Molybdenum has been reported as a limiting nutrient for BNF in many ecosystems, including tropical and temperate forests. Recent studies have suggested that alternative nitrogenases, which use vanadium or iron in place of molybdenum at their active site, might play a more prominent role in natural ecosystems than previously recognized. Here, we studied the occurrence of vanadium, the role of molybdenum availability on vanadium acquisition and the contribution of alternative nitrogenases to BNF in the ubiquitous cyanolichen Peltigera aphthosa s.l. We confirmed the use of the alternative vanadium-based nitrogenase in the Nostoc cyanobiont of these lichens and its substantial contribution to BNF in this organism. We also showed that the acquisition of vanadium is strongly regulated by the abundance of molybdenum. These findings show that alternative nitrogenase can no longer be neglected in natural ecosystems, particularly in molybdenum-limited habitats.

Microcystins affect zooplankton biodiversity in oxbow lakes

The authors tested the hypothesis that zooplankton diversity and density are affected by the presence of cyanotoxins in the water. The authors focused on 4 oxbow lakes of the Vistula River in southern Poland, which are subjected to mass cyanobacterial development. In 2 of the oxbows (Piekary and Tyniec), microcystins released into the water were found. The highest concentration of microcystins (0.246 μg/L) was observed for microcystins LR. Zooplankton diversity showed a weak response to the presence of microcystins released into the water. The Shannon index (H') of total zooplankton diversity decreased in the Piekary and Tyniec oxbows during periods when the microcystin concentrations were highest. The same trend was noted for diversity of rotifers in both oxbows and for diversity of copepods in Piekary, but not for copepods in Tyniec. No such trends were found for the diversity of cladocerans in any of the oxbows, nor was a relationship found between density of zooplankton and microcystins. Statistical analyses showed that the number of species in individual samples was negatively correlated with the levels of sulfates, phosphates, and ammonia, but the microcystin concentration was positively related to those levels. This points to the complexity of the interactions and synergies among toxins, abiotic factors, and zooplankton biodiversity. In focusing on the problem of cyanotoxins, conservation studies should pay attention to this complexity. Environ Toxicol Chem 2017;36:165-174. © 2016 SETAC.

Influence of Metals on the Cyanobacterial Community in a Water Supply System in a Tropical Region

  This work aimed to study the influence of metals on the temporal dynamics of cyanobacteria community in Carpina Dam (7° 53' 22'' S and 35° 20' 34'' W). Samples were collected from Raw Water Pumping Station at the Water Treatment Station Feira Nova in the city of Feira Nova (Pernambuco, Brazil), from January 2011 to December 2013. The concentration of metals in water (aluminum, antimony, barium, lead, copper, chromium, cadmium, iron, manganese) was determined by atomic absorption spectroscopy in the laboratory. For the identification and counting of cyanobacteria, an inverted optical microscope and Sedgewick-Rafter counting chambers were used. Principal Component Analysis (PCA) was used for recognition of cluster patterns between the studied points. There were variations in abiotic and biotic components in the different years of study. The metals iron, aluminum, barium and manganese had the greatest influence on the temporal dynamics of cyanobacteria in the reservoir.

Study on formation of 2,4,6-trichloroanisole by microbial O-methylation of 2,4,6-trichlorophenol in lake water

To explore the mechanisms and influence factors on the production of 2,4,6-trichloroanisole (2,4,6-TCA) in surface waters, the 2,4,6-TCA formation potential (FP) test was conducted by incubating the real lake water with the addition of 2,4,6-trichlorophenol (2,4,6-TCP) precursor. Besides bacteria and fungi, two common cyanobacteria and algae species, i.e., Chlorella vulgaris and Anabaena flos-aquae, have been proved to have strong capabilities to produce 2,4,6-TCA, which may contribute the high 2,4,6-TCA FP (152.2 ng/L) of lake water. The microbial O-methylation of 2,4,6-TCP precursor is catalyzed by chlorophenol O-methyltransferases (CPOMTs), and their characteristics were identified by adding inductive methyl donors or excluding microorganisms via ultrafiltration. The results indicated both S-adenosyl methionine (SAM) dependent and non-SAM dependent CPOMTs played important roles; extracellular CPOMTs also participated in the biosynthesis of 2,4,6-TCA. Moreover, investigating the effects of various environmental factors revealed initial 2,4,6-TCP processor concentration, temperature, pH and some divalent metal cations (i.e., Mn²⁺, Mg²⁺ and Zn²⁺) had obvious effects on the production of 2,4,6-TCA.

