Cyanobacteria and cyanotoxins in freshwaters of Uruguay

Cyanobacterial blooms are a worldwide environmental problem. This phenomenon is typically associated with eutrophication (nutrient enrichment) and changes in hydrology. In this study we analysed the distribution of planktonic cyanobacteria in Uruguay and their toxins (microcystin, saxitoxin and cylindrospermopsin), working with an interagency team (OSE, DINAMA, IM, University of the Republic and IIBCE). An historical data base (n = 3061 for 64 ecosystems, years 1980-2014) was generated. Differences between lotic and lentic ecosystems were found in terms of chlorophyll a and nutrient concentrations, usually indicating eutrophication. Two geo-referenced maps for the country were generated with cyanobacteria biomass indicators and the most relevant toxin (microcystin), according to risk levels suggested by the World Health Organization for recreational waters. The areas of greatest risk of exposure were the reservoirs of large rivers (Uruguay and Río Negro) and Río de la Plata beaches. In the second part of the study, up to 20 mg L-1of microcystin was quantified in bloom (scum) samples, as well as the presence of genes that suggest more microcystin varieties, potentially with greater toxicity. This study provides basic information about the distribution of cyanobacteria in Uruguayan freshwaters that will be useful for national monitoring programs and scientific research

Cianobacterias y cianotoxinas en ecosistemas límnicos de Uruguay

Cyanobacterial blooms are a worldwide environmental problem. This phenomenon is typically associated with eutrophication (nutrient enrichment) and changes in hydrology. In this study we analysed the distribution of planktonic cyanobacteria in Uruguay and their toxins (microcystin, saxitoxin and cylindrospermopsin), working with an interagency team (OSE, DINAMA, IM, University of the Republic and IIBCE). An historical data base (n = 3061 for 64 ecosystems, years 1980-2014) was generated. Differences between lotic and lentic ecosystems were found in terms of chlorophyll a and nutrient concentrations, usually indicating eutrophication. Two geo-referenced maps for the country were generated with cyanobacteria biomass indicators and the most relevant toxin (microcystin), according to risk levels suggested by the World Health Organization for recreational waters. The areas of greatest risk of exposure were the reservoirs of large rivers (Uruguay and Río Negro) and Río de la Plata beaches. In the second part of the study, up to 20 mg L-1of microcystin was quantified in bloom (scum) samples, as well as the presence of genes that suggest more microcystin varieties, potentially with greater toxicity. This study provides basic information about the distribution of cyanobacteria in Uruguayan freshwaters that will be useful for national monitoring programs and scientific research.Las floraciones de cianobacterias en cuerpos de agua dulce constituyen un problema mundial, asociado a la eutrofización (enriquecimiento de nutrientes) y cambios hidrológicos de los ecosistemas. En este estudio se generó una base de datos históricos (n= 3061 para 64 ecosistemas, de 1980 a 2014), elaborada por un grupo de trabajo interinstitucional (OSE, DINAMA, IM, Universidad de la República e IIBCE), y se analizó la distribución de cianobacterias planctónicas y de cianotoxinas (microcistina, saxitoxina y cilindrospermopsina) en Uruguay. Los valores de clorofila ay nutrientes totales indicaron procesos de eutrofización en diversos ecosistemas. En dos mapas georreferenciados se visualiza la distribución de cianobacterias en el país, según indicadores cuantitativos globales, y de la microcistina (cianotoxina más frecuente). En dichos mapas se destacan los embalses (Río   Uruguay y Río Negro) y las playas del Río de la Plata como las zonas de mayor riesgo de exposición a cianobacterias según las categorías de la Organización Mundial de la Salud para aguas recreacionales. Además, se analizaron muestras de floraciones (espuma) y se cuantificó 20 mg L-1de microcistinas totales y la presencia de genes que sugieren diferentes variedades de microcistinas. Se generó información básica que podrá ser útil para programas de monitoreo nacionales e investigación