Publicaciones

Fuzzy-based assessment of groundwater intrinsic vulnerability of a volcanic aquifer in the Chilean Andean Valley

Duhalde, D., Arumí, J., Oyarzún, R. and Rivera, D.

A fuzzy logic approach has been proposed to face the uncertainty caused by sparse data in the assessment of the intrinsic vulnerability of a groundwater system with parametric methods in Las Trancas Valley, Andean Mountain, south-central Chile, a popular touristic place in Chile, but lacking of a centralized drinking and sewage water public systems; this situation is a potentially source of groundwater pollution. Based on DRASTIC, GOD, and EKv and the expert knowledge of the study area, the Mamdani fuzzy approach was generated and the spatial data were processed by ArcGIS. The groundwater system exhibited areas with high, medium, and low intrinsic vulnerability indices. The fuzzy approach results were compared with traditional methods results, which, in general, have shown a good spatial agreement even though significant changes were also identified in the spatial distribution of the indices. The Mamdani logic approach has shown to be a useful and practical tool to assess the intrinsic vulnerability of an aquifer under sparse data conditions.

Año: 2018

Palabras claves: Aquifer vulnerability, Data scarcity, Fuzzy logic

Chemistry and microbiology of the Critical Zone along a steep climate and vegetation gradient in the Chilean Coastal Cordillera

Oeser, R., Stroncik, N., Moskwa, L., Bernhard, N., Schaller, M., Canessa, R., van den Brink, L., Köster, M., Brucker, E., Stock, S., Fuentes, J., Godoy, R., Matus, F., Oses Pedraza, R., Osses McIntyre, P., Paulino, L., Seguel, O., Bader, M., Boy, J., Dippold, M., Ehlers, T., Kühn, P., Kuzyakov, Y., Leinweber, P., Scholten, T., Spielvogel, S., Spohn, M., Übernickel, K., Tielbörger, K., Wagner, D. and von Blanckenburg, F.

The Chilean Coastal Cordillera features a spectacular climate and vegetation gradient, ranging from arid and unvegetated areas in the north to humid and forested areas in the south. The EarthShape project (“Earth Surface Shaping by Biota”) uses this natural gradient to investigate how climate and biological processes shape the Earth's surface. We explored the Critical Zone, the Earth's uppermost layer, in four key sites located in desert, semidesert, Mediterranean, and temperate climate zones of the Coastal Cordillera, with the focus on weathering of granitic rock. Here, we present first results from 16 approximately 2 m-deep regolith profiles to document: (1) architecture of weathering zone; (2) degree and rate of rock weathering, thus the release of mineral-derived nutrients to the terrestrial ecosystems; (3) denudation rates; and (4) microbial abundances of bacteria and archaea in the saprolite.

From north to south, denudation rates from cosmogenic nuclides are ~10 t km−2 yr−1 at the arid Pan de Azúcar site, ~20 t km−2 yr−1 at the semi-arid site of Santa Gracia, ~60 t km−2 yr−1 at the Mediterranean climate site of La Campana, and ~30 t km−2 yr−1 at the humid site of Nahuelbuta. A and B horizons increase in thickness and elemental depletion or enrichment increases from north (~26°S) to south (~38°S) in these horizons. Differences in the degree of chemical weathering, quantified by the chemical depletion fraction (CDF), are significant only between the arid and sparsely vegetated site and the other three sites. Differences in the CDF between the sites, and elemental depletion within the sites are sometimes smaller than the variations induced by the bedrock heterogeneity. Microbial abundances (bacteria and archaea) in saprolite substantially increase from the arid to the semi-arid sites.

Año: 2018

Palabras claves: Weathering, Denudation, Microbial abundance, Climate, Chile.

The colonial ascidian Diplosoma listerianum enhances the occurrence of the hydrozoan Obelia sp. during early phases of succession

Krüger, I., Lenz, M. and Thiel, M.

Recruitment patterns of sessile species often do not reflect the composition of the local propagule pool. This is, among other processes, attributed to the stimulation or inhibition of settlement by resident species. In an experimental study, we evaluated the effects of different densities of the ascidian Diplosoma listerianum on the settlement of the hydrozoan Obelia sp. For this, we monitored the cover of the dominant fouler Obelia sp. on vertically orientated PVC tiles, which were either bare or pre-seeded with two different densities (sparse or dense) of Diplosoma colonies, over the course of 8 weeks. The settlement tiles were deployed at two study sites in La Herradura Bay, Chile. The presence of D. listerianum enhanced the settlement or the growth or both of the colonial hydrozoan, but this effect disappeared within 4–8 weeks. Furthermore, we tested whether the initial enhancement of Obelia sp. by Diplosoma colonies goes back to the fact that larvae, which reject the ascidian tunic as a settlement substratum after a first contact, colonize nearby surfaces because of their limited mobility. However, we found no support for this assumption. We rather suggest that D. listerianum facilitated colonization indirectly by the accumulation of organic material in its vicinity and/or by its pumping activity. Initial resident-mediated enhancement of the hydrozoan was overridden by processes such as competition between later colonizers within the course of weeks and we could not detect any lasting effects of D. listerianum on the structure of the developing communities.

