Confluence Areas Research Articles

Diversidade de mamíferos do baixo Rio Jufari, Roraima, Brasil

Faunal inventories are essential to directly access the diversity of a region. Although the Amazon rainforest exhibit large estimates of mammal species richness, the region still exhibits large sampling gaps. Aiming to fill a sampling gap on the mammalian diversity in the Brazilian Amazon rainforest, we conducted an inventory of non-volant mammals at “terra firme” forest near the mouth of Rio Jufari, an affluent of north bank of Rio Negro, near its confluence with Rio Branco. To sample small mammals, we applied a total effort of 3,673 live trap nights, and 2,700 pitfall trap nights. For large mammals we performed unstandardized line transect census, and included, as well, records from occasional encounters and material donated by Caicubi community members. The pitfall traps proved to be extremely valuable for the small mammals sampling. We observed a low mammalian diversity when compared to other inventories throughout the Amazon basin. We recorded 27 species belonging to 25 genera, 16 families and nine orders of the Class Mammalia. The majority of recorded species is known from Guianan subregion. However, we present: extension on the known distribution records for Marmosops bishopi; taxonomic comments on the marsupial Monodelphis brevicaudata; and new collection record for species of the genera Oecomys and Makalata. It is remarkable the extremely low number of species from the order Primates. Data based on interviews suggested that this small number of primate specimens is historical, and areas closer to Rio Negro and Rio Branco exhibit higher diversity. Our samples showed that Rio Negro-Rio Branco confluence do not present an endemic mammalian fauna, once the region shares its mammalian composition with other confluence areas in the Amazon basin, especially with those on the northeastern Amazon region.

Use of multi-objective dredging for remediation of contaminated sediments: a case study of a typical heavily polluted confluence area in China.

Sediments in confluence areas are typically contaminated by various pollutants that have been transported there by inflowing rivers. In this study, we evaluated the pollution status of a confluence area in Lake Chaohu (China). Both the nutrients and hazardous pollutants were analysed. Most sediment cores showed large variations in nutrient concentrations at depths of 10 to 18 cm. Positive release rates of NH4(+)-N and PO4(3-)-P were detected in sediment cores. Hg and Cd were the most typical problematic metal contaminants encountered, and their contamination levels extended to depths of 20 and 25 cm, respectively. Polycyclic aromatic hydrocarbons (mostly acenaphthene and fluorine) were the primary persistent organic pollutants (POPs) present in sediments, and contamination levels frequently could be detected up to a depth of 16 cm. Simulated dredging operations were implemented in the laboratory, with a dredging depth of 15 cm found to be suitable for nutrient suppression. With the goal of suppressing nutrients release and removing high-risk metals and POPs, a multi-objective dredging plan was developed. This plan subdivides the confluence area into five parts that were treated with different dredging depths. A demonstration area was dredged in the most heavily polluted part, and the observed dredging effects were consistent with those expected on the basis of the plan. Such an approach to dredging might also be useful in other areas in the future.

Zooplankton in the zones of confluence of unregulated rivers

The hydrophysical characteristics and indices of zooplankton are given for the confluence zones of small and medium tributaries and channels of the Don and Khoper rivers within the territory of Voronezh oblast. Three types of confluence areas of tributaries and recipient rivers are described. In these areas the water masses mix and habitats differing in physical parameters of water and structures of aquatic animal communities are formed.

Ecology and conservation status of tucuxi (Sotalia fluviatilis) in the Pacaya-Samiria Reserve, Peru

The distribution, relative abundance, group size, reproductive seasonality, and conservation status of tucuxi (Sotalia fluviatilis) were investigated in Peru’s Pacaya-Samiria National Reserve from 1996 to 2000. Data collection consisted of boat-based surveys of dolphins and habitat, necropsies, photo-identification of individual dolphins, and interviews with local people. Mean encounter rates were between 0.01-0.80 tucuxi/km in rivers, and 0.05-2.17 tucuxi/km2 in lakes, and were within the ranges reported for riverine tucuxi throughout their distribution. Encounter rates were highest in confluences, intermediate in lakes, and lowest in rivers. Encounter rates increased with river width. Most tucuxis were seen within 100m from shore in large rivers, and large groups were associated with confluence areas and mid-channel islands. Within lakes, tucuxis were associated with areas of deeper water. Tucuxis were not found in waters <3m depth in rivers, or <1.8m depth in lakes. Seasonal differences in encounter rates did not exist in lakes and rivers. In confluences tucuxis occurred in highest densities during low water, and lowest densities during high water. Diurnal patterns of occurrence were not observed. Tucuxis were seen most often as singles or pairs, although groups as large as 13 were observed. Significant seasonal differences in group size were not detected. Neonate tucuxi were observed in all seasons, with a slight peak in encounter rates during high water. Abundance estimates were affected by survey methods, and strengths and weaknesses of various methods are discussed. Photo-identification rates were low, and this method did not yield information about tucuxi site fidelity, movement patterns, social structure, or population size. Local people in the Reserve did not seem to have the same myths and general apprehension about tucuxis as for the other sympatric dolphin, Inia. There was no evidence that tucuxi were poisoned by fishermen, unlike Inia. Potential threats to tucuxi in this region were entanglement in fishing gear, mercury in migratory fish from gold mining elsewhere, oil spills, ship strikes, and disturbance from boats. Only one dead tucuxi was encountered, and had been entangled in a turtle net. Tucuxi teeth were found for sale in local markets.

