Gulf Of Venezuela Research Articles

Fibropapilomatosis en juveniles de Tortuga Verde (Chelonia mydas) del Golfo de Venezuela

Fibropapillomatosis (FP) is affecting multiple marine turtle (MT) species worldwide. In Venezuela, the understanding about this neoplastic condition is still in early stage. Hence, this paper aims to assess the occurrence and frequency of FP in green turtles (GT) in the Gulf of Venezuela (GV). Herein, it was compiled and analyzed the reports in the database of the NGO ‘Grupo de Trabajo en Tortugas Marinas del Golfo de Venezuela’, which includes all records of stranded MT in the GV from 2000 to 2011. Between 2000 and 2006, in the GV only 2 cases of FP in MT had been reported (1.71 % of total records). Subsequently, between 2008 and 2011, encounters of FP were more frequent; resulting in a total of 7 immature GT (2.93 % of the records) documented showing large masses or skin tumors in various parts of the body. The most affected area of the MT’s body was neck and venous sinus (37.50 %), followed by the anterior flippers (18.75 %), plastron (18.75 %), posterior region (cloaca 18.75 %) and lastly, the eyes (6.25 %). All individuals presented two or more body areas with FP. Although a correlation between the presence of FP and environmental factors observed in the study area was not assessed, the turtles evaluated came from coastal waters with high levels of eutrophication, habitat degradation, and pollution. It is necessary to monitor the occurrence of this disease and the environmental factors that may negatively affect the survival of MT populations in the GV.

Echinoderms from the Gulf of Venezuela, north-western coast of Venezuela

Echinoderms are a major group of marine invertebrates that often play integral roles within the marine ecosystem. Studies about their occurrence, abundance, and distribution in Venezuela are focused in the central-eastern coasts; hence the aim of this study is to describe the echinoderm community in the north-western coast of the Gulf of Venezuela. Samples were collected from three sites in the Venezuelan Guajira Peninsula (Castilletes, Porshoure, and Kazuzain) where patchy coral reefs and seagrass meadows are abundant. According to the substrate, two methods were performed using quantitative (1 m² quadrates), and qualitative free-diving observations. All organisms were counted and identified to the lowest possible taxonomic level; finally, diversity (Shannon diversity index), richness (number of species), and dominance in the different sampled substrates were recorded. The updated list of echinoderms of the Gulf of Venezuela reported in this research, includes 20 genera, 15 families, 10 orders, four classes, and 28 species. The richest class was Ophiuroidea, with 18 species, followed by Asteroidea, Echinoidea and Holothuroidea, with three species each. Castilletes was the sampling site with the higher number of species (18 species), followed by Porshoure (15 species), and lastly Kazuzain (12 species). Our observations indicate that the number of species and abundance were higher when found in coral reefs (21 species, 80.69% of the total collected individuals) in contrast to the species found in seagrass beds (16 species, 19.31% of the total of individuals collected). This updated list of echinoderms represents 11.54% of the total diversity of the phylum in the marine areas from the coast of Venezuela; it is suggested that this percentage is greatly influenced by the differences of habitats and substrates alongside the north-western coast in the Gulf of Venezuela.

Guiana Dolphin (Sotalia guianensis) in the Maracaibo Lake System, Venezuela: Conservation, Threats, and Population Overview

The Guiana dolphin (Sotalia guianensis) home range is located across Central and South American countries, in coastal habitats in the Caribbean and Atlantic Ocean. Its distribution is scattered, with multiple population centers which are under threats that vary based on local realities. We compiled and assessed biological data from multiple sources (published and unpublished data) to improve our understanding regarding the Maracaibo Lake Management Unit, which is an isolated and unique population core of this species. We identified at least two distinguishable population centers throughout the Maracaibo Lake System, one in the northern portion—in the Gulf of Venezuela, and another in the southern portion of the Maracaibo Lake itself. Both centers have differences in some biological aspects (e.g., group size and habitat use), but similarities in the human-induced pressures (e.g., intentional take, habitat degradation, and traditional use). We detailed the uses of Guiana dolphin (consumptive and non-consumptive) by community members, including the use as talismans for indigenous fishers and consumption of its meat as a religious belief (Easter period), and dolphin watching tours carried out by local companies. In one artisanal port, at least 15 animals are intentionally taken annually to be used for local consumption, shark-bait, or trade; however, we acknowledge that this annual take is likely an underestimate. Further research is needed to clarify how and at what magnitude mentioned and other key-threats are impacting over Guiana dolphin MU in the Maracaibo Lake System.

