Ephemeral Research Articles

Ecological effects of a supra-seasonal drought on macroinvertebrate communities differ between near-perennial and ephemeral river reaches

The duration, intensity and frequency of hydrological droughts are predicted to increase significantly over the 21st century globally, threatening the long-term stability of lotic communities. In this paper we examine the recovery and recolonization of macroinvertebrate taxa in ephemeral and near perennial reaches of the River Lathkill (UK) after a supra-seasonal drought event. Following flow resumption, species accumulation (recolonization) occurred rapidly over a 4-month period, with a steady increase observed thereafter. Taxonomic richness was significantly higher in the section with near perennial flow after the first month of the study than the naturally ephemeral reach. Serial correlation was observed in the near perennial section but not in the upstream ephemeral reach. Serial correlation in the near perennial section may reflect: (1) the ongoing process of recovery or (2) the macroinvertebrate community following a new ecological trajectory. Our results suggest that supra-seasonal droughts may cause initial reductions in lotic diversity during stream desiccation events but may re-set ecological succession and/or temporarily provide new ecological niches, thereby supporting increased taxonomic diversity when the full range of hydrological conditions are considered. Quantifying the recovery of ecological communities following supra-seasonal drought can provide information to help develop ecologically effective conservation and management strategies.

The role of local perched aquifers in regional groundwater recharge in semi-arid environments: evidence from the Cuvelai-Etosha Basin, Namibia

The influence of local perched aquifers on groundwater recharge in semi-arid areas at a regional scale remains inadequately studied, especially in southern Africa where data scarcity limits the understanding of recharge and groundwater flow processes. The objective of this study was to understand the interaction between localized perched aquifers and an underlying regional aquifer in the Cuvelai-Etosha Basin in Namibia. The connection between the perched and regional aquifers was assessed based on an extensive dataset of hydrochemical and isotope (δ18O and δ2H) measurements for groundwater from both shallow and deep hand-dug wells as well as boreholes. Ephemeral rivers and pans/depression landforms were analyzed separately. Recharge was calculated using the chloride mass balance method. It was found that groundwater originates from precipitation that undergoes strong evapotranspiration and water–rock interaction, especially carbonate dissolution. Overlapping chemical and isotopic compositions suggest a common or similar origin of groundwater in the perched and regional aquifers in the pan/depression hydrotope. No such similarity was established for the ephemeral river hydrotope, suggesting that ephemeral rivers contribute negligibly to regional groundwater recharge. This has important implications for groundwater management and helps to understand recharge processes in similar semi-arid environments.

Estimating Recharge From Recirculated Groundwater With Dissolved Gases: An End‐Member Mixing Analysis

AbstractIn many hydrological systems, groundwater is pumped from the aquifer onto the land surface, and a fraction of this water subsequently infiltrates to recharge the groundwater system (recirculated groundwater). Tracers that undergo different degrees of reequilibration with the atmosphere during this recirculation process can enable ambient groundwater and recirculated groundwater to be differentiated. In this paper, the recirculated groundwater has been pumped to dewater open pit mines and discharged into ephemeral creeks. Some of this water subsequently recharged back into the aquifer. Chlorofluorocarbon‐12 (CFC‐12), 14C, and 3H are used in a four end‐member mixing analysis to differentiate between (1) ambient groundwater, (2) recirculated groundwater, (3) river recharge from natural flows prior to commencement of mining operations (in 2007), and (4) natural river recharge post‐2007. Sampling of the surface water when discharge of mine water was the only source of river flow enabled the extent of reequilibration of both CFC‐12 and 14C to be accurately determined. Since CFC‐12 reequilibrates more rapidly than 14C, recirculating groundwater had a CFC‐12 concentration that was close to modern, but a 14C activity that was higher than the original groundwater, but less than modern recharge. As 3H does not reequilibrate, it enabled easy differentiation between recirculated groundwater and infiltration of natural creek flows. Uncertainty of end‐member compositions is due to changes in the end‐member concentrations over time in the case of natural river flows, uncertainty in the extent of tracer reequilibration for the groundwater recirculation end‐member, and spatial variations in the composition of the ambient groundwater end‐member.

