Labile Fe(II) concentrations in the Atlantic sector of the Southern Ocean along a transect from the subtropical domain to the Weddell Sea Gyre

[EN]Labile Fe(II) distributions were investigated in the Sub-Tropical South Atlantic and the Southern Ocean during the BONUS-GoodHope cruise from 34 to 57_ S (February? March 2008). Concentrations ranged from below the detection limit (0.009 nM) to values as high 5 as 0.125 nM. In the surface mixed layer, labile Fe(II) concentrations were always higher than the detection limit, with values higher than 0.060nM south of 47_ S, representing between 39% and 63% of dissolved Fe (DFe). Biological production was evidenced. At intermediate depth, local maxima were observed, with the highest values in the Sub-Tropical domain at around 200 m, and represented more than 70% of DFe. Remineralization processes were likely responsible for those sub-surface maxima. Below 1500 m, concentrations were close to or below the detection limit, except at two stations (at the vicinity of the Agulhas ridge and in the north of the Weddell Sea Gyre) where values remained as high as _0.030?0.050 nM. Hydrothermal or sediment inputs may provide Fe(II) to these deep waters. Fe(II) half life times (t1/2) at 4 _C were measured in the upper and deep waters and ranged from 2.9 to 11.3min, and from 10.0 to 72.3 min, respectively. Measured values compared quite well in the upper waters with theoretical values from two published models, but not in the deep waters. This may be due to the lack of knowledge for some parameters in the models and/or to organic complexation of Fe(II) that impact its oxidation rates. This study helped to considerably increase the Fe(II) data set in the Ocean and to better understand the Fe redox cycle.

Carbonate system in the water masses of the Southeast Atlantic sector of the Southern Ocean during February and March 2008

[EN]Carbonate system variables were measured in the South Atlantic sector of the Southern Ocean along a transect from South Africa to the southern limit of the Antarctic Circumpolar Current (ACC) from February to March 2008. Eddies detached from the retroflection of the Agulhas Current increased the gradients observed along the fronts. Minima in the fugacity of CO2, fCO2, and maxima in pH on either side of the frontal zone were observed, noting that within the frontal zone fCO2 reached maximum values and pH was at a minimum.Vertical distributions of water masses were described by their carbonate system properties and their relationship to CFC concentrations. Upper Circumpolar Deep Water (UCDW) and Lower Circumpolar Deep Water (LCDW) offered pHT,25 values of 7.56 and 7.61, respectively. The UCDW also had higher concentrations of CFC-12 (>0.2 pmol kg?1) as compared to deeper waters, revealing that UCDW was mixed with recently ventilated waters. Calcite and aragonite saturation states ( ) were also affected by the presence of these two water masses with high carbonate concentrations. The aragonite saturation horizon was observed at 1000m in the subtropical area and north of the Subantarctic Front. At the position of the Polar Front, and under the influence of UCDW and LCDW, the aragonite saturation horizon deepened from 800m to 1500m at 50.37_ S, and reached 700m south of 57.5_ S. High latitudes proved to be the most sensitive areas to predicted anthropogenic carbon increase. Buffer coefficients related to changes in [CO2], [H+] and with changes in dissolved inorganic carbon (CT)and total alkalinity (AT) offered minima values in the Antarctic IntermediateWater and UCDWlayers. These coefficients suggest that a small increase in CT will sharply decrease the status of pH and carbonate saturation. Here we present data that suggest that south of 55_ S, surface water will be under-saturated with respect to aragonite within the next few decades.

El cubo de proyecciones

[ES] Video tutorial que explica el mecanismo de los Sistemas de Representación para representar la realidad tridimensional en una superficie bidimensional.

Soporte para cable

[ES] Video tutorial en el que se explica la solución del conjunto Soporte para cale

Mordaza para cable

[ES] Vídeo tutorial en el que se explica la solución del conjunto Mordaza para cable

Soporte oscilante

[ES] Víedo tutorial en el que se explica la solución del conjunto Mordaza para cable

Escala

[ES] Vídeo tutorial en el que se explica la aplicación del concepto de Escala para cambiar el tamaño de los dibujos técnicos

Válvula de bola

[ES] Vídeo tutorial en el que se explica la solución del conjunto Válvula de bola

Gancho de sujeción

[ES] vídeo tutorial en el que se explica la solución del conjunto Gancho de sujeción

Soporte para cable. Alternativas

[ES] Video tutorial en el que se explican diversas alternativas de solucionar la pieza "base" del conjunto Soporte para cable

