Publicaciones

Response of photosynthesis and respiration to temperature under water deficit in two evergreen Nothofagus species.

Sanhueza, C., Bascunan-Godoy, L., Turnbull, M., & Corcuera, L.

Respiration and photosynthesis were studied in two Nothofagus species with different drought tolerance in order to evaluate the effect of water deficit on foliar carbon balance and the possible role of the alternative pathway on respiratory adjustment. We propose that under severe water deficit the more drought-tolerant species N. dombeyi is able to decrease its respiration more than the less drought-tolerant species N. nitida, thus carbon gain could be maintained when photosynthesis is suppressed by drought. Dark respiration (Rd) and carbon assimilation under saturating light (Asat) were evaluated under seasonal field conditions and during drying and re-watering cycles under glasshouse. In addition, respiratory pathway changes were evaluated by oxygen isotope fractionation. In the field, N. dombeyi displayed greater light-saturated photosynthetic capacity than N. nitida, but Rd did not differ between species during summer. In the glasshouse, N. dombeyi displayed an unchanged rate of Rd and increased carbon loss under severe water deficit. Nothofagus nitida displayed a more flexible respiratory response to water deficit, with a lower thermal sensitivity of respiration (decrease in Q10) and a decrease in Rd. This contributed to maintaining leaf carbon balance during the water deficit period. Respiratory electron flow was mainly via the cytochrome pathway for both species and under all treatments, indicating no strong participation of alternative respiration. Our results suggest that under severe water stress, N. dombeyi could be more injured than N. nitida and that the lack of control in the carbon loss under prolonged periods of drought could be limiting for its survival.

Año: 2015

Palabras claves: Alternative oxidase; carbon balance; drought tolerance; isotopic discrimination; temperate forest.

Litter and seabirds found across a longitudinal gradient in the South Pacific Ocean.

Miranda-Urbina, D., Thiel, M., & Luna-Jorquera, G.

Abundances and composition of marine litter and seabirds were estimated in the central South Pacific (SP) Ocean between the Chilean continental coast and the Easter Island Ecoregion. Litter was dominated by plastics throughout the study area, but the proportion of plastics was higher at sea and on the oceanic islands than in coastal waters and on continental beaches. Litter densities were higher close to the center of the SP subtropical gyre compared to the continental coast. The seabird assemblage was diverse (28 species), and several endemic species were recorded. Seabird abundances were higher in the coastal waters and around Juan Fernández Islands off the continental coast than in the Oceanic and Polynesian sectors. Endangered species breeding on Salas & Gómez Island were observed in the Polynesian sector, which suggests a high potential for negative interactions between seabirds and floating litter, both occurring in high densities in this sector.

Año: 2015

Palabras claves: Litter; Seabirds; South Pacific Subtropical gyre; Oceanic islands; Motu Motiro Hiva Marine Park.

Herbivore-Alga Interaction Strength Influences Spatial Heterogeneity in a Kelp-Dominated Intertidal Community.

Aguilera, M., Valdivia, N., & Broitman, B.

There is a general consensus that marine herbivores can affect algal species composition and abundance, but little empirical work exists on the role of herbivores as modifiers of the spatial structure of resource assemblages. Here, we test the consumption/bulldozing effects of the molluscan grazer Enoplochiton niger and its influence on the spatial structure of a low intertidal community dominated by the bull kelp Durvillaea antarctica and the kelp Lessonia spicata. Through field experiments conducted at a rocky intertidal shore in north-central Chile (~30°-32°S), the edge of the grazer and algae geographic distributions, we estimated the strength and variability of consumptive effects of the grazer on different functional group of algae. We also used data from abundance field surveys to evaluate spatial co-occurrence patterns of the study species. Exclusion-enclosure experiments showed that E. niger maintained primary space available by preventing algal colonization, even of large brown algae species. The grazing activity of E. niger also reduced spatial heterogeneity of the ephemeral algal species, increasing bare space availability and variability through time in similar ways to those observed for the collective effect with other grazers. Overall, our result suggests that E. niger can be considered an important modifier of the spatial structure of the large brown algae-dominated community. Effects of E. niger on resource variability seem to be directly related to its foraging patterns, large body size, and population densities, which are all relevant factors for management and conservation of the large brown algae community. Our study thus highlights the importance of considering functional roles and identity of generalist consumers on spatial structure of the entire landscape.

Año: 2015

Palabras claves: Algae, Niger, Seaweed, Herbivory, Grazing, Population density, Foraging, Fronds.

GRACE storage-runoff hystereses reveal the dynamics of regional watersheds.

Sproles, E., Leibowitz, S., Reager, J., Wigington, P., Famiglietti, J., & Patil, S.