Año: 2018

Palabras claves: Hard-bottom communities, Settlement, Facilitation, Diplosoma listerianum, Obelia sp.

Protected areas in Chile: are we managing them?

Petit, I., Campoy, A., Hevia, M., Gaymer, C. and Squeo, F.

Background
Human population growth since the mid-1900s has been accompanied by an unsustainable use of natural resources and a corresponding impact on terrestrial and marine biota. In response, most states have established protected areas as tools to decrease biodiversity loss, being Chile one of the signatories of international conservation agreements such as the Convention on Biological Diversity (CBD) and the 2010 Aichi Targets. This study reviews the Chilean protected areas that have been created to date, with an emphasis on the existence and effectiveness of management plans for all terrestrial and marine protected areas.

Effectiveness was individually evaluated using two filters: 1) the age of the management plan and 2) the first four steps of the Protected Areas Management Effectiveness (PAME) methodology recommended by the IUCN.

Results
We show that 84 out of a total of 145 protected areas (PAs), and only five out of a total of 20 marine protected areas (MPAs), have management plans. Only 12% (N = 16) of PAs are effectively managed; while in the marine realm, no MPA has an effective plan.

Conclusions
Our results show the lack of both the effectiveness of and updates to the management plans for the vast majority of the national territory and raise the following question: is it sustainable to continue adding protected areas to the national system even though it is clear that the existing support is insufficient to meet the minimum requirements for full implementation?

Año: 2018

Palabras claves: AICHI targets, Biodiversity, Conservation, Chile, Effective management, MPA

Spatio-temporal migratory dynamics of Jasus frontalis (Milne Edwards, 1837) in Alexander Selkirk Island, Juan Fernández archipelago, Chile

Román, C., Ernst, B., Thiel, M., Manríquez, P. and Chamorro, J.

Knowledge about the spatial patterns and movements of crustaceans has gained importance since the creation of marine protected areas and the development of spatial management for benthic ecosystems. The Juan Fernández spiny lobster (Jasus frontalis) is an endemic marine species and most valuable resource that exhibits migratory dynamics in a highly spatially regulated fishery. To study movement patterns around Alexander Selkirk Island, a mark-recapture program was implemented in 2008, when approximately 7000 non-commercial (undersized) lobsters were tagged and followed for nearly 14 months. Using quantitative georeferenced data, this study revealed spatial structuring of Juan Fernández spiny lobster and tested hypotheses about alongshore and inshore-offshore movements. Eight clusters were identified around Alexander Selkirk Island, with moderate time-varying connectivity between them. Seasonal inshore-offshore movements were detected all around the island, but more conspicuously to the north. Average travelling distance was 1.2 km (1.7 sd). Our results confirmed that towards the end of austral spring males and females embark in a seasonal offshore migration to deeper waters, returning to shallower waters only during winter. These findings quantitatively consolidate the conceptual migratory model that local fishermen had already inferred for this resource from about a century of sustainable fishing.

Año: 2018

Palabras claves:

Heritability, genetic correlations and genotype-environment interactions for growth and survival of larvae and post-larvae of the Caribbean scallop, Argopecten nucleus (Mollusca: Bivalvia)

Barros, J., Winkler, F. and Velasco, L.

The Caribbean scallop Argopecten nucleus is a species with a great potential for commercial aquaculture in the Caribbean given its fast growth and the availability of culture technology. However, its production relies completely on hatchery-reared seed, and the survival in early stages, particularly during the settling process, is the main limitation for this activity to become cost effective. Thus, in order to assess the feasibility of improving survival of larvae and post-larvae of A. nucleus through genetic selection without affecting growth, it was estimated the heritability and the genotype-environment interactions for such traits, as well as the genetic correlations between them. These parameters were estimated based on intraclass correlations of 40 full-sib families (10 half-sib families) at 1, 11 and 75 days post fertilization. Heritability values were very high for the post-larvae survival (0.49), while it was low and not significant for larvae survival (≤0.07) and medium to high for growth traits of larvae and post-larvae (>0.3). The traits analyzed in post-larvae exhibited significant genotype-environment interactions in relation to culture depth in the sea. No significant genetic correlations between the measured traits were found. The results suggest the existence of an important genetic component in the variation of post-larval survival, and larval and post-larval growth, as well as a high potential response to direct genetic selection, especially for post-larval survival (50% increase per generation), without affecting the growth traits.

Año: 2018

Palabras claves: Shell length, Shell height, Post-larvae recovery, Genetic improvement, Selective breeding, Genetic gain, Pectinid

Hormonal and physiological changes driven by fungal endophytes increase Antarctic plant performance under UV-B radiation

Ramos, P., Rivas, N., Pollmann, S., Casati, P. and Molina-Montenegro, M.

