EFEITO DE DIFERENTES CONCENTRAÇÕES DE CARBONO ORGÂNICO DISSOLVIDO E BACTÉRIAS NA DEGRADAÇÃO DE MICROCISTINAS (CIANOTOXINA)

Microcystins degradation depends on several factors like initial concentration in water, presence of microorganisms, temperature, pH, presence of other available sources of organic carbon, and others. The aims of this study were to measure microcystin degradation under different concentrations of dissolved organic carbon (DOC), and determine the influence of bacterial community on this process. For this purpose, water from the Jacarepaguá Lagoon (Rio de Janeiro, Brazil) was diluted in deionized water in order to obtain final concentrations of DOC of 60, 43 and 28mg L-1 (water with bacteria), and final DOC concentrations of 43 and 60mg L-1 (water without bacteria). A semi-purified microcystin extract was prepared and mixed with these samples, and the concentration of microcystin and bacteria were quantified through the time. We found that DOC concentrations of 43 and 60mg L-1 with bacteria promoted total degradation of microcystin within 14 days. On the other hand, a DOC concentration of 28mg L-1 with bacteria still contained detectable microcystin after 42 days. Higher DOC concentrations promoted bacterial growth and rapid microcystin degradation. Microcystin degradation just occurred after 30 days in the absence of bacteria, illustrating their importance in this process. However, Gram negative bacteria strains isolated during the tests were not able to biodegrade microcystin.revista vol 13 nº 2.indd El proceso de degradación de microcistinas está relacionado con diversos factores tales como: su concentración inicial, los microorganismos presentes, la temperatura del agua, el pH y la disponibilidad de fuentes de carbono orgánico, entre otros. El objetivo de este trabajo fue verificar el proceso de degradación demicrocistinas en aguas con diferentes concentraciones de carbono orgánico disuelto (COD) y la influencia de la comunidad bacteriana en la biodegradación de microcistinas. Para ello, un extracto acuoso semi-purificado de microcistinas fue adicionado al agua del Lago de Jacarepaguá (RJ), previamente diluido en agua desionizada para obtener las concentraciones de 28, 43 y 60mg L-1 de COD con bacterias presentes, y de 43 y 60mg L-1 en ausencia de bacterias. Durante el ensayo, fueron determinadas las concentraciones de microcistinas y cuantificadas las poblaciones bacterianas. Los resultados mostraron que las mayores concentraciones de COD (43 y 60mg L-1), las cuales presentaban 107 colonias mL-1 de bacterias, favorecen la total biodegradación de microcistinas en 14 días. Por otra parte, en una concentración de 28mg L-1 de COD, con 105 colonias mL-1, fue posible detectar 12.8 ?g microcistinas L-1 pasado los 42 días. Las mayores concentraciones de COD promovieron el crecimiento bacteriano y fueron más eficientes en la degradación de microcistinas. Fue posible observar que en ausencia de bacterias, los procesos de degradación de microcistinas fueron bastante lentos, confirmando los resultados anteriores que muestran la importancia de la actividad bacteriana en la biodegradación de microcistinas. No fue verificada la degradación de microcistinas por las bacterias Gram negativas aisladas.O processo de degradação de microcistinas está relacionado a diversos fatores como: a sua concentração inicial, os microrganismos presentes, a temperatura da água, o pH e a disponibilidade de fontes de carbono orgânico, dentre outros. Este trabalho teve como objetivo verificar o processo de degradação de microcistinas em águas com diferentes concentrações de carbono orgânico dissolvido (COD) e a influência da comunidade bacteriana nesse processo. Para tanto, um extrato aquoso de microcistinas semi-purificado foi adicionado a água da Lagoa de Jacarepaguá (RJ), previamente diluída em água deionizada para obtenção das concentrações de 28, 43 e 60mg L-1 de COD na presença de bactérias e 43 e 60mg.L-1 de COD na ausência de bactérias. Durante os testes foram determinadas as concentrações de microcistinas e a quantificação da população bacteriana. As maiores concentrações de COD (43 e 60mg L-1), que apresentavam 107 colônias mL-1 de bactérias, favoreceram a degradação total das microcistinas em 14 dias, enquanto que na condição de 28mg L-1 com 105 colônias mL-1, após 42 dias ainda era possível detectar 12,8?g L-1 de microcistinas. As maiores concentrações de COD favoreceram o crescimento bacteriano e também foram as mais eficientes na degradação das microcistinas. Na ausência de bactérias, o processo de degradação foi bastante lento (30 dias), confirmando os resultados anteriores que mostram a importância da atividade bacteriana nesse processo. Entretanto, não foi verificada a degradação das microcistinas pelas cepas de bactérias Gram negativas isoladas

