N-cycling and balancing of the N-deficit generated in the oxygen minimum zone over the Namibian shelf-An isotope-based approach

The northern Benguela upwelling system is a nutrient‐replete region with high plankton biomass production and a seasonally changing oxygen minimum zone. Nitrate:phosphate ratios in fresh upwelling water are low due to denitrification in the near‐seafloor oxygen minimum zone and phosphate efflux from sediments. This makes the region a candidate for substantial dinitrogen fixation, for which evidence is scarce. Nutrient and oxygen data, N isotope data of nitrate, nitrogen isotope ratios of particulate matter, particulate organic carbon content, and suspended matter concentrations on a transect across the shelf and upper slope at 23°S illustrate N‐cycling processes and are the basis for estimating the contribution of N‐sources and N‐sinks to the reactive nitrogen pool. It appears that N‐removal due to denitrification exceeds N gain by N2 fixation and physical mixing processes by a factor of >6, although inorganic N:P ratios again increase as surface water is advected offshore. Nitrate and ammonium regeneration, nutrient assimilation with N:P < 16, shelf break mixing, atmospheric input, and N2 fixation all contribute to the restoration of inorganic N:P ratios back to Redfield conditions, but in seasonally changing proportions. The Benguela upwelling system thus is a nutrient source for the oceanic‐mixed layer where N‐sources and N‐sinks are not in balance and Redfield conditions can only re‐adjust by advection and mixing processes integrated over time

Nutrients and δ15N measured in water samples in the oxygen minimum zone over the Namibian shelf during the Meteor campaign M76-2 in 2008

The northern Benguela upwelling system is a nutrient‐replete region with high plankton biomass production and a seasonally changing oxygen minimum zone. Nitrate:phosphate ratios in fresh upwelling water are low due to denitrification in the near‐seafloor oxygen minimum zone and phosphate efflux from sediments. This makes the region a candidate for substantial dinitrogen fixation, for which evidence is scarce. Nutrient and oxygen data, N isotope data of nitrate, nitrogen isotope ratios of particulate matter, particulate organic carbon content, and suspended matter concentrations on a transect across the shelf and upper slope at 23°S illustrate N‐cycling processes and are the basis for estimating the contribution of N‐sources and N‐sinks to the reactive nitrogen pool. It appears that N‐removal due to denitrification exceeds N gain by N2 fixation and physical mixing processes by a factor of >6, although inorganic N:P ratios again increase as surface water is advected offshore. Nitrate and ammonium regeneration, nutrient assimilation with N:P < 16, shelf break mixing, atmospheric input, and N2 fixation all contribute to the restoration of inorganic N:P ratios back to Redfield conditions, but in seasonally changing proportions. The Benguela upwelling system thus is a nutrient source for the oceanic‐mixed layer where N‐sources and N‐sinks are not in balance and Redfield conditions can only re‐adjust by advection and mixing processes integrated over time

Isotopic composition of nitrate in wet and dry atmospheric deposition on Crete in the eastern Mediterranean Sea

The eastern Mediterranean Sea (EMS) is a nutrient-poor ocean with unusually high nitrate-phosphate ratios (up to 28:1) and relatively depleted (15)N/(14)N ratios (expressed as delta(15)N) in deepwater nitrate (delta(15)NO(3)(-) of 2.5 parts per thousand) and sediments (<3.5 parts per thousand) that have been attributed to extensive N(2) fixation. To quantify the role of atmospheric NO(3)(-) deposition in the N cycle in the EMS, we analyzed NO(3)(-) and its delta(15)N in samples of dry and wet deposition on biweekly and per event basis from April 2006 to September 2007 on the island of Crete. Both dry and wet deposition samples have consistently negative delta(15)N compared to air N(2), implying a strongly depleted atmospheric source calculated to be (weighted annual estimate) -3.1 parts per thousand. The low delta(15)N of wet deposition is in agreement with data from other environments, but the consistently depleted nature of dry deposition is unusual and supports the view of an origin from association of atmospheric NO(3)(-) mainly with dust and sea salt. This situation is due to high levels of sulphate compared to ammonium, sea salt, and lithogenic material. Mass balance and isotope-mixing calculations show that the present-day inputs of nitrate from external sources into the surface water layer of the eastern Mediterranean Sea have a weighted mean delta(15)N-NO(3)(-) of 0.5 parts per thousand to 1.5 parts per thousand and that particle flux to and mineralization in the deepwater pool over the last 40-50 years can account for the unusually low delta(15)N ratios found in deepwater NO(3)(-) without the need of any significant N(2) fixation