Rapid ecotoxicological bioassay using delayed fluorescence in the marine cyanobacterium Cyanobium sp. (NIES-981)

The use of delayed fluorescence intensity as an endpoint for rapid estimation of the effective concentration (EC_x) has been reported as an alternative to standard growth inhibition (at 72 h after exposure) in some algal species including Pseudokirchneriella subcapitata. In marine algae, although an approach of bioassaying using delayed fluorescence measurements has not been performed yet, its development would provide many benefits for marine environmental risk assessment. In this study, we selected marine cyanobacterium Cyanobium sp. (NIES-981) as our test algal species and demonstrated that this species is valid for the standard growth inhibition test based on criteria provide by Organization for Economic Co-operation and Development guidelines. Furthermore, standard inhibition tests and shorter period test using DF were performed in NIES-981 using five chemicals (3,5-DCP, simazine, diflufenican, K₂Cr₂O₇, and CuSO₄), and their EC₅₀ and low-toxic-effect values (EC₁₀, EC₅, and NOEC) were determined from two dose-response curves. Based on comparisons of the two dose-response curves and the EC₅₀ values, we conclude that DF intensity is useful as an endpoint for rapid estimation of EC₅₀ in NIES-981.

Tolerance of cyanobacteria to the toxicity of BDE-47 and their removal ability

Polybrominated diphenyl ethers are ubiquitous and toxic contaminants in aquatic environments. The effect of polybrominated diphenyl ether BDE-47 on five species of cyanobacteria, along with their removal ability was investigated. Four species, namely Synechocystis sp., Oscillatoria planctonica, Microcystis flos-aquae and Nostoc sp., were exposed to BDE-47 at concentrations ranging from 0.05 to 1.0 mg L^-1 for 14 days, while the exposure time for Pseudanabaena sp. was 30 days. The first four species were very tolerant to BDE-47 while growth and photosynthesis of Pseudanabaena were significantly inhibited by BDE-47 at concentrations over 0.1 mg L^-1. However, this species could recover from the toxicity of high concentrations of BDE-47 after 30 days of exposure, indicating the development of some "resistance" after pre-exposure to 1.0 mg L^-1 BDE-47. The "resistant" cells had a higher growth rate, photosynthesis and glutathione S-transferase activity than normal Pseudanabaena cells. The sensitivity of Pseudanabaena to BDE-47 toxicity was affected by its initial filament density, with cultures having a low filament density (2.3 × 10⁶ filaments mL^-1) being up to 14-15 times more sensitive than cultures with a high filament density (13 × 10⁶ filaments mL^-1). All cyanobacteria could remove 70-82% of BDE-47 in their media, with more than 60% of BDE-47 accumulated in cells. This is the first study showing the high tolerance of different cyanobacteria species to BDE-47 toxicity and their removal ability. The study also revealed that the sensitive Pseudanabaena could acquire a "resistance" to BDE-47, which was transferred to the next generation.

Assessing the impacts of phosphorus inactive clay on phosphorus release control and phytoplankton community structure in eutrophic lakes

Addressing the challenge that phosphorus is the key factor and cause for eutrophication, we evaluated the phosphorus release control performance of a new phosphorus inactive clay (PIC) and compared with Phoslock^®. Meanwhile, the impacts of PIC and Phoslock^® on phytoplankton abundance and community structure in eutrophic water were also discussed. With the dosage of 40 mg/L, PIC effectively removed 97.7% of total phosphorus (TP) and 98.3% of soluble reactive phosphorus (SRP) in eutrophic waters. In sediments, Fe/Al-phosphorus and organic phosphorus remained stable whereas Ca-phosphorus had a significant increase of 13.1%. The results indicated that PIC may form the active overlay at water-sediment interface and decrease the bioavailability of phosphorus. The phytoplankton abundance was significantly reduced by PIC and decreased from (1.0-2.4) × 10⁷ cells/L to (1.3-4.3) × 10⁶ cells/L after 15 d simultaneous experiment. The phytoplankton community structure was also altered, where Cyanobacteria and Bacillariophyceae were the most inhibited and less dominant due to their sensitivity to phosphorus. After PIC treatment, the residual lanthanum concentration in water was 1.44-3.79 μg/L, and the residual aluminium concentration was low as 101.26-103.72 μg/L, which was much less than the recommended concentration of 200 μg/L. This study suggests that PIC is an appropriate material for phosphorus inactivation and algal bloom control, meaning its huge potential application in eutrophication restoration and management.

