Zika virus syndrome, lack of environmental policies and risks of worsening by cyanobacteria proliferation in a climate change scenario / Síndrome do zika vírus, carência de políticas ambientais e riscos de agravamento por proliferação de cianobactérias em um cenário de mudanças climáticas

ABSTRACT Almost half of the Brazilian population has no access to sewage collection and treatment. Untreated effluents discharged in waters of reservoirs for human supply favor the flowering of cyanobacteria - and these microorganisms produce toxins, such as saxitoxin, which is a very potent neurotoxin present in reservoirs in the Northeast region. A recent study confirmed that chronic ingestion of neurotoxin-infected water associated with Zika virus infection could lead to a microcephaly-like outcome in pregnant mice. Cyanobacteria benefit from hot weather and organic matter in water, a condition that has been intensified by climate change, according to our previous studies. Considering the new findings, we emphasize that zika arbovirus is widespread and worsened when associated with climate change, especially in middle- or low-income countries with low levels of sanitation coverage.

RESUMO No Brasil, quase metade da população não tem acesso a coleta e tratamento de esgotos. Os efluentes não tratados, devido a contaminação das águas de reservatórios para abastecimento humano, geram florações de cianobactérias - e esses microrganismos produzem toxinas, como a saxitoxina, uma neurotoxina bastante potente e presente nos reservatórios da região Nordeste. Estudo recente confirmou que a ingestão crônica de água contaminada com neurotoxinas associada a infeção pelo zika vírus em camundongos prenhes poderia levar a desfecho semelhante a microcefalia. Cianobactérias são beneficiadas por tempo quente e matéria orgânica na água, e essas condições estão sendo intensificadas pelas mudanças climáticas, segundo nossos estudos anteriores. Aqui, ressaltamos que, à luz dos novos achados, a arbovirose do zika, associada às mudanças do clima, se amplifica e se agrava, sobretudo em países de média ou baixa renda, com baixos níveis de cobertura de saneamento.

Periphytic algae dynamics in lentic ecosystems in the Brazilian semiarid / Estrutura da comunidade de algas perifíticas do semiárido brasileiro

Abstract The hydrological periods drive the structure and organization of aquatic communities in semiarid regions. We hypothesize that a decrease of the precipitation during the dry period will favor the development of the periphytic algal community, leading to higher richness and density in this period. To test this hypothesis, we investigated the changes in the periphytic algal community structure in three shallow and eutrophic ecosystems of the Brazilian semiarid. The sampling was performed between 2007 and 2010 at two-mensal intervals. The sampling of periphytic algal was performed in aquatic macrophytes and rocks. The abiotic variables were analyzed simultaneously. Dominance in diatoms, cyanobacteria and chlorophytes, respectively, was observed in two periods. In the dry period, waters were alkaline and had high concentrations of nitrate and total phosphorus associated with the highest densities of Bacillariophyceae. In the rainy period the water was warmer, oxygenated and high concentrations of ammonia and soluble reactive phosphorus with diatoms remained dominant but with reduced density, while cyanobacteria and chlorophytes increased. Overall, periphytic algal community composition no responded to changes in the hydrological periods. However, the hydrological periods altered the dynamics of periphytic algal community, supported by the alternation of the most representative classes (diatoms and cyanobacteria) between the hydrologic periods. Our data suggest that the morphometric and chemical and physical characteristics of lentic aquatic ecosystems studied were more important in the dynamics of periphytic algal community than the hydrological periods and types of substrates.

Resumo Os períodos hidrológicos impulsionam a estrutura e organização das comunidades aquáticas em regiões semiáridas. Nós hipotetizamos que uma diminuição da precipitação durante o período seco irá favorecer o desenvolvimento da comunidade de algas perifíticas, levando a uma maior riqueza e densidade nesse período. Para testar esta hipótese, nós investigamos as mudanças na estrutura da comunidade de algas perifíticas em três ecossistemas rasos e eutróficos do semiárido brasileiro. As amostragens foram realizadas entre 2007 e 2010 em intervalos de bimensais. A amostragem das algas perifíticas foi realizada em macrófitas aquáticas e rochas. As variáveis abióticas foram analisadas simultaneamente. A dominância de diatomáceas, cianobactérias e clorófitas, respectivamente, foi observada em todos os períodos. No período seco, as águas foram alcalinas com altas concentrações de nitrato e fósforo total associado às maiores densidades de Bacillariophyceae. Durante o período chuvoso as águas apresentaram-se mais quentes, oxigenadas e com altas concentrações de amônia e fósforo reativo solúvel. As diatomáceas permaneceram dominantes, mas com densidade reduzida, enquanto as cianobactérias e clorofíceas aumentaram. No geral, a composição da comunidade de algas perifíticas não respondeu as mudanças nos períodos hidrológicos. No entanto, os períodos hidrológicos alteraram a dinâmica da comunidade de algas perifíticas, apoiados pela alternância das classes mais representativas (diatomáceas e cianobactérias) entre os períodos hidrológicos. Nossos dados sugerem que as características morfométricas, químicas e físicas dos ecossistemas aquáticos lênticos estudados foram mais importantes na dinâmica da comunidade de algas perifíticas do que os períodos hidrológicos e tipos de substratos.

