960 resultados para Argentine_shelf-ocean


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Environmental histories of plant exchanges have largely centred on their eco- nomic importance in international trade and on their ecological and social impacts in the places where they were introduced. Yet few studies have at- tempted to examine how plants brought from elsewhere become incorporated over time into the regional cultures of material life and agricultural landscapes. This essay considers the theoretical and methodological problems in inves- tigating the environmental history, diversity and distribution of food plants transferred across the Indian Ocean over several millennia. It brings together concepts of creolisation, syncretism, and hybridity to outline a framework for understanding how biotic exchanges and diffusions have been translated into regional landscape histories through food traditions, ritual practices and articu- lation of cultural identity. We use the banana plant - which underwent early domestication across New Guinea, South-east Asia and peninsular India and reached East Africa roughly two thousand years ago - as an example for il- lustrating the diverse patterns of incorporation into the cultural symbolism, material life and regional landscapes of the Indian Ocean World. We show that this cultural evolutionary approach allows new historical insights to emerge and enriches ongoing debates regarding the antiquity of the plant's diffusion from South-east Asia to Africa.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Abstract. The deep outer margin of the Gulf of Lions and the adjacent basin, in the western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e., temperature and salinity), currents, and particle fluxes were monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350-m depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW-SE transect, while the fifth one was located on a sediment wave field to the west. The results of the main, central line SC2350 ("LION") located at 42 02.50 N, 4 410 E, at 2350-m depth, show that open-ocean convection reached midwater depth ( 1000-m depth) during winter 2007-2008, and reached the seabed ( 2350-m depth) during winter 2008-2009. Horizontal currents were unusually strong with speeds up to 39 cm s−1 during winter 2008-2009. The measurements at all 5 different locations indicate that mid-depth and near-bottom currents and particle fluxes gave relatively consistent values of similar magnitude across the study area except during winter 2008-2009, when near-bottom fluxes abruptly increased by one to two orders of magnitude. Particulate organic carbon contents, which generally vary between 3 and 5 %, were abnormally low ( 1 %) during winter 2008-2009 and approached those observed in surface sediments (0.6 %). Turbidity profiles made in the region demonstrated the existence of a bottom nepheloid layer, several hundred meters thick, and related to the resuspension of bottom sediments. These observations support the view that open-ocean deep convection events in the Gulf of Lions can cause significant remobilization of sediments in the deep outer margin and the basin, with a subsequent alteration of the seabed likely impacting the functioning of the deep-sea ecosystem.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Oceans, or other wide expanses of inhospitable environment, interrupt present day distributions of many plant groups. Using molecular dating techniques, generally incorporating fossil evidence, we can estimate when such distributions originated. Numerous dating analyses have recently precipitated a paradigm shift in the general explanations for the phenomenon, away from older geological causes, such as continental drift, in favour of more recent, long-distance dispersal (LDD). For example, the 'Gondwanan vicariance' scenario has been dismissed in various studies of Indian Ocean disjunct distributions. We used the gentian tribe Exaceae to reassess this scenario using molecular dating with minimum (fossil), maximum (geological), secondary (from wider analyses) and hypothesis-driven age constraints. Our results indicate that ancient vicariance cannot be ruled out as an explanation for the early origins of Exaceae across Africa, Madagascar and the Indian subcontinent unless a strong assumption is made about the maximum age of Gentianales. However, both the Gondwanan scenario and the available evidence suggest that there were also several, more recent, intercontinental dispersals during the diversification of the group.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Global wind patterns influence dispersal and migration processes of aerial organisms, propagules and particles, which ultimately could determine the dynamics of colonizations, invasions or spread of pathogens. However, studying how wind-mediated movements actually happen has been hampered so far by the lack of high resolution global wind data as well as the impossibility to track aerial movements. Using concurrent data on winds and actual pathways of a tracked seabird, here we show that oceanic winds define spatiotemporal pathways and barriers for large-scale aerial movements. We obtained wind data from NASA SeaWinds scatterometer to calculate wind cost (impedance) models reflecting the resistance to the aerial movement near the ocean surface. We also tracked the movements of a model organism, the Cory's shearwater (Calonectris diomedea), a pelagic bird known to perform long distance migrations. Cost models revealed that distant areas can be connected through"wind highways" that do not match the shortest great circle routes. Bird routes closely followed the low-cost"wind-highways" linking breeding and wintering areas. In addition, we found that a potential barrier, the near surface westerlies in the Atlantic sector of the Intertropical Convergence Zone (ITCZ), temporally hindered meridional trans-equatorial movements. Once the westerlies vanished, birds crossed the ITCZ to their winter quarters. This study provides a novel approach to investigate wind-mediated movements in oceanic environments and shows that large-scale migration and dispersal processes over the oceans can be largely driven by spatiotemporal wind patterns.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Vad händer i tidvattenzonen? Var går gränsen mellan land och hav, vad händer i tidvattenzonen och vem ansvarar för detta? I västra Indiska oceanen (VIO) kan avståndet mellan den lägsta nivån för lågvattnet och den högsta nivån för högvattnet vara flera kilometer och nivåskillnaderna upp till 6 meter och detta skapar ett stort och föränderligt område. Syftet med min avhandling är att öka förståelsen för tidvattenzonen i tropiska och subtropiska västra Indiska oceanen. Sammanfattningsvis visar mina studier att det finns ett mycket stort värde i den komplexa tidvattenzonen, men också att det här området hotas från både land och hav, genom t.ex. överexploatering, erosion och föroreningar. Uttnyttjandet av tidvattenzonen är stort och min avhandling har visat att aktiviteter såsom fiske i form av plocking av musslor och andra ryggradslösa djur och hamnaktiviteter påverkar den biologiska mångfalden negativt, vilket leder till försämrad levnadsstandard för resursutnyttjande människor i regionen. För att förbättra situationen krävs det mer forskning, miljöövervakning och bättre förvaltning av tidvattenzonen. Experter i regionen har rangordnat förslag på förvaltningsstrategier som skulle kunna testas för att förbättra miljön och skapa ett mer hållbart nyttjande. Avhandlingen visar även att det är möjligt att använda fjärranalysteknik såsom satellitbildsanalys för att kvantifiera mängden sjögräsvegetation (i form av biomassa), vilket kan ha stor betydelse för att förbättra storskalig miljöövervakning av kustnära naturtyper (habitat). I avhandlingsarbetet har jag använt mig av ett multidisciplinärt tillvägagångssätt och använt metoder såsom ekologisk och biologisk provtagning, intervjuer, observationer, diskussionsgrupper, frågeformulär och fjärranalys. Resultaten presenterade i denna avhandling ger en ökad kunskap om tidvattenzonen i utvecklingsländerna inom VIO-regionen som kan användas för att initiera och fortsätta att utveckla hållbara förvaltningsstrategier av biologiska resurser.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