ESPIRITUALIDADE DO DESERTO: UMA PROPOSTA MODERNA PARA UMA ESPIRITUALIDADE DE EXÍLIO E ENCONTRO

O presente artigo quer ser uma contribuição da Teologia da Espiritualidade aos questionamentos hodiernos sobre a escassez de sentido e efemeridade do tempo presente, propondo a espiritualidade do deserto como caminho de solidão, silêncio e oração. A solidão nos mostra o caminho para deixar que nosso comportamento seja moldado não por nossas compulsões, mas por nossa nova mente: a de Cristo. O silêncio nos impede de ser sufocados por nosso mundo repleto de palavras vãs e nos ensina a falar a Palavra de Deus. Por fim, a oração dá à solidão e ao silêncio uma realidade concreta, um solo fértil em que possam florescer. Essa é uma oração capaz de ser realizada com a mente ao coração. Assim, entramos no “coração de Deus”, que abraça toda a história com seu amor eternamente criador.

Presión antrópica sobre cuencas de drenaje en ecosistemas frágiles: variaciones en las existencias (stock) de carbono orgánico asociadas a cambios morfológicos fluviales

Cambios antrópicos en el área de drenaje de cuencas hidrológicas determinan los procesos de erosión dominante y las fuentes de sedimento, movilizando ciertos reservorios (pools) de carbono. Además, estos cambios en el área de drenaje influyen en la dinámica sedimentaria con consecuencias en la morfología fluvial. Éstas, a su vez, pueden crear las condiciones para estabilizar carbono orgánico (CO) en los sedimentos por enterramiento, preservación de carbono, ralentización de la mineralización y colonización vegetal terrestre o acuática; causando todo ello un efecto importante en el sumidero o fuentes de carbono fluvial. Este trabajo explora el impacto de las alteraciones en el área de drenaje (reforestaciones, construcción de diques, abandono agrícola) en la morfología fluvial y en el sumidero de CO sedimentario, en una cuenca semiárida y de elevada erodibilidad. La aproximación metodológica combina el análisis cartográfico de los usos del suelo, la fotointerpretación geomorfológica del cauce y formas adyacentes en dos escenarios (1956 y 2016); y muestreos recientes de suelos y sedimentos para la determinación de las existencias (stock) de CO. La cobertura del suelo varió de un escenario principalmente agrario hacia un patrón forestal. Esa evolución alteró la dinámica sedimentológica de la cuenca que se tradujo en importantes cambios morfológicos en el cauce, disminuyendo la superficie de cauce activo (52%), incrementando la erosión lateral (77%) y las cárcavas adyacentes (11%), así como llanuras (31%) y abanicos aluviales (37%). Además, el cauce se revegetó ligeramente (16%). Todo ello propició un aumento del reservorio total de CO en los sedimentos fluviales (12%), ligeramente por encima del aumento del reservorio en los suelos de la cuenca (10%). La razón de las existencias (stock) de CO sedimentos/suelos fue >0.8, lo cual nos indica la gran capacidad de secuestro de carbono de los sedimentos, con existencias de CO por encima de los suelos agrícolas. Se constató que la dinámica geomorfológica fluvial juega un papel relevante en los flujos de CO, y en la capacidad de estabilizar sedimentos que generan sumideros de CO, en condiciones de estrechamiento del cauce activo y reverdecimiento del lecho. Estos procesos de secuestro de carbono en lechos secos y efímeros, tienen una gran relevancia para variados servicios ecosistémicos, y deberían ponerse en valor en la gestión de zonas sedimentarias fluviales.

