Understanding biological invasions : an experimental study with "Carpobrotus edulis"

[Resumen] Las invasiones biológicas representan una de las amenazas más importantes para la conservación de la biodiversidad; sin embargo, los mecanismos que subyacen al éxito de los invasores continúan sin resolverse. Muchas de las plantas invasoras más agresivas muestran características como el crecimiento clonal o alelopatías que podrían contribuir a su capacidad invasora. El objetivo de este trabajo ha sido determinar el papel de dos características potencialmente importantes para el crecimiento y la habilidad competitiva de la especie invasora Carpobrotus edulis. En concreto, se determinó (i) la importancia del estolón como órgano de reserva en la supervivencia y crecimiento de C. edulis tras un proceso de perturbación que fragmenta el clon. Por otra parte, el trabajo ahonda en (ii) el potencial alelopático de C. edulis y su impacto sobre la germinación y crecimiento de otras especies con las que pudiera competir. Los resultados muestran que el estolón actúa como un reservorio de recursos, y que permite a aquellos fragmentos de mayor tamaño invertir una mayor proporción de biomasa en el desarrollo de parte aérea, y por lo tanto facilitando su expansión horizontal y capacidad invasora. Por otra parte, los resultados mostraron un efecto fitotóxico de las hojas de C. edulis sugiriendo que este podría ser un mecanismo facilitador en el desplazamiento de las especies con las que compite. Sin embargo, la ausencia de diferencias en potencial fitotóxico entre C. edulis (invasor agresivo) y su congénere Carpobrotus acinaciformis (exótico considerado menos agresivo) parecen indicar que la capacidad alelopática no sería en este caso un atributo clave en el proceso de invasión. El estudio de aquellas características que pudieran estar contribuyendo al éxito de las especies invasoras resulta una pieza clave a la hora de entender el proceso invasor, y por lo tanto necesario para establecer programas de prevención y recuperación de áreas invadidas.[Resumo] As invasións biolóxicas representan unha das ameazas máis importantes para a conservación da biodiversidade; non obstante, os mecanismos subxacentes ao éxito dos invasores continúan sen resolverse. Moitas das plantas invasoras máis agresivas mostran características como o crecemento clonal ou alelopatías que poderían contribuír á súa capacidade invasora. O obxectivo deste traballo foi determinar o papel de dúas características potencialmente importantes para o crecemento e a habilidade competitiva da especie invasora Carpobrotus edulis. En concreto, determinouse (i) a importancia do estolón como órgano de reserva na supervivencia e crecemento de C. edulis tras un proceso de perturbación que fragmenta o clon. Por outra parte, o traballo afonda (ii) no potencial alelopático de C. edulis e o seu impacto sobre a xerminación e crecemento doutras especies coas que puidese competir. Os resultados amosan que o estolón actúa como un reservorio de recursos, e que permite a aqueles fragmentos de maior tamaño investir unha maior proporción de biomasa no desenvolvemento da parte aérea, e polo tanto facilitan a súa expansión horizontal e capacidade invasora. Por outra banda, os resultados amosaron un efecto fitotóxico das follas de C. edulis suxerindo que este podería ser un mecanismo facilitador para o desprazamento das especies coas que compite. Non obstante, a ausencia de diferenzas no potencial fitotóxico entre C. edulis (invasor agresivo) e o seu conxénere C. acinaciformis (exótico, considerado menos agresivo) parecen indicar que a capacidade alelopática non sería neste caso un atributo clave no proceso de invasión. O estudo daquelas características que puidesen estar a contribuír ao éxito das especies invasoras resulta unha peza clave á hora de entender o proceso invasor, e polo tanto necesario para establecer programas de prevención e recuperación de áreas invadidas.Traballo fin de grao (UDC.CIE). Bioloxía. Curso 2013/201

Optimization of the anaerobic co-digestion of pasteurized slaughterhouse waste, pig slurry and glycerine

The feasibility of co-digestion of blends of two different animal by-products (pig manure and pasteurized slaughterhouse waste) and recovered glycerine was studied in mesophilic conditions. Experiments were performed in a lab-scale CSTR along 490 days, with a hydraulic retention time of 21–33 days and with a step-wise increased organic loading rate, by adding and/or changing the wastes ratio, from 0.8 to 3.2 kgCOD m-3 d-1. The best methane production rate (0.64 Nm3CH4 m-3 d-1) represented an increment of 2.9-fold the initial one (0.22 Nm3CH4 m-3 d-1 with pig manure solely). It was attained with a ternary mixture composed, in terms of inlet volatile solids, by 35% pig slurry, 47% pasteurized slaughterhouse waste and 18% glycerine. This blend was obtained through a stepwise C/N adjustment: this strategy led to a more balanced biodegradation due to unstressed bacterial populations through the performance, showed by the VFA-related indicators. Besides this, an improved methane yield (+153%) and an organic matter removal efficiency (+83%), regarding the digestion of solely pig slurry, were attained when the C/N ratio was adjusted to 10.3.Postprint (author's final draft

