Trends in recent years have indicated that cyanobacterial blooms in tropical reservoirs are increasing in frequency, magnitude and geographical distribution. Funil Reservoir in southeastern Brazil has experienced eutrophication in the recent decades, resulting in lasting and intense toxic cyanobacterial blooms. As input of nutrients is high during the year, the aim of the present study was to evaluate the role of other variables related to changes in cyanobacterial biomass and composition. The dominant group found over the entire study period was Cyanobacteria (97% of total biomass), which contributed to low diversity. A shift of nitrogen-fixing (Anabaena circinalis and Cylindrospermopsis raciborskii) and non nitrogen-fixing (Microcystis aeruginosa) cyanobacteria was observed. Redundancy analysis indicated that physical factors such as temperature, changes in the mixing zone and light intensity were the main driving factors of the seasonal succession. Nitrogenfixing cyanobacteria dominated in periods of low light in the deepest mixing zone, and also seemed to have experienced stronger grazing effects as the density of the large zooplankton group was related to cyanobacteria biomass. M. aeruginosa bloomed in warm stratified waters, high water levels and during months with more daylight, when the zooplankton density was drastically reduced. Although the long-standing dominance of cyanobacteria may be related to high nutrient availability, the present study showed that under high and constant input of nutrients, other factors, especially physical variables, present a more plausible explanation to promote changes in species composition.KEY WORDS: Cyanobacterial bloom · Cylindrospermopsis · Microcystis · Anabaena · Zooplankton Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 57: [137][138][139][140][141][142][143][144][145][146][147][148][149] 2009 reports of surface scum have become much more numerous since the mid-20th century. Harmful algal blooms caused by cyanobacteria (CyanoHABs) are one of the most severe problems in freshwater ecosystems nowadays. These often-toxic blooms and the dense surface scums are indicative of water quality deterioration and food-web changes, and can be responsible for the mortality of fish, domestic animals and even humans (Paerl & Huisman 2009).Cyanobacteria blooms occur in waters during calm stratified conditions with high temperatures and adequate nutrient supplies (Huszar et al. 2000). Cyanobacterial dominance is mostly related to favourable bottom-up factors (Briand et al. 2002, Marinho & Huszar 2002, since they are widely known for their ability to minimize grazing pressure, through different effects on zooplankton community: mechanical interference (difficulty in manipulating and ingesting large colonies or filaments), assimilation (low amounts of essential nutrients) and toxicity (De Bernardi & Giussani 1990). However, some zooplankton species have developed physiological resistance to cyanotoxins (Fulton & Paerl 1988...

resumo 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. palavras-chave: Cianobactérias, microcistinas, saxitoxinas, zooplâncton, testes de toxicidade. abstraCt CyanobaCterial blooms in tHe Funil Water reservoir: seasonal dynamiCs and ConsequenCes For zooplankton. 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 cyanobacte...

Glyphosate is a popular herbicide used worldwide, and several studies consider it to be an environmental hazard affecting human health. The present study aimed to detect glyphosate in six different reservoirs of Paraíba do Sul and Guandu River Basins in Southeast Brazil, used for multiple purposes, including fishery activities and domestic water supply. Ion chromatography was used to analyze the water samples, as it is a fast and environmentally friendly technique to detect glyphosate. Our results revealed that, despite differences related to trophic state, season of the year or distance to urban areas, glyphosate was detected in all reservoirs and in three of them with concentrations above the limit imposed by Brazilian legislation. Among the environmental variables studied, turbidity presented the highest correlation with glyphosate concentrations. The effect of rainfall increasing turbidity in the rivers reinforces the importance of draining waters from surrounding areas that transport glyphosate into the aquatic ecosystems. The detection of the herbicide in the various systems confirms the wide use of this compound in the drainage basins of the studied reservoirs and highlights the importance of water monitoring. Further, the results reveal how urgent and important it is to explore through laboratory experiments the pathways of degradation of this herbicide in tropical and subtropical aquatic environments together with its effects on flora and fauna.