Response of phytoplankton to an experimental fish culture in net cages in a subtropical reservoir / Resposta do fitoplâncton ao cultivo experimental de peixes em tanques-rede em um reservatório subtropical

Abstract This study aimed to evaluate nutrients concentration and spatial-temporal changes in phytoplankton biovolume during an experimental fish culture in net cages in a lateral arm of Salto Caxias reservoir, Brazil. Two sampling stations were placed in the affected lateral arm and other two in a cageless lateral arm. Neither abiotic variables nor phytoplankton biovolume presented significant differences between the treatments. Only temporal changes were confirmed by the analysis performed. Both lateral arms were classified as oligotrophic, reflecting low influence of the net cages. Phytoplankton growth seems to be limited by nitrogen. Biovolume values were, in general, low and five major functional groups were recognized (E, F, G, K and P). In summer higher biovolume values were observed and representatives of Chlorophyceae and Cyanobacteria belonging to the functional groups F and K, respectively, were the most important. In winter phytoplankton was mainly composed by Bacillariophyceae taxa from P group. G group was also restricted to winter and E group occurred in winter and summer. The variations recorded in phytoplankton structure appear to have been mainly influenced by seasonal changes in temperature, precipitation and nutrients availability. The effects of net cages on the abiotic variables and phytoplankton biovolume appear to have been small, probably due to the small number of net cages employed and the system dilution capacity. However, a permanent monitoring of phytoplankton is recommended, since this environment has a carrying capacity, from which the trophic state may increase.

Resumo Este estudo objetivou avaliar alterações nas variáveis abióticas e no biovolume fitoplanctônico durante o cultivo experimental de peixes em tanques-rede em um braço lateral do reservatório de Salto Caxias, Brasil. Foram selecionadas duas estações de amostragem no braço com tanques-rede e outras duas em um braço sem tanques. As variáveis abióticas e o biovolume fitoplanctônico não apresentaram diferenças significativas entre os locais estudados. Apenas mudanças temporais foram confirmadas pelas análises utilizadas. Os dois braços laterais foram classificados como oligotróficos, refletindo a baixa influência dos tanques-rede. O crescimento do fitoplâncton parece ter sido limitado principalmente por nitrogênio. Os valores de biovolume foram, em geral, baixos e cinco principais grupos funcionais foram observados (E, F, G, K e P). No verão, os maiores valores de biovolume foram observados e representantes de Chlorophyceae e Cyanobacteria dos grupos funcionais F e K, respectivamente, se destacaram. No inverno, o fitoplâncton foi composto principalmente por táxons de Bacillariophyceae do grupo P. O grupo G também foi restrito ao inverno e o grupo E ocorreu no inverno e verão. As variações registradas na estrutura do fitoplâncton parecem ter sido principalmente influenciadas pelas mudanças sazonais de temperatura, precipitação e disponibilidade de nutrientes. Os efeitos dos tanques-rede sobre as variáveis abióticas e biovolume fitoplanctônico parecem ter sido pequenos, provavelmente devido ao pequeno número de tanques utilizados e a capacidade de diluição do sistema. Entretanto, o monitoramento permanente do fitoplâncton é recomendado, uma vez que este ambiente possui uma capacidade de suporte, a partir da qual o estado trófico pode aumentar.

Can microcystins affect zooplankton structure community in tropical eutrophic reservoirs? / Microcistinas podem afetar a estrutura da comunidade zooplanctônica em reservatórios eutróficos tropicais?

