Publicaciones

Definition of sanitary boundaries to prevent ISAv spread between salmon farms in southern Chile based on numerical simulations of currents.

Olivares, G., Sepúlveda, H., & Yannicelli, B.

The infectious Salmon Anemia virus (ISAv) is a pathogen that mainly affects the Atlantic Salmon (Salmo salar). It was detected in Norway in 1984 and in June 2007 appeared in Chile, producing a drop of more than 30% in the country's production level. It is expected that with certain regularity, outbreaks will continue to appear in Chile without the need of reintroducing the virus from foreign countries. We present a numerical study of the influence of winds and tides in the dispersion of lagrangian particles to simulate the transport of ISAv in the Aysen region, in southern Chile. This study combines the use of numerical models of the ocean and atmosphere, lagrangian tracking and biological aspects of ISAv infections. As in previous results, a wider dispersion of ISAv was observed during spring tides. Temporal changes in wind significantly modified the transport of viral particles from an infected center. Under similar forcing conditions, the areas of risk associated to culture sites separated by a few kilometers could be very different. Our main results remark the importance of the use of a detailed knowledge of hydrographic and atmospheric circulation in the definition of boundaries for sanitary management areas. We suggest that a methodology similar to the one presented in this study should be considered to define sanitary strategies to minimize the occurrence of native outbreaks of ISAv.

Año: 2015

Palabras claves: sanitary boundaries; ISAv; Atlantic Salmon; spread; numerical model; Chile.

Detecting Subtle Seasonal Transitions of Upwelling in North-Central Chile.

Rahn, D., Rosenblüth*, B., & Rutllant, J.

Biological productivity in the ocean along the Chilean coast is tied to upwelling that is primarily forced by equatorward wind stress and wind stress curl on the ocean surface. Southerly alongshore flow is driven by the southeast Pacific (SEP) anticyclone, and its intensity and position vary on a range of time scales. Variability of the SEP anticyclone has been linked to large-scale circulations such as El Niño–Southern Oscillation and the Madden–Julian oscillation. The actual timing, duration, and nature of the seasonal meridional drift of the SEP anticyclone are associated with the onset, demise, and strength of the local upwelling season. Seasonal variation is especially marked at the Punta Lavapié (37°S) upwelling focus, where there is a clear upwelling season associated with a change of the cumulative upwelling index (CUI) slope between positive and negative. The Punta Lengua de Vaca (30°S) focus typically exhibits upwelling year-round and has less distinct transitions, making it more difficult to identify an enhanced upwelling season. A two-phase linear regression model, which is typically used to detect subtle climate changes, is applied here to detect seasonal changes in CUI at Punta Lengua de Vaca. This method objectively finds distinct transitions for most years. The spring-to-summer transition is more readily detected and the slackening of the upwelling-favorable winds, warmer waters, and longer wind strengthening–relaxation cycles change the coastal upwelling ecosystem. While the spring-to-summer transition at Punta Lengua de Vaca could be influenced by large-scale circulations, the actual dates of transition are highly variable and do not show a clear relationship.

Año: 2015

Palabras claves: Circulation/ Dynamics; Upwelling/downwelling; Atm/Ocean Structure/ Phenomena; Madden-Julian oscillation; Physical Meteorology and Climatology; Climate variability; Coastal meteorology; ENSO.

Characterization and pathogenicity of Vibrio splendidus strains associated with massive mortalities of commercial hatchery-reared larvae of scallop Argopecten purpuratus (Lamarck, 1819)

Rojas, R., Miranda, C., Opazo, R., & Romero, J.

Three strains (VPAP16, VPAP18 and VPAP23 strains) were isolated as the most predominant organisms from 3 different episodes of massive mortalities of larval cultures of the Chilean scallop Argopecten purpuratus occurred in different commercial hatcheries located in northern Chile. The main aims of this study were to identify the pathogenic strains and investigate their pathogenic activity. Based on selected phenotypic features and sequence identity of the 16S rRNA gene and the housekeeping gene, RNA polymerase α-chain rpoA, all pathogenic strains were identified as Vibrio splendidus. Healthy 10–day–old scallop larvae cultures exhibited mortality percentages of 69.61 ± 3.35%, 79.78 ± 6.11% and 61.73 ± 3.71% after 48 h when were inoculated with 1 × 106 CFU (colony forming units) mL−1 of VPAP16, VPAP18 and VPAP23 strains, respectively, and evidenced that concentrations ⩾104 CFU mL−1 would probably be detrimental for the larval culture. The main clinical signs observed in challenged larvae for 24 h were bacterial swarms on the margins of the larvae, extension and disruption of the velum, detachment of velum cilia cells and digestive tissue necrosis. Otherwise, challenge assays using pathogenic strains stained with 5-([4,6-dichlorotriazin-2-yl]amino)fluorescein hydrochloride (5-DTAF) evidenced that after 1 h stained bacteria were detected in high density in the digestive gland and the margin of the shell. When larval cultures were inoculated with cell-free extracellular products (ECP) of V. splendidus strains, exhibited larval mortalities higher than 70% (VPAP16), 80% (VPAP18) and 50% (VPAP23) after 24 h, even when ECP were treated with proteinase K or heat, indicating that extracellular pathogenic activity is mainly mediated by non-proteic thermostable compounds. In this study all Koch’s postulates were fulfilled and it was demonstrated for the first time the pathogenic activity of V. splendidus strains on reared-larvae of scallop A. purpuratus and prompt the necessity to maintain this species at concentrations lower than 104 CFU mL−1 to avoid episodes of mass mortalities in scallop hatcheries.