Enhanced Diversity at Network Nodes: River Confluences Increase Vegetation-Patch Diversity~!2010-03-22~!2010-04-30~!2010-07-07~!

Although dendritic networks within ecosystems have typically been considered a special case of network topology, they have attracted a great deal of attention in recent years. These systems exhibit unique features in that both the nodes and branches provide distinct habitats. Within a river discontinuum context, river confluences, which are nodes of dendritic river networks, are hypothesised to have particular hydrodynamic traits that create heterogeneous habitats through a unique disturbance regime, although this hypothesis has not yet been tested. We tested this hypothesis using a vegetation data set collected from 14 river basin systems in Hyogo Prefecture, Japan. We compared vegetation-patch diversity between confluence and single-flow areas using hierarchical Bayesian models. Our results demonstrated greater vegetation-patch diversity in confluence areas compared to single-flow areas. Our findings support the hypothesis that confluences result in highly heterogeneous habitats. To the best of our knowledge, this is the first empirical report to demonstrate that river confluences have high vegetation-patch diversity. We conclude that network nodes play an important role in maintaining the biodiversity of river networks.

Mesenchymal Cells and Fibrocytes in Peripheral Blood. Culture Conditions

The fibrocytes, the mesenchymal cells and the colony forming units are included in the concept fibroblast-like, peripheral-blood circulating stem cells. The aim of this work was to establish the culture conditions.Peripheral blood mononuclear cells were isolated from 25 samples collected from the cephalic vein. These were cultured in McCoy's 5A enriched with 20% of foetal bovine serum. The culture was read at 7, 14 and 21 days, evaluating the proliferation, confluence and the round cell/spindle cell ratio. Moreover the 21st day surface markers and phagocytic activity testing was carried out.Growth was achieved in all the cases but only in two dishes were confluence areas retrieved. Spindle cells were 36 ± 3.71% (mean ± SD). All the cells showed intense signal against vimentin, CD34 marker and the NBT test were positives.Clear CD34 expression, positivity against a connective tissue marker such as vimentin and positivity in a phagocytic assay like the NBT-test, support that stem cells, monocytes and fibroblasts share common characteristics.

Fotogenia literaria en <i>Carreteras secundarias</i>, de Ignacio Martínez de Pisón: un viaje de ida y vuelta

The cinema, his synthetic character, and the dialogue that it establishes from the origin with other arts as literature, has not stopped offering a wide space of synergies for the adaptation practice and for the study of confluence areas between image and word. New generations of writers and directors propiciate across their work an opening that, beside integrating the expressive resources of the literature and the screen, consider the text as a productive and plural activity, capable of being spread in a stereophony that postpones its meaning in every process of reading, making it coincide with a practice of writing and creation. Ignacio Martinez de Pison's literature contains sugerent keys to advance in the dialogue between literature and cinema in current Spanish narrative.

Conservation management of small core areas: key to survival of a Critically Endangered population of Irrawaddy river dolphins Orcaella brevirostris in Indonesia

Indonesia's only freshwater dolphin is the facultative Irrawaddy river dolphin Orcaella brevirostris in the Mahakam River in East Kalimantan, Borneo. To clarify the status of this Critically Endangered subpopulation we carried out a series of surveys from early 1999 until mid 2002 on abundance, habitat use, population dynamics and threats. Our estimates of total population size were 33–55 dolphins (95% confidence limits 31–76) based on direct counts, strip-transect analysis, and Petersen and Jolly-Seber mark-recapture analyses of photo-identified individuals. Mean minimum annual birth and mortality rates were similar, i.e. 13.6 and 11.4%, and no changes in abundance >8% were detected over 2.5 years. Dolphins died mainly from entanglement in gill-nets (73% of deaths). The dolphins' main habitat includes confluence areas between the main river and tributaries or lakes. Dolphins make intensive daily use of these confluences, moving up and downstream over an average length of 10 km of river and within a 1.1 km2 area. These areas are also important fishing grounds and subject to intensive motorized boat traffic. Sixty-four percent of deaths (1995–2001) with known location (n = 36) occurred in these areas. Interviews with local residents revealed a generally positive attitude towards the establishment of protected areas for this subpopulation. Because of the dolphins' dependence on areas that are also used intensively by people, primary conservation strategies should be to increase local awareness and introduce alternative fishing techniques.