We characterize how regional watersheds function as simple, dynamic systems through a series of hysteresis loops using measurements from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites. These loops illustrate the temporal relationship between runoff and terrestrial water storage in three regional-scale watersheds (> 150 000 km2) of the Columbia River Basin, USA and Canada. The shape and size of the hysteresis loops are controlled by the climate, topography, and geology of the watershed. The direction of the hystereses for the GRACE signals moves in opposite directions from the isolated groundwater hystereses. The subsurface water (soil moisture and groundwater) hystereses more closely resemble the storage-runoff relationship of a soil matrix. While the physical processes underlying these hystereses are inherently complex, the vertical integration of terrestrial water in the GRACE signal encapsulates the processes that govern the non-linear function of regional-scale watersheds. We use this process-based understanding to test how GRACE data can be applied prognostically to predict seasonal runoff (mean Nash-Sutcliffe Efficiency of 0.91) and monthly runoff during the low flow/high demand month of August (mean Nash-Sutcliffe Efficiency of 0.77) in all three watersheds. The global nature of GRACE data allows this same methodology to be applied in other regional-scale studies, and could be particularly useful in regions with minimal data and in trans-boundary watersheds.

Año: 2015

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Aeolian particles in marine cores as a tool for quantitative high-resolution reconstruction of upwelling favorable winds along coastal Atacama Desert, Northern Chile.

Flores-Aqueveque, V., Alfaro, S., Vargas, G., Rutllant, J., & Caquineau, S.

Upwelling areas play a major role in ocean biogeochemical cycles and ultimately in global climate, especially in higly productive regions as the South Eastern Pacific. This work is based on the analysis of the aeolian lithic particles accumulated in laminated sediments off Mejillones (23°S) in the eastern boundary Humboldt Current System. It proposes a high-resolution quantitative reconstruction of the upwelling-favorable southerly wind strength in the past ∼250 years, comparing its variability with changes in organic carbon export/preserved changes to the sea bottom. The increase of the intensity and variability in fluxes of particles larger than 35 μm and 100 μm since the second half of the 19th century and during the 20th century confirms a general strengthening of southerly winds in the region. Spectral analysis on the complete time-series of yearly depositional fluxes indicates that sedimentary variability can be explained by a combination of interannual (ENSO) to decadal (PDO) oscillations similar to the ones yielded by the analysis of the Interdecadal Pacific Oscillation index. However, when applied separately to the lithic fluxes of the first and last centuries of the time-series, the method shows that relative to the one of the interannual mode of variability, the influence of the decadal mode has increased in the recent period.

Based on the presence/absence of particles with sizes larger than 35/100 μm, each year of the time series is classified as a ‘Low wind’ (<6 m/s), ‘Intermediate wind’ (6–8 m/s), or ‘Strong wind’ (10 to >12 m/s) year. From the AD 1754–1820 period to the AD 1878–1998 one, the proportion of Low and Intermediate wind years decreased from 12% and 74% to 3% and 68%, respectively, whereas the proportion of strong wind years increased from 14% to 29%. For these periods the mean organic carbon also increased 22%, stating the strong relation between export/preservation productivity rate and southerly wind intensity.

In the recent period (from AD 1950 on) for which the Oceanic Niño Index is available, the strong wind years (AD 1982, 1983, 1994, and 1997) correspond to large values of this index, suggesting that constructive interferences that result from the interplay between interannual and decadal oscillations modes might explain in part the reinforcement of the winds along the North Chilean coast.

Año: 2015

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Scallop larvae hatcheries as source of bacteria carrying genes encoding for non-enzymatic phenicol resistance.

Miranda, C., Rojas, R., Geisse, J., Romero, J., & González-Rocha, G.

The main aim of the study was to evaluate the role of scallop hatcheries as source of the floR and cmlA genes. A number of 133 and 121 florfenicol-resistant strains were isolated from scallop larval cultures prior to their transfer to seawater and from effluent samples from 2 commercial hatcheries and identified by 16S rRNA gene sequence analysis, observing a predominance of the Pseudomonas, Pseudoalteromonas and Halomonas genera and exhibiting an important incidence of co-resistance to streptomycin, oxytetracycline and co-trimoxazole. A high percentage of strains from both hatcheries carried the floR gene (68.4% and 89.3% of strains), whereas a lower carriage of the cmlA gene was detected (27.1% and 54.5% of strains). The high prevalence of floR-carrying bacteria in reared scallop larvae and hatchery effluents contributes to enrich the marine resistome in marine environments, prompting the need of a continuous surveillance of these genes in the mariculture environments.

Año: 2015

Palabras claves: Florfenicol; Antimicrobial resistance; floR; Scallop hatchery; Chile.