RASPBERRY PI 3 MULTISPECTRAL LOW-COST SENSOR FOR UAV BASED REMOTE SENSING. CASE STUDY IN SOUTH-WEST NIGER

Abstract. The technology of UAV (Unmanned Aerial Vehicles) is rapidly improving and UAV-integrated sensors have kept up with it, providing more efficient and effective solutions. One of the most sought-after characteristics of on-board sensors is the low costing associated to good quality of the collected data. This paper proposes a very low-cost multiband sensor developed on a Raspberry device and two Raspberry Pi 3 cameras that can be used in photogrammetry from drone applications. The UAV-integrated radiometric sensor and its performance were tested in in two villages of South-west Niger for the detection of temporary surface water bodies (or Ephemeral water bodies): zones of seasonal stagnant water within villages threatening the viability and people’s health. The Raspberry Pi 3 cameras employed were a regular RGB Pi camera 2 (Red, Green, Blue) and a NoIR Pi 3 camera v2 (regular RGB without IR filter) with 8MPX resolution. The cameras were geometrically calibrated and radiometrically tested before the survey in the field. The results of the photogrammetry elaborations were 4 orthophotos (a RGB and NoIRGB orthophoto for each village). The Normalized Difference Water Index (NDWI) was calculated. The index allowed the localization and the contouring of the temporary surface water bodies present in the villages. The data were checked against the data collected with a Sony (ILCE-5100). Very high correspondence between the different data was detected. Raspberry-based sensors demonstrated to be a valid tool for the data collection in critical areas.

Makran continental margin sedimentation during the Late Holocene

Sedimentation in the Makran active margin is governed by a complex interaction of atmospheric, tectonics, and hydrodynamic setting of the northern flank of the Gulf of Oman. The mixed clastic carbonate sediments in the tectonically and hydrodynamically active environment have complicated the distribution pattern. The region is suffering from basic sedimentological data, and specifically, the sedimentation history of the Holocene deposits has been rarely studied in the Iranian coast. To deal with this deficiency, surface and core sediment samples from the Iranian continental shelf and upper slope of the Gulf of Oman have been studied using standard sedimentological techniques. The overall sediment distribution pattern demonstrates that the grain size gradually decreases from the shoreline to the deeper zones. However, some medium- to coarse-grained sand patches can be found in the deeper parts, especially in the middle part of the studied area that can be related to sediment supply of ephemeral rivers discharging into the sea in rainy seasons and (or) high-energy events (i.e., turbidites and tsunamis during the Holocene). Several horizons of the coarse-grained detrital sediments are detectable in the upper slope sediment cores. The coarse-grained materials are received from the hinterland during flash floods and could be accumulated due to mass wasting events. The elevated amount of organic materials in the upper slope indicates a deficit of dissolved oxygen that leads to preservation of organic materials in the bottom sediments.

The Globalisation Crisis: Populism and the Rise of an Anti-Trade Coalition

Extract ----- Abstract The contemporary sclerosis of trade policy challenges the merits of open markets and has raised significant attention to the unequal distribution of gains from international market forces. We argue that the failures of trade policy are more a consequence of past policy choices, particularly the purposeful design of both international and domestic institutions. Using a novel panel-survey of Americans through the great recession, we show that past apparent support for free trade and open markets was ephemeral. In the tradition of historical institutionalism, we show how institutions designed in one era to shield policy makers from import competing voices were `locked in’ and prevented otherwise efficient remedies for the distributive effects of globalisation. Keywords: US trade policy, populism, job displacement, GATT/WTO

Tillage effect on hydrophobicity and hydrological properties of oil-contaminated sediments in a hyper-arid region

A crude oil spill in 2014 led to the contamination of an extensive area in the Evrona Nature Reserve at the hyper-arid Arava Valley of Israel. In 2015, as a part of the restoration efforts, the oil-polluted braided ephemeral stream channels underwent a single session of tillage, to a depth of 10 cm. The rationale of this treatment was to break the hard, impermeable crust of the residual oil, aiming to reduce soil hardness and water repellency, and to improve the hydrological properties of the soil. In 2017, a study was conducted to assess the effect of chiseling tillage on the soil's hydrophobicity, mechanical strength, and infiltration capacity. Water drop penetration time, critical surface tension, penetration resistance, and near-saturated hydraulic conductivity were measured on-site, at depths of 0, 5, and 10 cm in contaminated-tilled, contaminated-non-tilled, and clean plots. We found that at the ground surface, tillage had a slight and non-significantly positive effect on the nearly-saturated hydraulic conductivity and a negative effect on the penetration resistance, while no improvement was recorded for the other properties. Further, some of these properties were inferior in the contaminated-tilled sediments compared to those in the contaminated-non-tilled sediments, an effect that could be attributed to the: (1) tillage-induced inversion of the most polluted surface layer into the sub-soil, (2) absence of a clayey sublayer, and (3) limited oil degradation due to the extremely dry conditions. Therefore, the results indicate that tillage is not an effective practice for restoring oil-polluted soils and sediments in hyper-arid regions.