Acute toxicity of neurotoxin-producing Raphidiopsis (Cylindrospermopsis) raciborskii ITEP-A1 (Cyanobacteria) on the neotropical cladoceran Macrothrix spinosa

Cyanobacterial blooms are recurrent phenomena in several water bodies, mostly eutrophic. They are considered a public health problem, especially considering harmful species like Raphidiopsis raciborskii, a bloom-forming cyanobacteria recorded as a producer of neurotoxic and cytotoxic alkaloids. The present study aimed to assess the acute toxicity of a saxitoxin-producing strain Raphidiopsis raciborskii ITEP-A1 on the zooplankter Macrothrix spinosa. Cladoceran clones isolated from an eutrophic system with cyanobacterial blooms records and an oligotrophic one with no bloom record; both from Pernambuco (Northeastern Brazil), were tested for R. raciborskii ITEP-A1 toxicity. Acute toxicity assays were carried out with newborns (<24h, n=10) and the animals were exposed to three concentrations of cyanobacterial cell biomass (μgC L-1). Quantification of saxitoxins (STX and neoSTX) was done by high-performance liquid chromatography coupled with fluorescence detector (HPLC-RF). The EC50(48h) for the Duas Unas and Prata clones were 359 and 189 μgC L-1, respectively. Obtained results showed that M. spinosa Prata was more sensitive to R. raciborskii than Duas Unas, reinforcing the importance of analyzing the previous life history of the test organisms regarding their native environments. However, both clones demonstrated high sensitivity to R. raciborskii, which enhances their potential for biomonitoring toxic cyanobacterial blooms in tropical reservoirs

Use of the cell quota and chlorophyll content for normalization of cylindropermopsin produced by two Cylindrospermopsis raciborskii strains grown under different light intensities

The production of cylindrospermopsin (CYN) by Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju (Cyanobacteria) was already shown to be changed by variations in light intensities. Influences of light intensity on CYN production by two different C. raciborskii strains (CYP011K and CYP030A) were studied in batch culture conditions. The strains were grown under photon light intensities from 40 to 348 μmol photons m-2 s-1. The growth rates were measured by exponential regression of cell number variation along the time. The concentration of chlorophyll-a (Chl-a) was measured by spectrophotometric methods and the CYN concentration was measured by high-performance liquid chromatographic methods. Data from these CYN analyses were evaluated as cell quota (ng CYN 10-6 cells) or as the relative proportion between toxin concentration and chlorophyll-a concentration (CYN Chl-a-1). The CYP011K showed higher growth rates than the CYP030A strains. According to the cell quota results, the production of CYN by these two strains of C. raciborskii is not affected by the intensity of the surrounding light during growth. However, analysis of the relative proportion of CYN Chl-a-1 led to different interpretations, as a negative relation between light intensity and CYN production

Florações de Cianobactérias tóxicas no Reservatório do Funil: dinâmica sazonal e consequências para o zooplâncton