Growth Inhibition of Bacterial Fish Pathogens and Quorum-Sensing Blocking by Bacteria Recovered from Chilean Salmonid Farms.

Fuente, M., Miranda, C., Jopia, P., González-Rocha, G., Guiliani, N., Sossa, K., & Urrutia, H.

The main goal of this study was to find bacterial isolates with the ability to inhibit the growth of the fish pathogens Aeromonas hydrophila, Vibrio anguillarum, and Flavobacterium psychrophilum and to inhibit the blockage of the quorum-sensing (QS) system. A total of 80 gram-negative strains isolated from various freshwater Chilean salmonid farms were studied. We determined that 10 strains belonging to the genus Pseudomonas inhibited at least one of the assayed fish pathogens. Of these, nine strains were able to produce siderophores and two strains were able to inhibit the growth of all assayed pathogenic species. When the 80 strains were examined for QS-blocking activity, only the strains Pseudomonas sp. FF16 and Raoultella planticola R5B1 were identified as QS blockers. When the QS-blocker strains were analyzed for their ability to produce homoserine lactone (HSL) molecules, thin-layer chromatography analysis showed that both strains were able to produce C6-HSL– and C8-HSL–type molecules. Strain R5B1 did not show growth inhibition properties, but strain FF16 also led to inhibition of growth in A. hydrophila and F. psychrophilum as well as to siderophore production. Pseudomonas sp. FF16 exhibited potentially useful antagonistic properties and could be a probiotic candidate for the salmon farming industry.

Año: 2015

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Mitochondrial DNA diversity of feral pigs from Karukinka Natural Park, Tierra del Fuego Island, Chile.

Aravena, P., Skewes, O., & Gouin, N.

: Control or eradication of exotic species is one of the greatest challenges facing biodiversity and ecosystem conservation. Domestic pigs (Sus scrofa domestica) were released and became feral in the southern region of Chilean Tierra del Fuego Island in the 1900s.
Currently, they inhabit part of Karukinka Natural Park, an area of global conservation concern. To gain insight into the control of this invasive species, we analyzed genetic variation in the mitochondrial DNA control region to determine the origin and population subdivision of feral pigs in Tierra del Fuego. Sequences from a sample of 42 feral pigs, 10 domestic pigs from local farms, and references from other countries and commercial breeds revealed 2 highly differentiated populations,
1 in the western and the other in the eastern area of the park, each harboring a different haplotype, suggesting no connectivity between populations. Comparison of these haplotypes with reference sequences from other countries and commercial breeds indicated that feral pigs from Chilean Tierra del Fuego are of European origin, very likely from
2 separate introduction events. The haplotype found in the western feral population was also identified in domestic pigs from a farm. This raises concerns regarding the possible connectivity between stocks from local farms and the wild population. Based on these results, we recommend the development of strategies for controlling the population of this invasive species in Karukinka Natural Park.

Año: 2015

Palabras claves: Feral pigs; Invasive species; mtDNA control region;Sus scrofa; Tierra del Fuego Island.

Effects of wind-driven spatial structure and environmental heterogeneity on high-altitude wetland macroinvertebrate assemblages with contrasting dispersal modes.

Bertin, A., Alvarez, E., Gouin, N., Gianoli, E., Montecinos, S., & Lek, S. et al.

Dispersal is a major determinant of connectivity between communities that may modulate the importance of environmental and spatial processes on taxonomic composition. While wind is likely to influence transport distance, rate and direction for numerous species, its effects on community composition remain poorly understood.
Using eigenvector-based spatial analyses, we investigated the influence of wind flows, estimated by mesoscale models, on the spatial structure of benthic macroinvertebrate assemblages with contrasting flying abilities in high Andean wetlands (26–32°S). We further quantified the relative importance of local and regional processes through a variation partitioning approach.
The influence of environmental heterogeneity was prevalent and of relatively similar amplitude in both flying and non-flying assemblages. Significant spatial structure more strongly driven by wind flows than by Euclidean schemes was detected for both assemblages. As expected, the highest levels of spatial structure were observed for the flying macroinvertebrate assemblage and they occurred at a much larger spatial scale in this group, suggesting a greater dispersal aptitude of the flying taxa.
Our results show that environmental effects are predominant in shaping the spatial structure of macroinvertebrate communities in high Andean wetlands, as generally found in other systems. They also demonstrate the significance of wind flows in regulating high-altitude wetland macroinvertebrate communities and illustrate the importance of considering adequate spatial models and biological characteristics of species to advance our understanding of community patterns.

Año: 2015

Palabras claves: Benthic macroinvertebrates; dispersal; eigenvector maps; wetlands; wind.