Ambiente de trabajo cooperativo en internet para la educación en valores

TesisEl presente trabajo de investigación que lleva por título "AMBIENTE DE TRABAJO COOPERATIVO EN INTERNET PARA LA EDUCACION EN VALORES" responde a la necesidad de desarrollar nuevas formas de planificar y desarrollar la educación, de manera que se promueva la participación sincrónica y asincrónica entre tos sujetos que no se encuentran físicamente en el mismo lugar, ni en las mismas coordenadas temporales. El objetivo fue desarrollar un Ambiente de Trabajo Cooperativo en Internet para la educación en valores utilizando la Metodología Orientada a objetos y la Filosofía de Software Libre propiciando básicamente la reunión síncrona y. asíncrona para los miembros de la Federación de Familias para la Paz Mundial. Se ha utilizado Moodle, el cual es un . proyecto en desarrollo diseñado para dar soporte a un marco de educación social . constructivista. Esta herramienta se ha integrado al Ambiente de Trabajo Cooperativo principalmente para diseñar diferentes cursos en diferentes niveles y a diferentes usuarios. Tambíén se ha empleado los indicadores de calidad del Estándar IS0-9126, tales como funcionalidad, fiabilidad, usabilidad, eficiencia, mantenibilidad y portabilidad en una escala de 1 a 5 puntos. Se llega a la conclusión de que los ambientes de trabajo cooperativos para la educación en valores, permite mejorar el proceso de educación básicamente en la comunicación de los miembros de la Federación de Familias para la Paz Mundial cumpliendo con aprobar el estándar de calidad de software ISO 9126 en el que se observa que un 60% de los profesionales de cada país dicen que el Ambiente de Trabajo Cooperativo es bueno y un 10% afirma que es muy bueno. Palabras Claves: Ambiente de trabajo cooperativo, valores, internet, educació

Profiles of Cuticular Hydrocarbons Mediate Male Mate Choice and Sexual Isolation Between Hybridising Chrysochus (Coleopterachrysomelidae)

Chemical signals frequently underlie sexual isolation between insect species. Our understanding of the evolutionary forces influencing these signaling systems is known for very few systems, challenging both our efforts to understand insect speciation, and our ability to predict long-term changes in the chemical communication systems of insects. Thus, we are in need of more systems in which both the chemical signals causing sexual isolation and the evolutionary forces driving sexual isolation are understood. Sexual isolation in the hybrid zone between Chrysochus cobaltinus and C. auratus has apparently increased in response to natural selection against hybridisation (i.e. reinforcement). Previous experiments suggested that this isolation was due, at least in part, to male preferences for conspecific females. Here, we confirm this role of male choice, and document that male mate choice in this system is influenced by cuticular hydrocarbon (CHC) profiles. Specifically, male C. cobaltinus responses to control cadavers and conspecific female cadavers painted with different cuticular hexane extracts, together with analyses of the composition of those extracts, revealed that male mate choice is governed by CHC profiles. Multivariate analyses of GC profiles demonstrated that those profiles are indeed both sex- and species-specific. Although GC-MS enabled identification and quantification of the specific cuticular hydrocarbons, we have not yet determined which individual compounds govern mate choice. Having established that CHCs influence sexual isolation in this system, we can now assess the evolutionary lability of these cues, which will inform both our understanding of speciation, and of the conditions under which the chemical signaling systems that influence mate choice in insects can evolve

Geographically extensive hybridization between the forest trees American butternut and Japanese walnut

We investigate the question of naturally occurring interspecific hybrids between two forest trees: the native North American butternut (Juglans cinerea L.) and the introduced Japanese walnut (Juglans ailantifolia Carrière). Using nuclear and chloroplast DNA markers, we provide evidence for 29 F1 and 22 advanced generation hybrids in seven locations across the eastern and southern range of the native species. Two locations show extensive admixture (95% J. ailantifolia and hybrids) while other locations show limited admixture. Hybridization appears to be asymmetrical with 90.9 per cent of hybrids having J. ailantifolia as the maternal parent. This is, to our knowledge, the first genetic data supporting natural hybridization between these species. The long-term outcome of introgression could include loss of native diversity, but could also include transfer of useful traits from the introduced species

Hoban_EvolApps_microsat_Data_For_Dryad

The genotypes for trees used in this study for all analyses, after clones, etc. have been removed. The data are referred to in the publication as "1515 unique genotypes for analysis: 79 J. ailantifolia reference, 7 hybrid 231 reference, 66 J. cinerea reference, and 1363 naturally occurring trees." The names of the populations are as in table one, or similar abbreviation. File format is Convert, tab delimited. All 12 microsatellite loci. Missing data with a '?'. Details about collections are in the manuscript

Hoban_J_cinerea_Mol_Ecol_2010_Microsat_Data_Dryad

This file contains the microsatellite genotypes for 11 loci and 904 individuals, in 29 natural populations (forest) of butternut (J cinerea L) across eastern North America. These are the data referred to in the first sentence of the Results. They are data AFTER removal of hybrid individuals, identical genotypes, or individuals with too much missing data. These data are therefore the data used to calculate all statistics in the paper. The data are in GENEPOP format. The names of individuals are unique identification numbers used in our lab. The names of the loci correspond to those from Robichaud et al, and Hoban et al, as described in the Materials and Methods of the paper

Hoban_J_cinerea_Mol_Ecol_2010_Microsat_Data_Dryad

This file contains the microsatellite genotypes for 11 loci and 904 individuals, in 29 natural populations (forest) of butternut (J cinerea L) across eastern North America. These are the data referred to in the first sentence of the Results. They are data AFTER removal of hybrid individuals, identical genotypes, or individuals with too much missing data. These data are therefore the data used to calculate all statistics in the paper. The data are in GENEPOP format. The names of individuals are unique identification numbers used in our lab. The names of the loci correspond to those from Robichaud et al, and Hoban et al, as described in the Materials and Methods of the paper