Diversity patterns along and across the Chilean margin: a continental slope encompassing oxygen gradients and methane seep benthic habitats

In the present study we review datasets available for the Chilean margin to assess the relationship between environmental (or habitat) heterogeneity and benthic diversity. Several factors, such as the presence of different water masses, including the oxygen-deficient Equatorial Sub-surface Waters (ESSW) at the continental shelf and upper slope, and the Antarctic Intermediate Waters (AIW) at mid slope depths appear to control the bathymetric distribution of benthic communities. The presence of methane seeps and an extended oxygen minimum zone (OMZ) add complexity to the benthic distribution patterns observed. All these factors generate environmental heterogeneity, which is predicted to affect the diversity patterns both along and across the Chilean continental margin. The response to these factors differs among different faunal size groups: meio-, macro-, and megafauna. Physiological adaptations to oxygen deficiency and constraints related to body size of each group seem to explain the larger-scale patterns observed, while sediment/habitat heterogeneity ( e.g. at water mass boundaries, hardgrounds, biogeochemical patchiness, sediment organic content, grain size) may influence the local fauna diversity patterns.     

Architecture and evolution of the Paine channel complex, Cerro Toro Formation (Upper Cretaceous), Silla Syncline, Magallanes Basin, Chile

The Upper Cretaceous Cerro Toro Formation in the Silla Syncline, Parque Nacional Torres del Paine, Magallanes Basin, Chile, includes over 1100 m of mainly thin‐bedded mud‐rich turbidites containing three thick divisions of coarse conglomerate and sandstone. Facies distributions, stacking patterns and lateral relationships indicate that the coarse‐grained sandstone and conglomerate units represent the fill of a series of large south to south‐east trending deep‐water channels or channel complexes. The middle coarse division, informally named the Paine member, represents the fill of at least three discrete channels or channel complexes, termed Paine A, B and C. The uppermost of these, Paine C, represents a channel belt about 3·5 km wide and its fill displays explicit details of channel geometry, channel margins, and the processes of channel development and evolution. Along its northern margin, Paine C consists of stacked, laterally offset channels, each eroded into fine‐grained mudstone and thin‐bedded sandy turbidites. Along its southern margin, the Paine C complex was bounded by a single, deeply incised but stepped erosional surface. The evolution of the Paine C channel occurred through multiple cycles of activity, each involving: (i) an initial period of channel erosion into underlying fine‐grained sediments; (ii) deposition of coarse‐grained pebble to cobble conglomerate and sandstone within the channel; and (iii) waning of coarse sediment deposition and accumulation of a widespread sheet of fine‐grained, thin‐bedded turbidites inside and outside the channel. The thin‐bedded turbidites deposited within, and adjacent to, the channel along the northern margin of the Paine C complex do not appear to represent levée deposits but, rather, a separate fine‐grained turbidite system that impinged on the Paine C channel from the north. The Cerro Toro channel complex in the Silla Syncline may mark either an early axial zone of the Magallanes Basin or a local slope mini‐basin developed behind a zone of slope faulting and folding now present immediately east of the syncline. If the latter, flows moving downslope toward the basin axis further east were diverted to the south by this developing structural high, deposited part of their coarse sediment loads, and exited the mini‐basin at a point located near the south‐eastern edge of the present Silla Syncline.     

A comparison of the sedimentary records of the 1960 and 2010 great Chilean earthquakes in 17 lakes: Implications for quantitative lacustrine palaeoseismology

Seismically‐induced event deposits embedded in the sedimentary infill of lacustrine basins are highly useful for palaeoseismic reconstructions. Recent, well‐documented, great megathrust earthquakes provide an ideal opportunity to calibrate seismically‐induced event deposits for lakes with different characteristics and located in different settings. This study used 107 short sediment cores to investigate the sedimentary impact of the 1960 M_w 9·5 Valdivia and the 2010 M_w 8·8 Maule earthquakes in 17 lakes in South‐Central Chile (i.e. lakes Negra, Lo Encañado, Aculeo, Vichuquén, Laja, Villarrica, Calafquén, Pullinque, Pellaifa, Panguipulli, Neltume, Riñihue, Ranco, Maihue, Puyehue, Rupanco and Llanquihue). A combination of image analysis, magnetic susceptibility and grain‐size analysis allows identification of five types of seismically‐induced event deposits: (i) mass‐transport deposits; (ii) in situ deformations; (iii) lacustrine turbidites with a composition similar to the hemipelagic background sediments (lacustrine turbidites type 1); (iv) lacustrine turbidites with a composition different from the background sediments (lacustrine turbidites type 2) and (v) megaturbidites. These seismically‐induced event deposits were compared to local seismic intensities of the causative earthquakes, eyewitness reports, post‐earthquake observations, and vegetation and geomorphology of the catchment and the lake. Megaturbidites occur where lake seiches took place. Lacustrine turbidites type 2 can be the result of: (i) local near‐shore mass wasting; (ii) delta collapse; (iii) onshore landslides; (iv) debris flows or mudflows; or (v) fluvial reworking of landslide debris. On the contrary, lacustrine turbidites type 1 are the result of shallow mass wasting on sublacustrine slopes covered by hemipelagic sediments. Due to their more constrained origin, lacustrine turbidites type 1 are the most reliable type of seismically‐induced event deposits in quantitative palaeoseismology, because they are almost exclusively triggered by earthquake shaking. Moreover, they most sensitively record varying seismic shaking intensities. The number of lacustrine turbidites type 1 linearly increases with increasing seismic intensity, starting with no lacustrine turbidites type 1 at intensities between V½ and VI and reaching 100% when intensities are higher than VII½. Combining different types of seismically‐induced event deposits allows the reconstruction of the complete impact of an earthquake.     

