Seasonal variation in epifaunal communities associated with giant kelp (Macrocystis pyrifera) at an upwelling-dominated site

Autores:

Winkler, N. S., Pérez-Matus, A., Villena, Á. A. and Thiel, M.

Resumen:

Kelp forests are highly productive and species-rich benthic ecosystems in temperate regions that provide biogenic habitat for numerous associated species. Diverse epifaunal communities inhabit kelp sporophytes and are subject to variations in the physical environment and to changes experienced by the kelp habitat itself. We assessed seasonal variations in epifaunal invertebrate communities inhabiting giant kelps, Macrocystis pyrifera, and their effects on this seaweed. Six seasonal samplings were conducted over a year at an upwelling-dominated site in northern-central Chile where physical conditions are known to fluctuate temporally. More than 30 taxa were identified, among which peracarid crustaceans stood out in both diversity and abundance. Species richness and abundance differed among sporophyte sections (holdfast and fronds) and throughout the year. The frond community was dominated by two grazers (the amphipod Peramphithoe femorata and the isopod Amphoroidea typa), while suspension feeders, grazers, and omnivores (the amphipod Aora typica, the isopod Limnoria quadripunctata, and polychaetes) dominated the holdfasts. Abundances of the dominant species fluctuated throughout the year but patterns of variation differed among species. The most abundant grazer (P. femorata) had highest densities in summer, while the less abundant grazer (A. typa) reached its peak densities in winter. Interestingly, the area of kelp damaged by grazers was highest in autumn and early winter, suggesting that grazing impacts accumulate during periods of low kelp growth, which can thus be considered as ‘vestiges of herbivory past.’ Among the factors determining the observed seasonal patterns, strong variability of environmental conditions, reproductive cycles of associated fauna, and predation by fishes vary in importance. Our results suggest that during spring and early summer, bottom-up processes shape the community structure of organisms inhabiting large perennial seaweeds, whereas during late summer and autumn, top-down processes are more important.

Año: 2017

Palabras claves: associated epifauna; kelp; Macrocystis pyrifera ; seasonal fluctuations; temperate regions

Genetic differentiation between humpback whales (Megaptera novaeangliae) from Atlantic and Pacific breeding grounds of South America

Autores:

Cypriano-Souza, A. L., Engel, M. H., Caballero, S., Olavarría, C., Flórez-González, L., Capella, J., Steel, D., Sremba, A., Aguayo, A., Thiele, D., Baker, C. S. and Bonatto, S. L.

Resumen:

Humpback whales wintering in tropical waters along the Atlantic and Pacific coasts of the South American continent are thought to represent distinct populations or “stocks.” Here we present the first analysis of genetic differentiation and estimates of gene flow between these breeding stocks, based on both mitochondrial DNA (mtDNA) control region sequences (465 bp) and 16 microsatellite loci from samples collected off Brazil (n = 277) and Colombia (n = 148), as well as feeding areas near the western Antarctic Peninsula (n = 86). We found significant differentiation between Brazilian and Colombian breeding grounds at both mtDNA (FST = 0.058) and microsatellite (FST = 0.011) markers and corroborated previous studies showing genetic similarity between humpbacks from Colombia and those from Antarctic Peninsula feeding areas. Estimates of long-term gene flow between Brazil and Colombia were low to moderate, asymmetrical, and mostly mediated by males. Assignment procedures detected some cases of interchange and individuals of admixed ancestry between breeding grounds, indicating limited mixing of individuals between these stocks. Overall, results highlight the differentiation of humpback whale breeding populations with adjacent feeding grounds. This appears to be a remarkable example of fidelity to seasonal habitat in the absence of any contemporary barriers.

