Publicaciones

Major hydrological regime change along the semiarid western coast of South America — Response to comments by Maldonado and Moreiras [page number in this issue].

Ortega, C., Vargas, G., & Rutllant, J.

Based on the sedimentology, geomorphology and geochronology of eolian and alluvial deposits at Quebrada Santa Julia (QSJ, 31°50′S) site, in a small coastal watershed in the semiarid central Chile, Ortega et al. (2012) interpreted a regional arid climate setting concomitantly with high local humidity due to reinforced coastal fog development between 13,000 and 8600 cal yr BP. Together with other continental proxies and paleo-SST records off central Chile, Ortega et al. (2012) proposed La Niña-like conditions during the latest Pleistocene‒early Holocene along this semiarid coast. A major hydrologic regime shift shortly after 8600 cal yr BP resulted in higher frequency of torrential rainfall episodes still under an arid climate setting, before the onset of El Niño at ~ 5500 cal yr BP (e.g., Rodbell et al., 1999). This hypothesis differs from that of Maldonado and Moreiras (2013) based on pollen records, who suggest humid conditions associated with precipitation around 13,000 and 10,500 cal yr BP (e.g., Maldonado et al., 2010).

Año: 2013

Palabras claves: Early Holocene; Coastal fog; Rainfall; Hydrologic change; Lifting condensation level; Sea level.

Morphogenesis by mass movements in western Andes (Chile).

Novoa Jerez, J.

Numerous examples of mass movements on slopes of western Andes and related landforms are analyzed. Regionalization of the country is fulfilled, taking into account climatic and hydrologic factors. 9 regions were distinguished with more or less similar physical-geographical conditions for mass movements’ development. Recommendations are suggested concerning future investigations in the field of mass movements risk under the rising anthropogenic impact.

Año: 2013

Palabras claves: ground mass movements, slope, morphogenesis, the Andes, zoning, risk, danger, anthropogenic impact.

Barotropic and baroclinic semidiurnal tidal currents in two contrasting coastal upwelling zones of Chile.

Bravo, L., Ramos, M., Sobarzo, M., Pizarro, O., & Valle-Levinson, A.

Current velocity observations from the continental shelves of Coquimbo (~30°S) and Concepcion (~36°30'S), central Chile, were analyzed to evaluate the role of water column stratification and shelf width on baroclinic semidiurnal tidal currents. Semidiurnal barotropic currents off both zones were typically < 5 cm/s, but depth-dependent semidiurnal flows could exceed 10 cm s-1 during stratified conditions. Both zones are recognized as pronounced upwelling centers, with maximum upwelling-favorable winds in spring and summer, respectively. At the northern zone, stratification was mainly controlled by temperature differences between surface and bottom waters with maximum stratification during summer. The southern zone showed more stratification during winter because of freshwater input from local rivers. Consequently, greater variability in the baroclinic semidiurnal currents was observed during summer at the northern continental shelf and in winter at the south. In both regions, much of the semidiurnal variability was consistent with an internal wave's first baroclinic mode of wavelengths of ~10–13 km. Nevertheless, during the period of maximum energy fluxes off the north, the second baroclinic mode (wavelength ~7 km) was also important and matched periods of low upwelling index (relaxation of upwelling favorable winds). Typical energy fluxes during summer integrated in the water column, related to the semidiurnal internal tides were 0.12 W/m of the northern site and 0.1 W/m off the southern site. Possible sites of internal wave generation off the south were the Biobío submarine canyon and the slope/shelf break, while off the north, the generation site was the slope/shelf break.

Año: 2013

Palabras claves: Baroclinic waves; semidiurnal; energy flux.

Estimating Spatial Distribution of Air Temperature from Meteorological Stations Using Atmospheric Model.

Montecinos, S., Bascuñán-Godoy, L., Salinas, P., Astudillo, O., & Lopez, D.

Planning agricultural procedures needs to take into account meteorological conditions. However, because of high associated costs, the density of meteorological stations is often not enough to cover all the cultivated or potentially cultivated areas. In this article we present a methodology to estimate seasonal maximum and minimum mean temperature in cultivated area using data registered in a sole or a few meteorological stations. The procedure is based on mesoscale modeling, which allows meteorological variables to be spatially distributed considering synoptic data and local characteristics.

Simulated daily cycle of temperature was compared with data registered at six meteorological stations located in the cultivated floor of the semiarid Limari Valley (Chile, 31°S). Although in some cases the simulated temperature differs in about 2°C with the observed one, a good fit between model results and experimental data was observed. Using the simulated seasonal minimum and maximum mean temperature fields, maps of temperature differences with respect to a reference station were drawn. In order to observe the influence of the orography on the lapse rate around a station, the methodology was applied for two reference stations located in places with different orographic characteristics. Results for winter and summer seasons are shown.

