Morphological variability of intertidal Eisenia arborea (Laminariales, Ochrophyta) at Punta Eugenia, Baja California Sur
Parada, G., Riosmena-Rodriguez, R., Martinez, E., & Hernandez-Carmona, G.
Water motion is one of the main drivers in morphological variability in species within de order Laminariales, and most of our current knowledge is based on subtidal populations. is a dominant kelp species in the North Pacific, widely distributed along the Baja California Peninsula from mid intertidal down to subtidal areas. This species presents great variability in the intertidal zone but it has not been yet evaluated such variability according to wave exposure. The present work also identifies the spatial / temporal variation, particularly respect to the presence of stipes without medulla (hollow stipes) a feature common among other brown seaweeds. We evaluated the effects of wave action in morphological variation of intertidal (Laminariales, Ochrophyta) at Punta Eugenia. The spatial and temporal variation sampling was surveyed between February, May, July, and August 2004 in the intertidal of Punta Eugenia, Baja California Sur. Our results have shown that exposed sites correlate with increased length and width of stipes as compared to more protected sites. Hollow stipes frequency changed more in association with temporal variation than with spatial heterogeneity suggesting nutrient limitation for thalli development. Our results suggest that compensate by morphological modifications the stress of living in the intertidal zone by showing larger stipes. Hollow stipes might be are also a mechanical adaptation to increase survival in high energy environments.
Palabras claves: Eisenia arborea;intertidal;Laminariales;morphological variability
Referencia APA: Parada, G., Riosmena-Rodriguez, R., Martinez, E., & Hernandez-Carmona, G. (2012). Morphological variability of intertidal Eisenia arborea (Laminariales, Ochrophyta) at Punta Eugenia, Baja California Sur. ALGAE, 27(2), 109-114.
Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 yr.
Gayo, E., Latorre, C., Santoro, C., Maldonado, A., & De Pol-Holz, R.
Paleoclimate reconstructions reveal that Earth system has experienced sub-millennial scale climate changes over the past two millennia in response to internal/external forcing. Although sub-millennial hydroclimate fluctuations have been detected in the central Andes during this interval, the timing, magnitude, extent and direction of change of these events remain poorly defined. Here, we present a reconstruction of hydroclimate variations on the Pacific slope of the central Andes based on exceptionally well-preserved plant macrofossils and associated archaeological remains from a hyperarid drainage (Quebrada Maní, ∼21° S, 1000 m a.s.l.) in the Atacama Desert. During the late Holocene, riparian ecosystems and farming social groups flourished in the hyperarid Atacama core as surface water availability increased throughout this presently sterile landscape. Twenty-six radiocarbon dates indicate that these events occurred between 1050–680, 1615–1350 and 2500–2040 cal yr BP. Regional comparisons with rodent middens and other records suggest that these events were synchronous with pluvial stages detected at higher-elevations in the central Andes over the last 2500 yr. These hydroclimate changes also coincide with periods of pronounced SST gradients in the Tropical Pacific (La Niña-like mode), conditions that are conducive to significantly increased rainfall in the central Andean highlands and flood events in the low-elevation watersheds at inter-annual timescales. Our findings indicate that the positive anomalies in the hyperarid Atacama over the past 2500 yr represent a regional response of the central Andean climate system to changes in the global hydrological cycle at centennial timescales. Furthermore, our results provide support for the role of tropical Pacific sea surface temperature gradient changes as the primary mechanism responsible for climate fluctuations in the central Andes. Finally, our results constitute independent evidence for comprehending the major trends in cultural evolution of prehistoric peoples that inhabited the region.
Referencia APA: Gayo, E., Latorre, C., Santoro, C., Maldonado, A., & De Pol-Holz, R. (2012). Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 yr. Climate Of The Past, 8(1), 287-306. http://dx.doi.org/10.5194/cp-8-287-2012
Inter-annual variability of southerly winds in a coastal area of the Atacama Desert: implications for the export of aeolian sediments to the adjacent marine environment.
Flores-Aqueveque, V., Alfaro, S., Caquineau, S., Foret, G., Vargas, G., & Rutllant, J.