La acción exterior del País Vasco (1980-2003)

Reseña bibliográfica de la obra "La acción exterior del País Vasco (1980-2003)" de José Luis de Castro Ruano y Alexander Ugalde Zubiri en la que analizan un fenómeno que está adquiriendo una especial relevancia en el ámbito de la realidad política internacional contemporánea. Se trata de la fundamentación teórica de ala acción exterior de los Gobiernos No Centrales, de una aproximación histórica partiendo de un primer Gobierno Vasco y abarcando la actividad desarrollada por los sucesivos Gobiernos en el exilio y concluyendo a finales del Siglo XX y de la presentación del marco jurídico y político que permite tal acción exterior vasca entre otros aspectos

Biochemical composition and growth of the marine microalga Dunaliella tertiolecta (Butcher) with different ammonium nitrogen concentrations as chloride, sulphate, nitrate and carbonate.

Cultures of the marine microalga Dunaliella tertiolecta were grown in ammonium chloride, sulphate, nitrate and carbonate at concentrations ranging from 0.25 to 16 mg.atom N/l. Cells were harvested in the stationary phase and cell density and biochemical composition determined. Biomass production at the end of the stationary phase, expressed as cell density, was affected by the concentration of ammonium-N in the medium but not by the ammonium compound used. Optimal growth conditions for obtaining maximum cell density, between 1.86×106 and 2.81×106 cells/ml, were 2, 4 and 8 mg.atom N/l. The compound and concentration of ammonium-N had little effect on the growth velocity of D. tertiolecta cultures in the logarithmic phase, with values of 0.35±0.06 doublings/day under all the conditions assayed. The ammonium compound and the concentration of nitrogen affected the concentration of different cellular constituents such as protein, carbohydrate, lipid and chlorophyll a, although these changes were not necessarily related to cell density in the culture. Protein, the most affected fraction, tended to increase with an increase in the nitrogen concentration for all the ammonium compounds used. Maximum protein/ml was obtained with ammonium carbonate at all the nitrogen concentrations used. Maximum protein/cell occurred at the higher nitrogen concentrations (16 and 32 mg/atom N/l) for all the ammonium compounds. Considering the optimum growth interval (2-8 mg.atom N/l), maximum protein/cell concentrations were also obtained in the cultures with ammonium carbonate. Carbohydrate and lipid concentrations varied less than protein concentration. Maximum values of carbohydrate/ml were also found in the ammonium carbonate cultures. Maximum lipid/cell concentrations occurred at the lowest nitrogen concentrations, in contrast to protein values. As a percentage of the total organic matter, protein increased and lipid decreased with the nitrogen concentration, whereas carbohydrate remained constant. Consequently, lipid seemed to be the storage product in this marine microalga. Gross energy values in the different cultures were a function of nitrogen concentration, maximum differences occurring in the ammonium carbonate cultures. The biochemicalvariability of this microalga must have a marked effect on its value as a source of single-cell protein, as chemicals or as feed in mariculture

El uso de Internet como recurso educativo: nuevos retos para una enseñanza de calidad

[Resumen] El presente estudio trata de establecer las especificaciones de un proyecto de red informática educativa que contenga como nodos todos los centros educativos no universitarios y todos los centros culturales de la ciudad de A Coruña, junto con un nodo (o nodos) centrales desde los cuales se gestionen los recursos tanto técnicos como de servicios de dicha instalación.[Abstract] The present study tries to establish the specifications of a project of educative informatica network that contains like nodes allnonuniversity the educative centers and all the cultural centers of the city of A Coruna, along with a node (or nodes) central from which the tecnicos resources as of services of this installation are managed as much

High yield mixotrophic cultures of the marine microalga Tetraselmis suecica (Kylin) Butcher (Prasinophyceae)

