Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria.

We evaluated the effect of crude extracts of the microcystin-producing (MC+) cyanobacteria Microcystis aeruginosa on seed germination and initial development of lettuce and arugula, at concentrations between 0.5 µg.L(-1) and 100 µg.L(-1) of MC-LR equivalent, and compared it to crude extracts of the same species without the toxin (MC-). Crude extracts of the cyanobacteria with MC (+) and without MC (-) caused different effects on seed germination and initial development of the salad green seedlings, lettuce being more sensitive to both extracts when compared to arugula. Crude extracts of M. aeruginosa (MC+) caused more evident effects on seed germination and initial development of both species of salad greens than MC-. Concentrations of 75 µg.L(-1) and 100 µg.L(-1) of MC-LR equivalent induced a greater occurrence of abnormal seedlings in lettuce, due to necrosis of the radicle and shortening of this organ in normal seedlings, as well as the reduction in total chlorophyll content and increase in the activity of the antioxidant enzyme peroxidase (POD). The MC- extract caused no harmful effects to seed germination and initial development of seedlings of arugula. However, in lettuce, it caused elevation of POD enzyme activity, decrease in seed germination at concentrations of 75 µg.L(-1) (MC-75) and 100 µg.L(-1) (MC-100), and shortening of the radicle length, suggesting that other compounds present in the cyanobacteria extracts contributed to this result. Crude extracts of M. aeruginosa (MC-) may contain other compounds, besides the cyanotoxins, capable of causing inhibitory or stimulatory effects on seed germination and initial development of salad green seedlings. Arugula was more sensitive to the crude extracts of M. aeruginosa (MC+) and (MC-) and to other possible compounds produced by the cyanobacteria.

Vertical and temporal variation in phytoplankton assemblages correlated with environmental conditions in the Mundaú reservoir, semi-arid northeastern Brazil.

The goal of this study was to analyse the vertical structure of the phytoplankton community at the Mundaú reservoir, located in the semi-arid region of northeastern Brazil, and to correlate it to environmental conditions over two distinct seasons, dry and rainy. Samples were collected bimonthly at eight depths in the dry and rainy season for analyses of the physical and chemical variables of the water, as well as density, abundance, dominance, species diversity index and equitability of the community. Analysis of variance (ANOVA-two way) was used to analyse the vertical and seasonal differences, and Canonical Correspondence Analysis (CCA) was used to assess associations between phytoplankton and environmental variables Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju was the only dominant species and Geitlerinema amphibium (C. Agardh) Anagnostidis, Merismopedia punctata Meyen and Synedra rumpens Kützing. Others six taxa were abundant in at least one of the samples. Distinct vertical distribution patterns were observed for the abundant taxa between depths and seasons. The cyanobacteria, with the exception of C. raciborskii, showed similar seasonal patterns, with higher densities in the dry season. The CCA showed a strong correlation between the density of the phytoplanktonic species and abiotic variables. The vertical changes in abundant taxa revealed distinct patterns regulated by the variation in the environmental factors that were directly linked to seasonality, with the success of one or more species being dependent on their life strategies and ecological needs. The present study restates the importance of environmental and seasonal factors for phytoplankton composition and distribution in a freshwater tropical reservoir through a vertical gradient.

Phytotoxicity associated to microcystins: a review.

Microcystins (MC) are the most studied toxins of cyanobacteria since they are widely distributed and account for several cases of human and animal poisoning, being potent inhibitors of the serine/threonine protein phosphatases 1 (PP1) and 2A (PP2A). The phosphatases PP1 and PP2A are also present in plants, which may also suffer adverse effects due to the inhibition of these enzymes. In aquatic plants, biomass reduction is usually observed after absorption of cyanotoxins, which can bioaccumulate in its tissues. In terrestrial plants, the effects caused by microcystins vary from inhibition to stimulation as the individuals develop from seedling to adult, and include reduction of protein phosphatases 1 and 2A, oxidative stress, decreased photosynthetic activity and even cell apoptosis, as well as bioaccumulation in plant tissues. Thus, the irrigation of crop plants by water contaminated with microcystins is not only an economic problem but becomes a public health issue because of the possibility of food contamination, and this route of exposure requires careful monitoring by the responsible authorities.