At present stage the analytical design of wave tolerance for floating structures and vessels is still imperfect due to the mutually complex and nonlinear phenomena between structures and waves. Wave tolerance design is usually carried out through iterative evaluations of results from model tests in a wave basin, and this is done in order to reach a final structural design. The wave generation has then become an important technology in the field of the coastal and ocean engineering. This paper summarizes the facilities of a test basin and a wave maker in Japan and also surveys the methodology of the generation of ocean waves in a test basin.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Lectio praecursoria, Åbo Akademi University 7 June 2013.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Espírito Santo State lies in the transition region (18°-21° S) between the tropical and subtropical marine-algal provinces and is considered the richest area of the Brazilian flora. The subtidal substratum presents extensive areas of rhodoliths associated with a diversified marine biota. A detailed exploration using Scuba diving technique has revealed many little-known and previously unreported taxa that are new to the Brazilian coast. Among the algae recently discovered, Reticulocaulis mucosissimus I. A. Abbott was found at a depth of 25 meters, thus consisting of the second member of the infrequently encountered family Naccariaceae growing in the same region. This work has revealed additional distribution records of this species not yet reported from the western Atlantic. Description of the morphological and reproductive features of the species as well as illustrations and comments are presented.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper presents a taxonomic study of taxa of the red algae genus Herposiphonia (Ceramiales) occurring on Maracajaú Reef in the Coral Reefs Environmental Protection Area (CREPA - Área de Proteção Ambiental dos Recifes de Corais) in Rio Grande do Norte State, along the northeastern coast of Brazil. The CREPA comprises coastline and continental shelf areas of the municipalities of Touros, Rio do Fogo, and Maxaranguape and includes sand dunes, coastal lagoons, and the adjacent shoreline and offshore reefs. Detailed morphological studies were made, considering recent taxonomic criteria for species delimitation of Herposiphonia, and five species were identified: H. delicatula, H. nuda, H. parca, H. secunda, and H. tenella, thus increasing the number of species in the genus from three to six. Herposiphonia delicatula and H. parca represent new occurrences for Brazil, and H. nuda is reported for the first time for the Atlantic Ocean.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Kartta kuuluu A. E. Nordenskiöldin kokoelmaan

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Kartta kuuluu A. E. Nordenskiöldin kokoelmaan

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Kartta kuuluu A. E. Nordenskiöldin kokoelmaan