The effects of three organic compounds were tested on one of the most used marine micro-algae in the aquaculture of molluscs and crustaceans, Tetraselmis suecica. Studies were made in axenic conditions with yeast extract, peptone and glucose added to the culture medium, each alone, in combinations of two or all together. Medium without any organic compound was used for the control. Cultures containing yeast extract grew best, reaching maximum cell density of 3.79 × 106 and 3.84 × 106 cells ml−1. The organic carbon source affected the biochemical composition. The components most affected were the carbohydrates, with values between 6.5 pg cell−1 in control cultures and 48.5 pg cell−1 in glucose cultures. Protein content ranged between 27.5 pg cell−1 in control cultures and 88.6 pg cell−1in yeast + glucose + peptone cultures. The lipid content changed little. Maximum protein yields were reached in cultures with yeast + glucose and with yeast - glucose - peptone, with values of 24.6 and 28.2 mg 1−1 d−1, respectively. These values are 22 and 25 times those in control cultures. A maximum carbohydrate yield of 7.9 mg carbohydrate per litre per day was obtained in yeast + glucose + peptone cultures, 27 times that in the control cultures. The maximum lipid yield was obtained with yeast + glucose + peptone and yeast + glucose. Maximum energy values were 308 kcal 1− in yeast extract - glucose - peptone cultures and 279 kcal 1−1 in yeast extract + glucose cultures. Gross energy values in control cultures were 24.5 kcal 1−1, but peptone cultures presented the minimum energy value, 22 kcal 1−1. The yeast extract: glucose ratio in the culture medium was optimized. A ratio 2:1 produced the best yields in cells, protein, carbohydrate and gross energy.Dirección General de Investigación Científica y Técnica; PB 87-049

Isobolographic analysis of the interaction between cadmium (II) and sodium sulphate: toxicological consequences

Sulphate is an essential nutrient for autotrophic organisms and has been shown to have important implications in certain processes of tolerance to cadmium toxicity. Sodium sulphate is the main salt of sulphate in the natural environments. The concentration of this salt is increasing in the aquatic environments due to environmental pollution. The aim of this study was to investigate, using an analysis of isobolograms, the type and the degree of the interaction between Cd(II) and sodium sulphate in the freshwater microalga Chlamydomonas moewusii. Two blocks of experiments were performed, one at sub-optimal sodium sulphate concentrations (14.2 mg/L). Three fixed ratios (2:1, 1:1, and 1:2) of the individual EC50 for cadmium and sodium sulphate were used within each block. The isobolographic analysis of interaction at sub-optimal concentrations showed a stronger antagonistic effect with values of interaction index (γ) between 1.46 and 3.4. However, the isobologram with sodium sulphate at supra-optimal concentrations revealed a slight but significant synergistic effect between both chemicals with an interaction index between 0.54 and 0.64. This synergic effect resulted in the potentiation of the toxic effects of cadmium, synergy that was related to the increase of the ionic strength and of two species of cadmium, CdSO4 (aq), and Cd(SO4) 2 2 − , in the medium. Results of the current study suggest that sodium sulphate is able to perform a dual antagonist/synergist effect on cadmium toxicity. This role was concentration dependent

Composition and production of thiol constituents induced by cadmium in the marine microalga Tetraselmis suecica

Time course of intracellular levels of different thiols (phytochelatins, desglycyl-phytochelatins, glutathione, γ-glutamylcysteine [γ-Glu-Cys], and cysteine) were studied in the microalga Tetraselmis suecica exposed to different cadmium concentrations for 8 d. The cadmium concentrations assayed were 3, 7.9, 15, and 30 mg/L. Contents of thiol compounds synthesized by this microalga changed with cadmium concentration and with time of exposure. Cysteine concentrations increased significantly compared with those of γ-Glu-Cys and glutathione in cultures containing 7.9, 15, and 30 mg/L. The increase in the amount of glutathione was significant only in cells exposed to the higher cadmium concentrations (15 and 30 mg/L). Nevertheless, in all the cadmium concentrations assayed, γ-Glu-Cys levels were constant. A rapid increase in phytochelatins was observed with increased cadmium concentration during the first days of culture. The type of phytochelatins (number of subunits) also was dependent on the concentration of cadmium. The rate of (γ-Glu-Cys)3-Gly accumulation was higher than those of other types of phytochelatins throughout the culture in cells exposed to 3, 15, and 30 mg/L. However, in cultures treated with 7.9 mg/L, (γ-Glu-Cys)4-Gly increased substantially after 8 d of culture, exceeding the amount of (γ-Glu-Cys)3-Gly. Cultures exposed to the higher cadmium concentrations (15 and 30 mg/L) showed a decrease in phytochelatins after 4 and 3 d of culture, respectively, whereas an increase in cysteine and glutathione occurred at the same time. A rapid decrease in phytochelatins also was measured when cells were placed into cadmium-free medium. This decrease is consistent with a degradation of the phytochelatins.Ministerio de Educación, Cultura y Deporte; REN 2003–0241