Characteristics of hollows and hollow‐bearing trees in semi‐arid river red gum woodland and potential limitations for hollow‐dependent wildlife

AbstractUp to 37 species of the birds and microbats inhabiting inland Australia are dependent on tree cavities for breeding or roosting. The river red gum (Eucalyptus camaldulensis), a well‐known hollow‐bearing tree species, occurs in linear semi‐arid woodland along thousands of kilometres of ephemeral river channels and is the only tree species that provides widespread, aggregated hollow resources across a landscape otherwise dominated by shrublands. Here we assess the type and quantity of hollows available along ephemeral rivers of the MacDonnell Ranges bioregion in central Australia and determine which characteristics of river red gums best predict the abundance and characteristics of different tree hollows, as first steps towards assessing the current availability of hollows in the region. Approximately a third of all river red gums sampled were hollow‐bearing, but individual trees with abundant hollows were rare. Further, 36% of hollows had an entrance ≤ 5 cm, and 37% had entrances which were 6–10 cm in diameter, whereas only 13% of hollows had an entrance diameter > 20 cm suitable for larger hollow‐using species. Large and high hollows only occurred on trees that did not display post‐disturbance resprouting. Trees with multiple and diverse hollows were rare and tended to be in advanced stages of senescence and had larger stems (82.3 ± 3.33 cm) and were taller (14.4 ± 0.53 m) compared to non‐hollow‐bearing trees (23.44 ± 1.68 cm, 8.0 ± 0.34 m). Further research is required to establish whether the current abundance of hollows and diversity of hollow types are limiting to cavity‐dependent wildlife, and to identify any threats to availability of hollows.

Effectiveness of straw bale check dams at reducing post-fire sediment yields from steep ephemeral channels

Post-fire flooding and elevated sediment loads in channels can pose hazards to people and structures within the wildland-urban interface. Mitigation of these hazards is essential to protect downstream resources. Straw bale check dams are one treatment designed to reduce sediment yields in small ephemeral catchments (<2ha). This study investigated their effectiveness in five paired catchments burned at high severity during the 2010 Twitchell Canyon Fire in Utah. Rainfall, ground cover and hillslope erosion rates were also measured during the two-year study. Adjacent paired catchments were physically similar and ranged in size from 0.2 to 1.6ha across pairs. Within pairs, one catchment was an untreated control and the other treated at a rate of four straw bale check dams ha−1. High intensity rainfall, erodible soils and slow regrowth contributed to the observed high hillslope sediment yields (> 60Mgha−1). 1- and 2-yr I30 return period rain events early in the study quickly filled the straw bale check dams indicating the treatment did not statistically reduce annual sediment yields. First year annual sediment yields across all catchments were 19.6 to 25.7Mgha−1. Once the check dams were full, they had limited storage capacity during the second post-fire year, allowing 3.8 to 13.1Mgha−1 of sediment to pass over the check dams. The mean mass of sediment trapped by individual straw bale check dams was 1.3Mg, which allowed them to trap a mean of 5.9Mgha−1 of sediment at the given treatment rate. Straw bale check dams trapped <50% of the total mass delivered from catchments with efficiency decreasing over time. Increasing straw bale check dam treatment rate in stable channels may improve trap efficiency. Application of this treatment in areas with lower expected rainfall intensities and less erodible soils may be justifiable.