Sources and movements of marine turtles in the Gulf of Venezuela: Regional and local assessments

Marine turtles are challenging species to protect because they occur over large geographic scales. Tagging individual turtles at nesting beaches and foraging areas, and the resulting mark-recapture data sets have gradually enabled us to understand marine turtle migratory behaviour and dispersal. Within the Caribbean region, several turtle tagging projects have led to longer-term evaluations and assessments of connectivity. Thus, marine turtle mark-recapture data is important for developing conservation strategies at regional-scale. In this study, we analyse turtle tagging data from the Gulf of Venezuela to determine regional (Caribbean and Atlantic geographic level) and local (within the Gulf of Venezuela) links. To achieve this, we retrieved, compiled, and analysed multiple databases with records of marine turtles that were tagged and then recaptured in the Gulf of Venezuela. Sixty-six tag return records were evaluated, 43 from animals initially tagged outside of the Gulf of Venezuela and then recaptured inside, plus 23 records retrieved from turtles that were tagged and recaptured within the Gulf of Venezuela. We found evidence of connectivity between 12 different locations where initial tagging events occurred, eight from other feeding areas and four from nesting beaches. We described four different movement patterns for 23 turtles tagged and re-captured within the Gulf of Venezuela. Most of the recapture records we obtained occurred after the turtles were known, or presumed, to have been killed by local fishers. Hence, knowing patterns of dispersal and connectivity are crucial to improving local and regional conservation and threat mitigation.

Planktonic foraminifera as indicators of oceanographic complexity on the southern Caribbean Sea continental shelf

The southern Caribbean Sea over the northern South American continental shelf is oceanographically complex. It is subject to (1) widespread coastal upwelling, (2) wakes and eddies in the NW-flowing Guiana and Caribbean Currents to the lee of islands, and (3) the hypopycnal Orinoco River plume. Upwelled water is dispersed NW along high-productivity filaments. Offshore northern Trinidad, an intra-plume front separates higher-productivity Orinoco-derived water to the west from lower-productivity Amazon-derived water. This paper examines planktonic foraminiferal assemblages in surface sediment samples (a) below upwelling foci in the Gulf of Venezuela (GoV). North of Lake Maracaibo, and (b) at an upwelling focus in the North Coast Marine Area (NCMA) offshore northern Trinidad, near but west of the intra-plume front. The samples were collected for previous studies and only certain size fractions, which differed between the study areas, were available for current study.Samples from the GoV (>250 μm fraction; taken using an Alpine corer or a Petersen dredge) were assigned a priori to groups underlying upwelled and non-upwelled water. Discriminant analysis after cluster analysis confirmed these assignments. Total recovery was dominated by Neogloboquadrina dutertrei with lesser Globigerinoides ruberpink and the upwelling indicator Globigerina bulloides. All four non-upwelled samples, co-dominated by N. dutertrei and Gs. ruberpink, reflect seasonal freshwater outflow from Lake Maracaibo. Five upwelled-area samples were dominated by G. bulloides with subdominant N. dutertrei or Globigerinoides ruber Morphotype B. The remaining two upwelled samples (dominant N. dutertrei, subdominant Gs. ruber Morphotype A) apparently reflect the transition between upwelling and non-upwelling areas. The mean proportions of assemblages as Trilobatus sacculifer Morphotype A did not differ markedly between the upwelled and non-upwelled GoV clusters. This morphotype was absent from the Gulf proper but present to the north.NCMA total recovery (>150 μm fraction; samples taken using a van Veen grab) was dominated by Gs. ruber Morphotype B. Cluster analysis here indicated three clusters: Cluster 1, proximal to the intra-plume front; Cluster 2, distal to the intra-plume front; and Cluster 3, scattered throughout the NCMA. Upwelling was pervasive, canonical variate analysis (CVA) verifying that G. bulloides did not differentiate the clusters. Instead, these clusters were differentiated by Gs. ruber Morphotype B only, the proportional abundance of which was highest in Cluster I and lowest in Cluster 2. This pattern indicates that the influence of the Orinoco plume on assemblage composition is stronger than that of upwelling, Cluster 1 reflecting higher productivity near the front.