Effects of Antibiotics on the Growth and Physiology of Chlorophytes, Cyanobacteria, and a Diatom

The occurrence of antibiotics in surface waters has been reported worldwide with concentrations ranging from ng L^-1 to low µg L^-1 levels. During environmental risk assessments, effects of antibiotics on algal species are assessed using standard test protocols (e.g., the OECD 201 guideline), where the cell number endpoint is used as a surrogate for growth. However, the use of photosynthetic related endpoints, such as oxygen evolution rate, and the assessment of effects on algal pigments could help to inform our understanding of the impacts of antibiotics on algal species. This study explored the effects of three major usage antibiotics (tylosin, lincomycin, and trimethoprim) on the growth and physiology of two chlorophytes (Desmodesmus subspicatus and Pseudokirchneriella subcapitata), a cyanobacteria (Anabaena flos-aquae), and a diatom (Navicula pelliculosa) using a battery of parameters, including cell density, oxygen evolution rate, total chlorophyll content, carotenoids, and the irradiance-photosynthesis relationship. The results indicated that photosynthesis of chlorophytes was a more sensitive endpoint than growth (i.e., EC₅₀ derived based on the effects of tylosin on the growth of D. subspicatus was 38.27 µmol L^-1 compared with an EC₅₀ of 17.6 µmol L^-1 based on photosynthetic rate), but the situation was reversed when testing cyanobacteria and the diatom (i.e., EC₅₀ derived based on the effects of tylosin on the growth of A. flos-aquae was 0.06 µmol L^-1; EC₅₀ 0.33 µmol L^-1 based on photosynthetic rate). The pigment contents of algal cells were affected by the three antibiotics for D. subspicatus. However, in some cases, pigment content was stimulated for P. subcapitata, N. pelliculosa, and A. flos-aquae. The light utilization efficiency of chlorophytes and diatom was decreased markedly in the presence of antibiotics. The results demonstrated that the integration of these additional endpoints into existing standardised protocols could provide useful insights into the impacts of antibiotics on algal species.

Response of three biofilm-forming benthic microorganisms to Ag nanoparticles and Ag+: the diatom Nitzschia palea, the green alga Uronema confervicolum and the cyanobacteria Leptolyngbya sp

Although the industrial use of nanoparticles has increased over the past decade, the knowledge about their interaction with benthic phototrophic microorganisms in the environment is still limited. This study aims to characterize the toxic effect of ionic Ag⁺ and Ag nanoparticles (citrate-coated silver nanoparticles, AgNPs) in a wide concentration range (from 1 to 1000 μg L^-1) and duration of exposure (2, 5 and 14 days) on three biofilm-forming benthic microorganisms: diatom Nitzschia palea, green algae Uronema confervicolum and cyanobacteria Leptolyngbya sp. Ag⁺ has a significant effect on the growth of all three species at low concentrations (1-10 μg L^-1), whereas the inhibitory effect of AgNPs was only observed at 1000 μg L^-1 and solely after 2 days of exposure. The inhibitory effect of both Ag⁺ and AgNPs decreased in the course of the experiments from 2 to 14 days, which can be explained by the progressive excretion of the exopolysaccharides and dissolved organic carbon by the microorganisms, thus allowing them to alleviate the toxic effects of aqueous silver. The lower impact of AgNPs on cells compared to Ag⁺ can be explained in terms of availability, internalization, reactive oxygen species production, dissolved silver concentration and agglomeration of AgNPs. The duration of exposure to Ag⁺ and AgNPs stress is a fundamental parameter controlling the bioaccumulation and detoxification in benthic phototrophic microorganisms.