Año: 2017

Palabras claves: Megaptera novaeangliae; population genetic structure; microsatellites; mtDNA; migration; individual assignment

La quinua, un modelo de sistema agroalimentario saludable y sostenible

Autores:

Enrique Alfonso Martinez Mosqueira

Resumen:

Nuestro planeta vive cambios sociales y climáticos acelerados y de magnitudes sin precedentes. En particular desde la Revolución Industrial del siglo XVIII. Entre ellos, la agricultura y su industrialización significó que el trabajo de la tierra dejó de ser una actividad agroalimentaria benéfica e inocua y se tornó agresiva y erosiva. Hoy es parte importante de la degradación de la biodiversidad y de los cambios climáticos planetarios, contribuyendo en forma importante a incrementar los gases de efecto invernadero. La pequeña agricultura que no ha sido contaminada con las prácticas de aceleración de la productividad ni con el uso extremo de agroquímicos produce aun un 70% de la alimentación mundial y es un patrimonio vivo que no debe perderse. Entre ellos está la gente y el cultivo de la quinua, una planta de las culturas andinas. Este libro busca dar a conocer sus sorprendentes propiedades nutricionales y las formas en que este cultivo puede contribuir a ser un modelo para la salud de la tierra, de las plantas, de los campesinos y de los consumidores. Formando a su vez un sistema económico también más justo y más saludable para todos: un sistema agroalimentario más sostenible.

Año: 2017

Palabras claves: agricultura ecológica, cambio climático, desarrollo sustentable, nutrición, quinua, salud, sostenibilidad, economía transparente

Meteorological Interpretation of Orographic Precipitation Gradients along an Andes West Slope Basin at 30°S (Elqui Valley, Chile)

Autores:

Scaff, L., Rutllant, J., Rahn, D., Gascoin, S. and Rondanelli, R.

Resumen:

To better forecast streamflow and water resource availability, it is important to have an understanding of the meteorological drivers of the orographic precipitation gradient (OPG), especially critical in semiarid mountainous areas. Although forced ascent over topography typically results in precipitation increasing with altitude (positive OPGs), mean annual OPGs and especially OPGs associated with individual storms can change widely in magnitude and even sign. Precipitation measurements from the Elqui Valley in the semiarid Andes of Chile (30°S) reveal a mean annual OPG of 6.3 mm km−1 (millimeters of precipitation over kilometers in elevation) ranging from −42 to 52 mm km−1 for individual storms over the last 35 years (1979–2013). Reanalysis data and precipitation measurements are used to characterize the observed OPG in this region in relation with their synoptic-scale flow. It is found that the Froude number correlates positively with the OPG, reflecting stronger zonal winds and less static stability during storms that have positive OPGs. Altitude of the Andes barrier jet shows only a weak relationship with the OPG. Significant storms with positive OPGs are typically linked with an austral blocking of the westerlies and an equatorward migration of the midlatitude storm track. For negative OPGs, either a cutoff low or the northern edge of a surface migratory cyclone reaches the Elqui Valley in such a way that significant rainfall only occurs in the near-coastal region without major snowfall accumulation over the Andes.

Año: 2017

Palabras claves: Cutoff lows; Orographic effects; Synoptic climatology; Cold fronts; Precipitation; Valley/mountain flows

Surface winds off Peru-Chile: Observing closer to the coast from radar altimetry

Autores:

Astudillo, O., Dewitte, B., Mallet, M., Frappart, F., Rutllant, J., Ramos, M., Bravo, L., Goubanova, K. and Illig, S.

Resumen:

The near-shore surface mesoscale atmospheric circulation in the upwelling systems off Peru and Chile is influential on the Sea Surface Temperature through Ekman transport and pumping. There has been a debate whether or not the so-called “wind drop-off”, that is a shoreward decrease of the surface wind speed near the coast, can act as an effective forcing of upwelling through Ekman pumping. Although the wind drop-off has been simulated by high-resolution atmospheric models, it has not been well documented due to uncertainties in the scatterometry-derived wind estimates associated with land contamination. Here we use the along-track altimetry-derived surface wind speed data from ENVISAT, Jason-1, Jason-2, and SARAL satellites, to document the spatial variability of the mean wind drop-off near the coast as estimated from the inversion of the radar backscattering coefficient. The data are first calibrated so as to fit with the scatterometer observations of previous and current satellite missions (QuikSCAT, ASCAT). The calibrated data are then analyzed near the coast and a wind drop-off scale is estimated. The results indicate that the wind drop-off takes place all along the coast, though with a significant alongshore variability in its magnitude. Differences between products are shown to be related both to the differences in repeat cycle between the different altimetry missions and to the peculiarities of the coastline shape at the coastal latitudes of the incident tracks. The relative contribution of Ekman pumping and Ekman transport to the total transport is also estimated indicating a comparable contribution off Chile while transport associated to Ekman pumping is on average ~ 1.4 larger than Ekman transport off Peru. Despite the aliasing effect associated with the weak repetitivity of the satellite orbit and the high frequency variability of the winds in this region, the analysis suggests that the seasonal cycle of the surface winds near the coast could be resolved at least off Peru.