These generated maps can be used by farmers and agricultural planners to obtain information of seasonal minimum and maximum mean temperature from a station in any site of the cultivated area. This technique is a good alternative to obtain meteorological information at low costs, contributing to territorial planning for climate resilient agriculture sustainability.

Año: 2013

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Meteorological observations on the northern Chilean coast during VOCALS-REx.

Rutllant, J., Muñoz, R., & Garreaud, R.

Surface coastal observations from two automatic weather stations at Paposo (~25° S) and radiosonde observations at Paposo and Iquique (~20° S) were carried out during VOCALS-REx (VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment). Within the coastal marine boundary layer (MBL), sea–land breezes are superimposed on the prevailing southerlies, resulting in light northeasterly winds from midnight to early morning and strong southwesterlies in the afternoon. The prevailing northerlies above the MBL and below the top of the Andes are modulated by the onshore-offshore (zonal) flow forced by the diurnal cycle of surface heating/cooling along the western slope of the Andes. The daytime phase of this diurnal cycle is consistent with an enhanced afternoon coastal subsidence manifested in afternoon warming near the top of the subsidence inversion (~1.8 K at 800 hPa), lowering (~130 m) of its base (top of the MBL), and clearing of coastal Sc (stratocumulus) clouds. Results from a numerical simulation of the atmospheric circulation in a mean zonal cross section over the study area capture the afternoon zonal wind divergence and resulting subsidence of about 2 cm s−1 along a narrow (~10 km) coastal strip maximizing at around 800 hPa. Day-to-day variability in the MBL depth during VOCALS-REx shows sub-synoptic oscillations, aside from two major disruptions in connection with a deep trough and a cutoff low, as described elsewhere. These oscillations are phase-locked to those in sea-level pressure and afternoon alongshore southerlies, as found in connection with coastal lows farther south.

From 24-h forward trajectories issued from significant points at the coast and inland at the extremes of the diurnal cycle, it can be concluded that the strong mean daytime Andean pumping prevents any possibility of continental sulfur sources from reaching the free troposphere above the Sc cloud deck in at least a one-day timescale, under mean conditions. Conversely, coastal sources could contribute with sulfur aerosols preferentially in the morning, provided that the weak daytime inland flow becomes partially blocked by the coastal terrain.

Año: 2013

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Ecophysiological constraints on the larvae of Pleuroncodes monodon and the implications for its reproductive strategy in poorly oxygenated waters of the Chile-Peru undercurrent.

Yannicelli, B. & Castro, L.

Pleuroncodes monodon is a conspicuous component of the Humboldt Current ecosystem. Benthic adults south of ∼22°S are associated with low temperature (T) ∼11°C and low dissolved oxygen (DO) (<0.5 mL L−1) waters during the hatching period. Because P. mondon inhabits an oxygen minimum zone and larval release is assumed to match most favorable environmental conditions, larval performance under cold hypoxic conditions and its implications have not yet been assessed experimentally. We quantitatively assessed the effect of DO and T within environmental ranges, and initial starvation on survival, developmental time, and growth of P. monodon zoeae. Molting success from zoea I to zoea II was significantly and positively dependent on DO rearing levels. Age at molting was a negative power function of oxygen concentration. Initial exposure to low DO increased larval mortality by 3% per day of exposure. After ∼4 and ∼1.5 days of starvation after birth under normoxia and hypoxia, respectively, 50% of larvae failed to molt to zoea II. Rearing in 1 mL L−1 DO produced 50% lighter larvae after molting into zoea II. Mortality of larvae reared at 11°C was 40% higher than that at 15 and 20°C. Functions for development time and growth negative/positive dependence on temperature were also fitted. Pleuroncodes monodon zoea I are highly tolerant of low oxygen when compared with other crustacean. Nevertheless, DO and T conditions during hatching season are suboptimal for development. Early larval survival as an ultimate cause of reproductive/environmental coupling in this case should be critically revised.

Año: 2013

Palabras claves: Developmental time, growth, hypoxia, Pleuroncodes monodon, point-of-no-return, survival, temperature.

Metabolic responses of the squat lobster (Pleuroncodes monodon) larvae to low oxygen concentration.

Yannicelli, B., Paschke, K., González, R., & Castro, L.

