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La dynamique temporelle des communautés de mégafaune épibenthique associées aux marges continentales demeurent peu connue. Face à ce constat, l’objectif de cette thèse est de mettre en évidence les échelles temporelles, les facteurs environnementaux et les processus qui régissent la dynamique des communautés vivant entre 400 et 1000 m de profondeur sur la pente et dans le Canyon de Barkley (Colombie-Britannique, Canada). Pour répondre à cet objectif, nous avons utilisé les séquences vidéo et les données océanographiques fournies sur chaque site par l’observatoire NEPTUNE d’Ocean Networks Canada. Ces données ont été couplées aux paramètres météorologiques et océanographiques de surface fournis par la bouée La Perouse bank, ainsi qu’aux images satellitaires (NASA) de concentration en chlorophylle de surface. Le gradient bathymétrique et oxique entre la pente et les sites du canyon sont vraisemblablement responsables de la composition spécifique distincte de ces communautés. Les variations saisonnières dominaient de la même manière la dynamique temporelle des trois communautés. Celles-ci ont été associées à la variation de production primaire de surface qui semble exercer son influence au travers de nombreux processus tels que l’arrivée de nourriture sur le fond ou par effets de cascade via la chaîne trophique. Nous avons également montré au travers de l’étude du cycle de vie du crabe tanneur Chionoecetes tanneri l’importance des cycles de vie des espèces et l’influence potentielle des interactions biotiques dans cette dynamique des communautés. Des indices concernant des phénomènes de plus longue durée, probablement de l’ordre de la décennie, confirment l’importance de continuer ce type de suivi sur un plus long terme. / The temporal dynamics of epibenthic megafaunal communities inhabiting continental margins remain poorly studied. The objectives of this thesis were to describe the time scales, environmental factors and processes influencing the temporal dynamic of the communities living at 900 and 1000 m depth at the wall and the axis (respectively) of Barkley Canyon and at the adjacent slope at 400m depth (British Columbia, Canada). To this end, we used video sequences and oceanographic data acquired at each site by Ocean Networks Canada's NEPTUNE observatory. These data were combined with meteorological and oceanographic surface parameters provided by the LaPerouse bank buoy and the NASA satellite images for surface chlorophyll concentration.The bathymetric and oxic gradients between the slope and the canyon sites are likely responsible for the distinct species compositions observed for these communities. Seasonal variations equally dominated the temporal dynamics of the three communities.These results were associated with the variations in primary surface production through many processes such as the arrival of food at the bottom and/or by cascading effects via the trophic food chain. The study of the life cycle of the tanner crab Chionoecetes tanneri revealed the importance of species life cycles and the potential influence of biotic interactions in communities’ temporal dynamics. Some clues on phenomena of longer duration, probably decadal, confirmed the importance of maintaining long-term monitoring in the area.

<p>Koordinatne merne mašine (KMM) su dominantni merni instrumenti u<br />dimenzionalnoj metrologiji. NJihovom upotrebom se može izmeriti<br />bilo koja makro tolerancija označena na tehničkoj dokumentaciji.<br />Tolerancija ravnosti je često prisutna u cilju izvršenja zahtevanih<br />funkcionalnih zahteva radnog predmeta. Istraživanja sprovedena u<br />ovom radu se bave problemom procene greške ravnosti merene na KMM<br />zasnovane na metodi minimalne zone i procene merne nesigurnosti za<br />ovaj merni zadakat. Aksenat je stavljen na primeni Monte Karlo<br />metode kao simulacionog alata za procenu merne nesigurnosti.<br />Razvijena je nova metodologija za procenu greške ravnosti kao i<br />simulacioni model za procenu merne nesigurnosti za ovaj merni<br />zadatak.</p> / <p>Coordinate measuring machines (CMMs) are dominant measuring<br />instruments in dimensional metrology. These machines can measure any<br />macro-tolerance indicated in the technical documentation. Flatness tolerance<br />is often present with the aim of completing the needed functional<br />requirements of a workpiece. The investigation conducted in this paper<br />considers the problem of assessing the flatness error measured on a CMM<br />based on the minimum zone method and on the method of evaluating<br />measurement uncertainty for this measuring task. The emphasis is on the<br />use of Monte Carlo method as a simulation tool for evaluating measurement<br />uncertainty. A new methodology for assessing the flatness error has been<br />developed, as well as a simulation model for evaluating measurement<br />uncertainty for this measuring task.</p>