Using H2O2 treatments for the degradation of cyanobacteria and microcystins in a shallow hypertrophic reservoir

Toxins produced by cyanobacteria in freshwater ecosystems constitute a serious health risk worldwide for humans that may use the affected water bodies for recreation, drinking water, and/or irrigation. Cyanotoxins have also been deemed responsible for loss of animal life in many places around the world. This paper explores the effect of H₂O₂ treatments on cyanobacteria and microcystins in natural samples from a hypertrophic reservoir in microcosm experiments. According to the results, cyanobacteria were more easily affected by H₂O₂ than by other phytoplanktonic groups. This was shown by the increase in the fractions of chlorophyll-a (a proxy for phytoplankton) and chlorophyll-b (a proxy for green algae) over total phytoplankton pigments and the decrease in the fraction of phycocyanin (a proxy for cyanobacteria) over total phytoplankton pigments. Thus, while an overall increase in phytoplankton occurred, a preferential decrease in cyanobacteria was observed with H₂O₂ treatments over a few hours. Moreover, significant degradation of total microcystins was observed under H₂O₂ treatments, while more microcystins were degraded when UV radiation was used in combination with H₂O₂. The combination of H₂O₂ and ultraviolet (UV) treatment in natural samples resulted in total microcystin concentrations that were below the World Health Organization limit for safe consumption of drinking water of 1 μg/L. Although further investigation into the effects of H₂O₂ addition on ecosystem function must be performed, our results show that the application of H₂O₂ could be a promising method for the degradation of microcystins in reservoirs and the reduction of public health risks related to the occurrence of harmful algal blooms.

Characterization of akinetes from cyanobacterial strains and lake sediment: A study of their resistance and toxic potential

Nostocalean cyanobacteria are known to proliferate abundantly in eutrophic aquatic ecosystems, and to produce several cyanotoxins, including anatoxin-a. In this study, we investigated both the resistance and toxic potential of the akinetes (resistant cells), using cyanobacterial cultures and akinetes extracted from the sediment of Lake Aydat (France) sampled in the winter and spring. Intact and lysed akinetes were differentiated using a double control based on the autofluorescence of akinetes and SYTOX-green staining. The percentage of resistant akinetes found in several different abiotic stress conditions was highly variable, depending on the species and also on the sampling season. Thus, the resistance of akinetes and their ability to germinate seems to follow a species-specific process, and akinetes can undergo physiologic changes during the sedimentary phase of the Nostocale life cycle. This study also revealed the first evidence of anatoxin-a genes in akinetes, with anaC and anaF genes detected in akinetes from all cyanobacterial producer cultures. The low number of anaC genes, almost exclusively detected using nested PCR, in the sediment at Lake Aydat suggests a limited but existent past population of toxic Nostocales in this lake. Given the key role of akinetes in the annual cycle and subsequent summer proliferation, it can be interesting to integrate the surveillance of akinetes in the management of lakes exposed to recurrent cyanobacterial blooms.

Comparing the sensitivity of chlorophytes, cyanobacteria, and diatoms to major-use antibiotics

The occurrence of antibiotic residues in the aquatic environment is an emerging concern. In contrast to daphnia and fish, algae are known to be particularly sensitive to antibiotic exposure. However, to date, a systematic evaluation of the sensitivity of different algal species to antibiotics has not been performed. The aim of the present study was therefore to explore the sensitivity of a battery of algal species toward antibiotic exposures. The present study investigated the growth inhibition effects of 3 major-use antibiotics, tylosin, lincomycin, and trimethoprim, on 7 algal species from the chlorophyte, cyanobacteria, and diatom groups. Based on median effective concentration (EC50) values, cyanobacteria (EC50 = 0.095-0.13 μmol/L) were found to be the most sensitive group to lincomycin followed by chlorophytes (EC50 = 7.36-225.73 μmol/L) and diatoms (EC50 > 225.73 μmol/L). Cyanobacteria were also the most sensitive group to tylosin (EC50 = 0.09-0.092 μmol/L), but, for this compound, diatoms (EC50 = 1.33-5.7 μmol/L) were more sensitive than chlorophytes (EC50 = 4.14-81.2 μmol/L). Diatoms were most sensitive to trimethoprim (EC50 = 7.36-74.61 μmol/L), followed by cyanobacteria (EC50 = 315.78-344.45 μmol/L), and chlorophytes (EC50 > 344.45 μmol/L) for trimethoprim. Although these results partly support the current approach to regulatory environmental risk assessment (whereby cyanobacterial species are recommended for use with antibiotic compounds), they indicate that for some antibiotics this group might not be the most appropriate test organism. It is therefore suggested that environmental risk assessments consider data on 3 algal groups (chlorophytes, cyanobacteria, and diatoms) and use test species from these groups, which are consistently found to be the most sensitive (Pseudokirchneriella subcapitata, Anabaena flos-aquae, and Navicula pelliculosa). Environ Toxicol Chem 2016;35:2587-2596. © 2016 SETAC.