Cetacean habitat in the northern oceanic Gulf of Mexico

Cetaceans (whales and dolphins) are diverse and abundant upper trophic level predators in the Gulf of Mexico, a semi-enclosed, intercontinental sea with a total area of about 1.5 million km 2. The objectives of this study were to better define the habitat of cetaceans in the northern oceanic Gulf of Mexico. An integrated methodology was used that included visual surveys and hydrographic collections from ships. Near real-time sea surface altimetry from the TOPEX/POSEIDON and ERS satellites was used during ship surveys to determine the location of hydrographic features (e.g., cyclones, anticyclones and confluence zones). Archival satellite sea surface altimetry data were also used to retrospectively determine the location of hydrographic features for analysis with earlier cetacean sightings. We estimated zooplankton and micronekton biomass using both net and acoustic sampling to indicate the amount of potential food available for higher trophic level foraging by cetaceans. Nineteen cetacean species were identified during ship surveys. Cetaceans were concentrated along the continental slope in or near cyclones and the confluence of cyclone–anticyclone eddy pairs, mesoscale features with locally concentrated zooplankton and micronekton stocks that appear to develop in response to increased nutrient-rich water and primary production in the mixed layer. A significant relationship existed between integrated zooplankton biomass and integrated cephalopod paralarvae numbers, indicating that higher zooplankton and micronekton biomass may correlate with higher concentrations of cetacean prey. In the north-central Gulf, an additional factor affecting cetacean distribution may be the narrow continental shelf south of the Mississippi River delta. Low salinity, nutrient-rich water may occur over the continental slope near the mouth of the Mississippi (MOM) River or be entrained within the confluence of a cyclone–anticyclone eddy pair and transported beyond the continental slope. This creates a deep-water environment with locally enhanced primary and secondary productivity and may explain the presence of a resident, breeding population of sperm whales within 100 km of the Mississippi River delta. Overall, the results suggest that the amount of potential prey for cetaceans may be consistently greater in the cyclone, confluence areas, and south of the MOM, making them preferential areas for foraging. However, this may not be true for bottlenose dolphins, Atlantic spotted dolphins and possibly Bryde's whales, which typically occur on the continental shelf or along the shelf break outside of major influences of eddies.

A three-dimensional numerical model of the confluence area of Unteraargletscher, Bernese Alps, Switzerland

AbstractWith the use of a numerical three-dimensional (3-D) model the flow dynamics of the confluence area of Unteraargletscher, Bernese Alps, Switzerland, are studied. Previous predictions, based on conceptual two-dimensional models, about flow characteristics at confluence areas are tested against results from the fully 3-D model. Measured winter velocities are used for model verification. Despite some consistent systematic differences, good overall agreement between measured and calculated surface velocities is obtained. The calculated vertical strain-rate variation with depth is in good agreement with available measurements from boreholes. The ice is found to be almost three times stiffer than standard estimates of rheological parameters for glacier ice would predict. The model predicts a complicated yet realistic pattern of vertical velocity variation along the surface. The most noticeable features of the vertical velocity distribution across the surface are listed, and their relation to topographic surface undulations and the overall dynamics of the confluence discussed. In accordance with previous results from analytical models, a strongly localized surface trough and a concomitant negative (downward orientation) vertical velocity anomaly develop at the junction point. Although depth-integrated strain rates are positive (extension), the basal layer is compressed vertically. The ice-cored medial moraine is formed by differential ablation. The flow mechanics of the confluence area play only an indirect role, by enabling transfer of debris-covered marginal ice towards the confluence center. In the absence of differential ablation, an elongated surface depression would be formed in the down-glacier direction from the junction point instead of an elevated ice-cored medial moraine.

A three-dimensional numerical model of the confluence area of Unteraargletscher, Bernese Alps, Switzerland

AbstractWith the use of a numerical three-dimensional (3-D) model the flow dynamics of the confluence area of Unteraargletscher, Bernese Alps, Switzerland, are studied. Previous predictions, based on conceptual two-dimensional models, about flow characteristics at confluence areas are tested against results from the fully 3-D model. Measured winter velocities are used for model verification. Despite some consistent systematic differences, good overall agreement between measured and calculated surface velocities is obtained. The calculated vertical strain-rate variation with depth is in good agreement with available measurements from boreholes. The ice is found to be almost three times stiffer than standard estimates of rheological parameters for glacier ice would predict. The model predicts a complicated yet realistic pattern of vertical velocity variation along the surface. The most noticeable features of the vertical velocity distribution across the surface are listed, and their relation to topographic surface undulations and the overall dynamics of the confluence discussed. In accordance with previous results from analytical models, a strongly localized surface trough and a concomitant negative (downward orientation) vertical velocity anomaly develop at the junction point. Although depth-integrated strain rates are positive (extension), the basal layer is compressed vertically. The ice-cored medial moraine is formed by differential ablation. The flow mechanics of the confluence area play only an indirect role, by enabling transfer of debris-covered marginal ice towards the confluence center. In the absence of differential ablation, an elongated surface depression would be formed in the down-glacier direction from the junction point instead of an elevated ice-cored medial moraine.