The eastern tropical north Pacific (ETNP) is characterized by one of the ocean's most severe midwater oxygen minimum zones (OMZs), where oxygen levels are often less than 5 µM. The copepod family Eucalanidae is a numerically abundant and diverse zooplankton group in the ETNP, and displays a wide range of vertical distributions related to environmental oxygen concentrations. The goal of this dissertation was to develop a better understanding of the ecology, physiology, and biochemistry of closely related copepod species (family Eucalanidae) that inhabit the ETNP OMZ system. This was accomplished through examining different parameters relating to (1) metabolic rates, (2) detailed lipid composition and biomarkers, and (3) body composition, enzyme activity and survivorship in low oxygen water. Oxygen consumption, ammonium, urea, and phosphate excretion rates were generally highest in Subeucalanus subtenuis, a copepod primarily residing in the upper euphotic zone. Eucalanus inermis, typically found in the lowest oxygen environment of the species examined, showed significantly lower metabolic rates largely due to high water content. Rhincalanus rostrifrons, residing primarily in the upper oxycline, showed intermediate rates, likely relating to its higher reliance on lipid catabolism than S. subtenuis and E. inermis. Urea excretion rates showed a complicated relationship with temperature and oxygen, which calls for further study. Knowledge of such interactions is necessary for accurate modeling of nitrogen cycles in OMZ and other oceanic regions. Lipid biomarkers suggested that S. subtenuis, E. inermis and Pareucalanus attenuatus all fed primarily on particulates near the chlorophyll maximum region, while R. rostrifrons and R. nasutus likely fed on sinking particulates at depth. These results also emphasized the difference in lipid composition between wax esters and triacylglycerol components of storage lipids. This study suggested a much larger role of phylogeny in characterizing lipid contents than previously thought. Body composition, enzyme assays and survivorship studies suggested that E. inermis, S. subtenuis, P. attenuatus, R. nasutus and R. rostrifrons formed four separate ecological groups based on genus. E. inermis had low organic matter, moderate lactate dehydrogenase (LDH) activity, and high survivorship at oxygen concentrations < 20 µM. Rhincalanus spp. also had moderate LDH activity and high survivorship in low oxygen, but were unique in particularly low protein and high lipid content. S. subtenuis was characterized by high protein content, no measurable LDH activity and low survivorship in < 20 µM O2. P. attenuatus was similar to S. subtenuis in many respects, but had lower protein content and a different lipid accumulation strategy. In conclusion, eucalanoid copepods utilized many different ecological strategies in the ETNP OMZ system. Features of different ecological groups fit well with their observed vertical distributions in the water column. Understanding the ecology of organisms in OMZ systems will allow us better predictive capability for the effects of expanding OMZs in other regions.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-03-22T15:19:27Z No. of bitstreams: 1 CARINE MACHADO DE ALMEIDA pos pre banca final 2(2).pdf: 5568479 bytes, checksum: 1a895c472c5982479e7968a63a1f834a (MD5) / Made available in DSpace on 2016-03-22T15:19:28Z (GMT). No. of bitstreams: 1 CARINE MACHADO DE ALMEIDA pos pre banca final 2(2).pdf: 5568479 bytes, checksum: 1a895c472c5982479e7968a63a1f834a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / A margem central peruana, no Pacífico leste é caracterizada por possuir sedimentos laminados, formados sob condições oceanográficas específicas, tais como intensa ressurgência, disoxia e alta taxa de sedimentação. Nesta região, a presença da Zona Mínima do Oxigênio (ZMO), inibe a bioturbação favorecendo a preservação de registros sedimentares de alta resolução e proporcionando enorme potencial para estudos paleoceanográficos e paleoclimáticos em escalas centenarias a interanuais, principalmente para períodos curtos de variabilidade climática. Estas variabilidades vêm sendo amplamente estudadas, principalmente por corresponder a importantes eventos climáticos recentes, tais como Anomalia Climática Medieval (ACM- 900 a 1350 A.D.) e Pequena Idade do Gelo (PIG- 1500 a 1800 A.D), o qual foi associados a mudanças nas atividades solar e vulcânica. Neste trabalho, a paleoecologia a geoquímica inorgânica e isotópica de foraminíferos bentônicos foram utilizados como proxies para avaliar fases de variabilidades na ventilação (oxigenação) e condições redox na interface sedimento/água da ZMO Peruana durante os últimos 1000 anos. Foram analisados sedimentos laminados de um box core e um gravity-core coletados na Plataforma Central Peruana (Pisco- ~ 14°S, 300m de profundidade). Os resultados paleoecológicos mostraram alterações na assembléia de foraminíferos sugerindo que para o período da ACM, a ZMO peruana apresentou maiores condições de postoxia (anoxia sem presença de sulfetos-H2S) e um deslocamento vertical para profundidades mais rasas, evidenciados principalmente pela presença das espécies Globobulimina auriculata e Cancris inflatus. Posteriormente, durante o período da PIG, os resultados mostraram uma maior oxigenação das águas de fundo, evidenciadas pela dissolução do carbonato e alta ocorrência de bioerosão. Finalmente, após a PIG, para o Período Moderno (PM ~1820 até o recente), o aumento da abundância de espécies indicadoras de anoxia e sulfetos, tais como Nonionella stela e Virgulinella fragilis, sugerem intensificação e expansão da ZMO para o recente. As análises geoquímicas nas testas de foraminíferos foram realizadas