revista vol 13 nº 2.indd The Funil water reservoir, located in the Paraíba do Sul River Valley in the municipality of Resende (Rio de Janeiro State, Brazil), has become eutrophic during the last two decades and undergone recurrent blooms of cyanobacteria. This study presents temporal series of physical, chemical and biological data from the reservoir encompassing an overall period of four years (from June/02 to March/06). Monthly, measurements of conductivity, transparency, temperature, pH, dissolved oxygen, and water samples for the analyses of nutrients (N and P), chlorophyll-a, phytoplankton and zooplankton composition and cyanotoxins in seston and in net plankton were performed. Toxicity tests with native and temperate cladocerans species were also performed. The results showed that the high input of N and P favored the persistent dominance of cyanobacteria. A temporal pattern was observed mainly related to changes in water temperature, characterizing two distinct periods: a warm-wet period with cyanobacterial bloom, and a cold-dry period with general reduced biomass. Cyanobacteria included potential hepatotoxins (microcystins) producers like Microcystis spp., and potential neurotoxins (saxitoxins) producers like Anabaena circinalis and Cylindrospermopsis raciborskii. In fact, elevated concentrations of microcystins and saxitoxins were found in the phytoplankton, and high levels of microcystins in the zooplankton, suggesting that these toxins may be transferred through the food chain. The toxicity tests revealed that the cyanobacterial blooms had toxic effects on cladocerans, causing death, reduction in the rate of population increase (r), and paralysis, in agreement with the mechanism of action of the cyanotoxins present.revista vol 13 nº 2.indd El Embalse de Funil, localizado en el valle del Río Paraíba do Sul, municipio de Resende (RJ), se convirtió en un ambiente eutrófico a lo largo de las últimas dos décadas, con floraciones recurrentes de cianobacterias. Este estudio presenta una serie temporal de datos físicos, químicos y biológicos del embalse abarcando un período de cuatro años (Junio/02 a Marzo/06). Durante dicho período, se tomaron mensualmente medidas de conductividad eléctrica, transparencia de la columna de agua, temperatura, pH, oxigeno disolvido, muestras de agua para análisis de nutrientes (N y P), clorofila-a, de la composición de la comunidad fitoplanctônica y zooplanctónica y cianotoxinas en el seston y colectas en red de plancton. También fueron realizados ensayos de toxicidad con cladóceros nativos así como también con una especie de zonas templada. Los resultados encontrados evidencian que el elevado y constante aporte de N y P favorece la ocurrencia de cianobacterias durante todo el año. Sin embargo, los patrones temporales están principalmente relacionados con el cambio en la temperatura, caracterizando dos períodos diferentes: cálido-húmedo, con floraciones de cianobacterias, y frío-seco, con una biomasa reducida. Entre las cianobacterias presentes están las especies potencialmente productoras de hepatotoxinas (microcistinas), como Microcystis spp., y de neurotoxinas (saxitoxinas), como Anabaena circinalis e Cylindrospermopsis raciborskii. Fueron encontradas concentraciones elevadas de microcistinas y saxitoxinas en el fitoplancton y microcistinas en el zooplancton, sugiriendo que puede existir transferencia trófica de dichas toxinas en la cadena alimenticia. Los ensayos de toxicidad revelaron que las floraciones de cianobacterias ejercieron efectos tóxicos sobre los cladóceros, como alta mortalidad, reducción de la tasa de crecimiento poblacional (r) y parálisis de los movimientos natatorios, que parecen estar relacionados con el mecanismo de acción de las cianotoxinas presentes.O Reservatório do Funil, situado no vale do Rio Paraíba do Sul, município de Resende (RJ), tornou-se ao longo das últimas duas décadas um ambiente eutrófico, com florações recorrentes de cianobactérias. Este estudo apresenta uma série temporal de dados físicos, químicos e biológicos do reservatório, abrangendo um período amostral de quatro anos (junho/02 a março/06). Mensalmente, foram realizadas medidas de condutividade elétrica, transparência da coluna d'água, temperatura, pH, oxigênio dissolvido, e coletas de água para análise de nutrientes (N e P), clorofila-a, cianotoxinas do seston e do plâncton de rede, e da composição da comunidade fitoplanctônica e zooplanctônica. Foram também realizados testes de toxicidade com cladóceros nativos e de origem temperada. Os resultados mostraram que o elevado e constante aporte de N e P favorece a ocorrência de cianobactérias durante todo ano. Entretanto, a variabilidade temporal está principalmente relacionada às alterações de temperatura, caracterizando dois períodos distintos: quente-chuvoso, com floração de cianobactérias e frio-seco, com reduzidas biomassas. Entre as cianobactérias presentes estão espécies potencialmente produtoras de hepatotoxinas (microcistinas), como Microcystis spp., e de neurotoxinas (saxitoxinas), como Anabaena circinalis e Cylindrospermopsis raciborskii. Foram encontradas concentrações elevadas de microcistinas e saxitoxinas no fitoplâncton e microcistinas no zooplâncton, sugerindo que pode haver transferência trófica destas toxinas na cadeia alimentar. Os testes de toxicidade revelaram que as florações de cianobactérias exerceram efeitos tóxicos para os cladóceros, como alta mortalidade, redução da taxa de crescimento populacional (r) e paralisia dos movimentos natatórios, que parecem estar relacionados ao mecanismo de ação das cianotoxinas presentes