Abstract The aim of our study was to assess whether cyanotoxins (microcystins) can affect the composition of the zooplankton community, leading to domination of microzooplankton forms (protozoans and rotifers). Temporal variations in concentrations of microcystins and zooplankton biomass were analyzed in three eutrophic reservoirs in the semi-arid northeast region of Brazil. The concentration of microcystins in water proved to be correlated with the cyanobacterial biovolume, indicating the contributions from colonial forms such as Microcystis in the production of cyanotoxins. At the community level, the total biomass of zooplankton was not correlated with the concentration of microcystin (r2 = 0.00; P > 0.001), but in a population-level analysis, the biomass of rotifers and cladocerans showed a weak positive correlation. Cyclopoid copepods, which are considered to be relatively inefficient in ingesting cyanobacteria, were negatively correlated (r2 = – 0.01; P > 0.01) with the concentration of cyanotoxins. Surprisingly, the biomass of calanoid copepods was positively correlated with the microcystin concentration (r2 = 0.44; P > 0.001). The results indicate that allelopathic control mechanisms (negative effects of microcystin on zooplankton biomass) do not seem to substantially affect the composition of mesozooplankton, which showed a constant and high biomass compared to the microzooplankton (rotifers). These results may be important to better understand the trophic interactions between zooplankton and cyanobacteria and the potential effects of allelopathic compounds on zooplankton.

Resumo Com o objetivo de avaliar se as cianotoxinas (microcistinas) podem afetar a composição da comunidade zooplanctônica, levando à dominância de formas microzooplanctônicas (protozoários e rotiferos), as variações nas concentrações de microcistina e a biomassa do zooplâncton foram analisadas em três reservatórios eutróficos na região semi-árida do nordeste brasileiro. A concentração de microcistinas na água esteve correlacionada com o biovolume de cianobactérias, indicando a contribuição de formas coloniais como Microcystis na produção de cianotoxinas. A nível de comunidade, a biomassa total do zooplâncton não apresentou correlacão com a concentração de microcistina (r2 = 0.00; P > 0.001), mas em uma análise a nível de populações, a biomassa de rotíferos e cladóceros apresentou uma fraca correlação positiva. Copépodos Cyclopoida, os quais são considerados relativamente ineficientes na ingestão de cianobactérias, estiveram negativamente correlacionados com a concentração de microcistinas (r2 = - 0.01; P > 0.01). Surpreendentemente, a biomassa de copépodos Calanoida foi positivamente correlacionada com a concentração de cianotoxinas (r2 = 0.44; P > 0.001). Os resultados indicam que mecanismos de controle alelopáticos (efeitos negativos da microcistina sobre o zooplâncton) parecem não afetar substancialmente a composição do mesozooplâncton, que apresentou uma alta e constante biomassa, quando comparada à biomassa do microzooplâncton (rotíferos). Esses resultados podem ser importantes para um melhor entendimento das interações tróficas entre o zooplâncton e cianobactérias, e do efeito potencial de compostos alelopáticos sobre o zooplâncton.

Structure and dynamics of the phytoplankton community within a maturation pond in a semiarid region / Estrutura e dinâmica da comunidade fitoplanctônica de uma lagoa de maturação em região semiárida

Abstract In northeastern Brazil, stabilization ponds are very suitable for wastewater treatment because of the relative great land availability and environmental conditions (e.g., high temperature) favorable for microorganism optimal development. However, blooms of potentially toxic cyanobacteria may affect the use of these treatment ponds due to resulting effluent poor quality. The objective of this study was to evaluate the dynamics of phytoplankton communities and the occurrence of cyanobacteria in a maturation pond located immediately after a series of two ponds. Temperature, dissolved oxygen, pH, BOD, N, and P were measured during a period of four months when samples were collected from the surface and the bottom of 7 sampling points distributed inside the pond. The phytoplankton of collected samples was also identified and classified using a conventional optical microscopy. Analysis of variance and Tukey test were used to evaluate the results. The three phytoplankton divisions found (Cyanophyta, Chlorophyta, and Euglenophyta) did not change considerably through surface and bottom. However, they changed greatly over the sampled months; great dominance of Cyanophyta was found at April and October, while Chlorophyta dominated the lagoon in September. Low superficial organic loads (between 78 and 109 kg BOD.ha–1.d–1) and N:P ≤ 10 were the determinant factors that favored the predominance of Cyanophyta. The presence of two potentially toxic species of Cyanophyta, Oscillatoria sp. and Microcystis aeruginosa, indicates that caution is required when considering the final destination of treated effluent and suggests a need to assess the risks and benefits associated with the use of the treatment technology.

