Coast Of Central Chile Research Articles

Influence of large scale oscillations on upwelling‐favorable coastal wind off central Chile

Along the central coast of Chile is typically equatorward, upwelling‐favorable wind associated with the southeast Pacific anticyclone. A coastal low‐level jet often develops, and its wind speed is mostly controlled by the meridional pressure gradient. While the low‐level jet is a mesoscale feature forced by an interaction between synoptic conditions and coastal topography, regional sea level pressure anomalies are associated with changes of the Antarctic, Madden Julian, and El Niño–Southern Oscillation. The connection between the alongshore wind and changes to the large‐scale circulation is examined and quantified using 31 years of the Climate Forecast System Reanalysis, which resolves coastal features better than previous, coarser analyses. Composites based on each index reveal the modulation of the sea level pressure and significant alongshore wind anomalies of ±0.5–1.5 m s−1 that correlate well to meridional surface pressure gradient changes and are centered near 35°S. Constructive and destructive interference exists between the three indices that either enhance or cancel the alongshore wind anomaly. During favorable upwelling conditions the distribution of meridional wind is generally clustered around positive anomalies with a tail toward negative values, representing a stronger and persistent anticyclone. During unfavorable upwelling conditions the anomalies are generally more normally distributed, representing a weaker anticyclone and the passage of more cyclones.

A novel phytomyxean parasite associated with galls on the bull-kelp Durvillaea antarctica (Chamisso) Hariot.

Durvillaea antarctica (Fucales, Phaeophyceae) is a large kelp of high ecological and economic significance in the Southern Hemisphere. In natural beds along the central coast of Chile (Pacific Ocean), abnormal growth characterized by evident gall development and discolorations of the fronds/thallus was observed. Analysing these galls by light microscopy and scanning electron microscopy revealed the presence of endophytic eukaryotes showing typical characteristics for phytomyxean parasites. The parasite developed within enlarged cells of the subcortical tissue of the host. Multinucleate plasmodia developed into many, single resting spores. The affiliation of this parasite to the Phytomyxea (Rhizaria) was supported by 18S rDNA data, placing it within the Phagomyxida. Similar microorganisms were already reported once 23 years ago, indicating that these parasites are persistent and widespread in D. antarctica beds for long times. The symptoms caused by this parasite are discussed along with the ecological and economic consequences. Phytomyxean parasites may play an important role in the marine ecosystem, but they remain understudied in this environment. Our results demonstrate for the first time the presence of resting spores in Phagomyxida, an order in which resting spores were thought to be absent making this the first record of a phagomyxean parasite with a complete life cycle so far, challenging the existing taxonomic concepts within the Phytomyxea. The importance of the here described resting spores for the survival and ecology of the phagomyxid parasite will be discussed together with the impact this parasite may have on ‘the strongest seaweed of the world’, which is an important habitat forming and economic resource from the Southern Hemisphere.

New insights into the life-history of the isopod Edotia dahli (Valvifera: Idoteidae): report of host-use and distribution records in the central Chilean coast

Unreported aspects of the life-history of the isopod Edotia dahli are described based on intertidal collections carried out during 2002, 2005 and 2011 in 5 locations in central Chile (29-33°S; Pacific coast). Isopods were recorded for the first time living on 2 species of echinoderms, the sea-star Heliaster helianthus and the sea-urchin Arbacia sp. The observation of sea-urchins hosting isopods was casual (i.e., no formal samplings); however, nearly 20% of the sampled sea-stars hosted isopods (from 2 to > 100 individuals per host). This association was similar through years. Surveys also revealed that E. dahli was present at higher latitudes than those previously recorded in the central Chilean coast, extending the northern distribution range 3° to 29°S.