Año: 2017

Palabras claves: Satellite altimetry, Peru-Chile upwelling system, Coastal surface winds, Wind drop-off

Dynamic Interactions among Boundaries and the Expansion of Sustainable Aquaculture

Autores:

Broitman, B., Halpern, B., Gelcich, S., Lardies, M., Vargas, C., Vásquez-Lavín, F., Widdicombe, S. and Birchenough, S.

Resumen:

Aquaculture is the fastest growing food production system in the world, generating more than half of the global seafood harvested today. These type of activities are crucial to provide key nutritional components for humanity in the future as populations worldwide are increasing and the demands for securing food resources are imperative. Multiple socio-ecological factors such as weak regulations and focus on maximizing production limit production and threaten the sustainable growth of aquaculture. We present a novel policy framework to evaluate and pursue growth in aquaculture considering four boundaries: biological productivity, environmental constraints to that productivity, policy that inhibits or promotes different kinds of aquaculture, and social preferences that determine aquaculture markets. Using a range of scenarios, we have shown that sustainable growth in aquaculture requires simultaneous consideration of all four boundaries and the potential interactions between all of these options. Our proposed conceptual framework shows that to further expand the boundaries of aquaculture production, the policy focus must remain flexible to enable the adaptation of from single-boundary approaches. Our approach takes account of the current boundaries, helping to consider the adaptive policy, which is deemed as a necessary tool for considering the dynamic interactions among boundaries, thus addressing the problem of defining the evolving limits of sustainable aquaculture.

Año: 2017

Palabras claves: sustainability, aquaculture research, socioecology, molusks, fishes

Context-dependent functional dispersion across similar ranges of trait space covered by intertidal rocky shore communities

Autores:

Valdivia, N., Segovia-Rivera, V., Fica, E., Bonta, C., Aguilera, M., & Broitman, B.

Resumen:

Functional diversity is intimately linked with community assembly processes, but its large-scale patterns of variation are often not well understood. Here, we investigated the spatiotemporal changes in multiple trait dimensions (“trait space”) along vertical intertidal environmental stress gradients and across a landscape scale. We predicted that the range of the trait space covered by local assemblages (i.e., functional richness) and the dispersion in trait abundances (i.e., functional dispersion) should increase from high- to low-intertidal elevations, due to the decreasing influence of environmental filtering. The abundance of macrobenthic algae and invertebrates was estimated at four rocky shores spanning ca. 200 km of the coast over a 36-month period. Functional richness and dispersion were contrasted against matrix-swap models to remove any confounding effect of species richness on functional diversity. Random-slope models showed that functional richness and dispersion significantly increased from high- to low-intertidal heights, demonstrating that under harsh environmental conditions, the assemblages comprised similar abundances of functionally similar species (i.e., trait convergence), while that under milder conditions, the assemblages encompassed differing abundances of functionally dissimilar species (i.e., trait divergence). According to the Akaike information criteria, the relationship between local environmental stress and functional richness was persistent across sites and sampling times, while functional dispersion varied significantly. Environmental filtering therefore has persistent effects on the range of trait space covered by these assemblages, but context-dependent effects on the abundances of trait combinations within such range. Our results further suggest that natural and/or anthropogenic factors might have significant effects on the relative abundance of functional traits, despite that no trait addition or extinction is detected.

Año: 2017

Palabras claves: community assembly; desiccation; environmental filtering; functional beta-diversity; functional traits; marine; mesoscale; seasonal

Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity

Autores:

Vargas, C., Lagos, N., Lardies, M., Duarte, C., Manríquez, P., & Aguilera, V., Broitman, B., Widdicombe, S., & Dupont, S.