Resumo No nordeste do Brasil, as lagoas de estabilização são muito adequadas para o tratamento de águas residuárias por causa da disponibilidade relativamente grande de terra e das condições ambientais (por exemplo, altas temperaturas) favoráveis ao melhor desenvolvimento dos microorganismos. Entretanto, florações de cianobactérias potencialmente tóxicas podem afetar o uso dessas lagoas de tratamento, devido à consequente qualidade inferior do efluente. O objetivo deste estudo foi avaliar a dinâmica das comunidades de fitoplâncton e a ocorrência de cianobactérias em uma lagoa de maturação situada após duas lagoas em série. Temperatura, oxigênio dissolvido, pH, DBO, N e P foram medidos durante um período de quatro meses, durante o qual amostras foram coletadas na superfície e fundo em sete pontos de amostragem da lagoa. As comunidades de fitoplâncton das amostras coletadas foram também identificadas e classificadas utilizando-se um microscópio óptico convencional. Para avaliar os resultados utilizou-se a análise de variância e o teste de Tukey. Para as três divisões de fitoplâncton encontradas (Cyanophyta, Chlorophyta e Euglenophyta), não houve diferença significativa para as amostras de superfície e de fundo de um mesmo mês. Entretanto, ocorreu grande variação para as amostras dos diferentes meses; nos meses de abril e outubro houve uma predominância de Cyanophyta, ao passo que em setembro o predomínio na lagoa foi de Chlorophyta. Os fatores determinantes que favoreceram o predomínio de Cyanophyta foram a baixa carga orgânica superficial aplicada (entre 78 e 109 kg DBO.ha–1.d–1) e N:P ≤ 10. A presença de duas das espécies de Cyanophyta, Oscillatoria sp. e Microcystisaeruginosa, consideradas potencialmente tóxicas, indica que é necessária precaução quando se considera o destino final do efluente tratado e sugere a necessidade de avaliar os riscos e benefícios associados ao uso da tecnologia de tratamento.

Morphofunctional changes of phytoplankton community during pluvial anomaly in a tropical reservoir / Alterações morfofuncionais da comunidade fitoplanctônica durante anomalia pluvial em um reservatório tropical

AbstractThe present study focuses on the structure and function of phytoplankton community during periods of marked changes in hydrological traits, influenced by an atypical climatic event (La Niña) and its impact on Armando Ribeiro Gonçalves Reservoir of Rio Grande do Norte, situated in the Caatinga biome of northeastern Brazil. The main questions addressed were: What are the effects of environmental factors on the temporal variation of Morphologically Based Functional Group (MBFG) of phytoplankton community? How does the composition of cyanobacterial species shift in relation to high and low trends of phytoplankton diversity? The samples were collected monthly during 2008-2009 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen content and the nutrients, such as, nitrate-nitrogen, ammoniacal nitrogen, total nitrogen and orthophosphate. Phytoplankton samples were collected for both qualitative and quantitative analyses to evaluate species richness index and species diversity index. The data was divided into two distinct hydrodynamic periods of instability and stability. The results demonstrate considerable changes in dissolved oxygen content, water transparency and nitrogen nutrients, which directly influenced the MBFG of phytoplankton community in space and time. The instability of reservoir water was caused by heavy rainfall, which exerts atypical external disturbances. The seasonal variation of MBFG demonstrates a change in cyanobacterial composition and their diversity during instability and stability periods. MBFG VII, composed by colonial cyanobacteria with mucilage, was associated with reduced values of electrical conductance and alterations in pH. The predominance of filamentous species with heterocyst (MBFG III) occurs only during the hydrodynamic stability period and did not show significant association with analyzed parameters. The co-dominance of MBGFs III, V and VII along with high species diversity of phytoplankton community occurred during the second hydrodynamic instability period which was associated with the reduction in water temperature. It is concluded that the decrease in cyanobacterial species dominance and the general increase in the diversity of phytoplankton community are influenced by pluvial anomaly. The higher water level during the period of pluvial anomaly resulted in nutrient pulse and the mixing of water column in the reservoir, which determined the MBPG phytoplankton community distribution.