Seasonal dynamics of cyanobacteria in a eutrophic reservoir (Arcoverde) in a semi-arid region of Brazil.

Environmental conditions favor the predominance of dense populations of cyanobacteria in reservoirs in northeastern Brazil. The aim of this study was to understand cyanobacterial population dynamics in the rainy and dry seasons at two depths in the Arcoverde reservoir. Microalgae and cyanobacteria samples were collected during 24 hours with intervals of 4 hours (nycthemeral) at sub-surface and 10 m using a van Dorn bottle and a determined biomass. Physical and chemical variables were obtained and the data were analyzed using the principal component analysis (PCA). No nycthemeral variations in the taxonomic composition or distribution of the populations of cyanobacteria were found between the different times of day in either the rainy or dry season. In both seasons, the greatest biomass of the phytoplankton community was made up of cyanobacteria at two depths and all times of the day. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju was dominant at all times of the day on both the surface and at the bottom. In the rainy season, the differences in cyanobacterial biomass between the surface and bottom were less significant than in the dry season. The differences in cyanobacterial biomass between surface and bottom were less pronounced than those found in the dry season. We concluded that a) physical variables better explain the alterations of species in the phytoplankton community in an environment dominated by cyanobacteria throughout the year; b) seasonal climatic factors associated to periods of stratification and de-stratification are important for alterations in the community and variations in biomass and, c) the turbidity caused by rainfall favored the emergence and establishment of other cyanobacteria, especially Planktothrix agardhii (Gomont) Anagnostidis & Komárek.

Effects of light intensity and temperature on Cylindrospermopsis raciborskii (Cyanobacteria) with straight and coiled trichomes: growth rate and morphology.

Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju (Ordem Nostocales) is one of the most troublesome bloom-forming species in Brazil. Understanding the population dynamics of the different morphotypes of C. raciborskii (straight and coiled) could assist in the prediction of favourable conditions for the proliferation of this potentially toxin-producing species. The aim of the present study was to assess the effects of two different light intensities and temperatures on the growth rate and morphology of the trichomes of the straight and coiled morphotypes. For such, two non-toxin producing strains of C. raciborskii were used - one with a coiled trichome (ITEP31) and another with a straight trichome (ITEP28). The strains were cultured in BG-11 medium in a climatic chamber under controlled conditions. Two light intensities (30 and 90 µmol.m-2.s-1 ) were combined at temperatures of 21 and 31 °C and the growth rate and morphological changes were analysed. The morphotypes responded differently to the different temperatures and light intensities. Both strains exhibited faster growth velocities when submitted to higher light intensity and temperature. The lower temperature and higher luminosity hampered the development of both strains. Variations in cellular morphology and an absence of akinetes in both strains were related to the lower temperature (21 °C). The coiled morphotype demonstrated considerable phenotype plasticity, changing the morphology of trichome throughout its growth curve. Although molecular analysis does not sustain the separation of the morphotypes as distinct species, their different eco-physiological responses should be considered further knowledge of extreme importance for the population control of these potentially toxic organisms.

Vertical and temporal dynamics of cyanobacteria in the Carpina potable water reservoir in northeastern Brazil.

This study analysed vertical and temporal variations of cyanobacteria in a potable water supply in northeastern Brazil. Samples were collected from four reservoir depths in the four months; September and December 2007; and March and June 2008. The water samples for the determination of nutrients and cyanobacteria were collected using a horizontal van Dorn bottle. The samples were preserved in 4% formaldehyde for taxonomic analysis using an optical microscope, and water aliquots were preserved in acetic Lugol solution for determination of density using an inverted microscope. High water temperatures, alkaline pH, low transparency, high phosphorous content and limited nitrogen content were found throughout the study. Dissolved oxygen stratification occurred throughout the study period whereas temperature stratification occurred in all sampling months, with the exception of June. No significant vertical differences were recorded for turbidity or total and dissolved forms of nutrients. There were high levels of biomass arising from Planktothrix agardhii, Cylindrospermopsis raciborskii, Geitlerinema amphibium and Pseudanabaena catenata. The study demonstrates that, in a tropical eutrophic environment with high temperatures throughout the water column, perennial multi-species cyanobacterial blooms, formed by species capable of regulating their position in the water column (those that have gas vesicles for buoyancy), are dominant in the photic and aphotic strata.

