Differential Effect of Hydroxen Peroxide οn Toxic Cyanobacteria of Hypertrophic Mediterranean Waterbodies

Cyanobacterial blooms have been known since ancient times; however, they are currently increasing globally. Human and ecological health risks posed by harmful cyanobacterial blooms have been recorded around the world. These risks are mainly associated with their ability to affect the ecosystem chain by different mechanisms like the production of cyanotoxins, especially microcystins. Their expansion and their harmful effects have led many researchers to seek techniques and strategies to control them. Among them, hydrogen peroxide could be a promising tool against cyanobacteria and cyanotoxins and it is well-established as an environmentally friendly oxidizing agent because of its rapid decomposition into oxygen and water. The aim of the present study was to evaluate the effect of hydrogen peroxide on phytoplankton from two hypertrophic waterbodies in Greece. The effect of hydrogen peroxide on concentration of microcystins found in the waterbodies was also studied. Treatment with 4 mg/L hydrogen peroxide was applied to water samples originated from the waterbodies and Cyanobacterial composition and biomass, phycocyanin, chlorophyll-a, and intra-cellular and total microcystin concentrations were studied. Cyanobacterial biomass and phycocyanin was reduced significantly after the application of 4 mg/L hydrogen peroxide in water treatment experiments while chlorophytes and extra-cellular microcystin concentrations were increased. Raphidiopsis (Cylindrospermopsis) raciborskii was the most affected cyanobacterial species after treatment of the water of the Karla Reservoir in comparison to Aphanizomenon favaloroi, Planktolyngbya limnetica, and Chroococcus sp. Furthermore, Microcystis aeruginosa was more resistant to the treatment of Pamvotis lake water in comparison with Microcystis wesenbergii and Microcystis panniformis. Our study showed that hydrogen peroxide differentially impacts the members of the phytoplankton community, affecting, thus, its overall efficacy. Different effects of hydrogen peroxide treatment were observed among cyanobacerial genera as well as among cyanobacterial species of the same genus. Different effects could be the result of the different resistance mechanisms of each genus or species to hydrogen peroxide. Hydrogen peroxide could be used as a treatment for the mitigation of cyanobacterial blooms in a waterbody; however, the biotic and abiotic characteristics of the waterbody should be considered.

Biochemical Mapping of Pyrodinium bahamense Unveils Molecular Underpinnings behind Organismal Processes

Proteins, lipids, and carbohydrates from the harmful algal bloom (HAB)-causing organism Pyrodinium bahamense were characterized to obtain insights into the biochemical processes in this environmentally relevant dinoflagellate. Shotgun proteomics using label-free quantitation followed by proteome mapping using the P. bahamense transcriptome and translated protein databases of Marinovum algicola, Alexandrium sp., Cylindrospermopsis raciborskii, and Symbiodinium kawagutii for annotation enabled the characterization of the proteins in P. bahamense. The highest number of annotated hits were obtained from M. algicola and highlighted the contribution of microorganisms associated with P. bahamense. Proteins involved in dimethylsulfoniopropionate (DMSP) degradation such as propionyl CoA synthethase and acryloyl-CoA reductase were identified, suggesting the DMSP cleavage pathway as the preferred route in this dinoflagellate. Most of the annotated proteins were involved in amino acid biosynthesis and carbohydrate degradation and metabolism, indicating the active roles of these molecules in the vegetative stage of P. bahamense. This characterization provides baseline information on the cellular machinery and the molecular basis of the ecophysiology of P. bahamense.

Tunisian inland water microflora as a source of phycobiliproteins and biological activity with beneficial effects on human health

Ten monoclonal microalgal cultures were obtained from several Tunisian inland water bodies, and their dichloromethane and methanolic extracts were screened for antibacterial, antileishmanial, and antioxidant properties, as well as phycobiliprotein production capacity. Cylindrospermopsis raciborskii has been shown to synthesize high levels of phycocyanin and may be an effective alternative source to other sources used for commercial production of phycocyanin. Chroococcus sp. and Leptolyngbya sp1. exhibited the strongest radical scavenging activity against DPPH (IC50 = 212.15 and 263.91 μg ml−1, respectively), indicating their promising potential for use as new effective and non-toxic antioxidants. Furthermore, Dunaliella sp. showed an interesting antileishmanial activity against the pathogens Leishmania infantum and Leishmania major (IC50 = 151 and 284 μg ml−1, respectively), thus representing a good candidate for use against cutaneous and visceral leishmaniasis in Tunisia, a country endemic to these diseases where thousands of new cases are registered every year. These results suggest that the strains of microalgae featured in this work have the potential to serve as natural alternative, safe and sustainable sources of high value-added products that could be used to improve the final biomass value.