Foro técnico: La pesca en Gran Canaria

[ES] foro organizado por la Universidad de Las Palmas de Gran Canaria y la Comisión de Pesca de la Unión Europea celebrado en la Facultad de Ciencias del Mar de la Universidad de Las Palmas de Gran Canaria, el 25 de enero de 2013. Presenta el acto el Rector de la Universidad de Las Palmas de Gran Canaria, don José Regidor García, el Decano de la Facultad de Ciencias del Mar, don Melchor González Dávila, el Presidente de la Comisión de Pesca del Parlamento Europeo, don Gabriel Mato Adrover, el Secretario General de Pesca del Ministerio de Agricultura, Alimentación y Medio Ambiente, don Carlos Domínguez, finalmente el Consejero de Agricultura, Ganadería, Pesca y Aguas del Gobierno Canario, Juan Ramón Hernández. Asimismo, se desarrollaron tres ponencias que recogieron algunos de los aspectos más relevantes en estos momentos, como son la pesca artesanal, en la que José Pascual Fernández, del Instituto Universitario de Ciencias Políticas y Sociales de la Universidad de La Laguna, puso el acento en las experiencias existentes en cogestión y gobernanza. La economía de la pesca en Canarias fue otro de los puntos tratados, a través de la ponencia desarrollada por Javier Macías, representante de la consultoría de pesca, CANAEST, así como la opinión de la Consejería de Agricultura, Ganadería y Pesca del Cabildo de Gran Canaria, a través de la exposición que realizarán Alejandro Báez y María Marrero. La nueva propuesta de gestión pesquera para Gran Canaria, a cargo del Centro de Investigación en Biodiversidad y Gestión Ambiental del Departamento de Biología de la Universidad de Las Palmas de Gran Canaria (Bioges), en la figura de José Juan Castro, fue otro de los puntos abordados.

Effect of organic exudates of Phaeodactylum tricornutum on the Fe(II) oxidation rate constant

[EN] Fe(II) oxidation kinetics were studied in seawater and in seawater enriched with exudates excreted by Phaeodactylum tricornutum as an organic ligand model. The exudates produced after 2, 4, and 8 days of culture at 6.21 .. 107, 2.29 .. 108, and 4.98 .. 108 cell L?1 were selected. The effects of pH (7.2?8.2), temperature (5?35 ºC), and salinity (10?36.72) on the Fe(II) oxidation rate were studied. All the data were compared with the results for seawater without exudates (control). The Fe(II) rate constant decreased as a function of culture time and cell concentration in the culture at different pH, temperature, and salinity. All the experimental data obtained in this study were fitted to a polynomial function in order to quantify the fractional contribution of the organic exudates from the diatoms to the Fe(II) oxidation rate in natural seawater. Experimental results showed that the organic exudates excreted by P. tricornutum affect Fe(II) oxidation, increasing the lifetime of Fe(II) in seawater. A kinetic model approach was carried out to account for the speciation of each Fe(II) type together with its contribution to the overall rate.

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

[EN] We used 5-yr concomitant data of tracer distribution from the BATS (Bermuda Time-series Study) and ESTOC (European Station for Time-Series in the Ocean, Canary Islands) sites to build a 1-D tracer model conservation including horizontal advection, and then compute net production and shallow remineralization rates for both sites. Our main goal was to verify if differences in these rates are consistent with the lower export rates of particulate organic carbon observed at ESTOC. Net production rates computed below the mixed layer to 110m from April to December for oxygen, dissolved inorganic carbon and nitrate at BATS (1.34±0.79 molO2 m?2, ?1.73±0.52 molCm?2 and ?125±36 mmolNm?2) were slightly higher for oxygen and carbon compared to ESTOC (1.03±0.62 molO2 m?2, ?1.42±0.30 molCm?2 and ?213±56 mmolNm?2), although the differences were not statistically significant. Shallow remineralization rates between 110 and 250m computed at ESTOC (?3.9±1.0 molO2 m?2, 1.53±0.43 molCm?2 and 38±155 mmolNm?2) were statistically higher for oxygen compared to BATS (?1.81±0.37 molO2 m?2, 1.52± 0.30 molCm?2 and 147±43 mmolNm?2). The lateral advective flux divergence of tracers, which was more significant at ESTOC, was responsible for the differences in estimated oxygen remineralization rates between both stations. According to these results, the differences in net production and shallow remineralization cannot fully explain the differences in the flux of sinking organic matter observed between both stations, suggesting an additional consumption of nonsinking organic matter at ESTOC.

Vistas auxiliares simples

[ES] Monografía dedicada al estudio de las Vistas Auxiliares Simples.