Año: 2015

Palabras claves: Bacteria; Vibrio splendidus; Scallop larvae; Vibriosis; Shellfish pathology; Argopecten purpuratus.

Comparison of DNA extraction methods for polymerase chain reaction amplification of guanaco (Lama guanicoe) fecal DNA samples.

Espinosa, M., Bertin, A., Squeo, F., Cortés, A., & Gouin, N.

Feces-based population genetic studies have become increasingly popular. However, polymerase chain reaction (PCR) amplification rates from fecal material vary depending on the species, populations, loci, and extraction protocols. Here, we assessed the PCR amplification success of three microsatellite markers and a segment of the mitochondrial control region of DNA extracted from field-collected feces of guanaco (Lama guanicoe) using two protocols - Qiagen DNA Stool Kit and 2 cetyltrimethylammonium bromide/phenol:chloroform:isoamyl alcohol (2CTAB/PCI) method. Chelex resin treatment to remove inhibitors was also tested. Our results show that the mitochondrial locus was the most difficult to amplify. PCR success rates
improved for all markers after Chelex treatment of extracted DNA, and 2CTAB/PCI method (95.83%) appeared to perform slightly better than stool kit (91.67%) for the nuclear markers. Amplification success was significantly influenced by the extraction method, Chelex treatment, and locus (P < 0.001) but not by the freshness of the feces (fresh vs old, P = 0.17). The repeatability levels were high without Chelex treatment (> 0.89), but they decreased slightly after treatment for amplification of nuclear markers and markedly after treatment for amplification of the mitochondrial control region. Thus, we showed that Chelex treatment gives high PCR success, especially for nuclear markers, and adequate DNA extraction rates can be achieved from L. guanicoe feces even from non-fresh fecal material. Although not significant, 2CTAB/PCI method tended to provide higher successful amplification rates on a whole set of samples, suggesting that the method could be particularly useful when using small sample sizes.

Año: 2015

Palabras claves: Non-invasive genetics; Mitochondrial control region;Microsatellites; Polymerase chain reaction inhibitors;Chelex treatment; Lama guanicoe.

Genetic diversity in Chilean populations of rainbow trout, Oncorhynchus mykiss.

Carcamo, C., Diaz, N., & Winkler, F.

The rainbow trout Oncorhynchus mykiss, was first introduced in Chile between 1905 and 1920 and is currently widely distributed in Chile from Antofagasta (23°S) to Patagonia (55ºS). The broad range of the geographic and climatic distributions of this species in Chile offers a unique opportunity to study the effect of naturalization of an introduced species on its genetic variability. It is of particular importance to observe the genetic variability of populations in the northern range of this species distribution, in a transition zone where a Mediterranean-type climate changes to an arid climate. The present study analyzed allozymic variability and distribution within and between populations of O. mykiss from the river basins of Elqui and Limarí rivers, and six culture strains, using starch-gel protein electrophoresis. Populations were found to be in Hardy-Weinberg equilibrium and the average values of He (0.045), polymorphism (13.9%) and allele per locus (1.19) are similar to rainbow trout in its native distributional range. About 77.8% of the genetic variability was within population, similar to the variability reported for wild populations in the northern hemisphere. However, a marked genetic differentiation between wild populations was also found. This is likely to be the consequence of initial founder effects followed by subsequent introgression of resident populations caused by reseeding with trout of different origins in both basins.

Año: 2015

Palabras claves: Oncorhynchus mykiss, rainbow trout, Salmonidae, genetic variation, aquaculture, conservation.

A 700-year record of climate and environmental change from a high Andean lake: Laguna del Maule, central Chile (36 S).

Carrevedo, M., Frugone, M., Latorre, C., Maldonado, A., Bernardez, P., & Prego, R. et al.