Coseismic Tectonic Surface Deformation during the 2010 Maule, Chile, Mw8.8 Earthquake

Tectonic deformation from the 2010 Maule (Chile) Mw8.8 earthquake included both uplift and subsidence along about 470 km of the central Chilean coast. In the south, deformation included as much as 3 m of uplift of the Arauco Peninsula, which produced emergent marine platforms and affected harbor infrastructure. In the central part of the deformation zone, north of Constitución, coastal subsidence drowned supratidal floodplains and caused extensive shoreline modification. In the north, coastal areas experienced either slight uplift or no detected change in land level. Also, river-channel deposition and decreased gradients suggest tectonic subsidence may have occurred in inland areas. The overall north-south pattern of 2010 coastal uplift and subsidence is similar to the average crestal elevation of the Coast Range between latitudes 33°S and 40°S. This similarity implies that the topography of the Coast Range may reflect long-term permanent strain accrued incrementally over many earthquake cycles.

Behaviour of fish by‐catch in the mouth of a crustacean trawl

The behaviour of fish by-catch was recorded and characterized by in situ observations in the mouth of a crustacean trawl using an underwater camera system with artificial light, at depths between 106 and 461 m, along the central coast of Chile. The groups or species studied were rattails (family Macrouridae), Chilean hake Merluccius gayi gayi, sharks (orders Carcharhiniformes and Squaliformes), skates (family Rajidae), flatfishes (genus Hippoglossina) and small benthopelagic and demersal fishes (orders Osmeriformes, Stomiiformes, Gadiformes, Ophidiiformes and Perciformes). The fish behaviour was categorized in terms of (1) position in the water column, (2) initial orientation with respect to the trawl, (3) locomotion and (4) swimming speed with respect to the trawl. Rattails, sharks, skates and flatfishes were passive in response to the trawl and showed similar behavioural patterns, with most fishes observed sitting or touching the bottom with no swimming or other activity. Merluccius gayi gayi was the most active species, displaying a wide combination of behavioural responses when the trawl approached. This species showed several behavioural patterns, mainly characterized by swimming forward at variable speed. A fraction of small bentho-pelagic and demersal fishes also showed an active behaviour but always at lower speed than the trawl. The species-specific differences in behaviour in the mouth of the trawl suggest that improvements at the level of the footrope can be made to reduce by-catch, especially of passive species.

Seasonal variability of turbid river plumes off central Chile based on high-resolution MODIS imagery

We have studied the seasonal variability of four turbid river plumes along the central Chilean coast using daily, high-resolution images of surface turbidity from MODIS (Moderate Resolution Imaging Spectroradiometer) in combination with measurements of wind, river flow, and hydrographic data. Atmospherically corrected MODIS data reveal strong seasonal variability in the areal extent of plume water, as well as in turbidity levels, which are significantly correlated with seasonality in river discharge. A seasonal climatology of turbid plume patterns shows individual plumes merging into an extensive body of turbid waters attached to the coast during fall (April–June)–winter (July–September) (occurs about 10% of days in fall–winter). During spring (October–December) and summer (January–March), the individual plumes remain distinct and occupy a smaller area close to the coast, when observed (evident on less than 30% of days in spring–summer). In spring–summer most plumes are detected for the northern rivers (Mataquito and Maule). When the plumes merge into a coastal band in fall–winter, a turbid area of more than 1000km2 is observed in the study area between 34.85°S and 37.15°S. This occurs following peaks in river discharge combined with the effect of strong southward (downwelling-favorable) winds. An analysis of key non-dimensional numbers shows that buoyancy dominates plume dynamics during summer, whereas inertial forcing associated with river outflow is more important in winter near the coast. Farther offshore (>10km), the effects of rotation and wind tend to dominate the plume dynamics.

Large extensional aftershocks in the continental forearc triggered by the 2010 Maule earthquake, Chile