Antarctic environments are amongst the most stressful habitats for life on Earth, with high intensities of solar UV-B radiation reaching the land surface. In this study, we evaluated how the photochemical efficiency, cell damage and reproductive biomass of Antarctic pearlwort (Colobanthus quitensis) were affected by different intensities of UV-B radiation in the absence and presence of fungal endophytes. In addition, we evaluated the hormonal content of plants at different UV-B radiation intensities and how hormonal content was affected by endophytes. Overall, plants exposed to UV-B radiation showed higher numbers of flowers, higher total biomass and lower lipid peroxidation in the presence of endophytes compared with plants without endophytes. Photochemical efficiency was unaffected. Fungal endophytes affected the content of salicylic acid, jasmonate, indole-3-acetate and abscisic acid in shoot tissue of plants exposed to UV-B radiation. These results suggest that endophytes could modulate the hormonal content of C. quitensis to improve its ecophysiological performance under high UV-B radiation.

Año: 2018

Palabras claves: Antarctica, Climate change, Colobanthus quitensis, Ecophysiological performance, Fungal endophytes

High acclimation potential in floating Macrocystis pyrifera to abiotic conditions even under grazing pressure – a field study

Rothäusler, E., Reinwald, H., López, B., Tala, F. and Thiel, M.

The persistence of floating seaweeds, which depends on abiotic conditions but also herbivory, had previously been mostly tested in outdoor mesocosm experiments. In order to investigate if the obtained mesocosm results of high seaweed persistence under natural environmental conditions and under grazing pressure can be extrapolated to field situations, we conducted in situ experiments. During two summers (2007 and 2008), Macrocystis pyrifera was tethered (for 14 d) to lines in the presence and absence of the amphipod Peramphithoe femorata at three sites (Iquique, Coquimbo, Calfuco). We hypothesized that grazing damage and seaweed persistence vary among sites due to different abiotic factors. By incubating the sporophytes in mesh bags, we were either able to isolate (grazing) or exclude (control) amphipods. To test for a mesh bag artifact, a set of sporophytes was incubated without mesh bags (natural). Mesh bags used to exclude herbivores influenced sporophyte growth and physiological performance. The chlorophyll a (Chl a) content depended largely on grazers and grazed sporophytes grew less than natural and control sporophytes within the two summers. A decrease in Chl a content was found for the sites with the highest prevailing irradiances and temperatures, suggesting an efficient acclimation to these sea surface conditions. Our field-based results of sporophyte acclimation ability even under grazing pressure widely align with previous mesocosm results. We conclude that M. pyrifera and other temperate floating seaweeds can function as long-distance dispersal vectors even with hitchhiking mesoherbivores.

Año: 2018

Palabras claves: Macrocystis pyrifera; Peramphithoe femorata; amphipods; herbivory; kelp rafts; solar radiation; temperature.

Geographic variation in biochemical and physiological traits of the red seaweeds Chondracanthus chamissoi and Gelidium lingulatum from the south east Pacific coast

Véliz, K., Chandía, N., Karsten, U., Lara, C. and Thiel, M.

Diverse phenotypic characteristics have evolved in seaweeds to cope with environmental stress, but these traits can vary among populations of the same species especially if these are distributed along environmental gradients. In this study, natural populations of the carrageenophyte Chondracanthus chamissoi and the agarophyte Gelidium lingulatum from a latitudinal gradient along the Chilean coast (between 20° S and 41° S) were compared. We determined physiological and biochemical traits in field and culture samples. Sulfated polysaccharide contents ranged from 15.4 to 52.7% dry weight (DW) in C. chamissoi and from 10.9 to 25.1% DW in G. lingulatum. Carrageenan amounts were higher in gametophytes than tetrasporophytes and were also, depending on life cycle phase, negatively correlated with the geographic variation of temperature, photosynthetically active radiation (PAR), and chlorophyll a (Chl a), whereas agar showed no significant correlation with these variables. The UV-absorbing mycosporine-like amino acids (MAAs) shinorine and palythine in both species ranged from 0.8 to 6.8 mg g−1 DW and these contents were positively correlated to PAR and Chl a levels at the sampling site. In C. chamissoi variation among populations in their photosynthetic characteristics, pigment concentrations, antioxidant capacity, and MAA contents were persistent after acclimation under common-garden conditions, suggesting ecotypic differentiation in this species. Contrary, G. lingulatum seems to have a more generalist strategy because differences after cultivation were observed only in some photosynthetic parameters and phycobiliprotein concentration. This study confirms that intraspecific differences in phenotypic traits along the same geographic area are strongly dependent on species and life cycle phases.

Año: 2019

Palabras claves: Rhodophyta, Carrageenans, Agar, Mycosporine-like amino acids, Ecotypes, Chile