The importance and quality of governance in the Chilean wine industry

The central theme of this paper is the issue of the governance of cooperation within the Chilean wine industry. The effects of the internationalization of this industry for the importance and the quality of governance of intra-cluster cooperation involving firms and other actors are analysed. Two questions stand central. First, what has been the relative importance of external and internal factors in improving the export performance of the Chilean wine industry over the past 20 years? Second, to what extent have collective actions and investments played a part in this growth, and what has been the quality of the various governance regimes dealing with the associated collective action problems? Empirical evidence suggests that world-market developments and upgrading efforts by individual wineries largely explain the good export performance of the Chilean wine industry until the year 2000. The evidence also shows that the industry’s success in world markets is stimulating cooperation between firms and other actors in areas where the industry needs to improve: marketing and promotion, internationalization, innovation and training. The enhanced cooperation has not only stimulated cluster development, but has also turned the quality of cluster governance into a central variable for future export growth. Nevertheless, several collective action problems await resolution before essential intra-cluster cooperation can develop. Overall, the evidence suggests that, in the case of the Chilean wine industry, industrial and cluster development do not automatically follow enhanced integration in world markets, but depend on the strategic skills of actors within the industry, in particular their ability to identify, prioritize, and realize collective investments while effectively managing the associated collective action problems. Internationalization stimulates firms to consider such investments, however, and provides them with an incentive to upgrade strategic skills at the local level as new opportunities arise and the pressure is there to exploit them in world markets.     

Larval fish assemblages in nearshore coastal waters off central Chile: temporal and spatial patterns

In this study we identified spatial and temporal patterns in the distribution and abundance of larval stages of several fish species in nearshore waters off central Chile. Larvae were sampled monthly at two close (20 km apart) but contrasting localities, El Quisco and Las Cruces. Surveys corresponded to standard plankton tows stratified according to bathymetry and distance from shore. Our results indicate that at both localities: (1) there is a seasonal reproductive pattern for most of the species studied; (2) there is a seasonal-related change in larval species composition and abundance, with austral Winter–Spring being the time of greatest diversity; (3) larval stages of several species that, as adults occupy intertidal, estuarine–riverine, subtidal, benthic-demersal, epipelagic or mesopelagic habitats, are found within these coastal environments; (4) there is a distinctive cross-shelf pattern of larval distribution, which seems to correspond, at least for the intertidal species, with the shallower (<30 m depth) portion of area surveyed; and (5) there is a coupling between the patterns of distribution and abundance of the entire ichthyoplankton assemblage with short-term physical features such as wind forcing, Ekman transport, and local currents. Our findings suggest that both the specific composition as well as the abundance of larval fish species varies spatially and temporally and that this variability may result from the interaction of physical and biological factors at different scales.     

A geomorphological approach to determining the Neogene to Recent tectonic deformation in the Coastal Cordillera of northern Chile (Atacama)