SUMMARY The Mw 8.8 Maule earthquake occurred off the coast of central Chile on 2010 February 27 and was the sixth largest earthquake to be recorded instrumentally. This subduction zone event was followed by thousands of aftershocks both near the plate interface and in the overriding continental crust. Here, we report on a pair of large shallow crustal earthquakes that occurred on 2010 March 11 within 15 min of each other near the town of Pichilemu, on the coast of the O’Higgins Region of Chile. Field and aerial reconnaissance following the events revealed no distinct surface rupture. We infer from geodetic data spanning both events that the ruptures occurred on synthetic SW-dipping normal faults. The first, larger rupture was followed by buried slip on a steeper fault in the hangingwall. The fault locations and geometry of the two events are additionally constrained by locations of aftershock seismicity based on the International Maule Aftershock Data Set. The maximum slip on the main fault is about 3 m and, consistent with field results, the onshore slip is close to zero near the surface. Satellite radar data also reveal that significant aseismic afterslip occurred following the two earthquakes. Coulomb stress modelling indicates that the faults were positively stressed by up to 40 bars as a result of slip on the subduction interface in the preceding megathrust event; in other words, the Pichilemu earthquakes should be considered aftershocks of the Maule earthquake. The occurrence of these extensional events suggests that regional interseismic compressive stresses are small. Several recent large shallow crustal earthquakes in the overriding plate following the 2011 Mw 9.0 Tohoku-Oki earthquake in Japan may be an analogue for the triggering process at Pichilemu.

Potential changes in larval dispersal and alongshore connectivity on the central Chilean coast due to an altered wind climate

[1] Climate change is likely to result in significant alterations in the atmospheric and oceanic circulation, which may, as a result, affect species that depend on an ocean-driven nutrient supply and particularly those that possess a dispersal phase in their life history. In this paper we investigate the potential changes in larval dispersal and connectivity of marine populations on the Chilean coast due to altered wind forcing consistent with a future climate change scenario. Numerical ocean simulations forced by modeled present-day and future winds under the Intergovernmental Panel on Climate Change A2 scenario are used to investigate the potential changes in nearshore circulation. Off-line particle-tracking simulations are then analyzed to determine resulting changes in larval dispersal and connectivity under each scenario as a function of pelagic larval duration and for two different possible larval behaviors: passive and vertical migration. It is found that the projected future winds drive an intensification of the upwelling circulation, which results in a relative annual mean surface cooling of 1°C over much of the domain, an increase in the strength of the poleward undercurrent, and a more energetic mesoscale eddy field. Neutrally buoyant larvae are inferred to have low rates of settlement under present conditions and are more strongly disadvantaged under the simulated future conditions than larvae with vertically migrating behavior. Larvae that posses an ability to sink out of the surface Ekman layer are found to have higher rates of settlement under present conditions and are, in fact, favored slightly in the A2 scenario for pelagic larval durations longer than 2 days. This behavior-dependent response to future conditions may potentially drive a reorganization of coastal communities.

Standardization of the catch per swept area (CPUA) for direct stock assessment cruises of nylon shrimp (Heterocarpus reedi) (1998-2006)

This work analyzes the operational data of direct stock assessment cruises carried out on nylon shrimp (Heterocarpus reedi) off the central coast of Chile between 1998 and 2006. These data were modeled using the product of the expected CPUA (catch per unit area) for hauls with catch and the probability of catch (that is, catch greater than zero) to estimate the CPUA. A generalized linear model was applied; the model used four effects as factors: year, zone, depth layer, and year-zone interaction. The results showed that the year was the most relevant effect, followed by the year-zone interaction for each model analyzed. The effects of the year of the assessment and the probability of catch showed sustained growth during the study period. The interaction effect showed growth in the shrimp population mainly from Valparaiso southward. Moreover, we found that shrimp abundance was related positively to the probability of catch and inversely to the area of aggregation of the population. Finally, the discrepancy found between the analyzed abundance indexes and the biomass (particularly north of 32°S) due to the geomorphological characteristics of the sea floor and the diverse methodological criteria used in the "swept-area" assessment of this species leads us to we recommend CPUA modeling as the best option for obtaining a relative abundance index comparable over time and space.