ResumoO presente estudo centra-se na estrutura e função da comunidade fitoplanctônica nos períodos de alterações marcantes nas características hidrológicas, influenciado por um evento climático atípico (La Niña) e seu impacto sobre o Reservatório: Armando Ribeiro Gonçalves, no Rio Grande do Norte, situado no bioma Caatinga, localizado na Região Nordeste do Brasil. As principais questões abordadas foram: Quais são os efeitos dos fatores ambientais sobre a variação temporal, baseados no grupo funcional da morfologia (GFBM) da comunidade fitoplanctônica? Como seria a composição das espécies de cianobactérias, em relação a varição das tendências de alta e baixa diversidade do fitoplâncton? As amostras foram coletadas mensalmente durante os anos de 2008-2009 e analisadas em relação a: pH, temperatura, condutividade elétrica, teor de oxigênio dissolvido e os nutrientes, tais como, tais como: nitrato, amônio, nitrogênio total e ortofosfato. As amostras de fitoplâncton foram coletadas para análises quantitativas, bem como, qualitativas para avaliar o índice de riqueza e de diversidade das espécies. Os dados foram divididos em dois períodos diferentes: instabilidade e estabilidade. Os resultados demonstraram alterações significativas no teor de oxigênio dissolvido, transparência da água e nutrientes de nitrogênio, que influenciaram diretamente os GFBM da comunidade do fitoplâncton no espaço e no tempo. A instabilidade da água do reservatório foi causada por fortes chuvas, que exerceu perturbações externas atípicas. Os resultados demonstraram alterações significativas no teor de oxigênio dissolvido, transparência da água e nutrientes de nitrogênio, que influenciaram diretamente os grupos morfofuncionais do fitoplâncton no espaço e no tempo. A instabilidade da água do reservatório foi causada por fortes chuvas, que exerceu perturbações externas atípicas. A sucessão sazonal de GFBM demonstrou a mudança na composição da cianobactéria e sua diversidade, durante os períodos de instabilidade e estabilidade. GFBM VII, composto por cianobactéria colonial com mucilagem esteve associado com baixos valores de condutividade elétrica e alterações no pH. A predominância das espécies filamentosas com heterocistos (GFBM III) ocorreu apenas durante o período de estabilidade hidrodinâmica e sem associação significativa com os parâmetros analisados. A codominância de GFBM III, V e VII juntamente com a elevada diversidade das espécies fitoplanctônicas ocorreram durante o segundo período da estabilidade hidrodinâmica e estiveram associadas com a redução da temperatura da água. Conclui-se que a diminuição da dominância de espécies de cianobactérias e o aumento geral na diversidade da comunidade do fitoplâncton são influenciadas pela anomalia pluvial. O nível da água mais elevado durante o período de anomalia pluvial resultou em um pulso de nutrientes e uma mistura da coluna de água no reservatório, que determinou a distribuição da comunidade fitoplanctônica MBPG.

The morphology and bioactivity of the rice field cyanobacterium Leptolyngbya / Morfología y bioactividad de la cianobacteria Leptolyngbya en los campos de cultivo de arroz

The genus Leptolyngbya comprises filamentous cyanobacteria that are important in rice fields. In the rhizosphere, cyanobacteria produce a variety of secondary metabolites such as auxins that are important in agriculture soil performance. To assess this, Leptolyngbya strain MMG-1, was isolated from the rhizosphere of rice plants and described. For this, the morphology of this strain was studied by light microscopy as well as by confocal laser scanning microscopy. Besides, the ability of this strain to synthesize an auxin-like bioactive compound was demonstrated under various culture conditions (different amounts of tryptophan; pH; different alternating light:dark periods; duration of the incubation). The auxin-like compound was extracted from the culture of Leptolyngbya strain MMG-1 and identified as indole-3-acetic acid (IAA) by thin layer chromatography (TLC) as well as by high performance liquid chromatography (HPLC). Our results showed that the strain required the precursor L-tryptophan for the synthesis of IAA. Leptolyngbya strain MMG-1 accumulated IAA intracellularly. The IAA secreted by Leptolyngbya strain MMG-1 was significantly correlated with the initial concentration of L-tryptophan in the medium, as well as with the duration of the incubation. The bioactivity of the secreted IAA was determined by its effect on the rooting pattern of Pisum sativum seedlings. The culture supernatant of Leptolyngbya strain MMG-1 stimulated the seedling lateral rooting, while it decreased root length. Hence, rhizospheric Leptolyngbya produced auxin under different conditions and affected the plants rooting pattern. Rev. Biol. Trop. 62 (3): 1251-1260. Epub 2014 September 01.

El género Leptolyngbya comprende cianobacterias filamentosas que son importantes en los campos de cultivo de arroz. En la rizosfera, las cianobacterias producen una variedad de metabolitos secundarios, tales como auxinas, que son importantes en el rendimiento de la agricultura del suelo. La cepa Leptolyngbya MMG-1, fue aislada de la rizosfera de plantas de arroz y se describe en este trabajo. La morfología de esta cepa se estudió por microscopía de luz, así como por microscopía confocal de barrido láser. Además, se estimó la capacidad de esta cepa para sintetizar el compuesto bioactivo auxina como se demostró en diversas condiciones de cultivo (diferentes cantidades de triptófano; pH; diferente luz alterna: períodos oscuros; duración de la incubación). La auxina se extrajo a partir del cultivo de la cepa Leptolyngbya MMG-1 y se identificó como ácido indol-3-acético (AA) por cromatografía de capa fina (TLC), así como por cromatografía líquida de alta resolución (HPLC). Nuestros resultados mostraron que la cepa requiere el precursor de L-triptófano para la síntesis de IAA. La cepa Leptolyngbya MMG-1 acumula intracelularmente IAA. El IAA secretada por la cepa Leptolyngbya MMG-1 se correlacionó significativamente con la concentración inicial de L-triptófano en el medio, así como con la duración de la incubación. La bioactividad de la IAA secretada se determinó por su efecto sobre el patrón de enraizamiento de plantas de semillero de Pisum sativum. El sobrenadante del cultivo de la cepa Leptolyngbya MMG-1 estimuló el enraizamiento lateral en la plántula, mientras que se redujo la longitud de la raíz. Por lo tanto, la producción de auxina por Leptolyngbya rizosférica afectó el crecimiento de las plantas.