Comment on “Tectonic and environmental factors controlling on the evolution of Oligo-Miocene shallow marine carbonate factories along a tropical SE Circum-Caribbean” by Silva-Tamayo et al. (2017)

Silva-Tamayo et al. (2017) study the Chattian to Langhian carbonate succession of the Siamana Formation in the Cocinetas Basin (La Guajira, Colombia). They identify a change in carbonate factory from mixed photozoan-heterozoan and photozoan associations dominated by corals in the Chattian-early Burdigalian to a heterozoan rhodalgal association in the late Burdigalian-Langhian. To validate the regional scale of this shift in carbonate-producing biota along the southeastern Circum-Caribbean realm, Silva-Tamayo et al. compare the Siamana Formation with the San Luis carbonate succession in the Falcón Basin (NE Venezuela) and the Perla carbonates in the Urumaco Trough (Gulf of Venezuela). Referring to Albert-Villanueva (2016) they state that, as in the case of the Siamana Formation, the carbonates of the San Luis Formation also recorded a change in carbonate-producing biota, from a photozoan/heterozoan carbonate factory in the late Oligocene-early Miocene to a heterozoan/rhodalgal carbonate factory in the middle Miocene. Notwithstanding, Albert-Villanueva (2016) interprets the carbonate units cropping out in the Falcón Basin (San Luis and Churuguara formations) as early Miocene in age, and the passage from photozoan to heterozoan carbonate factory as a lateral change of facies within the lower Miocene carbonate platforms of the Falcón Basin.

Geology of the Falcón Basin (NW Venezuela)

ABSTRACTThis paper presents a geological map and cross-section of the Falcón Basin based both on published and unpublished work and on new data collected in the northern and southern basin margins. The geological map covers an area of 4600 km2 at 1:100,000 scale. The cross-section is oriented NNW-SSE, traversing perpendicular to the main structures. In general, the structure of the study area results from the inversion of a graben (Oligocene-early Miocene back-arc basin), that started in the middle Miocene due to the convergence between the Caribbean and South American plates. The map, the cross-section and the observations made in the field have been used to generate a tectonostratigraphic reconstruction of the Falcón Basin. The Oligocene-early Miocene sedimentary succession mapped and described is relevant to the hydrocarbon exploration in the Caribbean and in the Gulf of Venezuela, where new hydrocarbon resources have recently been discovered (i.e. Perla gas field).

Acoustic Parameters of Guiana Dolphin (Sotalia guianensis) Whistles in the Southern Gulf of Venezuela

The Guiana dolphin (Sotalia guianensis) is widely distributed along the coasts of Central and South America. Similar to other delphinids, this species emits echolocation clicks, burst pulses, and whistles. Although whistling seems to play a major role in the social organisation of dolphins, there is a lack of knowledge about Guiana dolphin whistles outside of its populations in Brazil and Costa Rica. In this study, we describe the acoustic structure of Guiana dolphin whistles from the southern Gulf of Venezuela for the first time. We recorded the whistles using an omnidirectional hydrophone (CR1). For each whistle, we measured maximum frequency (kHz), minimum frequency (kHz), starting frequency (kHz), ending frequency (kHz), duration (s), and number of inflection points, using spectrograms created in SpectraLAB 4.32, Version 17. Whistles presented an average starting frequency of 10.58 kHz (SD = 2.49 kHz), a mean ending frequency of 13.96 kHz (SD = 2.60 kHz), an average minimum frequency of 10.31 kHz (SD = 2.33 kHz), a mean maximum frequency of 13.96 kHz (SD = 2.51 kHz), an average duration of 0.27 s (SD = 0.14 s), and a maximum of four inflection points (mode 0). This research provides new insights into the acoustic behaviour of the Guiana dolphin in the Gulf of Venezuela.