FLORAÇÕES DE CIANOBACTÉRIAS TÓXICAS EM UMA LAGOA COSTEIRA HIPEREUTRÓFICA DO RIO DE JANEIRO/RJ (BRASIL) E SUAS CONSEQUÊNCIAS PARA SAÚDE HUMANA

revista vol 13 nº 2.indd The Jacarepaguá Basin, Rio de Janeiro, Brazil has over the last four decades undergone a disordered process of urban and industrial growth with direct consequences on water quality and incidence of cyanobacterial blooms in the Jacarepaguá Lagoon Complex (JLC). The present study combines data aiming to evaluate water quality in Jacarepaguá Lagoon (JL) from monitoring of physical variables (pH, water transparency, temperature), chemical variables (salinity, dissolved oxygen, chlorophyll), the planktonic community, and the concentration of microcystins in fish from the region. The data herein presented were divided into three periods according to seasonal cycles: PI (aug/96 to sep/97), PII (jan/99 to nov/99), and PIII (feb/07 to jan/08). Dominance by cyanobacteria characterized most of the study period, interspersed with sudden peaks (e.g. during PII and PIII) of high diversity of phytoplankton. Phytoplanktonic peaks were represented by Chlorophyta, diatoms, Prasinophyta and Criptophyta. Interestingly, the events observed in 1999 repeated almost 10 years later, suggesting roughly seasonal community structure dynamism in the JLC. Disappearance of the bloom coincided with the lowest recorded water temperatures, suggesting that temperature is an important factor in the observed dynamics. The JL had a high abundance of zooplankton, yet species diversity was relatively low. Concentrations of microcystins found in muscles of fish from JL often contained values above the levels recommended by OMS for human consumption.  revista vol 13 nº 2.indd La Cuenca de Jacarepaguá (RJ/Brasil) ha sufrido, en las últimas cuatro décadas, un proceso desordenado de ocupación urbana e industrial, que se refleja en un cambio en la calidad del agua y en la incidencia de floraciones de las cianobacterias en el Complejo Lagunar Jacarepaguá (CLJ). El presente estudio reúne una serie de datos con el objeto de evaluar la calidad del Lago Jacarepaguá (LJ), a través del monitoreo físico (pH, transparencia del agua y temperatura), químico (salinidad, O.D. y clorofila a) y de la comunidad planctónica. También fue analizada la concentración de microcistinas en pescados comercializados en la región. Los datos fueron divididos en tres períodos de acuerdo con los diferentes ciclos estacionales estudiados: PI (ago/96 a sept/07), PII (ene/99 a nov/99) y PIII (feb/07 a ene/08). La dominancia de cianobacterias ocurre en la mayor parte del período de estudio, intercalada con pulsos de mayor diversidad fitoplanctónica, observada desde 1999 (PII y PIII). Dicha diversidad estuvo representada por las clorofíceas, diatomeas, prasinoficeas y criptoficeas. Cabe destacar que la dinámica observada en 1999 se repitió casi 10 años después, lo que sugiere una tendencia estacional para la estructura de la comunidad del CLJ. La desaparición de la floración coincide con épocas de bajas temperaturas sugiriendo que ésta es un factor regulador importante de la dinámica observada. El LJ presentó una elevada abundancia zooplanctónica, con baja diversidad de especies. Durante algunos meses, las concentraciones de microcistinas encontradas en los músculos de los peces estuvieron por encima de los valores recomendados por la OMS para el consumo humano.A baixada de Jacarepaguá (RJ/Brasil) vem sofrendo há pelo menos quatro décadas um processo desordenado de ocupação urbana e industrial, o que tem se refletido em mudança na qualidade da água e na incidência de florações de cianobactérias no Complexo Lagunar de Jacarepaguá (CLJ). O presente estudo reuniu uma série de dados temporais objetivando avaliar a qualidade hídrica da Lagoa de Jacarepaguá (LJ) através do monitoramento físico (pH, transparência da água e temperatura), químico (salinidade, O.D. e clorofila a) e da comunidade planctônica. Foi também analisado a concentração de microcistinas no pescado comercializado na região. Os dados foram divididos em três períodos de acordo com os diferentes ciclos sazonais estudados: PI (ago/96 a set/97), PII (jan/99 a nov/99) e PIII (fev/07 a jan/08). Dominância de cianobactérias ocorreu na maior parte do tempo, intercalada por pulsos de maior diversidade fitoplanctônica, observados a partir de 1999 (PII e III). Esta diversidade foi representada pelas clorofíceas, diatomáceas, prasinoficeas e criptoficeas. Foi interessante notar que a dinâmica observada em 1999 tenha se repetido quase 10 anos depois, o que sugere uma tendência sazonal de estruturação da comunidade no CLJ. O desaparecimento da floração coincidiu com épocas de menores temperaturas, sugerindo ser esse um importante fator regulador da dinâmica observada. A LJ apresentou uma elevada abundância zooplanctônica, com baixa diversidade de espécies. Durante alguns meses, as concentrações de microcistinas encontradas nos músculos dos peixes estiveram acima dos valores recomendados pela OMS para consumo humano