Seasonal dynamics of cyanobacteria in a eutrophic reservoir (Arcoverde) in a semi-arid region of Brazil / Dinâmica sazonal de cianobactérias em um reservatório eutrófico (Arcoverde) no semiárido brasileiro

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.

As condições ambientais favorecem a predominância de populações densas de cianobactérias no nordeste do Brasil. O objetivo deste estudo foi entender a dinâmica das populações de cianobactérias nas estações seca e chuvosa, em duas profundidades, no reservatório de Arcoverde. Amostras de microalgas e cianobactérias foram coletadas durante 24 horas em intervalos de quatro horas (nictemerais) na subsuperfície e em 10 m, com uma garrafa de van Dorn, para a determinação da biomassa. Variáveis físicas e químicas foram obtidas, e os dados investigados por meio da Análise de Componentes Principais (ACP). Não foram encontradas variações nictemerais na composição taxonômica ou na distribuição das populações de cianobactérias entre os diferentes horários do dia, bem como entre as estações seca e chuvosa. Em ambas as estações, horários do dia e profundidades amostrais, a maior biomassa da comunidade fitoplanctônica foi constituída por cianobactérias. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju foi dominante em todos os horários do dia, tanto na superfície como no fundo. Na estação chuvosa, as diferenças de biomassa de cianobactérias entre superfície e fundo foram menos pronunciadas do que na estação seca. Concluímos que: a) variáveis físicas explicam melhor as alterações das espécies na comunidade fitoplanctônica em um ambiente dominado por cianobactérias durante todo o ano; b) fatores climáticos sazonais associados a períodos de estratificação e desestratificação são importantes para as alterações na comunidade e as variações na biomassa, e c) a turbidez causada pela chuva favoreceu o aparecimento e o estabelecimento de outras cianobactérias, especialmente Planktothrix agardhii (Gomont) Anagnostidis & Komárek.

Cyanobacterial blooms in stratified and destratified eutrophic reservoirs in semi-arid region of Brazil

This study investigated the dynamics of cyanobacteria in two deep, eutrophic reservoirs in a semi-arid region of Brazil during periods of stratification and destratification. Four collections were carried out at each reservoir at two depths at three-month intervals. The following abiotic variables were analyzed: water temperature, dissolved oxygen, pH, turbidity, water transparency, total phosphorus, total dissolved phosphorus, orthophosphate and total nitrogen. Phytoplankton density was quantified for the determination of the biomass of cyanobacteria. The data were analyzed using CCA. Higher mean phytoplankton biomass values (29.8 mm³.L-1) occurred in the period of thermal stratification. A greater similarity in the phytoplankton communities also occurred in this period and was related to the development of cyanobacteria, mainly Cylindrospermopsis raciborskii (>3.9 mm³.L-1). During the period of thermal destratification, this species co-dominated the environment with Planktothrix agardhii, Geitlerinema amphibium, Microcystis aeruginosa and Merismopedia tenuissima, as well as with diatoms and phytoflagellates. Environmental instability and competition among algae hindered the establishment of blooms more during the mixture period than during the stratification period. Thermal changes in the water column caused by climatologic events altered other physiochemical conditions of the water, leading to changes in the composition and biomass of the cyanobacterial community in tropical reservoirs.