Salinity induced physiological and biochemical changes in the freshly separated cyanobionts of Azolla microphylla and Azolla caroliniana

Freshly separated cyanobionts of Azolla microphylla and Azolla caroliniana plants exposed to salinity showed decline in the cellular constituents such as chlorophyll (23.1 and 38.9%) and protein (12.9 and 19.3%). However, an increase in the carotenoid and sugar content was observed. Exposure to salinity stress reduced the heterocyst frequency (35.4 and 57.2%) and nitrogenase activity (37.7 and 46.3%) of the cyanobionts. Increase in the activity of antioxidant enzymes such as super oxide dismutase (50.6 and 11.5%), ascorbate peroxidase (63.7 and 57.9%), catalase (94.2 and 22.5%) as well as non-enzymatic antioxidant proline (18.8 and 13.3%) was also observed in response to salinity. The cyanobionts exhibited significant increase in the intracellular Na(+) level and reduced intracellular K(+)/Na(+) and Ca(2+)/Na(+) ratio in response to salinity. The results demonstrate the adverse impact of salinity on the freshly separated cyanobionts as similar to free living cyanobacteria. These results may be helpful in the critical evaluation of salinity tolerance mechanism of the cyanobiont and its interaction with the host.

Development of algal interspecies correlation estimation models for chemical hazard assessment

Web-based Interspecies Correlation Estimation (ICE) is an application developed to predict the acute toxicity of a chemical from 1 species to another taxon. Web-ICE models use the acute toxicity value for a surrogate species to predict effect values for other species, thus potentially filling in data gaps for a variety of environmental assessment purposes. Web-ICE has historically been dominated by aquatic and terrestrial animal prediction models. Web-ICE models for algal species were essentially absent and are addressed in the present study. A compilation of public and private sector-held algal toxicity data were compiled and reviewed for quality based on relevant aspects of individual studies. Interspecies correlations were constructed from the most commonly tested algal genera for a broad spectrum of chemicals. The ICE regressions were developed based on acute 72-h and 96-h endpoint values involving 1647 unique studies on 476 unique chemicals encompassing 40 genera and 70 species of green, blue-green, and diatom algae. Acceptance criteria for algal ICE models were established prior to evaluation of individual models and included a minimum sample size of 3, a statistically significant regression slope, and a slope estimation parameter ≥0.65. A total of 186 ICE models were possible at the genus level, with 21 meeting quality criteria; and 264 ICE models were developed at the species level, with 32 meeting quality criteria. Algal ICE models will have broad utility in screening environmental hazard assessments, data gap filling in certain regulatory scenarios, and as supplemental information to derive species sensitivity distributions. Environ Toxicol Chem 2016;35:2368-2378. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Phycoremediation and adsorption isotherms of cadmium and copper ions by Merismopedia tenuissima and their effect on growth and metabolism

The current study tends to investigate the removal of cadmium and copper ions by Merismopedia tenuissima, grown in different concentrations of cadmium and copper ions, as well to investigate their effects on growth and metabolism. Sorption isotherms of Langmuir and Freundlich were obtained for the quantitative description of cadmium and copper uptake by M. tenuissima. Langmuir model adequately to describe the data of biosorption for these metals. However, the Freundlich model could work well in case of Cu(2+) only. M. tenuissima appears to be more efficient for removing Cd(2+) ions than Cu(2+). However, the affinity constant of Cu(2+) on the biomass of M. tenuissima was higher than Cd(2+) indicating that M. tenuissima is more tolerant to Cd(2+) phytotoxicity than Cu(2+). FTIR analysis of algae with and without biosorption revealed the presence of carboxyl, amino, amide and hydroxyl groups, which were responsible for biosorption of Cd(+2) and Cu(+2) ions.

Toxicological effects of chlorpyrifos on growth, enzyme activity and chlorophyll a synthesis of freshwater microalgae