A three-dimensional numerical model of the confluence area of Unteraargletscher, Bernese Alps, Switzerland

AbstractWith the use of a numerical three-dimensional (3-D) model the flow dynamics of the confluence area of Unteraargletscher, Bernese Alps, Switzerland, are studied. Previous predictions, based on conceptual two-dimensional models, about flow characteristics at confluence areas are tested against results from the fully 3-D model. Measured winter velocities are used for model verification. Despite some consistent systematic differences, good overall agreement between measured and calculated surface velocities is obtained. The calculated vertical strain-rate variation with depth is in good agreement with available measurements from boreholes. The ice is found to be almost three times stiffer than standard estimates of rheological parameters for glacier ice would predict. The model predicts a complicated yet realistic pattern of vertical velocity variation along the surface. The most noticeable features of the vertical velocity distribution across the surface are listed, and their relation to topographic surface undulations and the overall dynamics of the confluence discussed. In accordance with previous results from analytical models, a strongly localized surface trough and a concomitant negative (downward orientation) vertical velocity anomaly develop at the junction point. Although depth-integrated strain rates are positive (extension), the basal layer is compressed vertically. The ice-cored medial moraine is formed by differential ablation. The flow mechanics of the confluence area play only an indirect role, by enabling transfer of debris-covered marginal ice towards the confluence center. In the absence of differential ablation, an elongated surface depression would be formed in the down-glacier direction from the junction point instead of an elevated ice-cored medial moraine.

Downstream Impacts of a Dam on a Bedrock Fluvial System, Brazos River, Central Texas

Impoundment of the Brazos River at Lake Whitney Dam had caused localized aggradation in the bedrock floored channel for over 22 mi (35 km) downstream. Patterns of aggradation are related to input of elastics from steep bedrock controlled, mixed-load tributaries. Surveyed tributary delta systems have shown steady growth since the dam was constructed in 1951. Five of the 21 tributary deltas are shown to affect river gradient, river planform, and channel dimensions. Thresholds of channel erosion on the Brazos River are related to delta planform size: armored tributary deltas with areas over 81,000 ft2 (7,525 m2) which occupy about 68 percent of the main stem width represent the threshold at which channel bank loss begins. Bank loss in these areas ranges from 5–14 ft (1.5–4.3 m) a year. Channel hydraulics at the confluences are inferred from 2D flow models. Five zones of flow are recognized in the confluence areas and appear to be related to delta planform and sediment transport. Delta growth is shown to be related to tributary drainage area and channel slope; most deltas are predicted to double their size in the next 35 years. Six management alternatives were considered for channel bank erosion control. Retention check dams on the tributaries built to retain the coarse bed load sediment are recommended. Mining trapped gravels in the tributaries for local road-base material is also advocated.

La dynamique des cours d'eau dans les zones de confluence au cours du Quaternaire

Fluvial action in the confluence areas throughout the Quaternary period. After describing and explaining the present fluvial action in the junction areas chosen in the middle course of the river Allier, we shall try to reconstitute the conditions of water discharge and the evolution of the junction areas throughout the Quaternary. This will be attempted from the study of the old alluvial sheets study dealing particularly with the extension of the alluvial plains of the end of each deposition period, with the longitudinal sections of the top and the bottom of the alluvial layers and with the analysis of the material. The evolution of the junction areas results from the successive diggings of the main river thus forcing the main tributaries to move their course downstream. That migration favours the conservation of tiers of terraces laid out in triangles upstream from the junction areas. The older the sheets, the wider their alluvial plain appears and the steeper its longitudinal slope is. However, the slope of the rivers contemporary with the different deposition periods isn't necessarily the same as that of the top of the latter, it mainly depends on the size of the material transported.

Establishing Global Traffic Flows

As vessels become more efficient and shipping demands continue to grow the population explosion of vessels at sea is outdistancing even its famous human counterpart. This increases the risk of accidents, particularly in confluence areas and straits, and to avert future disaster it is important to predict trends in global traffic flows so that appropriate measures may be taken in time. This poses a difficult problem. Due to the diversity of nationalities involved, the autonomy of ships and competitive secrecy, it is only possible to account for the present at-sea ship population within about 16 per cent. Geographical distribution is even more doubtful and predicting changes more speculative still.