Lake Maracaibo Research Articles

Seasonal prediction of lightning activity in North Western Venezuela: Large-scale versus local drivers

The Lake Maracaibo Basin in North Western Venezuela has the highest annual lightning rate of any place in the world (~200flkm−2yr−1), whose electrical discharges occasionally impact human and animal lives (e.g., cattle) and frequently affect economic activities like oil and natural gas exploitation. Lightning activity is so common in this region that it has a proper name: Catatumbo Lightning (plural). Although short-term lightning forecasts are now common in different parts of the world, to the best of the authors' knowledge, seasonal prediction of lightning activity is still non-existent. This research discusses the relative role of both large-scale and local climate drivers as modulators of lightning activity in the region, and presents a formal predictability study at seasonal scale.Analysis of the Catatumbo Lightning Regional Mode, defined in terms of the second Empirical Orthogonal Function of monthly Lightning Imaging Sensor (LIS-TRMM) and Optical Transient Detector (OTD) satellite data for North Western South America, permits the identification of potential predictors at seasonal scale via a Canonical Correlation Analysis. Lightning activity in North Western Venezuela responds to well defined sea-surface temperature patterns (e.g., El Niño-Southern Oscillation, Atlantic Meridional Mode) and changes in the low-level meridional wind field that are associated with the Inter-Tropical Convergence Zone migrations, the Caribbean Low Level Jet and tropical cyclone activity, but it is also linked to local drivers like convection triggered by the topographic configuration and the effect of the Maracaibo Basin Nocturnal Low Level Jet. The analysis indicates that at seasonal scale the relative contribution of the large-scale drivers is more important than the local (basin-wide) ones, due to the synoptic control imposed by the former. Furthermore, meridional CAPE transport at 925mb is identified as the best potential predictor for lightning activity in the Lake Maracaibo Basin.It is found that the predictive skill is slightly higher for the minimum lightning season (Jan–Feb) than for the maximum one (Sep–Oct), but that in general the skill is high enough to be useful for decision-making processes related to human safety, oil and natural gas exploitation, energy and food security.

PIGMENTOS CLOROFILICOS E HIDROGRAFIA EN LA REGION NOROCCIDENTAL DE VENEZUELA CON ENFASIS EN EL GOLFO DE VENEZUELA

Four oceanographic expeditions were carried out from 1982 to 1984. These surveys evaluated chlorophyll - a and pheopigments concentrations in surface waters of the "Golfo de Venezuela" and adjacent regions. Also, physical and chemical parameters were measured in order to locate the upwelling zones and the area where mixing with "Lago de Maracaibo" water is occurring. A total 424 surface samples taken every 20 miles (36 km aprox.) were analysed by Lorenzen,s (1967) method, obtaining values of chlorophyU-a and pheopigments ranging from less than 0.1 mg/m3 up to 5.2 mg/mi . During the first three surveys, a normal behavior of the Trade winds was observed; they blew from east to west, although they showed occasional variability. The winds induced strong upwellings on the western coast of the "Peninsula de Paraguaná" and in the "Golfete de Coro", both areas showing high chlorophyll concentrations. Mixing of "Golfo de Venezuela" with "Lagode Maracaibo" waters, which had low concentration values, was observed in the "Bahía de Calabozo", South of the "Península de la Guajira". Otherwise, the wind changed considerably during October and November of 1984; its speed decreased and its direction changed 180° bringing about an alteration of water dynamics in the upwelling zone as well as in the mixing area. During this period chlorophyll values were low.

Colección ex situ de plantas vivas de especies nativas del orden Zingiberales del Sur del Lago de Maracaibo, Venezuela

The loss of biological diversity in the Southern Part of the Lago de Maracaibo, Venezuela, due to cattle rising, has caused the extinction of 97 % of the original the Zingiberale s order for purpose of study and conservation, because of the importance of this subject in the tropical floriculture (cut flowers, foliage and landscaping). Using the biological diversity and the new native species flora could promote the efficient and sustainable use of the natural resources of the Southern Part of the Lago de Maracaibo. For that reason, it was collected 18 samples between varieties and species which passed the nursery stage, and then they were transplanted in the field after three months, besides, it was accounted the humidity and light conditions they had in their natural ecosystem; it resulted that the plants showed favorable adaptability indicators.