Nutrient Regulation of Relative Dominance of Cylindrospermopsin-Producing and Non-cylindrospermopsin-Producing Raphidiopsis raciborskii

Raphidiopsis raciborskii (previously Cylindrospermopsis raciborskii) can produce cylindrospermopsin (CYN) which is of great concern due to its considerable toxicity to human and animals. Its CYN-producing (toxic) and non-CYN-producing (non-toxic) strains co-exist commonly in natural water bodies, while how their relative dominance is regulated has not been addressed. In this study, we combined field investigation with laboratory experiments to assessed the relationship between toxic and non-toxic R. raciborskii abundances under different nutrient levels. The rpoC1- and cyrJ-based qPCR was applied for quantifying total and toxic R. raciborskii abundances, respectively. The field survey showed that toxic R. raciborskii was detected in 97 of 115 reservoirs where its proportion ranged from 0.3% to 39.7% within the R. raciborskii population. Both total and toxic R. raciborskii abundances increased significantly with trophic level of these reservoirs, consistent with our monoculture and co-culture experiments showing in an increase in R. raciborskii growth with increasing nitrogen (N) or phosphorus (P) concentrations. In the monoculture experiments, growth rates of non-toxic and toxic strains from Australia or China were not significantly different under the same culture conditions. On the other hand, in the co-culture experiments, the toxic strains displayed a significantly faster growth than non-toxic strains under nutrient-replete conditions, resulting in an obvious shift toward the dominance by toxic strains from day 3 to the end of the experiments, regardless of the strain originating from Australia or China. The reverse was found under N- or P-limited conditions. Our results indicated that the toxic strains of R. raciborskii have a competitive advantage relative to the non-toxic strains in a more eutrophic world. In parallel to an increase in dominance, both toxic strains grown in the mixed population significantly increased CYN production under nutrient-replete conditions as compared to nutrient-limited conditions, suggesting that CYN may be of significance for ecological advantage of toxic R. raciborskii. These results highlight the importance of nutrient availability in regulating abundances and strain dominance of two genotypes of R. raciborskii. Our findings demonstrated that elevated nutrients would favor the growth of CYN-producing R. raciborskii and CYN production, leading to more blooms with higher toxicity at global scale.

Bloom Forming and Toxic Cyanobacteria in New Zealand Species Diversity and Distribution, Cyanotoxin Production and Accumulation of Microcystins in Selected Freshwater Organisms

<p>The objective of this doctoral study was to identify waterbodies in New Zealand containing cyanobacterial blooms and mats, to assess the species composition and to establish types and concentrations of cyanotoxins in samples obtained. A total of 271 water and cyanobacterial mat samples from 147 different waterbodies around New Zealand were collected or received between January 2001 and December 2004. Sixty seven percent were found to contain cyanobacteria and 4l% of the samples contained cyanobacteria in sufficiently high concentrations to be termed a bloom. A total of 54 different cyanobacteria species were recorded. Prior to 1987, 33 lakes in New Zealand were recorded as having experienced cyanobacterial blooms. In the present study an additional 18 lakes were recorded as having experienced blooms. Eight bloom forming cyanobacteria species not previously identified in New Zealand (Anabaena planktonica, Cylindrospermopsis raciborskii, Microcystis botrys, M. panniformis, M. icthtyoblabe, M. wesenbergii, Planktothrix peronata f. attenuata and Sphaerocavum brasiliense) were found to be dominant or co-dominant in at least some cyanobacterial blooms. In addition to these species, three non-dominant species were identified that were also new records for New Zealand. The water and cyanobacterial mat samples were analysed using ELISA's, LC/MS, HPLC and neuroblastoma assays for cyanotoxins and identified; microcystins/nodularins (102 samples from 54 different locations), anatoxin-a (3 samples from 3 different locations), cylindrospermopsins (l sample) and saxitoxins (48 santples from 4l different locations). Species from the genera Microcystis, Anabaena, Cylindrospermopsis, Nostoc, Planktothrix, Oscillatoria and Phormidium produce these cyanotoxins. An in-depth study in Lakes Rotoehu and Rotoiti investigated the relationship between cyanobacteria species composition and levels of microcystins over a six month period and examined accumulation of microcystins in rainbow trout (Oncorhynchtts mykiss) and freshwater mussels (Hydridella menziesi). Weekly water samples collected from both lakes showed that cyanobacteria species and levels of microcystins can vary over time during a bloom event. When phytoplankton samples were dominated by very high cell concentration of Microcystis spp. they were found to contain microcystins. Generally cell counts were found to be a poor indicator of levels of microcystins in the water samples, suggesting that cell counts alone are not a satisfactory way of identifying human health dangers in waterbodies containing cyanobacteria. Microcystins were detected in rainbow trout liver and muscle tissue, and in freshwater mussels. The Total Daily Intake of microcystins recommended by the World Health Organisation for humans is 0.04 pg kg-1 tdoy-1. A 70kg human consuming 300g of muscle tissue would have exceeded this level in 50% (Lake Rotoiti) and 7l% (Lake Rotoehu) of the samples. Health problems could result if more than 300 g of trout muscle tissue was consumed on a regular basis over an extended period. This study has demonstrated that the prevalence of freshwater cyanotoxin-producing cyanobacteria is widespread in New Zealand waterbodies and these cyanotoxins pose a potential health risk to both humans and animals either directly or indirectly.</p>

