Importance of mixotrophic nanoplankton in Aysén Fjord (Southern Chile) during austral winter     

Till Czypionka  Cristian A. Vargas  Nelson Silva  Giovanni Daneri  Humberto E. González  José Luis Iriarte 《Continental Shelf Research》2011,31(3-4):216-224

Mixotrophy, the combination of autotrophic and heterotrophic nutrition in the same organism, is widespread in planktonic algae. Several reports from temperate and high-latitude fjords in Scandinavia suggest the occurrence of a niche in late summer and autumn during post-bloom conditions in which mixotrophic algae can become important grazers in pelagic ecosystems, accessing the nutrients bound in their prey to overcome nutrient limitation. Here, we experimentally determined the trophic modes and bacterivory rates for the nanoplankton community (2–20 μm) in Aysén Fjord located in the Chilean Northern Patagonia during two contrasting seasons: winter and spring. While mixotrophic nanoplankton was virtually absent from the system in spring, in winter at occasions it even constituted the dominant trophic group of the nanoplankton with abundances of >900 cells mL^?1. This indicates a second niche for mixotrophs in winter, when mixotrophy allows overcoming light limitation.  相似文献   

Latitudinal patterns of export production recorded in surface sediments of the Chilean Patagonian fjords (41–55°S) as a response to water column productivity     

Claudia Aracena  Carina B. Lange  José Luis Iriarte  Lorena Rebolledo  Silvio Pantoja 《Continental Shelf Research》2011,31(3-4):340-355

The Chilean Patagonian fjords region (41–56°S) is characterized by highly complex geomorphology and hydrographic conditions, and strong seasonal and latitudinal patterns in precipitation, freshwater discharge, glacier coverage, and light regime; all of these directly affect biological production in the water column. In this study, we compiled published and new information on water column properties (primary production, nutrients) and surface sediment characteristics (biogenic opal, organic carbon, molar C/N, bulk sedimentary δ¹³C_org) from the Chilean Patagonian fjords between 41°S and 55°S, describing herein the latitudinal pattern of water column productivity and its imprint in the underlying sediments. Based on information collected at 188 water column and 118 sediment sampling sites, we grouped the Chilean fjords into four main zones: Inner Sea of Chiloé (41° to ～44°S), Northern Patagonia (44° to ～47°S), Central Patagonia (48–51°S), and Southern Patagonia (Magellan Strait region between 52° and 55°S). Primary production in the Chilean Patagonian fjords was the highest in spring–summer, reflecting the seasonal pattern of water column productivity. A clear north–south latitudinal pattern in primary production was observed, with the highest average spring and summer estimates in the Inner Sea of Chiloé (2427 and 5860 mg C m^?2 d^?1) and Northern Patagonia (1667 and 2616 mg C m^?2 d^?1). This pattern was closely related to the higher availability of nutrients, greater solar radiation, and extended photoperiod during the productive season in these two zones. The lowest spring value was found in Caleta Tortel, Central Patagonia (91 mg C m^?2 d^?1), a site heavily influenced by glacier meltwater and river discharge loaded with glacial sediments. Biogenic opal, an important constituent of the Chilean fjord surface sediments (Si_OPAL ～1–13%), reproduced the general north–south pattern of primary production and was directly related to water column silicic acid concentrations. Surface sediments were also rich in organic carbon content and the highest values corresponded to locations far away from glacier influence, sites within fjords, and/or semi-enclosed and protected basins, reflecting both autochthonous (water column productivity) and allochthonous sources (contribution of terrestrial organic matter from fluvial input to the fjords). A gradient was observed from the more oceanic sites to the fjord heads (west–east) in terms of bulk sedimentary δ¹³C_org and C/N ratios; the more depleted (δ¹³C_org ?26‰) and higher C/N (23) values corresponded to areas close to rivers and glaciers. A comparison of the Chilean Patagonian fjords with other fjord systems in the world revealed high variability in primary production for all fjord systems as well as similar surface sediment geochemistry due to the mixing of marine and terrestrial organic carbon.  相似文献   

The Westerly Index as complementary indicator of the North Atlantic oscillation in explaining drought variability across Europe   总被引：1，自引：0，他引：1  

Sergio M. Vicente-Serrano  Ricardo García-Herrera  David Barriopedro  Cesar Azorin-Molina  Juan I. López-Moreno  Natalia Martín-Hernández  Miquel Tomás-Burguera  Luis Gimeno  Raquel Nieto 《Climate Dynamics》2016,47(3-4):845-863

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Agricultural impact assessment and management after three widespread tephra falls in Patagonia,South America     

Heather Craig  Thomas Wilson  Carol Stewart  Gustavo Villarosa  Valeria Outes  Shane Cronin  Susanna Jenkins 《Natural Hazards》2016,82(2):1167-1229

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A multi-tracer approach to delineate groundwater dynamics in the Rio Actopan Basin,Veracruz State,Mexico     

Juan Pérez Quezadas  Victor M. Heilweil  Alejandra Cortés Silva  Luis Araguas  María del Rocío Salas Ortega 《Hydrogeology Journal》2016,24(8):1953-1966

