El objetivo del estudio fue contribuir al conocimiento de la composición y estructura de la taxocenosis conformada por cianobacterias, clorofitas y euglenofitas de estos ambientes extremos, en relación a variables abióticas (conductividad eléctrica, salinidad y pH del agua, altura sobre el nivel del mar y superficie lacustre). En 2005, se efectuó un muestreo interdisciplinario de veintiséis puntos de colecta en tres provincias del noroeste argentino (NOA). Los datos abióticos y bióticos registrados en campo y en laboratorio se hicieron según protocolos convencionales. De acuerdo a los resultados, la mayoría de los ejemplares identificados en Catamarca (coincidente con Jujuy y Salta) fueron cosmopolitas y afines con la salinidad, destacándose, en general, las cianobacterias y Chroococcus turgidus dentro de este grupo; en segundo lugar, estuvieron las algas verdes y, en el caso de las euglenofitas, no fueron registradas en dicha provincia. La taxocenosis estuvo constituida tanto por especies propias del fitoplancton como de otros hábitats. Los valores bajos a intermedios de diversidad (0,01-2,85) estarían vinculados al predominio de especies raras y de unas pocas dominantes. La biomasa mostró sensibilidad a las condiciones ambientales, en general disminuyó con el aumento de la salinidad, varió entre 24.007-60.396.324 mg/ml de C. La aplicación del Análisis de Componentes Principales, tanto para variables abióticas como bióticas, fueron de utilidad porque aportaron datos complementarios sobre la ocasionar floraciones y potencialÂmente tóxicas, como Chroococcus turgidus, Microcystis flos-aquae y Nodularia spumigena conducen a sugerir un control periódico de estos cuerpos de agua.

The aim this study was to contribute to the knowledge of the composition and structure of taxocenosis formed by cyanobacteria, chlorophytes and euglenophytes of these extreme environments in relation to abiotic variables (water electrical conductivity, salinity, pH, height above sea level and lake surface). In 2005, an interdisciplinary sampling was carried out covering twenty-six collection sites in three provinces from Argentinean Northwest. Abiotic and biotic data were recorded in the field and in the laboratory following conventional protocols. According to the results, most of the specimens in the province of Catamarca (coinciding with Jujuy and Salta) were cosmopolitan and related to salinity, with Cyanobacteria and Chroococcus turgidus standing out in general within this group; green algae were in second place, while euglenophytes were not recorded in this province. Taxocenosis was made up of phytoplankton species and those coming from other habitats. The low to intermediate values ​​of diversity (0.01-2.85) would be linked to the dominance of rare species and presence of a few taxa with high numbers of individuals. Biomass showed sensitivity to environmental conditions, highlighting in general a decrease of this variable with the increase in salinity, whose records varied between 24,007- 60,396,324 mg/ml of C. The application of the Principal Components Analysis for abiotic and biotic variables was a useful tool because it provided complementary information on the distribution of the selected sites. Finally, the quantification of cyanobacterial species potentially toxic and capable of producing blooms, such as Chroococcus turgidus, Microcystis flos-aquae and Nodularia spumigena lead to suggest a periodic control of these water bodies.

OBJETIVO: A represa Escaba está localizada ao sul da província de Tucumán, a 650 metros de altitude, sua extensão é de 541 ha, tem 65 m de profundidade e seus afluentes são os Rios Chavarria, Las Moras, El Chorro e Singuil. O clima é temperado, com invernos secos e verões chuvosos. O objetivo do estudo foi caracterizar as propriedades físicas e químicas das águas limnéticas da represa e da foz dos seus afluentes, para interpretar a qualidade de suas águas. MÉTODOS: Realizaram-se amostragens estacionais de agosto de 2010 até maio de 2012. As variáveis medidas in situ foram: temperatura, transparência, pH, condutividade elétrica, e no laboratório foram analisados: oxigênio dissolvido, demanda bioquímica de oxigênio (DBO5), íons principais, compostos nitrogenados e fosfatados. RESULTADOS: O tipo de água é bicarbonatada-cálcica-sódica, de neutra a alcalina e detectou-se estratificação térmica na primavera e verão. Com exceção da zona limnética: fundo, nos meses mais quentes, as águas estiveram bem oxigenadas. Em novembro de 2011 no rio El Chorro, obteve-se o valor mais baixo de transparência: 0,12 m e o valor mais elevado foi de 4,1 m no rio Singuil no inverno de 2010. Observou-se uma mineralização fraca com condutividades que variaram entre 83 e 218 µS.cm-1. A DBO5 atingiu o registro máximo de 183 mg L-1 na primavera de 2010 no rio Singuil. Os valores mais altos dos compostos nitrogenados detectados foram: 7 mg NO3-.L-1 (zona limnética: fundo, agosto/2010), 0,07 mg NO2-.L-1 (rio Las Moras, maio/2011) e 1,8 mg NH4+.L-1 (rio Chavarría, março/2011). No verão de 2012, o ortofosfato atingiu 0,22 mg.L-1 no fundo da zona limnética. A proporção NT/PT mostrou o fósforo como limitante, e o nitrogênio em raras ocasiões. CONCLUSÕES: O ecossistema analisado foi classificado como hipertrófico considerando NT, PT e transparência. O ACP permitiu uma diferenciação estacional dos sítios, os eixos 1 e 2 separaram as amostras de acordo aos gradientes dos nutrientes, oxigênio dissolvido, DBO5 e temperatura.