Impact of managed aquifer recharge structure on river flow regimes in arid and semi-arid climates

Managed aquifer recharge (MAR) structure is widely used to expand groundwater resources. In arid regions with flash flooding, MAR can also be used as a flood control structure to decrease peak discharge of rivers. In this paper, we present a method for quantifying the role of MAR in head water systems and assess its impact on the total water balance in a river basin. The method is based on rainfall-runoff modeling, reservoir flood routing, recharge analysis and river flow analysis. For the case selected, Kamal Abad MAR in Lake Maharlou basin in southern Iran, we analyzed changes in the downstream river regime using two scenarios (with MAR and without MAR) with different return periods. The results revealed a significant impact of MAR on river flow in terms of changes in flow timing, magnitude and variability. With MAR, the ephemeral river studied became disconnected from the main stream, albeit, whereas the case without MAR, floods with return period higher than 10 years would be connected to the downstream. Even though, MAR structures are useful in arid and semi-arid climates for irrigation water supply, their placing and designing need more attention. The developed method can be used to assess the impacts of MAR on river flow and find the best location for it to make the connection of the ephemeral river and downstream river, an issue which has not received much attention in hydrological research.

Erosion Sediment Yield Characteristics of Storm-floods in the Ephemeral Desert Watershed

Erosion Sediment Yield Characteristics of Storm-floods in the Ephemeral Desert Watershed

Groundwater prospecting by the inversion of cumulative data of Wenner–Schlumberger and dipole–dipole arrays: A case study at Turamdih, Jharkhand, India

The present study deals with groundwater prospecting in hardrock terrain. Initially, the Wenner–Schlumberger array and the dipole–dipole array data have been acquired using Syscal Junior Switch-48. Furthermore, data acquired using both arrays have been merged using Prosys-II data handling software for the inversion of the cumulative data for possible mapping of water-bearing fracture rock masses with different structural distribution in a complex geological environment. The data have been analysed using RES2DINV software, based on the smoothness constrained least-square technique. Two numbers of 2D electrical resistivity tomography profiles (AA $$'$$ and BB $$'$$ ) have been selected over an official colony of the Turamdih uranium mine for groundwater prospecting, which is located at about 24 km west of Jaduguda, Jharkhand, India. High-resistivity features associated with a dyke-like structure have been delineated in both the profiles. Three low-resistivity features have been delineated as water saturated alluvium/aquifers in profile AA $$'$$ . A low-resistivity feature associated with the water-saturated fracture zone has been identified in profile BB $$'$$ , which is well correlated with the surficial location of an ephemeral channel at the bottom of the hill across the slope. It is observed that geoelectric sections generated by the inversion of cumulative data of both arrays provide superior results compared with the Wenner–Schlumberger and dipole–dipole arrays, separately.

Wadis as dryland river parks: challenges and opportunities in designing with hydro-ecological dynamics

ABSTRACTDryland rivers (wadis in Arabic) are characterised by high levels of flow unpredictability due to their severe dry-wet hydrological regimes. In the Arabian Peninsula, recent attention has focused on revitalising the socio-ecological values of wadis by rejuvenating them as linear public parks. In this paper, we review the key hydro-ecological characteristics of wadis and examine a range of design responses to address their dynamics in urban areas. Three case studies of recent and ongoing rehabilitation projects in Muscat, Oman, were spatially analysed and interviews with stakeholders involved in the projects were conducted. Design strategies and system-based approaches were suggested, including taking account of the hydro-ecological processes and relationships across multiple spatial and temporal scales, interdisciplinary collaborations, and testing the systems’ performance through design experimentation. The findings can be applied to the rehabilitation of ephemeral rivers in dry and drying environments globally.