Resumen:

Global stressors, such as ocean acidification, constitute a rapidly emerging and significant problem for marine organisms, ecosystem functioning and services. The coastal ecosystems of the Humboldt Current System (HCS) off Chile harbour a broad physical–chemical latitudinal and temporal gradient with considerable patchiness in local oceanographic conditions. This heterogeneity may, in turn, modulate the specific tolerances of organisms to climate stress in species with populations distributed along this environmental gradient. Negative response ratios are observed in species models (mussels, gastropods and planktonic copepods) exposed to changes in the partial pressure of CO2 (pCO2pCO2) far from the average and extreme pCO2pCO2 levels experienced in their native habitats. This variability in response between populations reveals the potential role of local adaptation and/or adaptive phenotypic plasticity in increasing resilience of species to environmental change. The growing use of standard ocean acidification scenarios and treatment levels in experimental protocols brings with it a danger that inter-population differences are confounded by the varying environmental conditions naturally experienced by different populations. Here, we propose the use of a simple index taking into account the natural pCO2pCO2 variability, for a better interpretation of the potential consequences of ocean acidification on species inhabiting variable coastal ecosystems. Using scenarios that take into account the natural variability will allow understanding of the limits to plasticity across organismal traits, populations and species.

Año: 2017

Palabras claves:

Molecular characterization of endophytic fungi associated with the roots of Chenopodium quinoa inhabiting the Atacama Desert, Chile.

Autores:

González-Teuber, M., Vilo, C., & Bascuñán-Godoy, L.

Resumen:

Plant roots can be highly colonized by fungal endophytes. This seems to be of particular importance for the survival of plants inhabiting stressful habitats. This study focused on the Identification of the fungal endophytic community associated with the roots of quinoa plants (Chenopodium quinoa) growing near the salt lakes of the Atacama Desert, Chile. One hundred endophytic fungi were isolated from healthy quinoa roots, and the internal transcribed spacer (ITS) region was sequenced for phylogenetic and taxonomic analysis. The isolates were classified into eleven genera and 21 distinct operational taxonomic units (OTUs). Despite a relatively high diversity of root endophytic fungi associated with quinoa plants, the fungal community was dominated by only the Ascomycota phyla. In addition, the most abundant genera were Penicillium, Phoma and Fusarium, which are common endophytes reported in plant roots. This study shows that roots of C. quinoa harbor a diverse group of endophytic fungi. Potential roles of these fungi in plant host tolerance to stressful conditions are discussed.

Año: 2017

Palabras claves: Fungal endophytes; Quinoa; Internal transcribed spacer; Phylogenetic analysis; Atacama Desert

Rootstock effect on irrigated grapevine yield under arid climate conditions are explained by changes in traits related to light absorption of the scion

Autores:

Bascuñán-Godoy, L., Franck, N., Zamorano, D., Sanhueza, C., Carvajal, D., & Ibacache, A.

Resumen:


The purpose of this study was to investigate the mechanisms underlying the effect of rootstocks on table grapevines grown under irrigated conditions in the arid North macro-zone of Chile.

Grapevine cv. Red Globe grafted onto three rootstocks (Harmony, Saint George and Salt Creek) were studied Structural and physiological parameters were monitored at different phenological stages under optimal production conditions.

An outstanding yield increment brought about by the rootstocks Harmony and Salt Creek was correlated with increased individual leaf and specific leaf area, pruning weight (proxy for total leaf area), photosynthesis per unit leaf mass, sugar in leaves and root carbon reserves. In addition, these high yielding rootstocks induced higher contents of light-harvesting chlorophyll a/b protein of photosystem II and total chlorophyll in the leaves of the scion. No correlations of yield with traits involved in water use (relative water content or instantaneous water use efficiency) were observed.

The effects of rootstocks on the light capture capacity of the scion directly affected carbon assimilation and storage and, accordingly, yield. Therefore, the identified traits are valuable targets for screening and selecting yield efficient rootstocks for irrigated table grape production in arid zones.

Año: 2017

Palabras claves: Grapevine rootstock, Light capture, Photo synthesis, Pruning weight, Red Globe, Yield