Pesquería y parámetros biométricos de los cangrejos del género <i>Calappa</i>(Brachyura: Calappidae) en el oriente de Venezuela<

The box crabs, genus Calappa, are important crab species landed by the industrial trawl fleet in Venezuela. These crabs have a wide distribution in the country, from the Gulf of Venezuela to the Orinoco River, but major landings take place in such gulf, near Margarita Island and northern Sucre State. Average annual landing in the eastern region was 69 t during 1970-2001, with a maximum of 221 t. For this study a sample of 2 398 box crabs was collected by observers on board of industrial trawl vessels, which operated in eastern Venezuela from 1994 to 2000. Three species were found in the landings, Calappa sulcata and C. flammea. each represented 47% of the sample, and C. nitida, which accounted for 5% of the sample. Sex ratio was strongly biased towards males in C. sulcata (2.8:1) and in C. flammnea (1.9:1). while it was only slightly biased in C. nitida (1.4:1). Due to its large size, C. sulcuta is of great commercial interest, with average weight 290 g and a maximum weight of 720 g: C. flammea showed an average weight of 140 g and a maximum weight of 418 g, while C. nitida is the smallest species, with average weight 46 g and maximum weight not beyond 113 g. Box crabs were captured by day and night in similar proportions, and were found in a wide depth range, from a few meters to 126 m deep; however, the largest captures were obtained in the interval 38 - 54 m. Regressions between weight of chelae and total weight were linear, and significantly different between sexes. The relation between total weight and carapace width was allometric, with a power exponent ca. three in C. sulcata, and less than three in C. flamea and C. nitida. Females of C. sulcata and C. nitida showed power exponents significantly smaller than males. Since claws are removed from the animal to be commercialized, while the rest of the animal is returned alive to the sea, for practical purposes a common equation among species and sexes to convert claws weight into total body weight is: total weight - 3 x claws weight. The relationship between catch per unit of effort (CPUE) and effort did not show a significantly decreasing trend, but landings follow the effort trend, with a decreasing tendency in recent years. No mature females were found in any of the three species, thus there could be reproductive migrations towards deeper waters from October to January, when abundance of crabs is lower in the study area. It is recommended that the practice of exploiting only one claw, returning the rest of the animal alive to the sea, should be promoted among fishers, while the removal of claws from female crabs should be avoided.

Catch per unit effort-environmental variables relations in the fishery of white shrimp (<i>Litopenaeus schmitti</i>) from the Gulf of Venezuela

During 15 months the white shrimp (Litopenaeus schmitti) fishing zone was characterized ecologically through the obtaining, compilation and analysis of environmental and physicochemical variables, and modeled the distribution of the relative abundance (CPUE) obtained in 21 fishing sites according to the environmental structure defined by the studied variables. A two-way factorial ANOVA with interaction was used to examine the spatial (fishing sites) and temporal (months) dynamics of CPUE, and a principal component analysis (PCA) was used to discern the environmental structure of the study area. To determine if the environmental structure modeled the distribution of white shrimp, the CPUE values were superimposed on maps of the study area showing strata of the most important physicochemical variables identified by PCA. ANOVA confirmed that the CPUE differed significantly among months (F = 15.6; GL = 11; P P = 0.1979); the interaction term was also not significant (F = 0.52; GL = 10; P = 0.8561). The superimposing of the CPUE on temperature and depth strata confirmed that white shrimp showed greater preference for intermediate temperatures and depths. Petróleos de Venezuela, S.A (PDVSA) contemplates the construction of a multiuse pipeline traversing the study area, by which the current environmental structure of the study area is prone to disturbance. Given the precedent effects represented by an aqueduct construction, it seems PDVSA should anticipate measures to minimize its impact on the fisheries of the zone, particularly on the white shrimp fishery.

Aruba: A re-evaluation of petroleum prospectivity following the recent discoveries in the Gulf of Venezuela

Following the only offshore wells drilled back-to-back in 1989/1990, whose primary targets turned out to be non-reservoir, Alan Holden makes the case for a fresh look at an area that has seen no active exploration since 1990.

