RESUMOFlorações de cianobactérias em reservatórios resultam na perda da qualidade da água e em efeitos negativos para a saúde humana. Faz-se, portanto, necessário o monitoramento da ocorrência de cianobactérias e cianotoxinas, bem como a aplicação de medidas de controle das florações. Uma estratégia viável para esse controle é a manipulação dos estoques de peixes onívoros filtradores, como a tilápia do Nilo. Neste trabalho foram avaliados: i) a presença de cianobactérias (composição, densidade e biovolume, pelo método da sedimentação) e cianotoxinas (bioensaios com camundongos) em cinco reservatórios do semi-árido do estado do Rio Grande do Norte, em cinco campanhas de coletas, entre setembro de 2002 e março de 2004; e ii) as taxas de consumo per capita de cianobactérias filamentosas pela tilápia, através de dois experimentos em laboratório, utilizando populações naturais de cianobactérias (experimento I) e uma cultura de Cylindrospermopsis raciborskii (experimento II), após a exposição de indivíduos jovens de tilápia a um gradiente de biomassa de cianobactérias. O fitoplâncton nos reservatórios estudados apresentou dominância de cianobactérias, incluindo várias espécies toxigênicas (C. raciborskii, Microcystis spp., Aphanizomenon e Anabaena circinalis). Cianotoxinas foram evidenciadas em três dos cinco reservatórios. O consumo de cianobactérias (µg clorofila-a.peixe-1.dia-1) foi de 0,29 no experimento I e de 0,5 no experimento II. Populações abastecidas pelos reservatórios investigados estão potencialmente expostas aos efeitos negativos das cianotoxinas. Esta pesquisa sugere que é viável a estocagem da tilápia do Nilo no controle de florações de cianobactérias. Entretanto, fatores como a ictioeutrofização e o acúmulo de cianotoxinas na biomassa dos peixes devem ser levados em consideração antes que um programa de biomanipulação possa ser implementado. Palavras-chave: Cianobactérias, cianotoxinas, tilápia, biomanipulação, reservatórios ABSTRACT CYANOBACTERIA AND CYANOTOXINS IN RESERVOIRS OF RIO GRANDE DO NORTE STATE AND THE POTENCIAL CONTROL OF BLOOMS BY NILE TILAPIA (Oreochromis niloticus).Cyanobacteria blooms in reservoirs result in loss of water quality and negative effects to human health. To reduce these impacts the monitoring of the cyanobacteria and cyanotoxin occurrence as well as the application of measures to counteract the cyanobacteria blooms are made necessary. The manipulation of filter-feeding omnivorous fish stock, as Nile tilapia, has been proposed as an strategy for cyanobacteria bloom control. The present work aimed to evaluate: I) the presence of cyanobacteria (composition, density and biovolume by sedimentation technique) and cianotoxins (mouse bioassay) in five reservoirs located at the semi-arid region of Rio Grande do Norte state, in five sampling campaigns between September 2002 and March 2004; II) the per capita consumption rates of filamentous cyanobacteria by Nile tilapia through laboratory experiments using a natural population of cyanobacteria (experiment I) and a culture of Cylindr...
Background: Brief Description of Deserts and Dust Storm FrontsDrylands, which make up 41-45% of the Earth's land area, are inhabited by 31% of the world's human population and are characterized by climatic forces which shape the physical environment and its biological life (UNCCD 2012;Prăvălie 2016; IPCC 2017;Maliva and Missimer, 2012). Although deserts were conceptualized singularly in the context of temperature maxima or lack of precipitation, aridity indices (AI) which take into consideration annual precipitation (P) and evapotranspiration (ET) potential are more accurate and efficient in describing deserts (UNESCO 1979; IPCC 2007 IPCC , 2017. This is because ET has an inherent co-linearity with additional climatic forces including temperature, wind speed, and Global Horizontal Irradiation (GHI). The water cycle, which influences soil type, vegetation cover and species abundance is factored in as well through incorporation of P in the aridity index (UNESCO 1979; IPCC 2007 IPCC , 2017.The Arabian Seas are surrounded by deserts in the hyper-arid (AI < 0.0) to arid (0.03 < AI < 0.20) continuum (MEA 2005; UNESCO 1979; UNCCD 2012), of yearly sums of GHI levels (2118-2775 kWh/m 2 ) comparable only to the Atacama (Chile and Peru), the driest hot desert in the world (Knight 2016; SSE 2017). These deserts also experience irregular rainfall of up to 80 mm on average per annum (hyper-arid) and between 80 and 350 mm on average per annum (arid), mainly occurring during the winter months when temperatures are low, with the exception
In some parts of the world, cyanobacteria are used as a food in the human diet, due to their ready availability. Lake Chad, has long been a traditional site for the collection of Arthrospira fusiformis which is dried and processed at the lake into thin wafers called Dihé for later consumption or is transported to market for sale. However, Dihé purchased from markets in Chad has not been analyzed for known cyanobacterial toxins or assessed for total amino acid content. Since BMAA in traditional foodstuffs of the indigenous Chamorro people of Guam causes neurodegenerative illness, it is important that Dihé from Chad be analyzed for this neurotoxin. BMAA and its isomer AEG were not detected in our analyses, but a further isomer DAB was detected as both a free and bound amino acid, with an increase in the free concentration after acid hydrolysis of this fraction. Microcystins were present in 6 samples at up to 20 μg/g according to UPLC-PDA, although their presence could not be confirmed using PCR for known microcystin synthetic genes. Amino acid analysis of the cyanobacterial material from Chad showed the presence of large amounts of canonical amino acids, suggesting that this may supplement indigenous people on low protein diets, although regular monitoring of the foodstuffs for the presence of cyanotoxins should be performed.
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