Bloom Forming and Toxic Cyanobacteria in New Zealand Species Diversity and Distribution, Cyanotoxin Production and Accumulation of Microcystins in Selected Freshwater Organisms

<p>The objective of this doctoral study was to identify waterbodies in New Zealand containing cyanobacterial blooms and mats, to assess the species composition and to establish types and concentrations of cyanotoxins in samples obtained. A total of 271 water and cyanobacterial mat samples from 147 different waterbodies around New Zealand were collected or received between January 2001 and December 2004. Sixty seven percent were found to contain cyanobacteria and 4l% of the samples contained cyanobacteria in sufficiently high concentrations to be termed a bloom. A total of 54 different cyanobacteria species were recorded. Prior to 1987, 33 lakes in New Zealand were recorded as having experienced cyanobacterial blooms. In the present study an additional 18 lakes were recorded as having experienced blooms. Eight bloom forming cyanobacteria species not previously identified in New Zealand (Anabaena planktonica, Cylindrospermopsis raciborskii, Microcystis botrys, M. panniformis, M. icthtyoblabe, M. wesenbergii, Planktothrix peronata f. attenuata and Sphaerocavum brasiliense) were found to be dominant or co-dominant in at least some cyanobacterial blooms. In addition to these species, three non-dominant species were identified that were also new records for New Zealand. The water and cyanobacterial mat samples were analysed using ELISA's, LC/MS, HPLC and neuroblastoma assays for cyanotoxins and identified; microcystins/nodularins (102 samples from 54 different locations), anatoxin-a (3 samples from 3 different locations), cylindrospermopsins (l sample) and saxitoxins (48 santples from 4l different locations). Species from the genera Microcystis, Anabaena, Cylindrospermopsis, Nostoc, Planktothrix, Oscillatoria and Phormidium produce these cyanotoxins. An in-depth study in Lakes Rotoehu and Rotoiti investigated the relationship between cyanobacteria species composition and levels of microcystins over a six month period and examined accumulation of microcystins in rainbow trout (Oncorhynchtts mykiss) and freshwater mussels (Hydridella menziesi). Weekly water samples collected from both lakes showed that cyanobacteria species and levels of microcystins can vary over time during a bloom event. When phytoplankton samples were dominated by very high cell concentration of Microcystis spp. they were found to contain microcystins. Generally cell counts were found to be a poor indicator of levels of microcystins in the water samples, suggesting that cell counts alone are not a satisfactory way of identifying human health dangers in waterbodies containing cyanobacteria. Microcystins were detected in rainbow trout liver and muscle tissue, and in freshwater mussels. The Total Daily Intake of microcystins recommended by the World Health Organisation for humans is 0.04 pg kg-1 tdoy-1. A 70kg human consuming 300g of muscle tissue would have exceeded this level in 50% (Lake Rotoiti) and 7l% (Lake Rotoehu) of the samples. Health problems could result if more than 300 g of trout muscle tissue was consumed on a regular basis over an extended period. This study has demonstrated that the prevalence of freshwater cyanotoxin-producing cyanobacteria is widespread in New Zealand waterbodies and these cyanotoxins pose a potential health risk to both humans and animals either directly or indirectly.</p>