A quasi-experimental setting of coarse clast transport by the 2010 Chile tsunami (Bucalemu, Central Chile)

On 27th February, 2010 a M W 8.8 earthquake occurred in central Chile, causing a tsunami that severely affected the central Chilean coast. In this study we present sedimentological data of the 2010 Chile tsunami from the coastal town of Bucalemu in Central Chile. The tsunami deposited both fine grained sediments as well as cobbles and boulders. The location offers a quasi-experimental setting for coarse clast transport because an artificial pile of cobbles and boulders was piled there for construction purposes some days before the tsunami. Therefore, the pre-tsunami transport setting and transport distances are well defined. Additionally, a local flow depth of ca. 2 m and flow speed of ca. 5.6 m/s are deduced from eyewitness reports and video recordings. The cobbles and boulders have been transported up to 155 m from the pile in landward direction. The size of the quarried clasts was restricted to max. 0.3 m 3 and 720 kg. Bigger boulders were not available at the location, even though calculations show that the tsunami would have been capable to transport them. Calculations of flow speeds required for the initialization of transport in different modes, such as sliding, rolling or saltation, indicate that all clasts that were moved by the tsunami in landward direction, were entrained by the flow given a minimum observed speed of 5.6 m/s, with 65% being transported by rolling and 35% by saltation. The transported clasts are arranged in three groups positioned in morphological depressions on the coastal plain. A landward fining trend is not present. The arrangement of clasts originating from a pile and being deposited in distinctive groups, entails that the landward transport of cobbles and boulders is a function of repeated entrainment, transport and deposition by several waves of the tsunami wave train. Consequently, we interpret the clast distribution as a result of a combination of the number of individual waves of the tsunami wave train, their respective energies, the local topography, and the pre-transport setting of a clast pile which releases wedged clasts with each successive wave.

Geological effects and implications of the 2010 tsunami along the central coast of Chile

Geological effects of the 2010 Chilean tsunami were quantified at five near-field sites along a 200 km segment of coast located between the two zones of predominant fault slip. Field measurements, including topography, flow depths, flow directions, scour depths, and deposit thicknesses, provide insights into the processes and morphological changes associated with tsunami inundation and return flow. The superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions. The most likely explanation for the diverse directions and timing of coastal inundation combines (1) variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with (2) resonant amplification of coastal edge waves. Other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of Peru. Coastal embayments amplified the maximum inundation distances at two sites (2.4 and 2.6 km, respectively). Tsunami vertical erosion included scour and planation of the land surface, inundation scour around the bases of trees, and channel incision from return flow. Sheets and wedges of sand and gravel were deposited at all of the sites. Locally derived boulders up to 1 m in diameter were transported as much as 400 m inland and deposited as fields of dispersed clasts. The presence of lobate bedforms at one site indicates that at least some of the late-stage sediment transport was as bed load and not as suspended load. Most of the tsunami deposits were less than 25 cm thick. Exceptions were thick deposits near open-ocean river mouths where sediment supply was abundant. Human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible, including flow histories, boulder dispersion, and vegetation controls on deposit thickness.

Un caso de baja segregada en niveles altos en el sur de Sudamérica: descripción del ciclo de vida y su relación con la precipitación

En este trabajo se analiza el ciclo de vida de una baja segregada que afectó el sur de Sudamérica entre el 26 de Marzo y el 2 de Abril del 2007 y se explora la relación existente entre las diferentes etapas de este sistema y la precipitación ocurrida sobre la franja central de Argentina. Además se evalúa si otros procesos coadyuvaron para la ocurrencia de la misma. Las características más relevantes de este sistema son su larga duración y el lento desplazamiento, ya que entre el inicio y el fin de su vida se desplaza sólo 780 km, manteniéndose estacionario, durante las etapas de segregación y madurez, por más de 56 hs frente a la costa central chilena. Esta última característica favorece la formación de un sistema de baja presión sobre el noroeste de Argentina y la persistencia de una corriente en chorro en capas bajas del norte que se extiende desde el centro de Bolivia hasta norte argentino. La masa de aire con características tropicales conducida por esta configuración y la convergencia en niveles bajos favorecieron el desarrollo convectivo. La precipitación acumulada durante estas etapas, en algunas regiones del sur del litoral argentino, superó los 300 mm, produciendo extensas inundaciones en la región. Durante la etapa de decaimiento (96 hs de duración), el sistema se debilita a medida que se desplaza hacia el este y las precipitaciones afectaron las provincias del centro-oeste de Argentina donde la lluvia en 48 horas duplicó el promedio mensual de marzo.