Central Chile is heavily exploited for mineral and water resources, with agriculture and large urban populations all creating intensive landscape use. Few records of past environmental and climate change are available that afford a broader context. To aid in this assessment, we present a 700-year reconstruction from Laguna del Maule (LdM) in the high Andes of central Chile based on sedimentological, geochemical, diatom and pollen analyses. The age model is based on 210Pb/137Cs and 14C dating tied into known volcanic eruptions. Sedimentology consists of organic-rich sediments and diatom oozes with several interspersed volcanic-rich facies and two tephra deposits. Sediment geochemistry exhibits increased productivity (high Br/Ti, biosilica) and more dominant oxic conditions (high Fe/Mn) from AD 1300 to 1400 and from AD 1650 to 1850, likely during periods of relatively lower lake levels and better development of littoral environments. However, during this later period, high elevation vegetation was dominant, indicative of regional cooler/wetter conditions. In contrast, sediments deposited from AD 1850 to 1930 evidence decreased productivity and increased anoxic lake bottom conditions. The ‘Little Ice Age’ (LIA) in LdM is characterized by significant variations in lake dynamics and hydrology with cooler/wetter conditions (AD 1570–1700), major environmental changes in the 18th century and ending at ca. AD 1850. LdM record documents the impact of the LIA in the southern hemisphere and stresses the global nature of this climate period. Large changes in lake dynamics and diatoms assemblages during the 20th century could be related to anthropogenic impacts, but recent changes in climate patterns cannot be excluded.

Año: 2015

Palabras claves: Chile, diatoms, geochemistry, Late Holocene, Little Ice Age, pollen.

Mid Holocene radiocarbon ages in the Subtropical Andes (∼29°–35° S), climatic change and implications for human space organization.

Méndez, C., Gil, A., Neme, G., Nuevo Delaunay, A., Cortegoso, V., & Huidobro, C., Durán, V., Maldonado, A.

This article discusses the distribution of radiocarbon age signatures obtained from archeological sites between 29° and 35° S in Central Chile and Midwest Argentina. The goal of this analysis is to establish bases from which to interpret regional trends in the distribution of the archaeological record that connect these areas, which have been traditionally considered to be geographically decoupled. We propose a standardized methodology for selecting ages that provide a reliable human signature. Variations in date frequencies in a regional scale are discussed with the use of summed probability distributions. Radiocarbon voids at the regional level previously identified in Midwest Argentina are explored. Regional chronological information is compared to the available paleoenvironmental records, thereby emphasizing the possible role of climate pulses in the spatial organization of human populations. Significant arid conditions between 7800 and 5700 cal BP are coincidental with a focused occupation of the Andes Mountains, an area which may have offered stable resources and thus was more effectively occupied than other environmental bands.

Año: 2015

Palabras claves: Radiocarbon dates; Climate change; Human paleoecology; Hunter–gatherers; Mid-Holocene; Subtropical Andes.

Late Quaternary climate change, relict populations and present-day refugia in the northern Atacama Desert: a case study from Quebrada La Higuera (18° S).

Mujica, M., Latorre, C., Maldonado, A., González-Silvestre, L., Pinto, R., de Pol-Holz, R., & Santoro, C.

In deserts, past climate change (and particularly past rainfall variability) plays a large role in explaining current plant species distributions. We ask which species were most and which were least affected by changes in rainfall during the late Quaternary in northernmost Chile.

Año: 2015

Palabras claves: Altiplano; Atacama Desert; central Andes; late Quaternary; pluvial events; refugia; relict populations; rodent middens.

Biogeographic structure of the northeastern Pacific rocky intertidal: the role of upwelling and dispersal to drive patterns.

Fenberg, P., Menge, B., Raimondi, P., & Rivadeneira, M.

Identifying the environmental conditions that drive biogeographic structure remains a major challenge of biogeography, evolutionary ecology and increasingly, conservation biology. Here, we use multivariate classification trees to assess the biogeographic structure of northeast Pacific (∼ 26–58°N) rocky intertidal species (406 species of algae and invertebrates) from 102 field sites. Random forest analyses are used to assess the importance of 29 environmental variables, encompassing a broad range of potential drivers, to predict biogeographic structure. Analyses are repeated for species with different larval dispersal capabilities and by broad taxonomic categories (invertebrates and algae). Results show that overall biogeographic structure is in general agreement with classic classification schemes, but patterns are variable among species with different larval dispersal capabilities. Random forest models show a very high fit (pseudo r2 > 0.94) and indicate that biogeographic structure can be predicted by a relatively modest subset of variables. Upwelling related variables are the best overall predictors of biogeographic structure (nutrient concentrations, sea-surface temperature, upwelling/downwelling seasonal switch index), but the relative importance of predictors is geographically variable and top predictors are dependent on the type of larval dispersal. Upwelling related variables are more important to predict biogeographic structure for invertebrates with lower-medium dispersal capabilities and algae, whereas species with high larval dispersal (planktotrophic) are better predicted by a different subset of variables (i.e. salinity, precipitation seasonality). Our results lend support to the influence of coastal upwelling in structuring biogeographic patterns and highlight the potential for climate change-induced alterations of upwelling regimes to profoundly affect biodiversity at biogeographic scales.

Año: 2015

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