Integrated hydrogeological modelling of hard-rock semi-arid terrain: supporting sustainable agricultural groundwater use in Hout catchment, Limpopo Province, South Africa

An integrated hydrogeological modelling approach applicable to hard-rock aquifers in semi-arid data-scarce Africa was developed using remote sensing, rainfall-runoff modelling, and a three-dimensional (3D) dynamic model. The integrated modelling approach was applied to the Hout catchment, Limpopo Province, South Africa, an important agricultural region where groundwater abstraction for irrigation doubled during 1968–1986. Since the 1960s, groundwater levels in irrigated areas have displayed extended periods of decline with partial or full recovery in response to major decadal rainfall events or periods. The integrated dynamic 3D hydrogeological flow model, based on the One-Water Hydrologic Flow Model (MODFLOW-OWHM), helped to understand recharge and flow processes and inform water use and management. Irrigation abstraction was estimated based on irrigated crop area delineated using the Landsat Normalized Difference Vegetation Index (NDVI) and crop water requirements. Using groundwater level data, the model was calibrated (2008–2012) and validated (2013–2015). Estimated mean diffuse recharge (3.3 ± 2.5% of annual rainfall) compared well with estimates from the Precipitation Runoff Modelling System model. Recharge and groundwater storage showed significant inter-annual variability. The ephemeral river was found to be losing, with mean net flux to the aquifer (focused recharge) of ~1.1% of annual rainfall. The results indicate a delicate human-natural system reliant on the small but highly variable recharge, propagating through variable pumping to an even more variable storage, making the combined system vulnerable to climate and anthropogenic changes. The integrated modelling is fundamental for understanding spatio-temporal variability in key parameters required for managing the groundwater resource sustainably.

The hunter-gatherer site BES II (Jacaré-Guaçu River low terraces, central Sao Paulo state, Brazil): Interface with geomorphical and environmental fluctuations of the Pleistocene-Holocene transition

The lithic site Boa Esperança II (BES II), in the São Paulo segment of the Brazilian Plateau, next to the boundary between the cities of Araraquara (SP) and Boa Esperança do Sul (SP), presents a collection of almost 2,000 lithic artifacts (predominantly chert and sandstone), being interpreted as a settlement of diversified functions with possibly continuous or successive occupation. In this work, we approach the site based on interface of its insertion in the regional physical-environmental context - with emphasis on the interface with relief frames, surface structure study and estimated geomorphic sequences of the alluvial plain of Jacaré-Guaçu river - and techno-typological analysis. It was verified that the BES II artifacts are distributed along vertical profiles and relief pictures lined by records that mark the transition from semi-arid conditions to others of increasing humidity, successive oscillations of base levels and modifications of fluvial regimes (ephemeral channels passing to perennial channels of different hydrological meandrings patterns), indicating that human occupation has dealt with conditions of quite distinct landscapes between the Late Pleistocene and the Holocene. Local lithic industry would have taken advantage of attributes derived from these modifications in the landscape over time - in particular the exposure of gravels of large river pebbles deposited by torrential ephemeral channels. The past abundance of raw material of fluvial origin would have contributed to the location of the site in the regional geomorphological context, as well as for a lithic assemblage based on the production of large unipolar flakes. We observed in the correlations between the position of artifacts, geomorphical and pedological data, OSL and Carbone-14 dates at archaeological levels, elements that allow us to discuss considering BES II as an archaeological site to integrate the interval of the Pleistocene-Holocene transition and to had interfaces with the geomorphological and environmental changes of such time. The archaeological implications of the issue and the fact that only one dating of photoluminescence has been reported from the deepest level of the site (basal gravel layer) emphasize the need for new, denser and more diversified studies.

Structural controls on the location and distribution of CO2 emission at a natural CO2 spring in Daylesford, Australia

