Publicaciones

Linking human activity and ecosystem condition to inform marine ecosystem based management.

Menzel, S., Kappel, C., Broitman, B., Micheli, F., & Rosenberg, A.

There is growing consensus that integrated marine management is needed. However, implementation of ecosystem-based management (EBM) faces major operational challenges, including accurately delineating the links between ecosystem components and benefits to humans, and quantifying trade-offs associated with different management decisions.
It is suggested using human activity level as an indicator of the benefit provided by marine ecosystems at a certain location in comparison with other locations and establishing links between human activity levels and ecological conditions.
This approach allows for the determination of what ecological conditions may provide the greatest human benefits and thus may be targets for management action.
This approach is used to investigate the link between scuba diving in the Monterey Bay area, California, USA, and different ecological characteristics of kelp forests. Diving intensity levels correlate with kelp persistence, suggesting that kelp persistence may be used as an indicator of benefits from diving and for evaluating the impact of potentially competing activities through their effects on kelp.
Overall, an operational definition of marine ecosystem services is provided and it is suggested that this method could be extended to a suite of different activities and systems and thus may become useful in considering trade-offs among different activities that depend upon the same ecosystem.

Año: 2013

Palabras claves: Ecosystem services; natural resource management; ecological indicators; Monterey Bay; California; kelp forest ecosystem; scuba diving; ecological production function; human benefits from ecosystems.

Spatial niche differentiation and coexistence at the edge: co-occurrence distribution patterns in Scurria limpets.

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

Examining the co-occurrence of taxonomically similar species can provide important information about their niches and coexistence. Segregation at smaller scales can be especially relevant for grazers living at the edge of their geographic distribution, because environmental factors can lead to similar distribution. Related grazer species may show dispersive, i.e. uniform, distribution at small scales (few centimetres) to reduce interference among individuals. We examined intra- and interspecific spatial distribution and habitat use in 2 phylogenetically related intertidal limpets, Scurria viridula and S. zebrina, at the polar and equatorial edge of their geographic distribution, respectively, and in S. araucana, a widely distributed species that overlaps the range of the other 2 species across the southeastern Pacific. S. viridula and S. zebrina overlapped in a narrow geographic zone (ca. 250 km) and reached relatively similar densities and sizes. Intraspecific spatial structure estimated through autocorrelation and individual-to-individual distances was random for S. viridula and variable for S. zebrina and S. araucana, depending on the scale considered; S. zebrina was aggregated at the individual-to-individual distances, while S. araucana was mostly random at this scale. Segregated distribution between S. viridula and S. zebrina was observed at the finer scale, whereas the association with S. araucana was random. Abundance of limpets loosely followed major habitats, namely bare rock and the alga Mazzaella laminarioides, which showed patchy distributions. We suggests that similarity in population traits between S. viridula and S. zebrina found in the overlap zone may be compensated by small-scale spatial segregation. Thus, at the edge of their geographic distribution, coexistence between related species may be influenced by spatial niche differentiation driven by habitat suitability or competition.

Año: 2013

Palabras claves: Coexistence, Geographic edge, Grazers, Habitat type, Niche partitioning, Nearest neighbour, Spatial autocorrelation.

Differential effects of grazer species on periphyton of a temperate rocky shore.

Aguilera, M., Navarrete, S., & Broitman, B.

Species-specific traits are relevant to understand variation in the effect of grazers on primary producers and are critical in determining their functional roles as controllers of productivity in marine ecosystems. In intertidal habitats, periphyton, composed of bacteria, cyanophytes, microalgae and early stages of macroalgae, constitutes the main food for many benthic grazers. Using field experiments, we examined the overall effect of grazers and the importance of direct and indirect effects of different grazer species on periphyton composition, richness, diversity and productivity. We manipulated the main grazer species present along Chilean rocky shores, enclosing adult individuals of the keyhole limpet Fissurella crassa, the chiton Chiton granosus, the scurrinid limpet Scurria araucana and the pulmonate limpet Siphonaria lessoni. These organisms overlap broadly in diet but exhibit differences in foraging behavior. Differences in the individual effects of grazer species on periphyton productivity, as well as on richness and diversity characterized the assemblage. C. granosus grazing led to lower periphyton productivity, richness and diversity compared with all other grazers, who had positive effects for all variables. Richness and diversity of the major periphyton groups were maximal at intermediate levels of total grazing pressure, highlighting the importance of ecological interactions within the periphyton assemblage. Our results demonstrate the complexity of functional roles and relationships of grazers involved in the control of composition and production of the periphyton assemblage. Given the importance of direct and indirect effects of grazers, understanding species interactions within the microbenthic community can shed light on the mechanisms through which herbivores modify community structure and productivity.