The large (≈10000 km²) and local-scale (<400 km²) geomorphologic, geomorphometric and field evidence indicates that, from the mid-Miocene onwards, the Atacama Fault System (AFS) accommodated the relative uplift of the western side of the Chilean Coastal Cordillera of the Chañaral region (southern Atacama Desert). The mean regional altitude systematically decreases eastwards crossing the AFS, independent of the lithological characteristics of the substratum cut by this system of faults. Topographic analysis reveals a more incised landscape west of the AFS that, at the local scale, is reported by the distribution of the altitudes (hypsometric curves and integrals) of tributary basins and by the presence of terraces. In the Middle and Upper Miocene, a thick (>300 m) sedimentary succession was deposited east of the AFS. The succession fills previously deep paleovalleys. And it consists of gravel, so-called “Atacama Gravels”, which passes laterally into fine-grained playa related deposits near the AFS. We interpret the deposition of this succession as a result of a blocking closure of the valley flowing from the Precordillera due to the activity on AFS. A pedimentation episode followed sediment deposition and is locally strongly re-incised by the main modern-day river valleys draining the Precordillera. Incision may result from either regional uplift of the forearc, and/or from more localized activity on the AFS. Furthermore, Recent (Quaternary?) tectonic activity on the AFS has been observed which is consistent with a localized relative uplift of the crustal block west of the AFS.     

Runoff and peak flow responses to timber harvest and forest age in southern Chile

Runoff and peak flows in three experimental catchments with different forest conditions were analysed in a rainy temperate climate in southern Chile. The hydrological effects of clearcutting a Pinus radiata plantation covering 79·4% of the La Reina catchment were studied by analysing runoff and peak flows in the pre‐ and post‐harvesting periods. Mean annual runoff increased 110% after timber harvesting. Clearcutting generated a 32% mean increase in peak flows. Peak flow and runoff were examined in two adjacent catchments with different forest conditions. The older plantation in Los Ulmos 1 increasingly consumed more water than the younger plantation established at Los Ulmos 2, whereas differences in peak flows between these two catchments were not significant. Runoff and peak flows comparisons not only reflected changes in forest cover, but also the effect of rainfall characteristics during the study periods and the basins' morphologies. Comparisons between pre‐ and post‐harvesting peak discharges must be undertaken with caution, because a previous analysis at La Reina using a partial set of data overestimated changes in peak flows after timber harvesting. Copyright © 2005 John Wiley & Sons, Ltd.     

Growth and Heterozygosity in a 12-Month-Old Cohort of Ostrea chilensis Obtained by Mass Spawning in the Laboratory

Abstract. Oysters Ostrea chilensis P hilippi 1845. from a 40-month-old cohort which came from the natural population of the Quempillen River Estuary Southern Chile, were used as parental stock n = 600 for a hatchery-produced cohort. At 12 months of age this cohort was analysed physiologically filtration rate, organic ingestion rate, absorption rate, assimilation efficiency, excretion rate, respiration rate and electrophoretically multilocus heterozygosity MLH using four loci: LAP, GPI, PGM, CA. Most physiological variables were positively correlated with dry weight P < 0.05. with the exception of assimilation efficiency, excretion size and net growth efficiency P > 0.05. Also. there was a positive correlation between body size, ingestion rate, absorption rate and net growth efficiency with MLH. Respiration rate and consequently energy losses were negatively correlated with MLH. The energetic efficiency product of a lower metabolic cost in the heterozygous individuals in this cohort is reflected in a higher net growth efficiency and a positive correlation between growth and MLH. The genetic basis for the relationship between metabolic parameters and heterozygosity can be due to an overdominance in this 12-month-old cohort.     

Density‐Dependent Effects in Jehlius cirratus (Darwin, 1854) (Cirripedia: Chthamalidae) under Different Growth Conditions

Abstract. We analyse the effects of crowding (‘hummocking’) on the growth, reproduction and mortality of the chthamaloid barnacle Jehlius cirratus ( Darwin, 1854 ) on the coast of Chile. Recruitment intensity, ranging from solitary individuals to dense groups, generates different growth conditions. Density‐dependent effects are reflected in the shape, growth parameters, fecundity, sexual maturity and mortality of solitary and crowded specimens. The skewing of size distribution during growth was not significant at the beginning of the growth period, irrespective of initial density. Nevertheless, skewness in size increased with time, both at high and low densities, indicating that the dominance and suppression exerted by larger specimens over smaller ones generate a density‐dependent effect on size during growth. Mortality was greatest when high‐density recruitment occurred immediately before the period when water temperature and food quantity are highest (spring), when it is assumed that growth is greatest; this seasonal effect was not detected at lower levels of recruitment density. Similarly, no differences in mortality were detected between recruitment densities during the period when temperatures are lowest (autumn) and growth is probably slower. In the middle‐high intertidal zone, where J. cirratus co‐exists with Notochthamalus scabrosus ( Darwin, 1854 ), the proportion of dead J. cirratus specimens was directly related both to the relative abundance of N. scabrosus and the total barnacle density. Although the mortality of J. cirratus was density dependent, the increase in the number of N. scabrosus towards the lower section of the middle intertidal zone could have a greater effect on J. cirratus mortality than intra‐specific competition.