Venezuela-Colombia Relations (1987-2007): Twenty Years of Diplomacy

The article deals with diplomatic relations between Venezuela and Colombia over the past twenty years. It starts with a review of the incident in the Gulf of Venezuela, the last major incident between the two countries, and the subsequent launching of a new round of negotiations. The negotiations are comprised of four different pillars, which have been developed during the time of the negotiation. The article shows the process of development of a new framework of negotiations, from a face-off situation to a more cooperative environment that has included five Colombian presidents and four Venezuelan presidents, including the polemic Hugo Chavez, who has supported the process of negotiation

The vanishing Carib Halite Formation (Neocomian), Colombia-Venezuela-Trinidad prolific petroleum province

Abstract Literature survey reveals evidence of a thick ( c . 3 km), largely dissolved, Berriasian–Valanginian ‘Carib Halite Formation’, deposited in a Jurassic to Coniacian ‘Carib Graben’ from Colombia through Venezuela to Trinidad. From Campanian time the graben inverted into the (partly metamorphosed) south-verging nappe/thrust-belt of northern South America (Guajira to Trinidad), and later the bivergent Eastern Cordillera and Mérida Andes. Outcropping halite is confined to Colombia. Numerous lines of evidence suggest buried halite in Colombia, Venezuela and Trinidad: drowning coastal geomorphology (halite-solution subsidence); subaerial and submarine closed depressions (solution pits); saline springs; mud-volcano-fluid analysis; heat-flow anomalies; gravity anomalies; and thrust-belt structural style. Other data suggest thick (kilometres) vanished halite: a Berriasian regional faunal gap; highly organic shales/phyllites (solution residues); intense fracturing (solution collapse); metamorphic-grade discontinuities (solution weld); and Neogene supraorogen basins attributable to buried-halite solution, for example Gulf of Venezuela, Monagas thrust belt, Gulf of Paria and onshore Trinidad. Halite solution by circulating meteoric water is inferred to have begun near 11 Ma, reflecting climate change (wetter) accompanying the onset of the Gulf Stream, induced by collision of the Panamá Arc against Colombia, interrupting deep-sea Caribbean–Pacific interchange. The Carib Halite concept has important implications for exploration in the oil-rich thrust belts of Colombia, Venezuela and Trinidad. There is also potential for new finds of emeralds and other evaporite-associated minerals.

Dynamics of a large tropical lake: Lake Maracaibo

The dynamics of a large tropical lake, Lake Maracaibo, Venezuela, are described using field data and the 3D Estuary and Lake Computer Model (ELCOM). ADCP data from November 1998 and CTD data spanning September 1998 to April 1999 are presented. Seawater enters Lake Maracaibo via an augmented natural connection to the Gulf of Venezuela, which allows an influx of seawater and results in almost perenial salt stratification within the lake. Spatially varying wind forcing is found to be necessary to simulate an observed basin-scale cyclonic gyre. The gyre maintains a doming of isopycnals through a geostrophic balance that lifts high-salinity bottom water closer to the surface where it is entrained into the surface mixing layer and subsequently advected by wind-induced circulations. Horizontal excursions of saline bottom water result in considerable variability of salinity stratification at any given location in the lake. September to December (wet season) was characterized by relatively high river inflow and weak winds, resulting in weak forcing of lake circulation and weak basin-wide vertical salt flux. January to April (dry season) was characterized by relatively weak river inflow and strong winds, resulting in strong forcing of lake circulation and enhanced, basin-wide vertical salt flux. The dry season of 1999 was relatively wet (compared with other dry seasons, but still drier than the previous wet season) and there was no indication of a saline underflow occurring from Maracaibo Strait into Lake Maracaibo. The combination of strong wind forcing, low river inflow (compared with the wet season), and little or no saline intrusion during the dry season of 1999 resulted in almost complete flushing of saline bottom water.

Mass transport between a semienclosed basin and the ocean: Maracaibo System

Field data and three‐dimensional numerical (Estuary and Lake Computer Model) simulations are used to investigate exchange between Lake Maracaibo and the Gulf of Venezuela. This exchange occurs along a dredged shipping lane 100 km long and 14 m deep. It is driven by a density difference between the lake and gulf and modulated at tidal and subtidal timescales by water level fluctuations in the gulf propagating to the lake. At tidal frequencies, exchange is modulated by barotropic forcing and nonlinear baroclinic response, leading to a severance of high‐salinity bottom water into seaward and landward segments. Bottom water in the landward segment is moved lakeward along the shipping lane, where it is mixed vertically and flushed out. Subtidal water level fluctuations in the gulf force barotropic currents along the shipping lane, dominating variability of volume and salt flux at timescales of 1–4 weeks. The barotropic component of simulated salt flux decreases from the gulf to the lake, as depth‐averaged salinity decreases, while simulated baroclinic exchange is only 20% of that predicted by quasi‐steady two‐layer hydraulic theory. These reductions in salt flux are due to intense mixing that occurs throughout the shipping lane.