Año: 2013

Palabras claves: Grazer assemblage, Periphyton, Productivity, Diversity, Foraging behavior.

Mesoscale Variation of Mechanisms Contributing to Stability in Rocky Shore Communities.

Valdivia N, González AE, Manzur T, Broitman BR.

Environmental fluctuations can generate asynchronous species’ fluctuations and community stability, due to compensatory dynamics of species with different environmental tolerances. We tested this hypothesis in intertidal hard-bottom communities of north-central Chile, where a persistent upwelling centre maintains a mosaic in sea surface temperatures (SST) over 10s of kilometres along the shore. Coastal upwelling implies colder and temporally more stable SST relative to downstream sites. Uni- and multivariate analyses of multiyear timeseries of SST and species abundances showed more asynchronous fluctuations and higher stability in sites characterised by warmer and more variable SST. Nevertheless, these effects were weakened after including data obtained in sites affected by less persistent upwelling centres. Further, dominant species were more stable in sites exposed to high SST variability. The strength of other processes that can influence community stability, chiefly statistical averaging and overyielding, did not vary significantly between SST regimes. Our results provide observational evidence supporting the idea that exogenously driven compensatory dynamics and the stabilising effects of dominant species can determine the stability of ecosystems facing environmental fluctuations.

Año: 2013

Palabras claves: Community ecology, Algae, Barnacles, Ecosystems, Oceanography, Surface temperature, Taxonomy, Species interactions.

Influence of Pacific Ocean multidecadal variability on the distributional properties of hydrological variables in north-central Chile.

Núñez, J., Rivera, D., Oyarzún, R., & Arumí, J.

This paper addresses the relationship between multitemporal variability and regime shifts in the Pacific Decadal Oscillation and El Niño Southern Oscillation, with precipitation and streamflows in Andean watersheds of the north-central region of Chile. In addition, an analysis of the effect of a regime shift displayed by annual streamflow records on their distributional properties is performed. By applying empirical fluctuation processes to monthly standardized PDO, Niño 3.4, precipitation and streamflow time series, the occurrence of a regime shift in the streamflow series, consistent with that for PDO, but highly dependent on the latitude of particular watersheds, is shown. No regime shift is detected for the precipitation time series. Using the ensemble Empirical Mode Decomposition procedure on all series, a relationship between climatic indices and hydrological variables in two main modes is determined: the former associated with a mean period of quasi 1.5–3 years related to interannual variability, and the latter with a mean period of quasi 30–35 years, related to decadal low frequency variability. Using the regional frequency analysis based on the L-moments procedure, it is found that the distributional properties of streamflow records are influenced by the phases of the PDO, with changes that affect the mean, L-CV, L-skewness and L-kurtosis in three identified homogeneous regions. The importance of incorporating low-frequency climate variability for distributional analysis and the implications of these results for water resources management and planning in north-central Chile and similar areas is discussed.

Año: 2013

Palabras claves: Climate variability; Distributional analysis; L-moments; Pacific Decadal Oscillation; Empirical Mode Decomposition.

Seasonal sediment fluxes forcing supraglacial melting on the Wright Lower Glacier, McMurdo Dry Valleys, Antarctica.

MacDonell, S., Fitzsimons, S., & Mölg, T.

Cold-based glaciers exist in low temperature and low humidity environments in which shortwave radiation is the largest source of energy to the glacier surface and the energy budget is very sensitive to the surface albedo. Consequently, the presence of relatively low volumes of debris on glacier surfaces has a significant impact on the timing, magnitude and rate of ablation at the surface. The aim of this study is to understand how the presence of sediment on the glacier surface at the start of the melt season can affect meltwater generation and delivery on a cold-based glacier. A combination of field measurements, energy balance modelling and chemical mixing modelling were used on the Wright Lower Glacier, McMurdo Dry Valleys, Antarctica, between October 2005 and January 2006 to address this aim. In this system, sediment was transported onto the glacier surface during the winter months (March–October) by foehn winds, which reduced surface albedo at the start of the summer melt season. The areas of the glacier on which sediment accumulated began to melt earlier than other parts of the glacier and experienced a longer melt season. Over the study period, the total ablation on the dirty surfaces was nine times greater than for clean ice. Ablation on the dirty surfaces is dominated by melting, whereas sublimation dominates the clean ice. As the sediment was unevenly distributed over the glacier surface, the variation in melt amount and timing drove the development of a cryoconite hole system. Copyright © 2012 John Wiley & Sons, Ltd.