The story of George Huntington and his disease.

George Huntington described some families with choreiform movements in 1872 in the United States of America and since then many such families have been described in other parts of the world and works on the genetics of the disease have brought new vistas in the understanding of the disease. In 1958, Americo Negrette, a young Venezuelan physician observed similar subjects in the vicinity of Lake Maracaibo which was presented by his co-worker, Ramon Avilla Giron at New York in 1972 when United States of America had been commemorating the centenary year of Huntington's disease. Nancy Wexler, a psychoanalyst, whose mother had been suffering from the disease attended the meeting and organized a research team to Venezuela and they systematically studied more than 18,000 individuals in order to work out a common pedigree. They identified the genetic locus of the disease in the short arm of chromosome 4 and observed that it was a trinucleotide repeat disorder.

Intra- and inter-field compositional changes of oils from the Misoa B4 reservoir in the Ceuta Southeast Area (Lake Maracaibo, Venezuela)

Here we analyzed oil samples from 35 wells in the Ceuta Southeast Area (Lake Maracaibo Basin, northwestern Venezuela) in order to evaluate lateral intra-reservoir continuity in the Misoa B4 unit. Biomarkers, isotopic signature, and also V and Ni were examined using gas chromatography–mass spectrometry (GC–MS), isotope ratio mass spectrometry (IRMS), and inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Multivariate statistical analysis was also applied to obtain useful information from geochemical data. On the basis of the characterization of these samples, we conclude that they all fall into various oil families derived from two pulses of hydrocarbon generation, migration and accumulation from the calcareous La Luna source rock, deposited in an anoxic marine environment under reducing conditions. Thus, these oils are a mixture of an earlier biodegraded, less mature oil charge and a later fresh non-biodegraded oil recharge. In addition, we applied asphaltene pyrolysis to one (LG-62) of the three “anomalous” oils. The LG-62 sample was confirmed as an almost “pure” paleobiodegraded end-member, whereas the VLF-3020 oil was tentatively classified as the unaltered end-member oil-type. Finally, the GC fingerprints and Fourier Transform Infra Red (FTIR) spectroscopic indices of the oils were used to detect minor variations in composition that are indicative of reservoir compartmentalization.

A Multilocus Molecular Phylogeny forChaetostomaClade Genera and Species with a Review ofChaetostoma(Siluriformes: Loricariidae) from the Central Andes

The rubbernose-pleco genus Chaetostoma comprises 47 currently valid and many undescribed species distributed along Atlantic and Pacific slopes of the Andes Mountains from Panama to southern Peru, the Coastal Mountains of Venezuela, and drainages of the Guiana and Brazilian shields. We present a five-locus molecular phylogeny for 21 described and six undescribed species of Chaetostoma spanning the geographic range of the genus. Bayesian and maximum likelihood analyses found Chaetostoma to be well supported as monophyletic and sister to a clade of central and northern Andean genera that have also been hypothesized to be closely related based on morphology (i.e., Andeancistrus, Cordylancistrus, Dolichancistrus, Leptoancistrus, and Transancistrus). Species of Chaetostoma were divided into a trichotomy consisting of: a Pacific Coast, Central American, Magdalena Basin, Lake Valencia, and Guiana Shield clade; a western Orinoco, Lake Maracaibo, and Lake Valencia clade; and a widespread upper Amazon/Orinoco clade inclusive of a single species on the Brazilian Shield. We also conducted a systematic review of species from the central Andes of northern Peru and Ecuador. Based on our phylogenetic results and direct examination of historical and recently collected type and non-type material, we describe two new species of Chaetostoma (C. bifurcum, from the Pacific Coast, and C. trimaculineum, from the Atlantic Slope), redescribe four species (C. breve, C. carrioni, C. dermorhynchum, and C. microps, all from the Atlantic Slope), transfer four species from Chaetostoma to Ancistrus and find two species to be junior synonyms.