Phenotypic plasticity and developmental noise in hybrid and parental clones of Daphnia longispina complex

According to the “temporal hybrid superiority hypothesis”, seasonal variability in environmental factors in temperate lakes gives hybrid clones within the D. longispina complex a temporary fitness advantage, thus allowing long-term, dynamic coexistence of hybrids and maternal taxa. However, the maintenance of hybrids would not require their superiority under any given set of environmental conditions if their average fitness over longer periods surpassed that of more specialized and less flexible parental clones. Phenotypic plasticity and developmental noise of several hybrid and maternal clones of Daphnia (Daphnia galeata, Daphnia hyalina, their hybrids and backcrosses) were compared in a series of laboratory experiments. Changes in depth selection and body size at first reproduction were scored in Daphnia exposed to predator (planktivorous fish) threat, to the presence of filamentous cyanobacteria (Cylindrospermopsis raciborskii), and to the presence of toxic compounds (PCB52 and PCB153). The hybrid clones were found to exhibit the broadest phenotypic plasticity of the studied traits in response to the different stress factors. Developmental noise in depth selection behaviour was the lowest in Daphnia galeata, the highest in Daphnia hyalina, and intermediate in hybrid and backcross clones. This diversity of reaction norms might permit the coexistence of closely related Daphnia clones in the variable and often unpredictable lake environment.

Validação de método analítico por extração líquido-líquido e análise por cromatografia gasosa acoplada à espectrometria de massas para detecção de ácidos haloacéticos em amostras ambientais

RESUMO O estudo teve como objetivo o desenvolvimento e a validação de um método analítico para detecção e quantificação de ácidos haloacéticos por meio da extração líquido-líquido e da análise por cromatografia gasosa acoplada à espectrometria de massas. Para a validação, consideraram-se parâmetros como linearidade, precisão, limites de detecção e quantificação e seletividade. Adicionalmente, aplicou-se o método para avaliar a formação de ácidos haloacéticos em ensaios de cloração de células de Cylindrospermopsis raciborskii com o oxidante hipoclorito de cálcio, simulando situações em estações de tratamento de água. O método apresentou baixo tempo de análise, excelente seletividade, precisão, repetitividade e sensibilidade, com possibilidade de aplicação para análises de rotina em substituição à cromatografia a gás por captura de elétrons. Observou-se a formação de ácidos haloacéticos durante os ensaios com doses de 2,5 e 5,0 mg.L-1 do oxidante, com destaque para os ácidos dicloroacético e tricloroacético.

Combining Imaging Flow Cytometry and Molecular Biological Methods to Reveal Presence of Potentially Toxic Algae at the Ural River in Kazakhstan

Algal blooms occur in freshwater bodies throughout the world, often leading to fish kills. Cases of these kills along the Ural River were reported in 2018–2019, involving significant amount of sturgeon in fish farming areas. In this study, the analysis of algal samples from the delta of the Ural River up to 100 km inland was carried out from August to December 2019 using imaging flow cytometry (IFC), molecular biological, and microscopic techniques. We identified the filamentous cyanobacteria Cuspidothrix issatschenkoi, Dolichospermum cf. flos-aquae, Dolichospermum cf. macrosporum, Pseudanabaena limnetica, and Planktothrix spp. as the dominant potentially toxic phytoplankton species, and we also found minor quantities of Cylindrospermopsis raciborskii. For the first time, molecular phylogenetic investigations of field clones of cyanobacteria from Ural River were carried out to establish the taxa of the dominant species and to identify the presence of genes encoding toxins. The complementary analysis with nanopore-based next-generation sequencing overlapped with the results of IFC and was instrumental in revealing minor cyanobacteria taxa. Real-time PCR analysis and sequencing indicated the presence of Microcystis and ADA-clade spp. as well as genes associated with the production of microcystin (mcyE) and the algal neurotoxin saxitoxin (sxtA) originating from cyanobacteria. These findings suggest that toxin-producing cyanobacteria could become a threat in the Ural River near Atyrau, which can significantly affect aquaculture in the region.