Año: 2013

Palabras claves: Glacier hydrology; cryoconite hole; glacier energy balance; hydrochemistry.

Evidencing a large body of ice in a rock glacier, Vanoise Massif, Northern French Alps.

Monnier, S., Camerlynck, C., Rejiba, F., Kinnard, C., & Galibert, P.

The Sachette rock glacier is an active rock glacier located between 2660 and 2480 m a.s.l. in the Vanoise Massif, Northern French Alps (45° 29′ N, 6° 52′ E). In order to characterize its status as permafrost feature, shallow ground temperatures were monitored and the surface velocity measured by photogrammetry. The rock glacier exhibits near-surface thermal regimes suggesting permafrost occurrence and also displays significant surface horizontal displacements (0.6–1.3 ± 0.6 m yr–1). In order to investigate its internal structure, a ground-penetrating radar (GPR) survey was performed. Four constant-offset GPR profiles were performed and analyzed to reconstruct the stratigraphy and model the radar wave velocity in two dimensions. Integration of the morphology, the velocity models and the stratigraphy revealed, in the upper half of the rock glacier, the good correspondence between widespread high radar wave velocities (>0.15–0.16 m ns–1) and strongly concave reflector structures. High radar wave velocity (0.165–0.170 m ns–1) is confirmed with the analysis of two punctual common mid-point measurements in areas of exposed shallow pure ice. These evidences point towards the existence of a large buried body of ice in the upper part of the rock glacier. The rock glacier was interpreted to result from the former advance and decay of a glacier onto pre-existing deposits, and from subsequent creep of the whole assemblage. Our study of the Sachette rock glacier thus highlights the rock glacier as a transitional landform involving the incorporation and preservation of glacier ice in permafrost environments with subsequent evolution arising from periglacial processes.

Año: 2013

Palabras claves: Rock glacier; ground-penetrating radar; ice.

Use of 222 radon as a simple tool for surface water-groundwater connectivity assessment: a case study in the arid Limarí basin, north-central Chile.

Oyarzún, R., Jofré, E., Maturana, H., Oyarzún, J., & Aguirre, E.

We report the results from a pilot study on the use of 222Rn (222radon) for river–aquifer interaction assessment in the Limarí watershed, north-central Chile. Previous studies on this tool for such applications are not abundant at international level, and no records exist for Chile. The lowest 222Rn levels (less than 1000 Bq/m3) were found in water reservoirs, thus indicating that this isotope is easily lost (and therefore usually absent) in surface waters. Conversely, the highest levels of 222Rn were found in groundwater, with maxima activities around 20 000 Bq/m3. This remarkable contrast allowed clear identification of zones of surface water–groundwater connectivity in the searched watershed domain.

Año: 2013

Palabras claves: Environmental tracer; radioactive isotope; watershed hydrology.

Internal structure and composition of a rock glacier in the Andes (upper Choapa valley, Chile) using borehole information and ground-penetrating radar.

Monnier, S. & Kinnard, C.

This study uses boreholes, ground temperature monitoring and ground-penetrating radar (GPR) in order to understand the internal structure and composition of a rock glacier in the upper Choapa valley, northern Chile. The rock glacier is a small valley-side feature, 200 m long and ranging between 3710 and 3780 m a.s.l. Two boreholes were drilled down to depths of 20 and 25 m, respectively, using the diamond drillhole technique. An ice–rock mixture was encountered in the boreholes, with heterogeneous ice content averaging 15–30%. Data from common-midpoint (CMP) and constant-offset (CO) GPR surveys acquired, respectively, near the boreholes and across the whole rock glacier were processed to highlight the internal stratigraphy and variations in the radar-wave velocity. The GPR profiles depict a rock glacier constituted of stacked and generally concordant layers, with a thickness ranging from 10 m in its upper part to ∼30 m towards its terminus. The CMP analysis highlights radar-wave velocities of 0.13–0.16 m ns–1 in the first 20 m of the structure. Larger vertical and lateral velocity variations are highlighted from CO data, reflecting the heterogeneous composition of the rock glacier and the likely presence of unfrozen water in the structure. Given the average air temperature registered at the site (+0.5°C), the near-melting-point temperature registered in the boreholes over more than a year and the presence of locally high water content inferred from GPR data, it is thought that the permafrost in the rock glacier is currently degrading.

Año: 2013

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