The analysis of the aeolian content of marine cores collected off the coast of the Atacama Desert (Mejillones Bay, Chile) suggests that marine sediments can record inter-annual to inter-decadal variations in the regional southerly winds responsible for particle entrainment at the surface of the nearby desert. However, the establishment of a simple and direct correlation between the sediment and wind records is complicated by the difference of time scales between the erosion and accumulation processes. The aim of this work is to: (i) assess the inter-annual variability of the surface winds responsible for the sand movements; and (ii) determine whether the integration over periods of several months completely smoothes the rapid changes in characteristics of the transported and deposited aeolian material. To accomplish this aim, 14 years of 10 m hourly wind speed, measured at the Cerro Moreno (Antofagasta) Airport between 1991 and 2003 and at the Orica Station between 2000 and 2004, were analyzed. For each year, the wind speed statistical distribution can be represented by a combination of two to three Weibull functions. Winds of the lowest Weibull mode are too weak to move the sand grains at the surface of the pampa; this is not the case for the intermediate mode and especially for the highest speed mode which are able to erode the arid surface and transport particles to the bay. In each individual year of the period of study, the highest speed mode only accounted for a limited number of strong erosion events. Quantitative analysis of the distribution of the friction velocities and of their impact on erosion using a saltation model suggests that, although all wind speeds above threshold produce erosion events, values around 0·45 m sec−1 contribute less to the erosion flux. This gap allows separation of the erosion events into low and high saltation modes. The correlation (r = 0·997) between the importance of the third Weibull mode and the extent of higher rate saltation indicates that the inter-annual variability of the erosion at the surface of the pampa, as well as the transport of coarse particles (>100 μm), are directly related to inter-annual variations in the prevalence of the strongest winds. Finally, a transport and deposition model is used to assess the possible impact of the wind inter-annual variability on the deposition flux of mineral particles in the bay. The results suggest that inter-annual differences in the wind speed distributions have a quantifiable effect on the intensity and size-distribution of this deposition flux. This observation suggests that a detailed analysis of the sediment cores collected from the bay could be used for reconstructing the inter-annual variability of past winds.
Palabras claves: Atacama Desert; dust transport and deposition; wind erosion; wind variability.
Referencia APA: Flores-Aqueveque, V., Alfaro, S., Caquineau, S., Foret, G., Vargas, G., & Rutllant, J. (2012). Inter-annual variability of southerly winds in a coastal area of the Atacama Desert: implications for the export of aeolian sediments to the adjacent marine environment. Sedimentology, 59(3), 990-1000.
Functional identity and functional structure change through succession in a rocky intertidal marine herbivore assemblage.
Aguilera, M. & Navarrete, S.
Despite the great interest in characterizing the functional structure and resilience of functional groups in natural communities, few studies have examined in which way the roles and relationships of coexisting species change during community succession, a fundamental and natural process that follows the release of new resources in terrestrial and aquatic ecosystems. Variation in algal traits that characterize different phases and stages of community succession on rocky shores are likely to influence the magnitude, direction of effects, and the level of redundancy and complementarity in the diverse assemblage of herbivores. Two separate field experiments were conducted to quantify per capita and population effects and the functional relationship (i.e., redundancy or complementarity) of four herbivore species found in central Chile during early and late algal succession. The first experiment examined grazer effects on the colonization and establishment of early-succession algal species. The second experiment examined effects on the late-successional, dominant corticated alga Mazzaella laminarioides. Complementary laboratory experiments with all species and under natural environmental conditions allowed us to further characterize the collective effects of these species. We found that, during early community succession, all herbivore species had similar effects on the ephemeral algae, ulvoids, but only during the phase of colonization. Once these algae were established, only a subset of the species was able to control their abundance. During late succession, only the keyhole limpet Fissurella crassa could control corticated Mazzaella. The functional relationships among these species changed dramatically from redundant effects on ephemeral algae during early colonization, to a more complementary role on established early-successional algae, to a dominant (i.e., keystone) effect on late succession. This study highlights that functional relationship within consumer assemblages can vary at different phases and times of community succession. Differentiation in herbivore roles emphasizes the need to evaluate consumer's impacts through different times of community succession, and through experimental manipulations to make even broad predictions about the resilience or vulnerability of diverse intertidal assemblages to human disturbances.
Palabras claves: Chile; ephemeral algae; functional redundancy; functional roles; grazing; herbivores; human impact; interaction strength; keystone species; rocky shore
Referencia APA: Aguilera, M. & Navarrete, S. (2012). Functional identity and functional structure change through succession in a rocky intertidal marine herbivore assemblage. Ecology, 93(1), 75-89. http://dx.doi.org/10.1890/11-0434.1
What do we know about high-altitude precipitation in the semi-arid Andes of Chile?
Bourgin P, Andreassian V, Gascoin S, Valery A.
Mapping precipitations on a regular grid is often required for hydrological and ecological modelling. The spatial interpolation methods are generally used to estimate such a distribution from ground-based measurements. In the case of mountainous areas, the estimation of precipitation amounts is still a challenging task and the results of spatial interpolation should be verified as much as possible. Here we describe a three-steps method for the validation of a precipitation map. This is used in the context of a mountainous semi-arid region, the Norte Chico in Chile (26°S-32°S). The implementation of this validation method showed the benefits of an interpolation method developed by Valéry  for mountainous areas. The hydrological balance of the high-altitude watersheds is now more realistic.
Palabras claves: Precipitation, spatial interpolation method, extrapolation, altitude, altitudinal corrections, validation, water equivalent, water balance.
Referencia APA: Bourgin P, Andreassian V, Gascoin S, Valery A. (2012). Que sait-on des précipitations en altitude dans les Andes semi-arides du Chili?. La Houille Blanche. 2012;(2):12-17.