El papel de la nueva PDVSA en la lucha contra la pobreza y la exclusión social en Venezuela

Se estudia el papel de Petróleos de Venezuela Sociedad Anónima (PDVSA, la principal empresa estratégica del Estado en este país) en la lucha contra la pobreza-exclusión social, en tanto organismo promotor, financista y ejecutor de programas y proyectos sociales, junto con el poder comunal, desde el año 2003 cuando pasa a control directo del gobierno bolivariano. El objetivo del trabajo es discernir algunos logros y limitaciones de esa intervención, a través de dos proyectos de desarrollo social ejecutados por PDVSA-Occidente (Maracaibo y Costa Oriental del Lago), en dos comunidades de los municipios Maracaibo y Lagunillas del estado Zulia, entidad-región petrolera por excelencia. Se toma como base la percepción de los actores involucrados, tanto de parte de la empresa como de las comunidades. Se realiza una breve revisión documental, especialmente de la normativa que le prescribe ese nuevo rol social a PDVSA; y un trabajo de campo dentro de una investigación cualitativa etnográfica, con uso del método estudio de casos, observación directa y entrevistas semiestructuradas en profundidad a informantes clave: gerentes de desarrollo social y coordinadores de los proyectos; voceros de los consejos comunales y beneficiarios directos. Según los informantes, el papel de PDVSA ha sido decisivo en el mejoramiento de las condiciones de vida aunque no suficiente para erradicar la pobreza; los beneficiarios se sienten incluidos y tienen expectativas positivas hacia el futuro, no obstante admiten limitaciones como retraso en los proyectos, débil comunicación industria-comunidad, escasa participación de ésta y ausencia de contraloría social.

Systems goat and sheep production in the coast sub region eastern of Lake Maracaibo

To characterize systems goats and sheep production in the Eastern Coast of Lake Maracaibo, a methodology of participatory action research in agricultural communities in the municipality Simon Bolivar was applied. Zone leaders were consulted, the Zuliano Team of Breeders Goats and Sheep, an instrument was applied to 60 producers. The COLM subregion’s oil region, however, rooted in traditional agricultural activity persists. In the municipality Miranda exists a population of 16,137 goats and 7,526 sheep, in Quisiro 30 producers with 2,250 acres were analyzed, in addition to 1,300 goats and 675 sheep. In Los Cilantrillos and La Esperanza 30 producers with 320 hectares, 375 goats and 430 sheep were studied, occupying 1% of the regional total, which is important for the persistence and interest of producers despite the difficulties arising from oil exploitation . The family group shown participatory in herd management, 88.3% of farmers use extensive grazing, there are family tradition, knowledge management herds through each generation, 56.7% are enrolled in the Mission Agro-Venezuela, races are mainly nubian goat, Alpine, Creole, as to sheep, Persian, mestizo or Creole, producers work more than 10 hours a day, 7 days a week, 56.7% produce goat cheese in farm gate for local markets. It is recommended to continue studies and participatory analysis for the overall improvement of the productive system.