Diversity of microcystin-producing genotypes in Brazilian strains of Microcystis (Cyanobacteria).

Microcystis Kützing ex Lemmermann is among the genera of cyanobacteria often associated to toxic blooms with the release of microcystins. A gene cluster codes for microcystin synthetases, which are involved in the biosynthesis of this toxin. The aim of the present study was to investigate the genetic diversity of the mcyB gene, specifically the B1 module, in Brazilian strains of Microcystis spp. and its microcystin variants. Broad genetic diversity was revealed in this region. From the phylogenetic analysis, three clusters were obtained that were not related to the geographic origin or morphospecies of the strains, nor with the variant of the microcystin produced. A group of strains that did not produce microcystins was found, despite the presence of the mcyB1 fragment. Eight microcystin isoforms were detected: MC-LR, [D-Asp³]-MC-LR, [Asp³]-MC-LR, MC-RR, [Dha7]-MC-LR, MC-LF, MC-LW and [D-Asp³, EtAdda5]-MC-LH, the latter of which is described for the first time in Brazil. Moreover, five other variants were not identified and indicate being new.

Toxic cyanobacteria in reservoirs in northeastern Brazil: detection using a molecular method.

Cyanobacterial blooms are a frequent occurrence in northeastern Brazil and constitute a serious public health problem. Using the polymerase chain reaction (PCR) method, eleven environmental samples with cyanobacteria from seven reservoirs were used to determine the presence of the gene involved in microcystin biosynthesis (mcyB). Two sets of oligonucleotide primers were designed from the sequencing of Brazilian populations of microcystin producing cyanobacteria (mcyB-F/R and mcyB-F/R-A). The presence of the mcyB gene involved in microcystin biosynthesis was found in all samples, indicating the potential of this gene for producing the toxin. The PCR method proved sensitive and appropriate for the detection of potential producers of microcystins in environmental samples. Its ability to reveal potentially toxic cyanobacteria demonstrates that it can be a valuable tool in the monitoring of blooms.

The role played by endogenous and exogenous electric fields in DNA signaling and repair.

Comments are made and new insights are provided on the key role played by endogenous and exogenous electric fields, where the former starts and conducts the repairing chain, while the latter is able to scramble the completion of the repair process and, as a consequence, may have important potential as a radiation sensitizer for clinical application.

Study of metals transfer from environment using teeth as biomonitor.

We investigated chronic incorporation of metals in individuals from poor families, living in a small, restrict and allegedly contaminated area in São Paulo city, the surroundings of the Guarapiranga dam, responsible for water supply to 25% of the city population. A total of 59 teeth from individuals 7 to 60 years old were collected. The average concentrations of Pb, Cd, Fe, Zn, Mn, Ni and Cr were determined with an Atomic Absorption Spectrophotometer. The concentrations of all metals as function of the individuals' age exhibited a remarkable similarity: peaks between 7 and 10 years and sharply decreasing at higher ages, which could be attributed to alimentary habits and persistence to metals exposure all along the individuals' life span. From all the measured metals, lead and cadmium were a matter of much more concern since their measured values are close to the upper limits of the world wide averages.

The role played by endogenous and exogenous electric fields in DNA signaling and repair

Comments are made and new insights are provided on the key role played by endogenous and exogenouselectric fields, where the former starts and conducts the repairing chain, while the latter is able to scramblethe completion of the repair process and, as a consequence, may have important potential as a radiationsensitizer for clinical application.

Zooplanktonic community of six reservoirs in northeast Brazil.