Este estudo investigou a dinâmica das cianobactérias em dois reservatórios eutróficos e profundos localizados na região semi-árida do Brasil durante períodos de estratificação e desestratificação térmica. Quatro coletas foram feitas em cada reservatório em duas profundidades em intervalo de três meses. As variáveis abióticas analisadas foram: temperatura da água, oxigênio dissolvido, pH, turbidez, transparência da água, fósforo total, fósforo total dissolvido, ortofosfato e nitrogênio total. A densidade do fitoplâncton foi quantificada para a determinação da biomassa de cianobactérias. Os dados foram analisados usando ACC. Elevados valores médios de biomassa fitoplanctônica (29,8 mm³.L-1) ocorreram no período de estratificação. A maior similaridade das comunidades fitoplanctônicas também ocorreu neste período e foi relacionada ao desenvolvimento de cianobactérias, principalmente Cylindrospermopsis raciborskii (>3,9 mm³ .L-1). Durante o período de desestratificação térmica, esta espécie co-dominou o ambiente com Planktothrix agardhii, Geitlerinema amphibium, Microcystis aeruginosa e Merismopedia tenuissima, bem como com diatomáceas e fitoflagelados. Instabilidade ambiental e competição entre as algas dificultaram o estabelecimento de blooms durante o período de mistura quando comparado com o período de estratificação. Modificações na condição térmica da coluna d'água, causadas por eventos climatológicos, alteraram as demais condições fisicoquímicas da água e ocasionaram mudanças na composição e biomassa da comunidade de cianobactérias em reservatórios tropicais.

Effect of UV-B and high visual radiation on photosynthesis in freshwater (nostoc spongiaeforme) and marine (Phormidium corium) cyanobacteria.

Human activity is causing depletion of ozone in stratosphere, resulting in increased UV-B radiation and global warming. However, impact of these climatic changes on the aquatic organism (especially marine) is not fully understood. Here, we have studied the effect of excess UV-B and visible radiation on photosynthetic pigments, fatty acids content, lipid peroxidation, nitrogen content, nitrogen reductase activity and membrane proteins, induction of mycosporine-like amino acids (MAAs) and antioxidant enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) in freshwater (Nostoc spongiaeform) and marine (Phormidium corium) cyanobacteria. UV-B treatment resulted in an increase in photosynthetic pigments in Nostoc and decrease in Phormidium, but high light treatment caused photobleaching of most of the pigments in both the species. Unsaturation level of fatty acids of both total and glycolipids remained unchanged in both the cyanobacteria, as a result of UV-B and high light treatments. Saturated fatty acids of total and glycolipids declined slightly in Nostoc by both the treatments. but remained unchanged in Phormidium. No changes in the unsaturated lipid content in our study probably suggested adaptation of the organism to the treatments. However, both treatments resulted in peroxidation of membrane lipids, indicating oxidative damage to lipids without any change in the level of unsaturation of fatty acid in the cell membrane. Qualitative and quantitative changes were observed in membrane protein profile due to the treatments. Cyanobacteria were able to synthesize MAAs in response to the UV-B treatment. Both treatments also increased the activities of SOD and APX. In conclusion, the study demonstrated induction of antioxidants such as SOD and APX under visible light treatment and screening pigment (MAAs) under UV-B treatment, which might protect the cyanobacteria from oxidative damage caused by high light and UV-B radiation.

Antioxidant potential of C-phycocyanin isolated from cyanobacterial species Lyngbya, Phormidium and Spirulina spp.

The antioxidant activity of C-Phycocyanin (C-PC) isolated from three cyanobacterial species Lyngbya (marine), Phormidium (marine) and Spirulina (fresh water) was studied in vitro. The results demonstrate that C-PCs from Lyngbya, Phormidium and Spirulina spp. are able to scavenge peroxyl radicals (determined by crocin bleaching assay) with relative rate constant ratio of 3.13, 1.89 and 1.8, respectively. C-PCs also scavenge hydroxyl radicals (determined by deoxyribose degradation assay) with second order rate constant values of 7.87 x 10(10), 9.58 x 10(10) and 6.42 x 10(10), respectively. Interestingly, Lyngbya C-PC is found to be an effective inhibitor of peroxyl radicals (IC50 6.63 microM), as compared to Spirulina (IC50 12.15 microM) and Phormidium C-PC (IC50 12.74 microM) and is close to uric acid (IC50 2.15 microM). Further, the studies suggest that the covalently-linked tetrapyrrole chromophore phycocyanobilin is involved in the radical scavenging activity of C-PC. The electron spin resonance (ESR) spectra of C-PCs indicate the presence of free radical active sites, which may play an important role in its radical scavenging property. This is the first report on the ESR activity of native C-PCs without perturbations that can cause radical formation.

