Morfologia y arquitectura de especies arboreas de la selva valdiviana

International audienceSe estudió el desarrollo arquitectural de las principales especies arbóreas que caracterizan a la selva valdiviana en Argentina. Se comparó el crecimiento y la ramificación (longitud, diámetro, número y tipo de hojas y producción axilar) al final del período de alargamiento de los brotes anuales producidos por plántulas, juveniles y adultos de Aextoxicon punctatun, Laureliopsis phillippiana, Embothrium coccineum, Gevuina avellana, Lomatia ferruginea, Lomatia hirsuta, Luma apiculata, Myrceugenia exsucca, Maytenus boaria, Maytenus chubutensis, Raukaua laetevirens, Dasyphyllum diacanthoides, Caldcluvia paniculata, y Weinmannia trichosperma. Se identificaron los marcadores morfológicos del crecimiento inter-anual y las unidades estructurales principales (metámeros, unidades de crecimiento y ejes foliados). Se caracterizaron los aspectos morfológicos principales de cada una de las categorías de ejes que componen el modelo y la unidad arquitectural de estas especies. Se verificó una marcada evolución de las principales variables morfo-arquitecturales a lo largo de la ontogenia de los individuos. Las yemas muestran diferentes estructuras desde desnudas a bien protegidas por catafilos y/o estipulas. Además para algunas de estas especies se realizaron seguimientos de crecimiento, mostrando una significativa correlación entre crecimiento primario y temperatura. Se agradece a APN y la Asociación Civil Sembrar

Phylogeny, distribution and biogeographic origin: a morpho-architectural approach from Valdivian trees

International audiencePreformation and neoformation in woody species are processes associated with the vigour of shoots which respond to endogenous and environmental factors. For four species of the family Proteaceae over several ontogenetic stages (seedling, juvenile and adult), the content of leaf primordia of winter buds were studied and compared with the number of leaves of shoots developed from buds in equivalent positions. Two of the species, Embothrium coccineum and Lomatia hirsuta, have scaly buds in which green leaf primordia are covered by leaves devoid of lamina and with a broad base (cataphylls). For both species shoot growth included neoformation, and the juvenile ontogenetic stage was the most vigorous one in terms of shoot growth. The other two species, Lomatia ferruginea and Gevuina avellana, had naked buds and entirely preformed shoots along their whole ontogenetic gradient; in these two species shoot vigor was relatively constant throughout ontogeny. Both species with naked buds are present exclusively in the phytogeographical Valdivian district, while both species with scaly buds are distributed throughout the gradient of the Andean-Patagonian forests. A detailed description of bud structure, preformation and neoformation through ontogeny may contribute in our understanding of the growth, functioning and distribution of Protaceae specie

In situ prey selection of mixotrophic and heterotrophic flagellates in Antarctic oligotrophic lakes: an analysis of the digestive vacuole content

12 pages, 4 figures, 3 tablesWe investigated the selective predation of mixotrophic and heterotrophic flagellates (MF and HF) on different heterotrophic prokaryote phylotypes (HPP; Bacteria + Archaea) living in natural assemblages from oligotrophic Antarctic lakes. In situ prey preference was analyzed for the first time on different mixotrophic taxa (Pseudopedinella sp., Ochromonas-like cells, Chrysophyceae >5 µm). The relative abundances of seven different HPP hybridized by CARD-FISH (catalyzed reporter deposition-fluorescent in situ hybridization) in natural community were compared with the proportions of hybridized cells inside digestive vacuoles. Our results showed some general trends to selectivity over some HPP. Alphaproteobacteria and Betaproteobacteria were the most abundant groups, and strikingly, a negative selection trend was detected in most samples by all bacterivorous protists. In contrast, for Actinobacteria a positive selection trend was observed in most samples, whereas Bacteroidetes seemed to be randomly preyed upon. Interestingly, similar prey preferences were observed in all bacterivorous flagellates. Our results suggest that phylogenetic affiliation determines part of the process of prey selection by protists in these lakes. Nevertheless, other features, such as cell size, morphology and the presence of the S-layer, might also significantly contribute to prey selectivity on the HPPThis study was financed by the Consejo Superior de Investigaciones Cientı´ficas – Consejo Nacional de Investigaciones Cientı´ficas y Te´cnicas (CSIC-CONICET) (Spain-Argentina) Project PROBA (2007 AR0018, CSIC), the Spanish Project MIXANTAR (REN 2002-11396-E/ANT) and the Argentinean projects CONICET-PIP 01301, FONCYT PICT 32732 and UNComahue 04/ B166. Marina Gerea and M. Romina Schiaffino were supported by CONICET fellowships. Irina Izaguirre, Claudia Queimalin˜os and Fernando Unrein are CONICET researchersPeer reviewe

In situ prey selection of mixotrophic and heterotrophic flagellates in Antarctic oligotrophic lakes: An analysis of the digestive vacuole content