AIM: The Escaba dam is located in the south of the Tucumán province, Argentina, at 650 m above sea level. It has an extension of 541 ha. and a depth of 65 m and its tributaries are the Chavarría, Las Moras, El Chorro and Singuil rivers. The climate is mild with dry winters and rainy summers. The objective of this study was to characterize physicochemical parameters in the limnetic zone of the dam and the mouths of the tributaries to determine the water quality. METHODS: Seasonal sampling was carried out between August 2010 and May 2012. Temperature, transparency, pH and electrical conductivity were field measured, whereas dissolved oxygen, biochemical oxygen demand (BOD5), major ion constituents and nitrogen and phosphate compounds were analyzed at the laboratory. RESULTS: The water was classified as sodium-calcium-bicarbonate with neutral to alkaline pH, and thermal stratification during spring and summer. The water assayed was well oxygenated except for the bottom of the limnetic zone during the summer months. Lowest transparency was measured in the El Chorro River in November 2011 (0.12 m) and highest degree of transparency in the Singuil River during the winter of 2010 (4.1 m). The waters assayed showed weak mineralization with conductivities between 83 and 218 µS.cm-1. Maximum BOD5 value (183 mg.L-1) was measured in the Singuil River in spring 2010. Highest values for the different nitrogen compounds were as follows: 7 mg NO3-.L-1 at the bottom of the limnetic zone in August 2010, 0.07 mg NO2-.L-1 in the Las Moras River in May 2011 and 1.8 mg NH4+.L-1 in the Chavarría River in March 2011. During the summer of 2012 orthophosphate reached a value of 0.22 mg.L-1 at the bottom of the limnetic zone. The TN/TP ratio revealed that phosphate was generally the limiting factor and rarely nitrogen. CONCLUSIONS: Considering the TN, TP and transparency parameters the ecosystem was classified as hypertrophic. PCA allowed a seasonal differentiation of the sites, and components 1 and 2 classified the samples according to nutrient gradient, dissolved oxygen, BOD5 and temperature.

Structure and abiotic controls of phytoplankton in high wetlands. The mismanagement of high wetlands is driving to accelerated deterioration of these fragile and dynamical environments. The aim of this paper is to study the abundance, biomass and diversity of some components of phytoplankton from high wetlands belonging to Jujuy Province, in relation to environmental variables such as water electrical conductivity and pH of the water, and altitude and size of the gaps. A sampling, including the study of 16 lakes, was realized in summer. The studied variables were altitude, aerea of the water body, electrical conductivity, pH, absolute algal density, biomass and diversity. According of results the water bodies were alkaline and with different salinities in base of the conductivities. The highest algal densities were obtained in lakes with intermediate salinities because principally to Chlamydomonas tremulans Rodhe et Skuja and, therefore, the least diversity, while in hipersaline and smallest lakes were the least values of abundance, correspondence exclusively to Cyanophyta. The Euglenophyta were prominent especially in Pululos Lake, saline environment where these were dominant. Finally, we would like comment the importance in the studied wetlands of non-biotic factors as altitude and pH, and biotic factors as density and/or biomass of Cyanophyta and Chlorophyta for delimitation of habitat and biota.

El mal manejo de los humedales de altura está conduciendo a un deterioro acelerado de estos ambientes dinámicos y frágiles. El objetivo de este trabajo es estudiar la abundancia, la biomasa y la diversidad de algunos componentes del fitoplancton de humedales altoandinos de la provincia de Jujuy, en relación a variables ambientales como la conductividad eléctrica y el pH del agua, y la altura sobre el nivel del mar y el tamaño de las lagunas. Se analizaron 16 lagunas en las que se documentó su altura sobre el nivel del mar, superficie, la conductividad eléctrica y el pH del agua, y la abundancia, biomasa y diversidad de algunos componentes del fitoplancton. La conductividad eléctrica permitió clasificar las lagunas en alcalinas, salinas e hipersalinas. Las lagunas de salinidad intermedia mostraron las mayores densidades algales, aportadas principalmente por Chlamydomonas tremulans Rodhe et Skuja y, por ende, la menor diversidad, mientras que en las hipersalinas y de dimensiones pequeñas se documentaron las menores densidades algales, correspondientes exclusivamente a Cyanophyta. Las Euglenophyta sobresalieron en particular en la laguna Pululos, ambiente salino en el que resultaron dominantes. La altitud de la laguna y su pH explicaron una proporción importante de la variación en la abundancia y la biomasa de Cyanophyta y de Chlorophyta en las lagunas analizadas.