This paper aims to acquire the experimental data on the eco-toxicological effects of agricultural pollutants on the aquatic plants and the data can support the assessment of toxicity on the phytoplankton. The pesticide of Chlorpyrifos used as a good model to investigate its eco-toxicological effect on the different microalgae in freshwater. In order to address the pollutants derived from forestry and agricultural applications, freshwater microalgae were considered as a good sample to investigate the impact of pesticides such as Chlorpyrifos on aquatic life species. Two microalgae of Chlorella pyrenoidosa and Merismopedia sp. were employed to evaluate toxicity of Chlorpyrifos in short time and long time by means of measuring the growth inhibition rate, the redox system and the content of chlorophyll a, respectively. In this study, the results showed that EC50 values ranging from 7.63 to 19.64mg/L, indicating the Chlorpyrifos had a relatively limited to the growth of algae during the period of the acute toxicity experiment. Moreover, when two kinds of algae were exposed to a medium level of Chlorpyrifos, SOD and CAT activities were importantly advanced. Therefore, the growth rate and SOD and CAT activities can be highly recommended for the eco-toxicological assessment. In addition, chlorophyll a also could be used as a targeted parameter for assessing the eco-toxicity of Chlorpyrifos on both Chlorella pyrenoidosa and Merismopedia sp.

Experimental iron amendment suppresses toxic cyanobacteria in a hypereutrophic lake

The effects of reducing nutrient inputs to lakes and reservoirs are often delayed by hysteresis resulting from internal phosphorus (P) loading from sediments. Consequently, controlling harmful algal blooms (HABs) in many eutrophic ecosystems requires additional management to improve water quality. We manipulated iron (Fe) concentrations in a hypereutrophic lake to determine if Fe amendment would suppress HABs by inhibiting P release from sediments. Our experiment consisted of 15 in situ mesocosms, 12 of which each received a different dose of Fe (ranging from 2 to 225 g/m² ); the remaining three were unmanipulated to serve as controls. Iron amendment decreased P accumulation in porewaters and the flux of P from sediments, which significantly lowered P concentrations in the water column. Iron exerted significant dose-dependent negative effects on the biomass of phytoplankton and periphyton, and reduced the dominance of cyanobacteria. Even at the lowest doses, Fe appeared to reduce the toxicity of cyanobacterial blooms, as measured by concentrations of hepatotoxic microcystins. Overall, our findings highlight the potential for Fe treatment as an effective strategy for minimizing HABs in eutrophic lakes and reservoirs. More broadly, our study reinforces the importance of Fe in regulating the trophic state of freshwaters, and the sensitivity of certain ecosystems to changes in Fe supply. Finally, we hypothesize that decreases in natural Fe supplies to lakes associated with anthropogenic activities may worsen outbreaks of toxic cyanobacteria.

Modern Methods for Isolation, Purification, and Cultivation of Soil Cyanobacteria

Up-to-date methods for isolation of cyanobacteria from soil samples, removal of accompanying microflora, obtaining axenic strains, and -conditions and media for subsequnt cultivation are reviewed. Char acterization of soil as a specific habitat for cyanobacteria is provided. Comparative analysis of pH and ele- mental composition of the liquid phase of most soil types with the media for cultivating cyanobacteria is car- ried out. The functional role of the major components required for the cultivation of cyanobacteria is de- scribed. The problems associated with isolation, purification, and cultivation of soil cyanobacteria, as well as the relevant solutions, are discussed.

Flocculation of cyanobacterial cells using coal fly ash modified chitosan

Harmful algal blooms (HABs) have increasingly occurred worldwide and pose serious threats to water environment safety. In this study, a compound flocculant (CFAL-Chitosan) was developed for HABs mitigation where chitosan was modified by coal fly ash leachate (CFAL). When using optimized dosage of CFAL-Chitosan flocculant, the zeta potential of Microcystis aeruginosa (M.A.) flocs stayed close to zero and algal removal efficiency plateaued over 90% in a wide dosage range from 3 to 6 mg L(-1). For chitosan without CFAL, removal efficiency peaked at 3 mg L(-1) with a maximum removal efficiency of 81%, which quickly decreased as the dosage increased (>3 mg L(-1)) due to the fast reversal of zeta potential. This indicated that CFAL-Chitosan could maintain a better removal efficiency over a wide dosage range as a result of improved charge neutralization compared with the chitosan only treatment. The flocs of CFAL-Chitosan were larger and denser than produced in the presence of chitosan without CFAL. However, excessive CFAL beyond the optimized dose inhibited M.A. removal due to hydrolysis and declining molecular weight of chitosan that weakened the bridging-netting properties, where surface charge reversal happened within a narrow dosage range and the removal-dosage curve became parabolic. The pH and metal residuals that were assumed to pose a threat to the aquatic environment were not significantly affected by adding optimized dosage of CFAL-Chitosan. The study provides a HABs control method using a cheap material of CFA. Further studies are needed to check the potential influence of leachable metals and persistent organic pollutants in CFA under a wide range of environmental condition.