Secure storage of CO2 is imperative for carbon capture and storage technology, and relies on a thorough understanding of the mechanisms of CO2 retention and leakage. Observations at CO2 seeps around the world find that geological structures at a local and regional scale control the location, distribution and style of CO2 emission. Bedrock-hosted natural CO2 seepage is found in the Daylesford region in Victoria, Australia, where many natural springs contain high concentrations of dissolved CO2. Within a few meters of the natural Tipperary Mineral Spring, small CO2 bubble streams are emitted from bedrock into an ephemeral creek. We examine the relationship between structures in the exposed adjacent outcropping rocks and characteristics of CO2 gas leakage in the stream, including CO2 flux and the distribution of gas emissions. We find that degassing is clustered within ˜1 m of a shale-sandstone geological contact. CO2 emission points are localised along bedding and fracture planes, and concentrated where these features intersect. The bubble streams were intermittent, which posed difficulties in quantifying total emitted CO2. Counterintuitively, the number of bubble streams and CO2 flux was greatest from shale dominated rather than the sandstone dominated features, which forms the regional aquifer. Shallow processes must be increasing the shale permeability, thus influencing the CO2 flow pathway and emission locations. CO2 seepage is not limited to the pool; leakage was detected in subaerial rock exposures, at the intersection of bedding and orthogonal fractures.These insights show the range of spatial scales of the geological features that control CO2 flow. Microscale features and near surface processes can have significant effect on the style and location and rates of CO2 leakage. The intermittency of the bubble streams highlights challenges around characterising and monitoring CO2 stores where seepage is spatially and temporally variable. CCS monitoring programmes must therefore be informed by understanding of shallow crustal processes and not simply the processes and pathways governing CO2 fluid flow at depth. Understanding how the CO2 fluids leaked by deep pathways might be affected by shallow processes will inform the design of appropriate monitoring tools and monitoring locations.

Variation in Life History May Allow Colonization of Diverse Habitats in an Invasive Fish Species

Successful colonization by an invasive species is often associated with flexibility in life-history traits. The number and timing of reproductive events are among the most important of those life-history traits and are often strongly influenced by habitat stability. An invasive fish, Brook Stickleback (Culaea inconstans), was first detected in eastern Washington in 1999. They have subsequently expanded their range into water bodies of variable habitat stability, i.e., permanent, semi-permanent, and ephemeral water bodies. We hypothesized that Brook Stickleback living in unstable and unpredictable habitats would exhibit “fast” life-history traits relative to Brook Stickleback living in more stable habitats. Brook Stickleback were collected from 18 water bodies and standard length was measured. Otoliths were then extracted to determine age. Average age of Brook Stickleback in permanent wetlands was significantly greater than that of fish in semi-permanent and ephemeral wetlands, but there was no significant difference in age structure between semi-permanent and ephemeral wetlands (permanent x = 1.24, semi-permanent x = 0.73, ephemeral x = 0.76, P < 0.001). Average length at age class 0+ was significantly less than age classes I, II, and III; however, there was no significant difference between age classes I, II, and III (0+: x= 39.73; I: x = 46.42; II: x= 45.14; III: x= 49.10; P < 0.001). The results suggest that Brook Stickleback exhibit different life-history characteristics depending upon the habitats in which they are found. Brook Stickleback in unstable habitats may be functionally semelparous; however, it is possible that some individuals may produce multiple clutches within a single spawning season. Finally, we found that the only accurate way to measure Brook Stickleback age is through otolith analysis, drawing into question the conclusions of previous work in which length was used as a surrogate for age.

Identidad, mundialización e «historización» de la experiencia

El texto se ocupa de las alteraciones de la personalidad individual y colectiva que ha traído aparejada la modernidad o la modernidad tardía. Partiendo de una glosa de las proposiciones de Anthony Giddens en Modernidad e identidad del yo, se analizan el impulso a la construcción de la identidad, las tribulaciones y las tensiones entre lo global y lo particular, entre lo efímero y lo durable en que viven los hombres de las sociedades desarrolladas actuales. Los medios de comunicación de masas hacen que las experiencias de los sujetos sean «desmesuradas» en su intensidad y amplitud. En las sociedades actuales se desarrolla una especie de nueva «rebelión de las masas» frente a las presiones homogeneizadores a ultranza que imponen las fuerzas sociales abstractas. Pero esa rebelión no pretende, sin embargo, romper el sistema. Una nueva forma de «historicidad» es el origen de una tendencia poderosa a la «historización de la experiencia» frente a la Historia-Pasado tradicional. Tal cosa es el fundamento para la construcción de una Historia del Presente.