ECOPHYSIOLOGICAL TRAITS OF ADULT TREES OF CRIOLLO COCOA CULTIVARS (THEOBROMA CACAOL.) FROM A GERMPLASM BANK IN VENEZUELA

SUMMARYWe studied physiological traits of 12 Criollo cocoa cultivars growing in a germplasm bank in the southern region of Maracaibo Lake Basin, during the rainy (RS) and dry seasons (DS) of 2007. A further evaluation of photosynthetic responses to changes in environmental parameters was done on three cultivars: Los Caños 001 (LCA001), Sur Porcelana 010 (SP010) and Escalante 001 (ESC001) in 2009 and 2010. Leaf water potential (ΨL) of most cultivars decreased during the DS of 2007, with the exception of ESC001. Maximum photosynthetic rate (Amax), stomatal conductance and water use efficiency varied among cultivars and seasons. The CO2-saturated photosynthetic rate (ACO2sat) was higher in LCA001 and ESC001 than in SP010, with no differences in carboxylation efficiency. Light curve responses of the three cultivars were similar. In all cultivars, no evidence of chronic photoinhibition was observed, since maximum quantum yield of photosystem II was high (0.77–0.81). We conclude that ESC001 has the best physiological performance (ΨLremained unchanged, highest Amax, ACO2satand photochemical activity), and it seems to be a promising cultivar for cocoa agroforestry systems in the southern region of Maracaibo.

Disappeared almost without a trace: Taphonomic pathways and the recognition of hidden bioturbation events in Eocene storm deposits (Paují Formation, Lake Maracaibo, Venezuela)

Shallow-marine deposits, included in the “Basal Sands” of the Eocene Pauji Formation of the Maracaibo Basin in western Venezuela, record deposition in fore shore to lower off shore settings. These deposits are stacked in coarsening-upward parasequences that reflect variable intensities and frequencies of storms. Of particular interest are sharp-based, amalgamated, hummocky cross-stratified and rippled, very fine-grained sandstone beds, observed in the core MOT-X from the Motatan Field. These beds record storm deposition, under purely oscillatory to combined flows in an offshore-transition setting. The amalgamated nature of the sand stone interval indicates repeated erosion, due to multiple storm events. The ichnofabrics in these tempestites result from a distinctive taphonomic pathway, reflecting the interplay between bioturbation events and storm erosion and deposition. The storm-related trace-fossil suite is represented by Diplocraterion parallelum and local occurrences of Palaeophycus tubularis , Bergaueria isp. and Thalassinoides isp., which is consistent with the relatively high energy of formation of these deposits. Fair-weather deposits are absent from the sand stone interval. However, high densities of Chondrites isp. are present in the infills of Diplocraterion parallelum and, more rarely, Thalassinoides isp. providing the sole evidence of the establishment of a resident fauna during inter-storm intervals. Deposits containing the fair-weather suites were erosionally removed during the subsequent storm. The deep-tier emplacement of Chondrites and the ability of its producer to rework other biogenic structures favour preservation, allowing recognition of a “hidden” bioturbation event that otherwise might have remained undetected.

Stratigraphic Columns Modeling and Cyclicity Analysis of the Misoa Formation, Maracaibo Lake, Venezuela, using Markov Chains

A stochastic characterization of a hydrocarbon reservoir, constituted by a sedimentary sequence of sandstones interbbeded with siltstones and shales, has been performed. The stratigraphic unit studied here mainly comprises the C4 sands of the Misoa Formation, located in the Lama Field, Maracaibo Lake (Venezuela). A Markov Chain algorithm, based on the definition of genetic lithofacies relationships along stratigraphic columns, was developed. The application of the Monte Carlo stochastic method using this algorithm, to log data from 11 wells, allowed the generation of pseudo sequences at 20 new locations. This algorithm was able to properly model pseudo stratigraphic sequences and to quantify the relative facies percentage, showing a 82% confidence level related to the proportional content of sediments at a test well. The net sand map obtained integrating the stratigraphic columns, derived from the well information, and the Markov pseudo-columns, suggests the presence of sand bodies with a northeast-southwest orientation that agree with previous geological studies in the area. This map could help in the definition of prospective zones in the field. The existence of stratigraphic memory along the evaluated columns was recognized after applying the algorithm. The embedded Markov method used in the cyclicity analysis of the whole area indicates cyclic transitions just from sandstones to siltstones and from shales to siltstones. Hence for the study area, on average, fining upward and coarsening upward processes can be identified with the Markovian approach, as was expected for the tide-dominated deltaic system associated to the analyzed reservoir.

