946 resultados para Dinoponera australis


Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Cores from the 11 sites drilled during Leg 180 showed radiolarian assemblages that appear only in the Quaternary sediments. The most diverse and well-preserved assemblages were found in hemipelagic sediments from Holes 1108A, 1110A, and 1115B.

Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Palmer Deep is a series of three glacially overdeepened basins on the Antarctic Peninsula shelf, ~20 km southwest of Anvers Island. Site 1098 (64°51.72'S, 64°12.48'W) was drilled in the shallowest basin, Basin I, at 1012 m water depth. The sediment recovered was primarily laminated, siliceous, biogenic, pelagic muds alternating with siliciclastic hemipelagic sediments (Barker, Camerlenghi, Acton, et al., 1999). Sedimentation rates of 0.1725 cm/yr in the upper 25 m and 0.7-0.80 cm/yr in the lower 25 m of the core have been estimated from 14C (Domack et al., 2001). The oldest datable sediments have an age of ~13 ka and were underlain by diamicton sediments of the last glacial maximum (Domack et al., 2001). The large-scale water-mass distribution and circulation in the vicinity of Palmer Deep is dominated by Circumpolar Deep Water (CDW) below 200 m (Hofmann et al., 1996). Palmer Deep is too far from the coast to be influenced by glacial meltwater and cold-tongue generation associated with it (Domack and Williams, 1990; Dixon and Domack, 1991). Circulation patterns in the Palmer Deep area are not well understood, but evidence suggests southward flow across Palmer Deep from Anvers Island to Renaud Island (Kock and Stein, 1978). The water south of Anvers Island is nearly open with loose pack ice from February through May. The area is covered with sea ice beginning in June (Gloersen et al., 1992; Leventer et al., 1996). Micropaleontologic data from the work of Leventer et al. (1996) on a 9-m piston core has revealed circulation and climate patterns for the past 3700 yr in the Palmer Deep. The benthic foraminifer assemblage is dominated by two taxa, Bulimina aculeata and Bolivina pseudopunctata, which are inversely related. High relative abundances of B. aculeata occur cyclically over a period of ~230 yr. The assemblage associated with high abundance of B. aculeata in Palmer Deep resembles that from the Bellingshausen shelf, which is associated with CDW. In addition to the faunal evidence, hydrographic data indicate incursions of CDW into Palmer Deep (Leventer et al., 1996). A distinctive diatom assemblage dominated by a single genus was associated with peaks in B. aculeata, whereas a few different assemblages were associated with lows in B. aculeata. Leventer et al. (1996) interpreted the variability in diatom assemblages as an indication of changes in productivity associated with changes in water column stability. Abelmann and Gowing (1997) studied the horizontal and vertical distributions of radiolarians in the Atlantic sector of the Southern Ocean. They show that the spatial distribution of radiolarian assemblages reflects hydrographic boundaries. In a transect from the subtropical Atlantic to polar Antarctic zones, radiolarians in the upper 1000 m of the water column occurred in distinct surface and deep-living assemblages related to water depth, temperature, salinity, and nutrient content. Living assemblages resembled those preserved in underlying surface sediments (Abelmann and Gowing, 1997). Circumantarctic coastal sediments from neritic environments contained a distinctive assemblage dominated by the Phormacantha hystrix/Plectacantha oikiskos group and Rhizoplegma boreale (Nishimura et al., 1997). Low diversity and species compositions distinguished the coastal sediments from the typical pelagic Antarctic assemblages. Factors that controlled the assemblages were water depth, proximity to the coast, occurrence of sea ice, and steepness of topography, rather than temperature and salinity. Nishimura et al. (1997) found a gradient of sorts from deep-water sites containing diverse assemblages typical of pelagic environments to coastal sites with low diversity assemblages dominated by P. hystrix/P. oikiskos group and R. boreale. In general, sites between these two extremes had increased proportions of the coastal assemblage with decreasing water depth (Nishimura et al., 1997). At a site near Hole 1098 (GC905), they showed that the relative abundance of the coastal assemblage increased downcore (Nishimura et al., 1997). The purpose of the research presented here was to make a cursory investigation into the radiolarian assemblages as possible paleoenvironmental indicators.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Historical archaeology, in its narrow temporal sense -as an archaeology of the emergence and subsequent evolution of the Modern world- is steadily taking pace in Spanish academia. This paper aims at provoking a more robust debate through understanding how Spanish historical archaeology is placed in the international scene and some of its more relevant particularities. In so doing, the paper also stresses the strong links that have united historical and prehistorical archaeology since its inception, both in relation to the ontological, epistemological and methodological definition of the first as to the influence of socio-political issues in the latter. Such reflection is partly a situated reflection from prehistory as one of the paper’s authors has been a prehistorian for most of her professional life.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The pottery found in the burials of El Cano is uniform in style to these made in the coclesanos valleys between 700 and 1000 AD. The coefficient of variability of the different pottery forms, evidence diverse standardizations values for polychrome and non-polychrome ceramics. Moreover, data of funerary contexts from the Cano recently excavated, suggest that elite has controlled ceramic production. This control over the production of certain goods reveals that these were important in the support or proper operational of the chiefdoms in Panama and mark the phase of splendour of this culture.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Quattro sistemi pilota, cilindrici, rappresentanti SFS a flusso verticale sono stati adoperati in parallelo per attività di ricerca. Il refluo trattato, defluente dalla sede di Ingegneria di via Terracini e classificabile come urbano, è stato immesso negli SFSV a valle di una sedimentazione primaria. Segue una breve descrizione dei sistemi. 1. VFF - Vertical Flow Filter - Reattore assimilabile ad un filtro a sabbia; 2. VFCWW - Vertical Flow Constructed Wetland with worms - Reattore dotato sia di piante (tipologia Phragmites Australis) sia di vermi (lombrichi); 3. VFCW - Vertical Flow Constructed Wetland - Reattore dotato di piante (tipologia Phragmites Australis); 4. VFFW - Vertical Flow Filter with worms - Reattore assimilabile ad un filtro a sabbia dotato di vermi (lombrichi). Il rendimento offerto da ciascun sistema è stato calcolato sulla base dei risultati forniti dalle analisi eseguite in laboratorio su campioni prelevati in input ed output da ciascun reattore. L'obiettivo dello studio è stato quello di valutare l'efficienza dei sistemi in relazione ai parametri misurati (azoto e fosforo totale, solidi sospesi, COD, ione ammoniacale, ortofosfato).

