Diatom motility and nuclear alterations are affected by sediment elutriates of agricultural streams.

Diatoms respond to toxicants in lotic systems, and they are commonly considered to be sensitive indicators in environmental safety assessment. In addition to the structural characteristics of the algal populations, recent studies have shown that endpoints such as nuclear anomalies or diatom motility measures can be affected quickly by environmental changes. We sought to determine if cell density, cell size, nuclear anomalies and motility of the diatom Nitzschia palea were useful indicators of sediment quality from agricultural streams. For this purpose, we exposed cultures of the diatom to elutriates from sediments of a stream that flows through an intensive agricultural area, and measured the responses of the populations for 7 days in laboratory tests. The bioassays showed that motility measures in Nitzschia palea and the condition of their nuclear membranes rapidly reflected the effects of sediment quality after only 48 h of exposure; mean cell density and length were affected by day 7. The sediment elutriates affected cell movements by shortening the total path length and decreasing cell velocity; they also increased the number of cells with nuclear membrane breakage. Our results from these bioassays show that diatom motility measurements and the condition of the nuclei might be indicators that respond faster to impacts than the traditional structural parameters, such as cell density, specific composition of the assemblage or diversity metrics of the algal communities more often used in biomonitoring.

Multibiomarker responses in aquatic insect Belostoma elegans (Hemiptera) to organic pollution in freshwater system.

The present study analyzes a battery of biomarkers in the water bug Belostoma elegans from a stream polluted with organic matter (OMS), and another one considered as reference site (RS) during spring-summer season (December to March). Biochemical parameters of glucidic, lipidic and oxidative metabolic pathways were analyzed in males and females of this insect. In general, no significant differences were observed in all biomarkers assayed between both sexes, except lactate concentration which was higher in males than in females (p < 0.0006) in the first three months. About carbohydrate metabolism parameters, only pyruvate-kinase showed significant differences between insects collected in both streams (p < 0.05) during December. However, the total lipid content, saturated fatty acid, and mainly triacylglycerol were higher in insects from RS compared to those from OMS (p < 0.002) in all sampled months. Levels of lipoperoxidation, protein oxidation, reduced glutathione and glutathione-S-transferase activity showed no differences between insects collected from both streams. Nevertheless, the significant increase observed in superoxide dismutase and catalase activities (p < 0.004) could be due to the elevated oxidative metabolism in insects from RS compared to those from OMS with lower dissolved oxygen. Regarding those responding parameters, males accounted for the differences between the two sites during the study period. In conclusion, our results support that lipidic energetic reserves and antioxidant enzyme activities in B. elegans could be used as biomarkers of environmental pollution by organic matter.

Evaluación del regimen térmico del Embalse del Río III

Para analizar cambios en el régimen térmico del Embalse, se calcularon las temperaturas medias mensuales de una estación central del lago a 5 y 15 m., para los períodos preoperacioanl (77-82) y operacional de la CNE (83-96). Los resultados de la información demuestra que el régimen térmico no ha sufrido modificaciones evidentes para el grado de precisión con que se hacen las mediciones

Cambios en el estado trófico del Embalse del Rio III posteriores al funcionamiento de una central nuclear

El Embalse del Río III se construyó entre 1927 y 19636 con fines de aprovechamiento hidroeléctrico, riego y retención de crecidas. El Embalses estA conformado por dos grandes cubetas comunicadas por estrechamiento muy marcado. Allí está ubicada la Central Nuclear Embalse, construida entre 1977 y 1983. Desde 1977 se realizan controles ambientales con el objetivo de evaluar el efecto del uso del agua sobre el régimen térmico, el estado trófico y las comunidades del embalse. Se dan los resultados parciales de los estudios, siendo la finalidad de este trabajo presentar una sínteris de los cambios ocurridos en el estado trófico del Embalse y analizar sus posibles causas