Las haciendas cañeras en el sur del lago de Maracaibo-Venezuela (siglos XVI-XVII)

This analysis studies sugar cane plantations located south of Lake Maracaibo, in the jurisdiction of Merida (Venezuela), where sugar cane was cultivated and processed from the sixteenth century. It is a quantitative and qualitative study of the origin, evolution, production, infrastructure, and profitability of the plantations. The research is based on unpublished documentary sources in national and foreign archives.

Relative yield-per-recruit and management strategies for <i>Cynoscion acoupa</i> (Perciformes: Sciaenidae) in Lake Maracaibo, Venezuela

Acoupa weakfish, Cynoscion acoupa, in Lake Maracaibo is subject to intense commercial fishing by an artisanal fleet, and a recent decrease in fish size observed from landings is of concern. This fishery has not yet been modeled, and its assessment and the establishment of management practices to overcome the current overfished condition are urgently needed. To address this, we used recent and past empirical growth estimates to model relative yield-per-recruit under different lengths at first capture. Our results from relative yield-per-recruit analysis showed evidence that growth and recruitment overfishing occur under current fishing practices in Lake Maracaibo. Particular attention was given to fishing practices in El Tablazo Bay where young, small fish predominate in the commercial catches (mean total length=33.7cm), well below the length at first sexual maturity (-40cm TL) for both sexes. As management strategies, we propose to set a mesh size limit at or above 8.89cm (3.5in), which will reduce fishing mortality of immature fish, increase yield-per-recruit, and will result in an increase of Acoupa weakfish recruitment for the long term in Lake Maracaibo.

Effectiveness of different trap types for control of bark and ambrosia beetles (Scolytinae) in Criollo cacao farms of Mérida, Venezuela

Scolytid wood-boring beetles, especially Xyleborus spp., are among the most harmful cacao (Theobroma cacao) pests in Venezuela because of their mutualistic association with a fungus (Ceratocystis cacaofunesta) that causes cacao wilt. The Criollo varieties of cacao are very susceptible to pests and diseases. We tested the effectiveness of two kinds of trap for collecting scolytids: bottle traps with windows (situated at 1 m and 3 m above ground level) and funnel traps, placed in a cacao farm south of Maracaibo Lake, Mérida state. Funnel traps collected significantly more individuals than bottle traps. The scolytid assemblages collected by each kind of trap were dissimilar, having only 60% of species in common.

Factores que afectan la vida útil de vacas doble propósito

RESUMENObjetivo. Determinar el efecto de factores no genéticos y de grupo racial, sobre la vida útil (VU) de vacas doble propósito. Materiales y métodos. Se utilizó información de 2098 vacas, que incluyó a todas las hembras que ingresaron a servicio y salieron del sistema productivo. La VU se cuantificó como el total de partos al salir del rebaño. Los efectos incluidos en el modelo fueron hacienda (H: AG, VV), año de primer parto (A1P: 1995-2006), época de primer parto (E1P: Enero-marzo, abril-mayo, junio-agosto, septiembre-diciembre) grupo racial (GR: C, 50C50E, ML) y las interacciones HxGR y A1PxGR. Resultados. La media de VU fue de 2.63 partos ± 0.07. Todos los factores tuvieron efectos altamente significativos (p<0.01) sobre VU, menos H. Es interesante resaltar que las interacciones HxGR y A1PxGR fueron altamente significativas (p<0.01) indicando que los grupos raciales se comportan diferente en cada hacienda y en el transcurso de los años. Conclusiones. Los efectos no genéticos y de grupo racial tienen una alta influencia sobre VU.

Trans-Andean Ancistrus (Siluriformes: Loricariidae).