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Lake Ovan with about 9 hectares is regarded a semi-shallow lake with an average depth 5.2 meter. It is situated in Ghazvin Province, with a 1910 m high in mountainous regime. A monthly sampling was done at 3 stations studying the physicochemical and biological parameters in water and sediment at the Lake for a year. The temperature annual was measured 12.3°C and other parameters are pH as 8.8, oxygen 10, with total mean phosphate and nitrate as 0.14 & 0.8 mg/lit respectively. The chl.a mean was also measured 1.94 mg/lit. The ratio of N to P was calculated as 1:59, indicating a limiting factor for growth. Considering the trophic statues of the lake taking into account as above parameters, it is a mesotrophic lake with medium trophy. Altogether, 53 phytoplankton species were identified mostly diatoms, green algae and cyanobacteria. Although, 14 zooplankton species were identified with daphnia dominating the group. Macrobenthoses were also surveyed and 11 families were identified comprising mainly by Annelids, Gastropod, Bivalves and Insect Larvae. Other organisms were 2 dominate water plant including Phragmites australis covering at the edge of the lake and potamogeton sp in the inner parts, and also 2 fish species, common carp and Pike Perch. The diversity Shannon—Wiener index was calculated for main taxa groups with all figures lower than 3. Regarding the fish potential production of the lake based on Bramic & Lemke and morphoedophic index, it was calculated to be 20.4 kg/ha fish and a total of about 150 kg for the entire lake.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Livestock industries have maintained a keen interest in pasture legumes because of the high protein content and nutritive value. Leguminous Indigofera plant species have been considered as having high feeding values to be utilized as pasture, but the occurrence of the toxic constituent indospicine in some species has restricted this utility. Indospicine has caused both primary and secondary hepatotoxicosis and also reproductive losses, but has only previously been determined in a small number of Indigofera species. This paper validates a high throughput ultra-performance liquid chromatography−tandem mass spectrometry (UPLC−MS/MS) method to determine indospicine content of various Indigofera species found in Australian pasture. Twelve species of Indigofera together with Indigastrum parviflorum plants were collected and analysed. Out of the 84 samples analyzed, *I. spicata contained the highest indospicine level (1003 ± 328 mg/kg DM, n = 4) followed by I. linnaei (755 ± 490 mg/kg DM, n = 51). Indospicine was not detected in 9 of the remaining 11 species, and at only low levels (<10 mg/kg DM) in 2 out of 8 I. colutea specimens and in 1 out of 5 I. linifolia specimens. Indospicine concentrations were below quantitation levels for other Indigofera spp. (I. adesmiifolia, I. georgei, I. hirsuta, I. leucotricha,* I. oblongifolia, I. australis and I. trita) and Indigastrum parviflorum. One of the more significant findings to emerge from this study is that the indospicine content of I. linnaei is highly variable (159 to 2128 mg/kg DM, n = 51), and differs across both regions and seasons. Its first re-growth after spring rain has a higher (p < 0.01) indospicine content than growth following more substantial summer rain. The species collected include the predominant Indigofera in Australia pasture, and of these, only *I. spicata and I. linnaei contain high enough levels of indospicine to pose a potential toxic threat to grazing herbivores.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Leptospirosis is an important but neglected zoonotic disease that is often overlooked in Africa. Although comprehensive data on the incidence of human disease are lacking, robust evidence of infection has been demonstrated in people and animals from all regions of the continent. However, to date, there are few examples of direct epidemiological linkages between human disease and animal infection. In East Africa, awareness of the importance of human leptospirosis as a cause of non-malarial febrile illness is growing. In northern Tanzania, acute leptospirosis has been diagnosed in 9% of patients with severe febrile illness compared to only 2% with malaria. However, little is known about the relative importance of different potential animal hosts as sources of human infection in this area. This project was established to investigate the roles of rodents and ruminant livestock, important hosts of Leptospira in other settings, in the epidemiology of leptospirosis in northern Tanzania. A cross-sectional survey of rodents living in and around human settlements was performed alongside an abattoir survey of ruminant livestock. Unusual patterns of animal infection were detected by real-time PCR detection. Renal Leptospira infection was absent from rodents but was detected in cattle from several geographic areas. Infection was demonstrated for the first time in small ruminants sub-Saharan Africa. Two major Leptospira species and a novel Leptospira genotype were detected in livestock. L. borgpetersenii was seen only in cattle but L. kirschneri infection was detected in multiple livestock species (cattle, sheep and goats), suggesting that at least two distinct patterns of Leptospira infection occur in livestock in northern Tanzania. Analysis of samples from acute leptospirosis in febrile human patients could not detect Leptospira DNA by real-time PCR but identified social and behavioural factors that may limit the utility of acute-phase diagnostic tests in this community. Analysis of serological data revealed considerable overlap between serogroups detected in cattle and human leptospirosis cases. Human disease was most commonly attributed to the serogroups Mini and Australis, which were also predominant reactive serogroups in cattle. Collectively, the results of this study led to the hypothesis that livestock are an important reservoir of Leptospira infection for people in northern Tanzania. These results also challenge our understanding of the relationship between Leptospira and common invasive rodent species, which do not appear to maintain infection in this setting. Livestock Leptospira infection has substantial potential to affect the well-being of people in East Africa, through direct transmission of infection or through indirect effects on food production and economic security. Further research is needed to quantify the impact of livestock leptospirosis in Africa and to develop effective interventions for the control of human and animal disease.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia - UL

