Soil characteristics and decomposition of organic matter on Anchorage, Signy and Falkland Islands

Antarctic terrestrial ecosystems have poorly developed soils and currently experience one of the greatest rates of climate warming on the globe. We investigated the responsiveness of organic matter decomposition in Maritime Antarctic terrestrial ecosystems to climate change, using two study sites in the Antarctic Peninsula region (Anchorage Island, 67°S; Signy Island, 61°S), and contrasted the responses found with those at the cool temperate Falkland Islands (52°S). Our approach consisted of two complementary methods: (1) Laboratory measurements of decomposition at different temperatures (2, 6 and 10 °C) of plant material and soil organic matter from all three locations. (2) Field measurements at all three locations on the decomposition of soil organic matter, plant material and cellulose, both under natural conditions and under experimental warming (about 0.8 °C) achieved using open top chambers. Higher temperatures led to higher organic matter breakdown in the laboratory studies, indicating that decomposition in Maritime Antarctic terrestrial ecosystems is likely to increase with increasing soil temperatures. However, both laboratory and field studies showed that decomposition was more strongly influenced by local substratum characteristics (especially soil N availability) and plant functional type composition than by large-scale temperature differences. The very small responsiveness of organic matter decomposition in the field (experimental temperature increase <1 °C) compared with the laboratory (experimental increases of 4 or 8 °C) shows that substantial warming is required before significant effects can be detected.

Poscosecha de ciruela variedad angeleno : conservación frigorífica tradicional y en atmósfera modificada

Objetivos: reducir pérdidas durante la conservación frigorífica, emplear atmósfera modificada como método suplementario a la refrigeración, alargar el período de aptitud comercial. Metodología: se trabajó con fruta acondicionada a 0±1 °C y 90±5 % HR, según las siguientes variantes: 1. testigo: 20 kg fruta a granel sin seleccionar en caja plástica; 2. granel + film PVC: 10 kg de fruta a granel en bandejas de madera más cartón corrugado recubierta con film de PVC; 3. celpack: bandejas de madera recubiertas de cartón corrugado con dos celpack de 23 frutos cada uno; 4. celpack + atmósfera modificada: ídem anterior pero cada celpack en bolsa de polietileno de baja densidad de 20 μ. A partir de los 30 días de conservación se extrajo semanalmente, durante 9 semanas, una muestra de 46 frutos, de los cuales 23 fueron analizados al momento de ser extraídos y los 23 restantes luego de 48 horas de comercialización simulada (sc). Para la evaluación estadística se aplicó análisis de la varianza con el programa SAS (Statistical Analysis System) y se determinaron las diferencias entre tratamientos con el test de Duncan. Para sabor, en cambio, se aplicó una prueba de homogeneidad de P2. La evaluación de sabor se realizó mediante degustación con panel de 5 catadores entrenados. Resultados: Los frutos tenían las siguientes características al inicio de conservación: calibre 61.4 mm, peso 117.8 g, firmeza de pulpa 3.1 kgf, sabor agridulce, contenido de sólidos solubles 17.5 °Bx, acidez 0.78 g ác. málico%g, % cubrimiento 83.69 %. Luego de la conservación frigorífica (97días): % de color de cobertura 95 %. La firmeza de la pulpa en el tratamiento celpack + bolsa se diferencia con valores más altos, media de 2.8 kgf , el resto con media 2.6 kgf. En sc la firmeza es inferior y esta disminución es menor en celpack + bolsa. Sólidos solubles, media 17.21 °Bx, en sc valores con media de un 0.3 % más. Acidez titulable: disminución progresiva, de 0.68 a 0.47 g%g al fin de conservación. Sabor: a partir de los 59 días aumentan los frutos insípidos y desagradables excepto en celpack + bolsa. Síntomas de deshidratación: a partir de los 79 días la única variante que no presenta síntomas es celpack + bolsa. Conclusiones: El acondicionamiento en celpack redujo la incidencia de ataque por mohos (fue el único tratamiento sin ataque durante 94 días); tampoco presentó sabores desagradables y su limitación en conservación se debió a la deshidratación evidente a partir de 74 días. La fruta embalada en celpack + bolsa tuvo mayores valores de resistencia a la presión y 100 % de frutos sin deshidratación a los 94 días de conservación; a partir de 80 días es evidente el ataque de mohos y frutos con sabores desagradables. Las variantes granel y granel + film presentan deterioro por deshidratación a partir de 74 días. La conservación no debería superar 80 días. Celpack + bolsa muestra mejores resultados, con mayores valores de resistencia a la presión que los otros tratamientos; con respecto al sabor, mantiene una mayor proporción de sabor dulce.

Biología de la psychidosmicra Brethesi Blanchard : enemigo natural del "bicho del cesto" común, Oiketicus Kirbyi Guild

La finalidad de este trabajo fué determinar las especies parásitas e hiperparásitas del "bicho del cesto" común, Oiketicus Kirbyi Guild, en Mendoza, a fin de obtener supervivencia de la que se encuentra en mayor número e intensidad. Como resultado de estas investigaciones se comprobó que el calcídido Psychidosmicra Brethesi Blanchard constituye un eficáz enemigo específico del psíquico, llegándose a la conclusión que debe preservarse dicho material por el método de aislamiento en su época oportuna, permitiendo esto incrementar las poblaciones por dispersión artificial y atenuar la acción del factor hiperparasitismo.