The aim of the present study was to investigate the zooplankton community at six reservoirs in the state of Pernambuco (Brazil). Zooplankton assemblages were identified using current literature and quantitatively analysed under a microscope and stereomicroscope. Concurrently to the sampling of zooplanktonic and phytoplanktonic communities, in situ measurements of abiotic variables, such as water temperature, dissolved oxygen and pH, were determined using field probes and transparency was determined with a Secchi disk. Total phosphorus concentrations were used for the determination of the Trophic State Index. The reservoirs were classified between eutrophic and hypertrophic, oxygenated, with pH varying from slightly acid to alkaline, high temperatures and low water transparency. A total of 27 zooplankton taxa were identified. Phytoplankton was represented by Cyanophyta, Chlorophyta, Baccilariophyta and phytoflagellates. The highest richness of species was observed for Rotifera (17), followed by Crustacea (8), Protozoa (1) and Insecta (1). Rotifers shared quantitative importance with Crustacea, which were mainly represented by juvenile forms. Jazigo Reservoir presented the highest diversity and equitability. Lowest diversity and equitability were recorded at the Poço da Cruz and Mundaú reservoirs, respectively. Dissimilarity was detected between the environments studied regarding zooplankton composition and structure.

Zooplanktonic community of six reservoirs in northeast Brazil / Comunidade zooplanctônica de seis reservatórios no nordeste do Brasil

The aim of the present study was to investigate the zooplankton community at six reservoirs in the state of Pernambuco (Brazil). Zooplankton assemblages were identified using current literature and quantitatively analysed under a microscope and stereomicroscope. Concurrently to the sampling of zooplanktonic and phytoplanktonic communities, in situ measurements of abiotic variables, such as water temperature, dissolved oxygen and pH, were determined using field probes and transparency was determined with a Secchi disk. Total phosphorus concentrations were used for the determination of the Trophic State Index. The reservoirs were classified between eutrophic and hypertrophic, oxygenated, with pH varying from slightly acid to alkaline, high temperatures and low water transparency. A total of 27 zooplankton taxa were identified. Phytoplankton was represented by Cyanophyta, Chlorophyta, Baccilariophyta and phytoflagellates. The highest richness of species was observed for Rotifera (17), followed by Crustacea (8), Protozoa (1) and Insecta (1). Rotifers shared quantitative importance with Crustacea, which were mainly represented by juvenile forms. Jazigo Reservoir presented the highest diversity and equitability. Lowest diversity and equitability were recorded at the Poço da Cruz and Mundaú reservoirs, respectively. Dissimilarity was detected between the environments studied regarding zooplankton composition and structure.

O objetivo deste trabalho foi estudar a estrutura e dinâmica do zooplâncton em seis reservatórios do Estado de Pernambuco. A comunidade zooplanctônica foi identificada com literatura atualizada e a densidade analisada sob microscópio e estereomicroscópio. Concomitantemente às coletas das comunidades zooplanctônicas e fitoplanctônicas, foram medidas in situ algumas variáveis abióticas como temperaturas da água e do ar, oxigênio dissolvido, condutividade elétrica, pH, turbidez, usando sondas de campo, transparência com disco de Secchi. As concentrações de fósforo total foram usadas para a determinação do Índice de Estado Trófico. Os reservatórios foram classificados entre eutróficos e hipertróficos, oxigenados, pH levemente ácido a alcalino, temperaturas altas e baixos valores de transparência da água. O zooplâncton esteve composto por 27 táxons. O fitoplâncton foi representado pelas Cyanophyta, Chlorophyta, Baccilariophyta e Fitoflagelados. A maior riqueza de espécies foi observada para Rotifera, (17), seguida por Crustacea (8), Protozoa (1) e Insecta (1). Rotifera compartilhou a importância quantitativa com os Crustacea, estes representados principalmente pelas formas jovens. No reservatório de Jazigo, foram obtidos os maiores valores para diversidade e equitabilidade. Os valores mais baixos foram registrados em Poço da Cruz e Mundaú, respectivamente. Foi detectada dissimilaridade entre os ambientes estudados quanto à composição e estrutura do zooplâncton.

Study of environmental burden of lead in children using teeth as bioindicator.