Natural and man-induced changes in a tidal channel mangrove system under tropical semiarid climate at the entrance of the Maracaibo lake (Western Venezuela)

Cano Paijana is a tidal channel that connected, until recently, theUruba bay at the mouth of the Limon river, to the Gulf of Venezuelanorth of Maracaibo, Venezuela. It separated the Island of San Carlos fromthe mainland. In the last 50 years the channel has been drying out rapidly,to the extent that presently there is no water flow into or from the seathrough its mouth opening on the Gulf of Venezuela. This mouth wascovered by healthy mangroves (mainly Avicennia germinans) until atleast 1952. The two extremes of the Paijana water channel differ radicallytoday. At Uruba bay end the channel is fringed by dense mangrovevegetation dominated by Rhizophora mangle, while at the Gulf ofVenezuela mouth the vegetation cover is mostly constituted by scrubby,scattered trees of Avicennia germinans, xerophytic shrubs acting asdune fixers, and halophytic strand vegetation. The process is the result ofcomplex interaction between: a) high frequency of low-rainfall years; b)high dune activity during dry years c) dam construction on tributaries ofthe Limon river that reduced discharge of fresh water into Uruba bay.

Computer Modeling of Oil Spill Trajectories With a High Accuracy Method

This paper proposes a high accuracy numerical method to model oil spill trajectories using a particle-tracking algorithm. The Euler method, used to calculate oil trajectories, can give adequate solutions in most open ocean applications. However, this method may not predict accurate particle trajectories in certain highly non-uniform velocity fields near coastal zones or in river problems. Simple numerical experiments show that the Euler method may also introduce artificial numerical dispersion that could lead to overestimation of spill areas. This article proposes a fourth-order Runge–Kutta method with fourth-order velocity interpolation to calculate oil trajectories that minimize these problems. The algorithm is implemented in the OilTrack model to predict oil trajectories following the “Nissos Amorgos” oil spill accident that occurred in the Gulf of Venezuela in 1997. Despite lack of adequate field information, model results compare well with observations in the impacted area.

Nissos Amorgos Oil Spill Experience

ABSTRACT The behavior of the Bachaquero crude oil spilled by tanker Nissos Amorgos, when it grounded in the Gulf of Venezuela, was studied through modelling its fate using the SIMAP model (Applied Science Associates, Inc.). The purpose of the simulations was to improve the cleanup activities, and to help in evaluating the environmental impact.

Tidal dynamics in a coupled ocean/lake system

Barotropic tides were studied in the Lake Maracaibo system, Venezuela. The system consists of two larger water bodies, the Gulf of Venezuela and Lake Maracaibo, connected by the Strait of Maracaibo and Tablazo Bay. The dominant semi-diurnal tide resonates in the gulf and co-oscillates roughly 180° out of phase in the lake. The narrow strait and shallow bay regulate their dynamical interaction. Two- and three-dimensional finite element models are used in conjunction with a fresh analysis of tidal data at seven stations, several of which lie in the strait and bay. A coupled model of the whole system is necessary to properly interpret these data, which show the influence of small-scale, near-field effects superimposed on the larger-scale dynamics of the gulf and lake. The detailed geometry at the connections with the gulf and the lake also plays a significant role in the local response in the strait and bay. Co-tidal charts are presented for nine major astronomical and shallow water tidal constituents found in the data. The velocity structure derived under simple eddy viscosity assumptions is shown to be highly dynamic. A characteristic phase lead is found in velocities at depth and near the shore, where vertical shear dominates over inertia in the force balance.

Realism and Internationalism in the Gulf of Venezuela

ritorial waters of Colombia. The Venezuelan navy responded by deploying frigates to the scene to reassert Venezuela's claim of territorial jurisdiction over the waters. A protracted naval encounter followed; Venezuelan warships crossed the prow of the Caldas and dispatched Mirage fighter aircraft to overfly it. As the confrontation proceeded, both governments appealed for calm but took steps which to many observers suggested preparations for war. On 21 August, at Colombia's request, the Organization of American States (OAS) met in special session. Official emissaries