Sergio Bagu : Entre la historia y la sociología. Contribuciones al estudio de América Latina

A través de las obras escritas por Sergio Bagú (1911-2002) referidas a los problemas sociológicos e históricos de América Latina se busca explorar la contribución científica e investigativa que este argentino construyó para pensar la unidad de nuestros pueblos, siguiendo la tradición intelectual de personajes como Alfonso Reyes, José Luis Romero, Justo Sierra, Pedro Henríquez Ureña, Rafael Gutiérrez Girardot, entre otros. La ponencia explora los contenidos metodológicos e investigativos de las principales obras sociológicas e históricas de Sergio Bagú y abre el debate hacia la pregunta de si es posible una ciencia propiamente latinoamericana en esos campos y cómo esos saberes enfrentan los profundos dilemas latinoamericanos en el siglo XX y XXI

Benthic and substrate cover data derived from photo-transect surveys in Heron Reef

Underwater georeferenced photo-transect survey was conducted on September 23 - 27, 2007 at different sections of the reef flat, reef crest and reef slope in Heron Reef. For this survey a snorkeler or diver swam over the bottom while taking photos of the benthos at a set height using a standard digital camera and towing a surface float GPS which was logging its track every five seconds. A standard digital compact camera was placed in an underwater housing and fitted with a 16 mm lens which provided a 1.0 m x 1.0 m footprint, at 0.5 m height above the benthos. Horizontal distance between photos was estimated by three fin kicks of the survey diver/snorkeler, which corresponded to a surface distance of approximately 2.0 - 4.0 m. The GPS was placed in a dry-bag and logged its position as it floated at the surface while being towed by the photographer. A total of 3,586 benthic photos were taken. A floating GPS setup connected to the swimmer/diver by a line enabled recording of coordinates of each benthic. Approximation of coordinates of each benthic photo was done based on the photo timestamp and GPS coordinate time stamp, using GPS Photo Link Software (www.geospatialexperts.com). Coordinates of each photo were interpolated by finding the gps coordinates that were logged at a set time before and after the photo was captured. Benthic or substrate cover data was derived from each photo by randomly placing 24 points over each image using the Coral Point Count excel program (Kohler and Gill, 2006). Each point was then assigned to 1 out of 80 cover types, which represented the benthic feature beneath it. Benthic cover composition summary of each photo scores was generated automatically using CPCE program. The resulting benthic cover data of each photo was linked to gps coordinates, saved as an ArcMap point shapefile, and projected to Universal Transverse Mercator WGS84 Zone 56 South.

Atmospheric carbon dioxide, methane, deuterium, and calculated Antarctic temperature of EPICA Dome C ice core

Understanding the role of atmospheric CO2 during past climate changes requires clear knowledge of how it varies in time relative to temperature. Antarctic ice cores preserve highly resolved records of atmospheric CO2 and Antarctic temperature for the past 800,000 years. Here we propose a revised relative age scale for the concentration of atmospheric CO2 and Antarctic temperature for the last deglacial warming, using data from five Antarctic ice cores. We infer the phasing between CO2 concentration and Antarctic temperature at four times when their trends change abruptly. We find no significant asynchrony between them, indicating that Antarctic temperature did not begin to rise hundreds of years before the concentration of atmospheric CO2, as has been suggested by earlier studies.

Geochemistry of Miocene Alborán Basin volcanism

We present new major and trace element and O-Sr-Nd-isotope data for igneous rocks from the western Mediterranean Alborán Sea, collected during the METEOR 51/1 cruise, and for high-grade schists and gneisses from the continental Alborán basement, drilled during the Ocean Drilling Programme (ODP Leg 161, Site 976). The geochemical data allow a detailed examination of crustal and mantle processes involved in the petrogenesis of the lavas and for the first time reveal a zonation of the Miocene Alborán Sea volcanism: (1) a keel-shaped area of LREE-depleted (mainly tholeiitic series) lavas in the central Alborán Sea, generated by high degrees of partial melting of a depleted mantle source and involving hydrous fluids from subducted marine sediments, that is surrounded by (2) a horseshoe-shaped zone with LREE-enriched (mainly calc-alkaline series) lavas subparallel to the arcuate Betic-Gibraltar-Rif mountain belt. We propose that the geochemical zonation of the Miocene Alborán Basin volcanism results from eastward subduction of Tethys oceanic lithosphere coupled with increasing lithospheric thickness between the central Alborán Sea and the continental margins of Iberia and Africa.