Shelf resonance and impact of near-field tsunami generated by the 2010 Chile earthquake

[1] The 2010 Chile earthquake of Mw 8.8 generated a destructive tsunami in the near field that resulted in warnings across the Pacific. Numerical modeling shows trapping and amplification of the energy over the continental shelf and slope. A spectral analysis of the computed surface elevation reveals resonance oscillations with periods up to 129 min along the central Chile coast. The temporal and spectral data provides an explanation for the long-period waves recorded by DART buoys and the prolonged wave activities and belated impacts reported by residents and survey teams. The present study of the 2010 Chile tsunami together with those of the 2006 Kuril and 2009 Samoa tsunamis has directly associated shelf resonance with impacts on insular and continental coasts and provided a tool to identify at-risk localities in tsunami hazard assessment.

Evaluation of potential hazards from teletsunami in China: Tidal observations of a teletsunami generated by the Chile 8.8 M w earthquake

At 14:34 Beijing time on February 27, 2010, an earthquake of M w 8.8 rocked the central coast of Chile. A teletsunami was triggered by the huge earthquake and then propagated across the entire Pacific in less than 24 h. The initial tsunami wave arrived at the southeast coast of China at 16:20 on February 28 and was recorded in real time by a number of tidal gauges off mainland China and Taiwan Province. The teletsunami waves have never been recorded with such a broad geographical scope in China before this event. The aim of the present work is to report the first description of sea-level oscillations generated by the Chile tsunami, and evaluate the potential hazards that teletsunami poses to the coast of China. The results reveal that the east coast of Taiwan Province, Zhejiang Province and the north coast of Fujian Province are vulnerable to transoceanic tsunami. In addition, spectral and wavelet analysis of the recorded sea-level oscillations shows that “seiches” are easily excited by the resonance resulting from the interaction between the initial tsunami waves and local geometry (such as semi-enclosed bays and ports). The superimposition of the two oscillations would amplify the wave height further.

Endoparasite fauna of five Gadiformes fish species from the coast of Chile: host ecology versus phylogeny

The aims of the present study were to compare, using multivariate analyses, the degree of similarity of the endoparasite fauna of five fish species belonging to the order Gadiformes: Merluccius gayi, Merluccius australis, Macruronus magellanicus (Gadoidei) and Micromesistius australis and Nezumia pulchella (Macrouroidei), from the southern and central Chilean coast, and to evaluate whether the composition of the endoparasite fauna was determined by phylogenetic or ecological relationships. We employed our database of Merluccius australis, M. magellanicus and Micromesistius australis, which was complemented with published information for M. magellanicus, Merluccius australis, Micromesistius australis, M. gayi and N. pulchella. A higher number of endoparasite species was recorded for Merluccius australis, Micromesistius australis and M. magellanicus, namely Anisakis sp. and Hepatoxylon trichiuri, which is the most prevalent parasite among these hosts. Aporocotyle wilhelmi and Hysterothylacium sp. were detected only in M. gayi, whereas Lepidapedon sp. was found exclusively in N. pulchella. These results suggest that fish ecology rather than host phylogeny was the most important factor for the determination of similarity in parasite composition. This result could be explained by the similar trophic patterns of hosts and by the predominance of generalist larval species among these fish parasite communities.

Gomortega keule, the neglected and endangered Chilean fruit tree

Gomortega keule (Mol.) Baillon is the only species belonging to the family Gomortegaceae and is regarded as an ancient surviving lineage within the Laurales. The tree is restricted to a small geographical area of the coast of central Chile, where it is in danger of extinction. Its edible fruits and excellent quality wood have been known from the earliest records of the species in the sixteenth and seventeenth centuries. This review consolidates many publications that are dispersed in the literature, covering aspects of taxonomy, morphology, systematics, propagation, biogeography, ecology, conservation and ethnobotany. Large gaps are present in our knowledge of the species, since many cited publications provide only brief descriptions or statements on diverse aspects of the tree. A limited number of publications represent formal research effort. Surprisingly, there is no major initiative aimed at the systematic cultivation of Gomortega, which is an excellent candidate for domestication, especially for fruit production.