Squat lobster populations found in the Humboldt Current System over the continental shelf from ~28 to 37°S release pelagic larvae in sub-surface cold (~11 °C) hypoxic waters. Larvae subsequently spread throughout the water column encountering both normoxic and hypoxic conditions. We analyzed some short- and long-term responses of Pleuroncodes monodon larval metabolism to hypoxia at 11 °C. Routine and postprandial aerobic respiration rates were lower in hypoxia than in normoxia for all zoeal stages. Zoea V oxyconformed, while megalopae oxyregulated down to very low oxygen concentrations. Throughout zoea I development, the rate of nitrogen (protein) accumulation in zoea I was lower, and C:N ratios were higher under hypoxic conditions than in normoxia. Citrate synthase (CS) and malate dehydrogenase (MDH) apparent specific activities (as indicators of aerobic and metabolic potentials, respectively) decreased and remained at the same level, respectively, throughout zoea I reared under hypoxic conditions. Anaerobic to aerobic potential (lactate dehydrogenase (LDH)/CS) was higher in organisms reared under hypoxia, and MDH/LDH potential ratios were characteristic of organisms tolerant to hypoxia. In spite of P. monodon zoea endurance and metabolic adaptations to decreasing oxygen tensions, intense hypoxia as such of their release site would affect their overall condition especially toward the end of the molt cycle. Our results indicate the importance of considering the interaction between environmental oxygen variability and recruitment success.

Communicated by H.-O. Portner.

Año: 2013

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Variabilidad ambiental y recursos pesqueros en el Pacifico suroriental: estado de la investigacion y desafios para el manejo pesquero.

Parada, C., Yannicelli, B., Hormazabal, S., Vasquez, S., Porobic, J., & Ernst, B. et al.

Las fluctuaciones en abundancia, biomasa, estructura de edad y patrones de distribución de los recursos pesqueros responden, entre otros, a la variabilidad ambiental. Estas respuestas son consecuencia tanto de efectos climáticos directos sobre los recursos como indirectos actuando sobre niveles tróficos relacionados. En este estudio se revisa: i) el estado del conocimiento de los mecanismos físicos asociados a la variabilidad océano-atmósfera y las escalas de variabilidad espaciales y temporales del ambiente y la relación con recursos marinos, basados en datos observacionales y modelos hidrodinámicos, ii) la relación ambiente-recurso para pesquerías pelágicas, demersales y bentónicas, y el uso de modelos biofísicos para entender estas relaciones, iii) manejo actual de recursos pelágicos, demersales y bentónicos y los alcances en relación al uso de variables ambientales, y iv) se discuten los desafíos hacia la asesoría en relación a las estrategias para mejorar la comprensión de la relación ambiente-recurso, así como, las estrategias para incorporar la modelación biofísica y variables ambientales en modelos operacionales para la asesoría hacia el manejo.

Año: 2013

Palabras claves: Variabilidad ambiental, sistemas de surgencia, recursos pesqueros, modelación biofísica, dinámica poblacional, modelos operacionales para el manejo pesquero, Pacífico suroriental, Chile.

Effect of florfenicol and oxytetracycline treatments on the intensive larval culture of the Chilean scallop Argopecten purpuratus (Lamarck, 1819).

Miranda, C., Rojas, R., Abarca, A., & Hurtado, L.

The administration of antimicrobials to control bacterial pathologies in Chilean scallop hatcheries is a frequent practice, but their effects on these cultures remained unknown. This study was undertaken to obtain information on the effect of the administration of florfenicol and oxytetracycline on the growth, survival and bacterial content of scallop larvae under farming conditions. Florfenicol-treated cultures exhibited high survival rates (44% after 17 days of culture), whereas cultures not treated or treated with oxytetracycline collapsed after 11 days of culture. Surprisingly, no significant differences in the heterotrophic (Tukey test; P = 0.226) and Vibrio (Tukey test; P = 0.666) concentrations between the oxytetracycline-treated and untreated larval cultures were observed. Otherwise, florfenicol administered directly into rearing tanks produced significantly higher larval growth (Tukey test; P = 0.0001) and survival (Tukey test; P = 0.011) than bath treatment. When 2 and 4 mg L−1 of florfenicol were compared, no significant differences in growth (t-test; P = 0.4596) and survival (Tukey test; P = 0.057) were observed, suggesting that a concentration of 2 mg L−1 is sufficient to ensure larval production. The present results demonstrate the efficacy of florfenicol-based therapy to increase larval survival and growth at commercial scale and prompt the necessity to standardize its use in Chilean scallop hatcheries.

Año: 2013

Palabras claves: Bacteria; florfenicol; Chilean scallop; shellfish bacteriology; Argopecten purpuratus ; Chile.