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Perez G.,Instituto Investigaciones Biologicas Clemente Estable | Farias L.,University of Concepcion | Fernandez C.,CNRS Microbial Oceanography Laboratory | Fernandez C.,French National Center for Scientific Research | And 3 more authors.
Journal of Limnology | Year: 2014

We analyzed the coupling between bacterioplankton and phytoplankton in Laguna de Rocha through an experimental approach. A freshwater zone of high turbidity and macrophytes growth and a brackish zone of higher light penetration and lower macrophytes biomass characterize this coastal lagoon. It has been shown that dissolved inorganic nitrogen, especially NH4 +, has decreased to undetectable levels during the last decade. One hypothesis for this trend is the rapid removal by phytoplankton and bacterioplankton uptake. In an attempt to test this, we performed incubations using lagoon water from both zones split in two treatments (pre-filtered by 1.2 μm and unfiltered water) and amended with 15N-NH4 +. After 4 h incubation we found that in both zones bacterioplankton showed significantly higher NH4 + uptake rates when incubated together with phytoplankton and that uptake rates of both microbial communities were higher in freshwater incubations. These results suggest that bacterial NH4 + uptake would be coupled to phytoplankton-derived exudates and hence that depletion of dissolved NH4 + in this system could be linked to rapid microbial uptake. The degree of this coupling would vary according to hydrological dynamics in this ecosystem. Source


Albin A.,Instituto Investigaciones Biologicas Clemente Estable | Simo M.,University of the Republic of Uruguay | Aisenberg A.,Instituto Investigaciones Biologicas Clemente Estable
Journal of Natural History | Year: 2016

Allocosa brasiliensis (Petrunkevitch, 1910) is a wolf spider that constructs silk-lined burrows along the coastal sand dunes of Argentina, Brazil and Uruguay. This species shows a reversal in typical sex roles and sexual size dimorphism expected for spiders. Females are the smaller and mobile sex, which initiates courtship at the male burrow entrance. Mating occurs in the male burrow, and when it ends, the male leaves and the female stays inside. Females prefer to mate with those males showing longest burrows, so burrow dimensions would be under strong sexual selection pressures. Previous studies in the laboratory indicated that male burrows are longer than those of virgin females, which were described as simple silk capsules. Preliminary observations suggested that juvenile burrows presented differences from those of adults; however, detailed observations of A. brasilienisis burrow characteristics at the field were lacking. The aim of this study was to characterise the burrows of adults and juveniles of A. brasiliensis under natural conditions. We recorded the dimensions of burrows inhabited by males, females and juveniles (n = 30 for each category) and created beeswax moulds that reflected burrow shape. Juveniles inhabited tubular burrows with two branches and two openings; on the contrary, adults were found in tubular burrows with a single entry. Males and females inhabited burrows of similar length and width, but those of juveniles were shorter and narrower. We discuss the results and their possible functional explanations according to the selective pressures expected for each developmental stage and sex. © 2015 Taylor & Francis. Source


Medina K.,University of the Republic of Uruguay | Boido E.,University of the Republic of Uruguay | Farina L.,University of the Republic of Uruguay | Gioia O.,Laboratory of R and D | And 6 more authors.
Food Chemistry | Year: 2013

Discovery, characterisation and use of novel yeast strains for winemaking is increasingly regarded as a way for improving quality and to provide variation, including subtle characteristic differences in fine wines. The objective of this work was to evaluate the use of a native apiculate strain, selected from grapes, Hanseniaspora vineae (H. vineae) 02/5A. Fermentations were done in triplicate, working with 225 L oak barrels, using a Chardonnay grape must. Three yeast fermentation strategies were compared: conventional inoculation with a commercial Saccharomyces cerevisiae strain, ALG 804, sequential inoculation with H. vineae and then strain ALG 804 and spontaneous fermentation. Yeast strain identification was performed during fermentation, in which the apiculate strain was found to be active, until 9% of alcohol in volume, for the co-fermentation and the spontaneous fermentation was completed by three native S. cerevisiae strains. Basic winemaking parameters and some key chemical analysis, such as concentration of glycerol, biogenic amines, organic acids, and aroma compounds were analysed. Sensory analysis was done using a trained panel and further evaluated with professional winemakers. Sequential inoculation with H. vineae followed by S. cerevisiae resulted in relatively dry wines, with increased aroma and flavour diversity compared with wines resulting from inoculation with S. cerevisiae alone. Wines produced from sequential inoculations were considered, by a winemaker's panel, to have an increased palate length and body. Characteristics of wines derived from sequential inoculation could be explained due to significant increases in glycerol and acetyl and ethyl ester flavour compounds and relative decreases in alcohols and fatty acids. Aroma sensory analysis of wine character and flavour, attributed to winemaking using H. vineae, indicated a significant increase in fruit intensity described as banana, pear, apple, citric fruits and guava. GC analysis of the relative accumulation of 23 compounds to significantly different concentrations for the three fermentation strategies is discussed in relation to aroma compound composition. © 2013 Elsevier Ltd. All rights reserved. Source

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