The south region of Sao Paulo city hosts the Guarapiranga dam, responsible for water supply to 25% of the city population. Their surroundings have been subject to intense and irregular occupation by people from very low socioeconomics classes. Measurements undertaken on sediment and particulate materials in the dam revealed concentrations of lead, copper, zinc and cadmium above internationally accepted limits. Epidemiological and toxicological studies undertaken by the World Health Organization in individuals exhibiting lead concentrations in blood, near or below the maximum recommended (10 microg dl(-1)), surprisingly revealed that toxic effects are more intense in individuals belonging to low socioeconomics classes. Motivated by these facts, we aimed at the investigation of chronic incorporation of lead, as well as the use of our BIOKINETICS code, which is based on an accepted ICRP biokinetics model for lead, in order to extrapolate the results from teeth to other organs. The focus of our data taking was children from poor families, living in a small, restrict and allegedly contaminated area in São Paulo city. Thus, a total of 74 human teeth were collected. The average concentration of lead in teeth of children 5 to 10 years old was determined by means of a high-resolution inductively coupled plasma mass spectrometer (ICP-MS). For standardization of the measurements, an animal bone certified material (H-Animal Bone), from the International Atomic Energy Agency, was analyzed. The amount of lead in children living in the surroundings of the dam, was approximately 40% higher than those from the control region, and the average lead concentration was equal to 1.3 microg g(-1) approximately. Grouping the results in terms of gender, tooth type and condition, it was concluded that a carious molar of boys is a much more efficient contamination pathway for lead, resulting in concentrations 70% higher than in the control region. We also inferred the average concentrations of lead in other organs of these children, by making use of our BIOKINETIC code.

Evaluation of uranium incorporation from contaminated areas using teeth as bioindicators--a case study.

The Southwest region of the Bahia state in Brazil hosts the largest uranium reserve of the country (100 kton in uranium, only), plus the cities of Caetité, Lagoa Real and Igaporã. In this work, aim was at the investigation of uranium burdens on residents of these cities by using teeth as bioindicators, as a contribution for possible radiation protection measures. Thus, a total of 41 human teeth were collected, plus 50 from an allegedly uranium free area (the control region). Concentrations of uranium in teeth from residents of 5- to 87-y old were determined by means of a high-resolution inductively coupled plasma mass spectrometer (ICP-MS). The highest uranium concentration in teeth was measured from samples belonging to residents of Caetité (median equal to 16 ppb). Assuming that the uranium concentrations in teeth and bones are similar within 10-20% (for children and young adults), it concluded that uranium body levels in residents of Caetité are at least one order of magnitude higher than the worldwide average. This finding led to conclude that daily ingestion of uranium, from food and water, is equally high.

Benthic Bacillariophyta of the Paripe River estuary in Pernambuco State, Brazil.

The aim of this study was to evaluate the benthic diatom composition from the estuary sediment in the Pernambuco State, based on 32 samples. Samples were collected monthly from September through December 1999 (dry period) and from April through July 2000 (rainy period) during four pre established sampling stations. Results indicated 19 families and 31 specific and infraspecific taxa. Eight new records were founded for Pernambuco State: Auliscus coelatus, Fallacia nummularia, Navicula algida, Plagiograma pulchellum, Terpsinoe americana, Triceratium antideluvianna and Tryblionella coarctata and one, Auliscus punctatus Bailey, in northeastern Brazil.

Benthic Bacillariophyta of the Paripe River estuary in Pernambuco state, Brazil

The aim of this study was to evaluate the benthic diatom composition from the estuary sediment in the Pernambuco State, based on 32 samples. Samples were collected monthly from September through December 1999 (dry period) and from April through July 2000 (rainy period) during four pre established sampling stations. Results indicated 19 families and 31 specific and infraspecific taxa. Eight new records were founded for Pernambuco State: Auliscus coelatus, Fallacia nummularia, Navicula algida, Plagiograma pulchellum, Terpsinoe americana, Triceratium antideluvianna and Tryblionella coarctata and one, Auliscus punctatus Bailey, in northeastern Brazil.

O objetivo do presente estudo foi avaliar a composição das diatomáceas bênticas do sedimento estuarino do estado de Pernambuco, Brasil, com base na análise de 32 amostras. As amostragens foram realizadas mensalmente de setembro a dezembro de 1999 (período seco) e de abril a julho de 2000 (período chuvoso) em quatro estações de coleta previamente estabelecidas. As diatomáceas estiveram representadas por 19 famílias e 31 taxons específicos e infraespecíficos. Ocorreram oito novas citações para o estado de Pernambuco, quais sejam: Auliscus coelatus, Fallacia nummularia, Navicula algida, Plagiograma pulchellum, Terpsinoe americana, Triceratium antideluvianna, Tryblionella coarctata e uma, Auliscus punctatus Bailey, para a região nordeste do Brasil.