Distribution of the cyanophyte Trichodesmium (Oscillatoriaceae) in the eastern Caribbean Sea: influence of the Orinoco River

Orinoco River influence in the Caribbean Sea, characterized by high nutrient input, causes a decrease of Trichodesmium populations. The Caribbean Time Series (CaTS) station, south of Puerto Rico (17 degrees 36'N 67 degrees 00'W), was monitored for 25 months in order to observe the Trichodesmium abundance pattern and the presence of the river plume. In general, mean Trichodesmium abundance was higher at the surface and decreased with depth. The mean upper water column (surface to 20 m) abundance was 54.1 +/- 32.6 col/m3. Within the sampling period, abundance was highly variable (1-700 col/m3). Correlation between Trichodesmium abundance and wind speed (p=0.002), chlorophyll a concentration (p=0.001), nitrate (p=0.02) and silicate (p=0.003) concentrations were statistically significant. However, Trichodesmium abundance was not correlated with salinity (p=0.70), temperature (p=0.16) and seawater density (p=0.71) variations at CaTS. Eastern Caribbean regions highly influenced by the Orinoco River discharge were devoid of Trichodesmium colonies.

Effect of hydration and dehydration on initiation and dynamics of some physiological reactions in desiccation tolerant cyanobacterium Scytonema geitleri.

The effect of hydration and dehydration has been studied on extent and recovery of some metabolic reactions in desiccation tolerant terrestrial cyanobacterium Scytonema geitleri. The results show that the energy transducing reactions like photochemical reactions of photosynthesis recover first, followed by increase in ATP pool size. During later phase of hydration, appearance of energy consuming processes such as CO2 fixation and nitrogen fixation have been observed. Sensitivity of reactions during dehydration followed the pattern reverse to recovery processes.

Physiological responses of phormidium fragile to naphthalene

The cyanobacterium, Phormidium fragile, was grown in culture media containing different concentrations of naphthalene. Tests were carried out under conditions allowing relatively free evaporation and volatilization of the hydrocarbon [open system] and in closed system in which hydrocarbon loss was minimized [closed system]. Under the former condition, the various naphthalene concentrations invariably affected dry weight gain of the organism. On the other hand, under the closed system, the dry weight decreased significantly. Under both cultural conditions, the algal protein content decreased, while the nucleic acids content was slightly affected by the type of cultural system. The alga accumulated larger amounts of carbohydrates under closed than open systems. Under the latter condition, naphthalene insignificantly affected MDH and stimulated GOT activity. On the contrary, under the closed system, MDH activity was stimulated by naphthalene, whereas GOT activity was hardly affected. Under both conditions, nitrate reductase was insensitive to naphthalene supplementation, while GPT activity increased at low concentrations, then dropped. There was a continuous increase in the different photosynthetic pigments with increased naphthalene concentrations. In the meantime, the lipid content of the alga was much higher under closed than open systems

Physiological responses of the cyanobacterium calothrix parietina and green alga scenedesmus dimorphus to iron, manganese, sulphate and sulphite

The uptake of manganese and iron ions by Scenedesmus dimorphus and Calothrix parietina was significantly increased by increasing the doses supplemented to the culture media of both algae up to 10[-5]molar concentration. The ability of Scenedesmus to accumulate the two metals was greater than that of Calothrix. Higher concentrations of sulphate, sulphite and manganese ions inhibited the accumulation of total carbohydrates in the two phytoplankter cells. All iron levels stimulated synthesis of total carbohydrates in Calothrix, but inhibited it in Scenedesmus. Under all concentrations of the four pollutant salts, nitrogen secretion by the two organisms, total nitrogen and almost all nitrogen fractions were increased particularly at moderate rates. However, 10[-4] M and 300 micro g S ml[-1] of iron and sulphite attenuated the synthesis of protein N in Calothrix, Sulphate, sulphite and iron suppressed phosphorus uptake by Calothrix but stimulated it in Scenedesmus. Manganese ions at all concentrations, encouraged phosphorus uptake from nutrient media by Calothrix. Sulphite, at al concentrations lowered total phosphorus content, total soluble and total insoluble phosphorus in the two organisms, a phenomenon that was associated with marked disturbances in phosphorus metabolism. Sulphite, at all concentrations inhibited the biosynthesis of nucleic acids [RNA, DNA] in Calothrix, while its low and moderate concentrations stimulated their biosynthesis in Scenedesmus. Sulphate and manganese on the other hand, stimulated their biosynthesis in the two phytoplankters. Iron, at 10[-8] M level encouraged the biosynthesis of nucleic acids in Calothrix, whereas 10[-6] M and 10[-4]M concentrations suppressed their formation in Scenedesmus. At all levels of manganese and sulphate, the cell length and width of both organisms and the diameters of heterocyst in Calothrix were increased. At all concentrations of iron and sulphite, the cell length and width of both organisms and also diameters of heterocysts in Calothrix were decreased