Bioaccesibilidad de arsénico y cálculos de ingestas en dietas consumidas por una población endémica de Taco Pozo. Comparación entre las ingestas infantiles y adultas / Bioavailability of arsenic and intake calculations in diets consumed by an endemic population of Taco Pozo. Comparison between infant and adult intakes

El arsénico es muy estudiado a nivel mundial, es altamente toxico en especial en su forma inorgánica arseniato [As(V)] y arsenito [As(III)]. El hombre se encuentra expuesto al arsénico principalmente mediante el agua de consumo y la dieta. El objetivo del trabajo fue determinar la bioaccesibilidad de arsénico en alimentos cocinados en una región endémica Chacosantiagueña de Argentina y estudiar la ingesta diaria en una población infantil y adulta a partir del arsénico bioaccesible cuantificable en los alimentos. Para la cuantificación de As-i bioaccesible se siguió el método in vitro de simulación del proceso de digestión gastrointestinal en sus dos etapas (gástrica e intestinal). Para el cálculo de la fracción bioaccesible se cuantificó el Arsénico luego del proceso de digestión gastrointestinal simulado y este valor corresponde al % de bioaccesibilidad con respecto al Arsénico cuantificado antes del proceso y que constituye el 100%. Para los mates y leches se consideró la totalidad del arsénico como inorgánico puesto que en el agua, éste es la principal especie. Los resultados muestran que el arsénico bioaccesible tiene valores entre 62,7-78 %, siendo el promedio 70,6%. Los rangos de las ingestas calculadas para la población infantil fueron de 11,3 a 350,9 µg/kgpc/día, mientras que en la población adulta fueron entre 5 a 30,2 µg/kgpc/día. La población infantil es la más expuesta al arsénico mediante la dieta

Arsenic is very studied worldwide, it is highly toxic especially in its inorganic form arsenate [As (V)] and arsenite [As (III)]. Man is exposed to arsenic mainly through drinking water and diet. The objective of the work was to determine the bioavailability of arsenic in cooked foods in a Chacosantiagueña endemic region of Argentina and to study the daily intake in a child and adult population from quantifiable bioavailable arsenic in foods. To calculate the bioaccessible fraction, Arsenic was quantified after the simulated gastrointestinal digestion process and this value corresponds to the% of bioavailability with respect to Arsenic quantified before the process and which constitutes 100%. For mates and milks the totality of arsenic was considered as inorganic since in water, this is the main species. The results show that bioaccessible arsenic has values between 62.7-78%, with an average of 70.6%. The ranges of the intakes calculated for the infant population were from 11.3 to 350.9 μg / kgpc / day, while in the adult population they were between 5 to 30.2 μg / kgpc / day. The infant population is the most exposed to arsenic through diet

Effects of the interannual variations in the flood pulse mediated by hypoxia tolerance: the case of the fish assemblages in the upper Parana River floodplain

The effects of the duration of the floods on abiotic variables and attributes of species tolerant and intolerant to hypoxia (STH and SIH respectively) were evaluated in rivers and lakes of the upper Paraná River. Fish were sampled once a year, in six sampling stations, during the high water period from 2000 to 2003. There were overall reductions in dissolved oxygen levels and increases in transparency of water in lakes in years of moderate floods. The duration of floods influenced species differentially based on their tolerance to hypoxia: in moderate floods, richness of STH increased and numerical abundance and biomass of SIH reduced significantly. Opposite relationships were detected between dissolved oxygen and the attributes of STH and SIH. Dissolved oxygen was the best predictor of variability of STH and SIH in years of moderate floods, whereas water transparency predicted significant amounts of STH in years of short floods. Being positively affected by dissolved oxygen reductions, STH seem to take advantages in persisting in seasonally harsh lentic habitats. The incorporation of abiotic data as well the differential tolerance of species to hypoxia would improve further investigations of the effects of interannual variations in the flood pulse on tropical fish assemblages.