Quaternary origin of the inverse latitudinal diversity gradient among southern Chilean mollusks

Mollusks along the Pacific coast of South America provide one of the main exceptions from the latitudinal diversity gradient of decreasing species numbers toward the poles. From 42 degrees S southward, coincident with the onset of the mosaic coastline of the southern Chilean fiord-lands, species numbers show a twofold to threefold increase compared to the central Chilean coast. Here we use the Neogene fossil record of central and southern Chile to test hypotheses on the origin of this unusual pattern. Contrary to previous suggestions, we did not find evidence for a buildup of biodiversity since the Eocene, or for the northward spread of Antarctic taxa into southern mid-latitudes. Rather, our data suggest that the mosaic coastline south of 42 degrees S was colonized after the retreat of the glaciers from their marine termini since the later Pleistocene, by taxa that were already present along the Chilean coast. The majority of the most species-rich genera in this area are shallow-water hardground inhabitants, suggesting a rapid adaptive radiation of these taxa. The unusually low present-day diversity to the north of 42 degrees S most likely results from the severe late Neogene extinction and only moderate subsequent origination in this area.

Ontogenetic Variation in Parasite infracommunities of the Clingfish Sicyases sanguineus (Pisces: Gobiesocidae)

This study analyzed the variation of the parasite infracommunities and their relationship with the diet and spatial distribution of the clingfish Sicyases sanguineus during its ontogeny. In total, 154 clingfish were collected from the intertidal and the upper subtidal zone of Pacific Ocean along the central Chilean coast. A wide range in body length (1.4-34.5 cm) was observed, including juvenile and adult specimens. Eleven parasite species were found in the clingfish, i.e., 2 Copepoda, 2 Hirudinea, 1 Monogenea, 5 Digenea, and 1 Cestoda. The prevalence, total abundance, Brillouin's diversity index, and the infracommunity species richness increased with fish body length. The parasite communities, the diet, and the spatial distribution changed during clingfish ontogeny, specifically between juveniles (<20 cm body length [BL]) and adults (>20 cm BL). When fish reached a 20-cm BL, a considerable increment in abundance and species richness of parasites was observed; this coincided with an increase in the number of prey items in the diet and with a change of the fish from the intertidal into the subtidal zone. Therefore, the ontogeny of S. sanguineus is important for the variation of parasite infracommunities, which also was associated with dietary and spatial distribution shifts of this fish.

New records of aplousobranch ascidians from Central Chile

Seven shallow-water colonial ascidians of the order Aplousobranchia, including three new species, are identified in the material collected by SCUBA divers off the coast of Central Chile. Three species including Aplidium falclandicum, A. fuegiense and Didemnum studeri were known previously from Subantarctic and South Chile. The range of one species, Distaplia arnbackae n. sp., extends to south to Guaitecas Islands, and the rest three species (Aplidium peruvianum, Aplidiopsis chilensis n. sp. and Eudistoma clivosum n. sp.) are not known from more southern localities and may represent a northern component.

Finding of a Holocene marine layer in Algarrobo (33°22'S), central Chile. Implications for coastal uplift

A buried Holocene marine bed was discovered upon drilling a water well in Algarrobo (33°22'S), located on the coast of central Chile. Radiocarbon dating of a wood fragment found within the deposit indicates an age of 6450 cal yr BP. The top of this bed, 0.25 m-thick, was reached at an elevation of 3.8 m above mean sea level. This bed contains abundant monospecific faunas of foraminifers (Ammonia tepida) and ostracodes (Cyprideis beaconensis), indicative of deposition in a very shallow, transitional marine environment. Palynologic analysis reveals a Chenopodiaceae-dominated (~70%) assemblage, indicating a relatively arid and warm climate.