Geochemistry and environmental tracers were used to understand groundwater resources, recharge processes, and potential sources of contamination in the Rio Actopan Basin, Veracruz State, Mexico. Total dissolved solids are lower in wells and springs located in the basin uplands compared with those closer to the coast, likely associated with rock/water interaction. Geochemical results also indicate some saltwater intrusion near the coast and increased nitrate near urban centers. Stable isotopes show that precipitation is the source of recharge to the groundwater system. Interestingly, some high-elevation springs are more isotopically enriched than average annual precipitation at higher elevations, indicating preferential recharge during the drier but cooler winter months when evapotranspiration is reduced. In contrast, groundwater below 1,200 m elevation is more isotopically depleted than average precipitation, indicating recharge occurring at much higher elevation than the sampling site. Relatively cool recharge temperatures, derived from noble gas measurements at four sites (11–20 °C), also suggest higher elevation recharge. Environmental tracers indicate that groundwater residence time in the basin ranges from 12,000 years to modern. While this large range shows varying groundwater flowpaths and travel times, ages using different tracer methods (¹⁴C, ³H/³He, CFCs) were generally consistent. Comparing multiple tracers such as CFC-12 with CFC-113 indicates piston-flow to some discharge points, yet binary mixing of young and older groundwater at other points. In summary, groundwater within the Rio Actopan Basin watershed is relatively young (Holocene) and the majority of recharge occurs in the basin uplands and moves towards the coast.  相似文献   

A robust debris-flow and GLOF risk management strategy for a data-scarce catchment in Santa Teresa,Peru     

Holger Frey  Christian Huggel  Yves Bühler  Daniel Buis  Maria Dulce Burga  Walter Choquevilca  Felipe Fernandez  Javier García Hernández  Claudia Giráldez  Edwin Loarte  Paul Masias  Cesar Portocarrero  Luis Vicuña  Marco Walser 《Landslides》2016,13(6):1493-1507

The town of Santa Teresa (Cusco Region, Peru) has been affected by several large debris-flow events in the recent past, which destroyed parts of the town and resulted in a resettlement of the municipality. Here, we present a risk analysis and a risk management strategy for debris-flows and glacier lake outbursts in the Sacsara catchment. Data scarcity and limited understanding of both physical and social processes impede a full quantitative risk assessment. Therefore, a bottom-up approach is chosen in order to establish an integrated risk management strategy that is robust against uncertainties in the risk analysis. With the Rapid Mass Movement Simulation (RAMMS) model, a reconstruction of a major event from 1998 in the Sacsara catchment is calculated, including a sensitivity analysis for various model parameters. Based on the simulation results, potential future debris-flows scenarios of different magnitudes, including outbursts of two glacier lakes, are modeled for assessing the hazard. For the local communities in the catchment, the hazard assessment is complemented by the analysis of high-resolution satellite imagery and fieldwork. Physical, social, economic, and institutional vulnerability are considered for the vulnerability assessment, and risk is eventually evaluated by crossing the local hazard maps with the vulnerability. Based on this risk analysis, a risk management strategy is developed, consisting of three complementing elements: (i) standardized risk sheets for the communities; (ii) activities with the local population and authorities to increase social and institutional preparedness; and (iii) a simple Early Warning System. By combining scientific, technical, and social aspects, this work is an example of a framework for an integrated risk management strategy in a data scarce, remote mountain catchment in a developing country.  相似文献   

Linear discriminant analysis to describe the relationship between rainfall and landslides in Bogotá, Colombia   总被引：1，自引：0，他引：1  

Alfonso Mariano Ramos-Cañón  Luis Felipe Prada-Sarmiento  Mario Germán Trujillo-Vela  Juan Pablo Macías  Ana Carolina Santos-R 《Landslides》2016,13(4):671-681

Bogotá is located in the central Andean region of Colombia, which is frequently affected by landslide processes. These processes are mostly triggered during the rainy season in the city. This fact remarks the importance of determining what rain-derived parameters (e.g. intensity, antecedent rain, daily rain) are better related with the occurrence of landslides. For this purpose, the linear discriminant analysis (LDA), a technique derived from multivariate statistics, was used. The application of this type of analysis led to obtain simple mathematical functions that represent the probability of occurrence of landslides in Bogotá. The functions also allow to identify the most relevant variables derived from records of rainfall linked to the generation of landslides. A proof of concept using the proposed methodology was done using historic rainfall data from a 9-km² area of homogenous climatology and geomorphology in the south part of Bogotá. Landslides needed to be grouped for the LDA. Each one of these grouping categories represents landslides that occurred in similar geomorphologic conditions. Another set of events with no landslides was generated synthetically. Results of the proof of concept show that rainfall parameters such as normalized rainfall intensity I _MAP, normalized daily rainfall R _MAP and rainy-days normal RDN have the best statistical correlation with the landslides observed in the zone of analysis.  相似文献   

Concentrations and physicochemical speciation of heavy metals in urban runoff sediment from São Gonçalo—Rio de Janeiro/Brazil     

José Antônio Baptista Neto  Carlos Marclei Arruda Rangel  Estefan Monteiro Da Fonseca  Marília Teresa Lima Do Nascimento  Ana Dalva De Oliveira Santos  Bruno Cezar Baptista Rodrigues  Gustavo Vaz De Melo 《Environmental Earth Sciences》2016,75(17):1209

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Hydrochemical and sedimentological dynamics in a subtropical plain river: assessment by multivariate statistical analysis     

Paola A. Suárez  Marisol Vega  Rafael Pardo  Oscar Orfeo  José Luis García Cuesta  Alicia Ronco 《Environmental Earth Sciences》2016,75(12):1004

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The Juchatengo complex: an upper-level ophiolite assemblage of late Paleozoic age in Oaxaca,southern Mexico     

Grajales-Nishimura  José Manuel  Ramos-Arias  Mario Alfredo  Solari  Luigi  Murillo-Muñetón  Gustavo  Centeno-García  Elena  Schaaf  Peter  Torres-Vargas  Ricardo 《International Journal of Earth Sciences》2018,107(3):1005-1031

International Journal of Earth Sciences - The Juchatengo complex (JC) suite is located between the Proterozoic Oaxacan complex to the north and the Xolapa complex to the south, and was amalgamated...  相似文献