Relevância:

10.00% 10.00%

Publicador:

Resumo:

With accelerating rates of urbanization worldwide, a better understanding of ecological processes at the wildland-urban interface is critical to conserve biodiversity. We explored the effects of high and low-density housing developments on forest-dwelling mammals. Based on habitat characteristics, we expected a gradual decline in species abundance across forest-urban edges and an increased decline rate in higher contrast edges. We surveyed arboreal mammals in sites of high and low housing density along 600 m transects that spanned urban areas and areas turn on adjacent native forest. We also surveyed forest controls to test whether edge effects extended beyond our edge transects. We fitted models describing richness, total abundance and individual species abundance. Low-density housing developments provided suitable habitat for most arboreal mammals. In contrast, high-density housing developments had lower species richness, total abundance and individual species abundance, but supported the highest abundances of an urban adapter (Trichosurus vulpecula). We did not find the predicted gradual decline in species abundance. Of four species analysed, three exhibited no response to the proximity of urban boundaries, but spilled over into adjacent urban habitat to differing extents. One species (Petaurus australis) had an extended negative response to urban boundaries, suggesting that urban development has impacts beyond 300 m into adjacent forest. Our empirical work demonstrates that high-density housing developments have negative effects on both community and species level responses, except for one urban adapter. We developed a new predictive model of edge effects based on our results and the literature. To predict animal responses across edges, our framework integrates for first time: (1) habitat quality/preference, (2) species response with the proximity to the adjacent habitat, and (3) spillover extent/sensitivity to adjacent habitat boundaries. This framework will allow scientists, managers and planners better understand and predict both species responses across edges and impacts of development in mosaic landscapes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Unprecedented global human population growth and rapid urbanization of rural and natural lands highlight the urgent need to integrate biodiversity conservation into planning for urban growth. A challenging question for applied ecologists to answer is: What pattern of urban growth meets future housing demand whilst minimizing impacts on biodiversity? We quantified the consequences for mammals of meeting future housing demand under different patterns of compact and dispersed urban growth in an urbanizing forested landscape in south-eastern Australia. Using empirical data, we predicted impacts on mammals of urban growth scenarios that varied in housing density (compact versus dispersed) and location of development for four target numbers of new dwellings. We predicted that compact developments (i.e. high-density housing) reduced up to 6% of the area of occupancy or abundance of five of the six mammal species examined. In contrast, dispersed developments (i.e. low-density housing) led to increased mammal abundance overall, although results varied between species: as dwellings increased, the abundance or occurrence of two species increased (up to ∼100%), one species showed no change, and three species declined (up to ∼39%). Two ground-dwelling mammal species (Antechinus stuartii and Rattus fuscipes) and a tree-dwelling species (Petaurus australis) were predicted to decline considerably under dispersed rather than compact development. The strongest negative effect of dispersed development was for Petaurus australis (a species more abundant in forested interiors) which exhibited up to a 39% reduction in abundance due to forest loss and an extended negative edge effect from urban settlements into adjacent forests. Synthesis and applications. Our findings demonstrate that, when aiming to meet demand for housing, any form of compact development (i.e. high-density housing) has fewer detrimental impacts on forest-dwelling mammals than dispersed development (i.e. low-density housing). This is because compact development concentrates the negative effects of housing into a small area whilst at the same time preserving large expanses of forests and the fauna they sustain. Landscape planning and urban growth policies must consider the trade-off between the intensity of the threat and area of sprawl when aiming to reduce urbanization impacts.