Translocation of Epipelic Biofilms and Their Short-Term Responses to Urbanization Impacts in Nutrient Rich Streams.

Stream biofilms are among the first to react to environmental degradation, since their structural and functional characteristics are tightly linked to the physicochemical variables in the water and sediment. The objectives of this research were to study the differences in chlorophyll-a, bacterial density and metabolism endpoints of epipelic biofilms in nutrient-rich streams under different physical-chemical conditions in the stream water in relation to changes in urbanization, and to measure the short-term responses (up to 72 h) in the biofilm when translocated to more urbanized sites. For these purposes, chlorophyll-a, bacterial density, biofilm respiration (electron transfer activity) and O2 consumption were measured in epipelic biofilms in nutrient-rich streams exposed to different levels of urbanization after a 30 day colonization. Afterward, biofilms were translocated downstream to more polluted sites, and sampled to identify any fast occurring changes to be considered as potential indicators of environmental degradation. Results show that in the nutrient-rich streams studied, the structural characteristics of the biofilm were linked to urbanization, and even after a short time following the translocation, chlorophyll-a and bacterial density varied, reflecting the environmental degradation. On the other hand, metabolic variables were highly variable and produced inconsistent results when representing an increase in urbanization.

Transplanting macrophytes as a rehabilitation technique for lowland streams and their influence on macroinvertebrate assemblages.

Lowland streams are usually affected by river engineering works that produce the loss of habitat heterogeneity. Our aim was to assess the transplantation of macrophytes with different complexity into a lowland stream which was dredged and widened. Stuckenia pectinata and Hydrocleys nymphoides were collected at an extraction site and installed at a transplant site. The growth and coverage of macrophytes beds were quantified. Taxonomic richness, Shannon-Wiener diversity, abundance, composition and proportion of functional feeding groups of the macroinvertebrate assemblage presented in macrophyte beds were assessed between sites and species. The growth of both macrophytes did not differ significantly between sites and the coverage of transplanted beds increased, therefore they established at the transplant site within a short period. Regarding to macroinvertebrate assemblage, only the functional feeding groups did not show differences between sites. Moreover, the proportion of predators presented differences between macrophytes at the same site, with H. nymphoides having a higher proportion. Our study showed that this technique is suitable for reintroducing these species and is applicable in rehabilitation projects that promote the restoration of habitat heterogeneity deteriorated by river engineering works. Also, we highlight the importance of incorporate macroinvertebrate functional traits to assess the ecological status after rehabilitation.

Soybean peroxidase immobilized onto silica-coated superparamagnetic iron oxide nanoparticles: Effect of silica layer on the enzymatic activity.

Peroxidase immobilization onto magnetic supports is considered an innovative strategy for the development of technologies that involves enzymes in wastewater treatment. In this work, magnetic biocatalysts were prepared by immobilization of soybean peroxidase (SBP) onto different silica-coated superparamagnetic iron oxide nanoparticles. The obtained magnetic biocatalysts were tested for the degradation of malachite green (MG), a pollutant often found in industrial wastewaters and with significant drawbacks for the human and environmental health. A deep physicochemical characterization of the materials was performed by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), High Resolution-Transmission Electron Microscope (HR-TEM) and magnetization measurements among others techniques. Results showed high immobilization yield of SBP onto nanomaterials with excellent properties for magnetic recoverability. A partial loss of activity with respect to free SBP was observed, compatible with the modification of the conformational structure of the enzyme after immobilization. The structural modification depended on the amount (and thickness) of silica present in the hybrid materials and the activity yield of 43% was obtained for the best biocatalyst. Thermal stability and reusability capacity were also evaluated.

Temporal distribution of cyanobacteria in the coast of a shallow temperate estuary (Río de la Plata): some implications for its monitoring.

The aim of this study was to analyze the temporal distribution of phytoplanktonic cyanobacteria in a site located in the freshwater tidal zone near the extraction point for the drinking water supply. Samples were taken considering three timescales as follows: hours, days, and weeks, during the period of highest development of cyanobacteria. The phytoplankton density, microcystin concentration (LR, RR, YR), and chlorophyll-a were related to meteorological variables (wind and temperature), tidal high, and physical-chemical variables (nutrients, pH, conductivity, light penetration). The results obtained in this study showed that the variables that primarily modulate the temporal distribution of cyanobacteria were temperature, pH, light penetration, conductivity, and nutrients (particularly NO3 (-) and NH4 (+)), while the winds and tide had a secondary effect, only evidenced at an hourly scale. Therefore, this timescale would be the most suitable for monitoring cyanobacterial populations, when the amount of cyanobacterial cells exceeds the alert I level proposed by the World Health Organization. This recommendation is particularly important for the water intake zones in Río de la Plata, which are vulnerable to the damage generated by cyanobacteria on the water quality.

Frequency, abundance and distribution of zoosporic organisms from Las Cañas stream (Buenos Aires, Argentina).

Zoosporic organisms are common inhabitants of aquatic environments; however there are few ecological studies made for Argentinean streams. In this contribution the taxonomic composition of zoosporic organisms from a stream and their abundance, frequency and diversity on cellulosic baits were analyzed. Samples of water and floating organic matter (vegetable debris) were taken at four dates and different environmental variables (temperature, dissolved oxygen and nutrient concentrations) were measured. Twenty-one taxa were recovered with the baiting technique. Physicochemical fluctuations affected the structure of the studied community; in spring the greatest species richness was related to high nutrient levels whereas in winter the greatest abundance and diversity was related to low water temperature, nutrient levels and well oxygenated conditions. aquatic environment,

Alternativas para la restauración del brazo de un río

La disminución del caudal del Brazo Sur del río Negro ha ocasionado un cambio ambiental desfavorable en términos del potencial desarrollo del área. Propone tres alternativas de restauración del brazo, consistentes en: 1) conservar la escotadura ajustando los caudales mínimos necesarios para mantener una calidad de agua aceptable durante los períodos críticos; 2) remover la escotadura y los sedimentos acumulados en la naciente, y 3) cerrar esta última definitivamente suministrando agua desde el sistema de riego. Cualquiera sea la alternativa elegida, se sugiere, a corto plazo, la derivación máxima permanente de los excedentes de riego y una vigilancia de la calidad del agua embalsada

Alternativas para la restauración del brazo de un río

La disminución del caudal del Brazo Sur del río Negro ha ocasionado un cambio ambiental desfavorable en términos del potencial desarrollo del área. Propone tres alternativas de restauración del brazo, consistentes en: 1) conservar la escotadura ajustando los caudales mínimos necesarios para mantener una calidad de agua aceptable durante los períodos críticos; 2) remover la escotadura y los sedimentos acumulados en la naciente, y 3) cerrar esta última definitivamente suministrando agua desde el sistema de riego. Cualquiera sea la alternativa elegida, se sugiere, a corto plazo, la derivación máxima permanente de los excedentes de riego y una vigilancia de la calidad del agua embalsada