We investigated the selective predation of mixotrophic and heterotrophic flagellates (MF and HF) on different heterotrophic prokaryote phylotypes (HPP; Bacteria + Archaea) living in natural assemblages from oligotrophic Antarctic lakes. In situ prey preference was analyzed for the first time on different mixotrophic taxa (Pseudopedinella sp., Ochromonas-like cells, Chrysophyceae >5 μm). The relative abundances of seven different HPP hybridized by CARD-FISH (catalyzed reporter deposition-fluorescent in situ hybridization) in natural community were compared with the proportions of hybridized cells inside digestive vacuoles. Our results showed some general trends to selectivity over some HPP. Alphaproteobacteria and Betaproteobacteria were the most abundant groups, and strikingly, a negative selection trend was detected in most samples by all bacterivorous protists. In contrast, for Actinobacteria a positive selection trend was observed in most samples, whereas Bacteroidetes seemed to be randomly preyed upon. Interestingly, similar prey preferences were observed in all bacterivorous flagellates. Our results suggest that phylogenetic affiliation determines part of the process of prey selection by protists in these lakes. Nevertheless, other features, such as cell size, morphology and the presence of the S-layer, might also significantly contribute to prey selectivity on the HPP. © 2012 The Author 2012. Published by Oxford University Press. All rights reserved.Fil:Queimaliños, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Schiaffino, M.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Izaguirre, I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Unrein, F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Inorganic mercury (Hg2+) uptake by different plankton fractions of Andean Patagonian lakes (Argentina)

The species composition and the size structure of natural planktonic food webs may provide essential information to understand the fate of mercury and, in particular, the bioaccumulation pattern of Hg2+ in the water column of lake ecosystems. Heterotrophic and autotrophic picoplankton and phytoplankton are the most important entry points for Hg in aquatic ecosystems since they concentrate Hg2+ and MeHg from ambient water, making them available to planktonic consumers at higher trophic levels of lake food webs. In this investigation we studied the uptake of 197Hg2+ in natural plankton assemblages from four Andean lakes (Nahuel Huapi National Park, Patagonia, Argentina), comprised in the size fractions 0.2-2.7 μm (picoplankton), 0.2-20 μm (pico and nanoplankton) and 20-50 μm (microplankton) through experiments using Hg2+ labeled with 197Hg2+. The experimental results showed that the uptake of Hg2+ was highest in the smallest plankton fractions (0.2-2.7 μm and 0.2-20 μm) compared to the larger fraction comprising microplankton (20-50 um). This pattern was consistent in all lakes, reinforcing the idea that among pelagic organisms, heterotrophic and autotrophic bacteria with the contribution of nanoflagellates and dinoflagellates constitute the main entry point of Hg2+ to the pelagic food web. Moreover, a significant direct relationship was found between the Hg2+ uptake and surface index of the planktonic fractions (SIf). Thus, the smaller planktonic fractions which bore the higher SI were the major contributors to the Hg2+ passing from the abiotic to the biotic pelagic compartments of these Andean lakes

Inorganic mercury (Hg

The species composition and the size structure of natural planktonic food webs may provide essential information to understand the fate of mercury and, in particular, the bioaccumulation pattern of Hg2+ in the water column of lake ecosystems. Heterotrophic and autotrophic picoplankton and phytoplankton are the most important entry points for Hg in aquatic ecosystems since they concentrate Hg2+ and MeHg from ambient water, making them available to planktonic consumers at higher trophic levels of lake food webs. In this investigation we studied the uptake of 197Hg2+ in natural plankton assemblages from four Andean lakes (Nahuel Huapi National Park, Patagonia, Argentina), comprised in the size fractions 0.2-2.7 μm (picoplankton), 0.2-20 μm (pico and nanoplankton) and 20-50 μm (microplankton) through experiments using Hg2+ labeled with 197Hg2+. The experimental results showed that the uptake of Hg2+ was highest in the smallest plankton fractions (0.2-2.7 μm and 0.2-20 μm) compared to the larger fraction comprising microplankton (20-50 um). This pattern was consistent in all lakes, reinforcing the idea that among pelagic organisms, heterotrophic and autotrophic bacteria with the contribution of nanoflagellates and dinoflagellates constitute the main entry point of Hg2+ to the pelagic food web. Moreover, a significant direct relationship was found between the Hg2+ uptake and surface index of the planktonic fractions (SIf). Thus, the smaller planktonic fractions which bore the higher SI were the major contributors to the Hg2+ passing from the abiotic to the biotic pelagic compartments of these Andean lakes

Presence, abundance and bacterivory of the mixotrophic algae Pseudopedinella (Dictyochophyceae) in freshwater environments