We review the trans-Andean species of Ancistrus from Panama, Colombia and Venezuela. Based on analyses of meristic, morphometric and pigmentation pattern data of preserved specimens, eight of sixteen species reported from this region are considered valid and two new species are described. Here we review Ancistrus chagresi Eigenmann & Eigenmann 1889 from both slopes of central Panama; A. centrolepis Regan 1913 from Pacific slopes of eastern Panama and western Colombia; Ancistrus caucanus Fowler 1943, from the Magdalena River drainage in northern Colombia; Ancistrus martini Schultz 1944, from the Lake Maracaibo Basin of Venezuela and Colombia. Ancistrus galani Pérez & Viloria 1994, from a cave in the Lake Maracaibo Basin of Venezuela is considered valid but was not examined. Ancistrus tolima new species is described from the upper Magdalena River drainage and Ancistrus vericaucanus new species is described from the upper Cauca River drainage. Ancistrus gymnorhynchus Kner 1854 and A. falconensis Taphorn, Armbruster & Rodriguez-O. 2010 were treated previously. One specimen of A. clementinae Rendahl 1937 from the Pacific coast of Ecuador was examined, it is considered a valid species. A key for identification and geographical ranges are provided.

Using gas geochemistry to delineate structural compartments and assess petroleum reservoir-filling directions: A Venezuelan case study

Here we examined the light hydrocarbon and nitrogen content and isotopic signatures of eleven gaseous samples in order to evaluate lateral intra-reservoir continuity in a Venezuelan reservoir in the central area of Lake Maracaibo Basin. At least three single compartments, located in the northern-central and southern parts of the reservoir, are revealed by nitrogen concentrations showing clear step-like compositional breaks. The occurrence of step-breaks was also supported by the isotopic signature of individual hydrocarbon compounds in the range of C1–C4 alkanes. Samples presented only slight differences in N2 and hydrocarbon gas compositions within the central and northern parts of the reservoir, and therefore it was not possible to infer structural barriers in coherence with the geological section. Some oil bulk parameters corroborate gradual changes that provide additional information on the reservoir-filling history, thus suggesting that the lateral physical–chemical equilibrium of fluids was not reached in this reservoir.

Hope, humanity, and Huntington's disease in Latin America

Hope, humanity, and Huntington's disease in Latin America

Enteroccoccus in Water, Sediment and Clams in a Tropical Environment,Maracaibo Lake, Venezuela

The genus Enterococcus has widespread extra enteric sources and reservoirs. It has been suggested that coastal and Great Lakes States adopt enterococci as an alternative indicator for the monitoring of recreational water quality. Limited information, however, is available about the presence of enterococci in Lake Maracaibo, which is an important estuary in Venezuela, with the income and interchange of the Caribbean Sea, and is used by the people for recreational purposes and the culture of marine organisms. In this study, the density and species composition of enterococci in sediment, clams and water were examined at Lake Maracaibo.Enterococci was enumerated by the Most Probable Number Technique (MPN), and isolated by standard methods. Results obtained by MPN analyses indicated that enterococci were present in all samples, and their densities were generally higher in clams than sediment and water with means of 1.0x106 MPN/100 g, 2.1x103 MPN/100 g, and 6.0x101 MPN/100 ml, respectively. Dominant Enterococcus species were E. faecalis (65%), E. casseliflavus (20%), E. sanguinicola (5%), E. faecium (5%), and unidentified strains (5%). Results suggest that some enterococci are able to persist in Lake Maracaibo, especially in clams and sediment, for a prolonged amount of time after being introduced.

Squamata reptiles of a fragment of tropical dry forest in northwestern Venezuela (Lake Maracaibo region)

We present a commented taxonomic list of the reptiles found during herpetological surveys carried out in an isolated fragment of tropical dry forest located in the municipality of San Francisco, Zulia state, northwestern Venezuela between January-December 2011. We report a total of 24 species belonging to the order Squamata, distributed in 12 families and 21 genera. Colubridae is the most diverse family with six species, followed by Dipsadidae (four species), Boidae, Gymnophthalmidae, Phyllodactylidae and Teiidae with two species each, and finally Dactyloidae, Iguanidae, Elapidae, Gekkonidae, Sphaerodactylidae and Viperidae with a single species each. The species composition at this site matches what would be expected in a tropical dry forest in the region. Our study suggests that this isolated tropical dry forest fragment is the last refuge of the herpetofauna that once occupied much of the dry forests of the northern Maracaibo basin and should therefore be considered for conservation purposes.