Os efeitos da duração da cheia sobre algumas variáveis abióticas e atributos das assembleias de peixes (espécies tolerantes e intolerantes à hipóxia, STH e SIH, respectivamente) foram avaliados em rios e lagoas do alto rio Paraná. Os peixes foram amostrados uma vez ao ano, em seis localidades, durante o período de águas altas entre 2000 e 2003. Houve reduções generalizadas nos níveis de oxigênio dissolvido e aumentos na transparência da água em lagos em anos de cheias moderadas. A duração das cheias influenciou as espécies diferencialmente em função de sua tolerância à hipóxia: em anos de cheias moderadas, a riqueza das STH aumentou e a abundância numérica e de biomassa das SIH reduziram significativamente. Relações opostas foram detectadas entre o oxigênio dissolvido e os atributos das STH e SIH. O oxigênio dissolvido foi o melhor preditor da variabilidade de STH e SIH em anos de cheias moderadas, enquanto a transparência da água explicou uma significativa proporção das STH em anos de cheias curtas. Por serem positivamente afetadas pelas reduções no oxigênio dissolvido, as STH parecem ter vantagens em persistir em ambientes lênticos sazonalmente inóspitos. A incorporação de dados abióticos bem como da tolerância diferencial das espécies à hipóxia deve aprimorar as investigações dos efeitos das variações interanuais no pulso de inundação nas assembleias de peixes tropicais.

Estudio preliminar de la ictiofauna y los hábitats acuáticos del Río Bajo Paraguá, Santa Cruz, Bolivia / Preliminary study of fish fauna and aquatic habitats in the Lower Paraguá River, Santa Cruz, Bolivia

A fin de conocer la riqueza íctica del Río Bajo Paraguá (cuenca del Iténez o Guaporé) se realizaron colectas de peces y análisis físico-químicos del agua en tres localidades del norte de Santa Cruz, sobre el límite oeste del Parque Noel Kempff Mercado. Los muestreos duraron 5 días en cada sitio (Piso Firme, Florida y El Refugio) y en dos épocas del año (aguas altas: Abril-Mayo; aguas bajas: Septiembre). Utilizando diferentes artes de pesca se capturaron 4098 peces pertenecientes a 124 especies, de las cuales 35 fueron nuevos registros para el Parque Noel Kempff Mercado. De las 124 especies, el 56 por ciento correspondió al orden Characiformes, 22 por ciento a Siluriformes (con 34 spp), 15 por ciento a Perciformes (18 cíclidos), 5 por ciento a Gymnotiformes y 2 por ciento a Synbranchiformes, Rajiformes y Beloniformes. La riqueza de especies fue menor en el curso superior del río (Piso Firme: 90 especies, Florida: 71 especies y El Refugio: 23 especies), al igual que la concentración de oxígeno que en El Refugio alcanzó niveles críticos en la época de escaso caudal por la mayor cobertura de plantas flotantes. La proporción de nuevos registros geográficos y los interrogantes sobre distribución y abundancia de los peces del Rio Paraguá indican la necesidad de implementar monitoreos sistemáticos asociados a los planes de manejo de la zona.

With the aim of improving our knowledge about the fish fauna of the Lower Paragua River (Iténez or Guaporé basin), fish collections and physic-chemical analyses of water were conducted in three localities in northern Santa Cruz, on the western border of the Noel Kempff Mercado National Park. Sampling periods lasted 5 days on each of three sites (Piso Firme, Florida y El Refugio) and two seasons (high waters: April-May, low waters: September). By using various fishing methods, 4098 fish belonging to 124 species were collected, 35 of them were new geographic records for the National Park. From all the species, 56 percent belonged to the Characiformes, 22 percent to Siluriformes (34 spp.), 15 percent Perciformes (18 spp. of cichlids), 5 percent Gymnotiformes and 2 percent Synbranchiformes, Rajiformes and Beloniformes. Species richness was low in the upper course of the river (Piso Firme: 90 species, Florida: 71 species, El Refugio: 23 species) as well as oxygen levels which reached a critical minimum at El Refugio during low waters and increased cover of floating vegetation. The proportion of new geographic records and the uncertainties about fish distribution and abundance indicate the need to conduct monitoring actions associated to the management plans in the area.