The genus Pseudopedinella has been described as mixotrophic; however, ecological information about this algal stramenopile (Heterokonta) is unclear. We investigate the environmental conditions that determine the presence, abundance and bacterivory rates of this genus in freshwater systems. To this end we analyzed 54 water bodies with different limnological features distributed along a latitudinal and trophic gradient in northern Patagonia (Argentina) and the Antarctic Peninsula. In addition, 14 grazing experiments were carried out in order to estimate ingestion rates and impact on the bacterioplankton. Our results indicate that this genus is exclusively found in oligotrophic environments, and that it develops well in a wide range of temperatures. Average cell-specific grazing rate was 2.83 bacteria cell-1 h-1, with a maximum value of 6.74 bacteria ml-1 h-1. Interestingly, grazing increased with prey abundance and decreased with increasing nutrient availability. These patterns are common in highly bacterivorous protists that use phagotrophy as a main source of nutrient acquisition. Despite their usually low abundance (avg. 182 cells ml-1), this single genus was responsible for up to 24% (avg. 10%) of the total grazing impact exerted by all phagotrophs in these lakes. Overall, our results support the idea that Pseudopedinella is a highly bacterivorous group of freshwater protists, with the ability to develop well in oligotrophic conditions and with a potentially significant impact on bacterioplankton.Fil: Gerea, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Saad, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Izaguirre, Irina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Queimaliños, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Gasol, Josep M.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Unrein, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentin

Distribution patterns of the abundance of major bacterial and archaeal groups in Patagonian lakes

We explored the distribution patterns of bacterial and archaeal abundances at the phylum and class level using cata-lyzed reporter deposition-fluorescencein situhybridization (CARD-FISH), examining the among (across 35 waterbodies) and within-lake (intra-annual seasonality) patterns in Patagonia (Argentina).Alphaproteobacteria,BetaproteobacteriaandActinobacteriaglobally dominated the bacterioplankton, whereasGammaproteobacteriaandArchaeanever exceeded 3and 6% of the community, respectively. The different groups showed seasonality, with simultaneous peaks of all bacter-ial group absolute abundances during late winter or spring, and with peaks ofArchaeaduring winter, late spring andsummer. The bacterial groups presented roughly similar relative abundances in all seasons, whereasArchaeavaried intheir relative contribution to community structure. Multivariate analyses showed that dissolved organic carbon was animportant variable structuring the community at the studied taxonomic resolution (using absolute and relative abun-dances), in both among and within-lake patterns. The absolute abundance of most bacterial groups was significantlyhigher in mesotrophic and eutrophic systems than in oligotrophic ones (exceptActinobacteria), whereas their relativeabundances did not change among trophic states (exceptBacteroidetes). The lake grouping obtained from CARD-FISHwas consistent with previous work using polymerase chain reaction-denaturing gradient gel electrophoresis data: deepoligotrophic lakes clustered together, whereas small and shallow water bodies grouped separatelyFil: Schiaffino, María Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires; ArgentinaFil: Sánchez, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Gerea, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Unrein, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas ; ArgentinaFil: Balagué, Vanessa. Consejo Superior de Investigaciones Científicas. Institut de Ciències del Mar; EspañaFil: Gasol, Josep M.. Consejo Superior de Investigaciones Científicas. Institut de Ciències del Mar; EspañaFil: Izaguirre, Irina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Variability of phytoplankton light absorption in stratified waters of the NW Mediterranean Sea: The interplay between pigment composition and the packaging effect

The Variability of chlorophyll-specific phytoplankton light absorption [a*ph (λ)] was examined over depth and time in stratified offshore waters of the North-Western Mediterranean Sea. Coherent water patches were tracked with Lagrangian drifters during two oceanographic cruises in September (late summer) and May (post-spring bloom phase). By simultaneously analysing the phytoplankton absorption and pigment measurements, we explicitly separated the impact of pigment composition from that of pigment packaging on a*ph (λ). We further partitioned the packaging effect by comparing the variation of the packaging index [Qa*(440)], the phytoplankton community size structure (derived from diagnostic pigment analysis), and the chlorophyll-specific beam attenuation by particles [cp* (660)] as an optical index of phytoplankton photophysiology. In the ensemble of cruises, around 50% of the a*ph (440) vertical variation was explained by changes in the pigment composition (ruled by the decrease of photoprotective pigments with depth). The remaining vertical and inter-cruise variation of a*ph (440) was attributed to the packaging effect. We found that differences in the cp*(660) index (most likely indicating changes in the intracellular pigment concentration due to photoacclimation) mainly explained the observed variation in the packaging effect. Differences in cp* (660) were coincident with either the vertical gradient of light availability or the lower mean daily PAR irradiance in the euphotic layer of the September cruise. These explained the stronger packaging and lower a*ph (440) values observed with increasing depth in both cruises, and in September relative to May. On the other hand, differences in the phytoplankton community size structure did not explain the observed patterns in the packing effect. Our results highlight the importance of phytoplankton short-term acclimation to the prevailing light conditions, determining the vertical and temporal variability of a*ph (λ). A better understanding of the a*ph (λ) variability and its main drivers are key to improve different bio-optical applications