Temperature Effect on Exploitation and Interference Competition among Microcystis aeruginosa, Planktothrix agardhii and, Cyclotella meneghiniana

We studied the effect of temperature (18 and 30°C) on growth and on the exploitation and interference competition of three species: Microcystis aeruginosa (MIJAC), Planktothrix agardhii (PAT), and Cyclotella meneghiniana (CCAP). Coculturing the organisms in batch systems allowed for the examination of both competitive interactions, while the interference competition was studied in cross-cultures. The experiments were done during 10–12 days, and samples were taken for chlorophyll-a analysis, using PHYTO-PAM. The temperature did not influence exploitation competition between MIJAC and other competitors and it was the best competitor in both temperatures. PAT presented higher growth rates than CCAP in competition at 18 and 30°C. The temperature influenced the interference competition. The growth of MIJAC was favored in strains exudates at 30°C, while CCAP was favored at 18°C, revealing that the optimum growth temperature was important to establish the competitive superiority. Therefore, we can propose two hypotheses: (i) different temperatures may results in production of distinct compounds that influence the competition among phytoplankton species and (ii) the target species may have different vulnerability to these compounds depending on the temperature. At last, we suggest that both the sensitivity and the physiological status of competing species can determine their lasting coexistence

Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness

The cosmopolitan and increasing distribution of Cylindrospermopsis raciborskii can be attributed to its ecophysiological plasticity and tolerance to changing environmental factors in water bodies. In reservoirs in the semi-arid region of Brazil, the presence and common dominance of C. raciborskii have been described in waters that are considered hard. We investigated the response of a Brazilian C. raciborskii strain to water hardness by evaluating its growth and saxitoxin production. Based on environmental data, a concentration of 5 mM of different carbonate salts was tested. These conditions affected growth either positively (MgCO3) or negatively (CaCO3 and Na2CO3). As a control for the addition of cations, MgCl2, CaCl2 and NaCl were tested at 5 or 10 mM, and MgCl2 stimulated growth, NaCl slowed but sustained growth, and CaCl2 inhibited growth. Most of the tested treatments increased the saxitoxin (STX) cell quota after six days of exposure. After 12 days, STX production returned to concentrations similar to that of the control, indicating an adaptation to the altered water conditions. In the short term, cell exposure to most of the tested conditions favored STX production over neoSTX production. These results support the noted plasticity of C. raciborskii and highlight its potential to thrive in hard waters. Additionally, the observed relationship between saxitoxin production and water ion concentrations characteristic of the natural environments can be important for understanding toxin content variation in other harmful algae that produce STX

Microcystins in South American aquatic ecosystems: Occurrence, toxicity and toxicological assays

The acute poisoning of chronic renal patients during hemodialysis sessions in 1996 in Caruaru City (Pernambuco State, Brazil) stimulated an intensive search for the cause of this severe complication. This search culminated in the identification of microcystins (MC), hepatotoxic cyclic heptapeptides produced by cyanobacteria, as the causative agents. More than ten years later, additional research data provides us with a better understanding of the factors related to cyanobacterial bloom occurrence and production of MC in Brazil and other South American countries. The contamination of water bodies and formation of toxic blooms remains a very serious concern, especially in countries in which surface water is used as the main source for human consumption. The purpose of this review is to highlight the discoveries of the past 15 years that have brought South American researchers to their current level of understanding of toxic cyanobacteria species and that have contributed to their knowledge of factors related to MC production, mechanisms of action and consequences for human health and the environment. (C) 2010 Elsevier Ltd. All rights reserved