Mesopelagic fish collected during Maria S. Merian cruise MSM26, spring 2013

Mesopelagic fish were collected using a 1 m**2 Double-MOCNESS (Multiple Opening and Closing Net and Environmental Sensing System) and 4.5 m**2 IKMT (Isaacs-Kidd midwater trawl). The main portion of the IKMT was 20 mm knotted nylon, and the tail bag was 3 mm knotless nylon. Oblique IKMT tows were made to a maximum depth of 500 m at a tow speed of 3.5 knots. The original cruise plan intended for nighttime IKMT tows, but tow times varied due to operational constraints. The MOCNESS was equipped with 20 nets of 333 µm mesh size; 10 nets per side. The towing speed was 2 knots. Samples were collected to a maximum depth of 1250 m. The first oblique nets sampled from the surface to the max depth, and the other nets sampled depth stratified bins of the water column. MOCNESS hauls were performed during day and night to investigate diel vertical migrations. Mesoplelagic fish were processed on board. All fish were picked from all IKMT nets, most oblique MOCNESS nets, and the left side nets of the depth stratified MOCNESS samples. The Depth stratified nets from the right side of the MOCNESS frame were preserved in 5 % formalin for future quantitative analyses of the nekton. Fish were identified to the lowest possible taxa using Whitehead et al. (1984) and Fahay (2007). Standard length of each fish was measured to the nearest 0.1 mm using a digital caliper. Measured and identified fish were frozen in an -80 °C freezer, and shipped to the University of Hamburg at the end of the cruise.

Effects of ocean acidification on visual risk assessment in coral reef fishes

1. With the global increase in CO2 emissions, there is a pressing need for studies aimed at understanding the effects of ocean acidification on marine ecosystems. Several studies have reported that exposure to CO2 impairs chemosensory responses of juvenile coral reef fishes to predators. Moreover, one recent study pointed to impaired responses of reef fish to auditory cues that indicate risky locations. These studies suggest that altered behaviour following exposure to elevated CO2 is caused by a systemic effect at the neural level. 2. The goal of our experiment was to test whether juvenile damselfish Pomacentrus amboinensis exposed to different levels of CO2 would respond differently to a potential threat, the sight of a large novel coral reef fish, a spiny chromis, Acanthochromis polyancanthus, placed in a watertight bag. 3. Juvenile damselfish exposed to 440 (current day control), 550 or 700 µatm CO2 did not differ in their response to the chromis. However, fish exposed to 850 µatm showed reduced antipredator responses; they failed to show the same reduction in foraging, activity and area use in response to the chromis. Moreover, they moved closer to the chromis and lacked any bobbing behaviour typically displayed by juvenile damselfishes in threatening situations. 4. Our results are the first to suggest that response to visual cues of risk may be impaired by CO2 and provide strong evidence that the multi-sensory effects of CO2 may stem from systematic effects at the neural level.

Results of micropaleontological examination and age of dredge samples collected from the lower slopes of the Kuril Basin, Sea of Okhotsk

An integrated (petrographical and micropaleontological) study of sedimentary cover samples dredged from the lower slopes of the Kuril deep-sea basin was carried out. Pliocene-Pleistocene sediments are mainly represented by tuffaceous sedimentary rocks (tuffites, tuffaceous muds, tuffaceous diatomites, tuffaceous silts, tuffaceous sandstones, etc.). Significant admixtures of pyroclastic matter, especially of volcanic glasses, indicates that sedimentation process was accompanied by explosive volcanism. The data obtained give evidence about intensification of tectonomagmatic regime within the region under study during Pliocene-Pleistocene time. By the beginning of Pliocene, a deep-sea basin with a well-manifested continental and/or island slope and a narrow shelf already existed. Pliocene-Pleistocene deposits accumulated in a cold well-aerated deep-sea basin under oxic conditions and downslope sediment transport.

Abundance mesopelagic fish collected during Maria S. Merian cruise MSM26, spring 2013

Mesopelagic fish were collected using a 1 m**2 Double-MOCNESS (Multiple Opening and Closing Net and Environmental Sensing System) and 4.5 m**2 IKMT (Isaacs-Kidd midwater trawl). The main portion of the IKMT was 20 mm knotted nylon, and the tail bag was 3 mm knotless nylon. Oblique IKMT tows were made to a maximum depth of 500 m at a tow speed of 3.5 knots. The original cruise plan intended for nighttime IKMT tows, but tow times varied due to operational constraints. The MOCNESS was equipped with 20 nets of 333 µm mesh size; 10 nets per side. The towing speed was 2 knots. Samples were collected to a maximum depth of 1250 m. The first oblique nets sampled from the surface to the max depth, and the other nets sampled depth stratified bins of the water column. MOCNESS hauls were performed during day and night to investigate diel vertical migrations. Mesoplelagic fish were processed on board. All fish were picked from all IKMT nets, most oblique MOCNESS nets, and the left side nets of the depth stratified MOCNESS samples. The Depth stratified nets from the right side of the MOCNESS frame were preserved in 5 % formalin for future quantitative analyses of the nekton. Fish were identified to the lowest possible taxa using Whitehead et al. (1984) and Fahay (2007). Standard length of each fish was measured to the nearest 0.1 mm using a digital caliper. Measured and identified fish were frozen in an -80 °C freezer, and shipped to the University of Hamburg at the end of the cruise.