nas testas de Bolivina seminuda, somente para os períodos da PIG e PM. Os resultados das análises de laser ablation e isótopos de δ13C demonstraram ocorrência de calcificação secundária por carbonato inorgânico nas testas dos foraminíferos as quais evidenciaram mudanças biogeoquímicas nas águas intersticiais do fundo oceânico, principalmente após a PIG caracterizando também um aumento da anoxia de fundo. Os resultados de δ18O realizado para espécie B. seminuda não foram satisfatórios para o período de PIG devido a dissolução do carbonato e, para o período moderno, evidenciou uma diminuição da temperatura principalmente para os últimos 50 anos. As mudanças ocorridas na intensidade da ZMO peruana durante ACM e PIG foram relacionadas com as variabilidades zonais das temperaturas de superfície oceânicas (TSMs) do Pacífico Equatorial, além do gradiente de variabilidade norte sul da ZCIT (como?). Para o Período Moderno, além dos fatores de gradiente zonais das TSMs, sugere-se que as mudanças climáticas e fatores locais estejam influenciando e intensificando a ZMO na região estudada tornando-a extremamente anóxica e mais produtiva para o período pós pig / The central Peruvian margin, in the eastern Pacific, is characterized by intense upwelling and presence of an intense Oxygen Minimum Zone (OMZ), which favor a high sedimentation rates and deposition of laminated sediments without bioturbation respectively. These characteristics allow preservation of high-resolution sedimentary marine records with great potential to paleoclimatic and paleoceanographic reconstructions from the centennial to interannual time scale. These variabilities have been widely studied, mainly due to important recent paleoclimatic events such as Medieval Climate Anomaly (MCA, AD 900-1350) and the Little Ice Age (LIA-1500-1800 AD), which were associated with changes in solar and volcanic activities. In this work, the study of paleoecology and geochemistry of benthic foraminifera were used as proxy to access phases of greater or less oxygenation and redox conditions at the sediment/water interface in the Peruvian ZMO during the last 1000 years. Laminated sediments of a box core (B-14) and gravity-core (G10) retrieved in the Central Peruvian Shelf (Pisco-14°S, 300m depth) were sub-sampled and analyzed. The paleoecological reconstructions showed changes in the benthic foraminiferal assemblage suggesting, during the MCA, higher postoxic conditions (anoxia without the presence of sulfides, H2S) and a vertical offset to shallower depths evidenced mainly by the presence of Globobulimina auriculata and Cancris inflatsu species. A decrease in OMZ intensity was identified during the LIA which based on carbonate dissolution and high bioerosion occurrence. Finally, after the LIA, to the Modern Period (MP ~1820 to the recent), the increase of abundances of anoxia and sulfides proxy species such as Nonionella stella and Virgulinella fragilis, which were correlated with the intensification and expansion of OMZ toward the recent. The geochemical analyses at foraminiferal tests were done on Bolivina seminuda tests only for the LIA and MP. The results of the laser ablation and δ13C isotope analysis showed inorganic carbonate secondary calcification on the foraminiferal tests, which was correlated to biogeochemical changes in the interstitial waters of the ocean floor, especially after the LIA featuring also a rise in bottom anoxia. The results of δ18O performed on Bolivina seminuda for the LIA period were not satisfactory due to carbonate dissolution; for the Modern Period, on the other hand, there was a decrease of the temperature especially for the last 50 years. The variability on the intensity of Peruvian OMZ during the MCA and LIA were correlated to zonal variability of sea surface temperatures (SSTs) in the equatorial Pacific, besides the north-south gradient variability of the ITCZ. To the Modern Period, besides the oceanic gradient factors of SST, it is suggested that climate change and local factors could be intensifying the OMZ in the study region making it extremely anoxic toward recent.

Cette thèse a pour objectifs de documenter les variations spatiotemporelles de la zone de minimum d’oxygène (OMZ) du Pacifique Nord-Est, et d’identifier les mécanismes qui ont causé ces variations. L’étude est fondée sur l’analyse géochimique des composants majeurs, mineurs et traces de sédiments prélevés dans le Pacifique Nord-Est, en combinant des mesures par ICP-MS et scanneur XRF. Ces mesures ont permis de distinguer l’effet de la productivité biologique de celui de la ventilation océanique sur l’oxygénation du sédiment. J’ai pu mettre en évidence le rôle prépondérant de la productivité au niveau de la Basse Californie (23°N), qui varie en phase avec les températures en Atlantique Nord durant les 120.000 dernières années. Par ailleurs, la ventilation océanique a probablement joué un rôle important au niveau du golfe de Papagayo (12°N), par l’advection de masses d’eau provenant des hautes latitudes nord et sud. L’intensité de l’OMZ du Pacifique Nord-Est serait donc influencée par des modifications des circulations océaniques et atmosphériques, liées aux climats des hautes latitudes des deux hémisphères. / This thesis aims at documenting the spatiotemporal variations of the Oxygen Minimum Zone (OMZ) of the northeastern Pacific, and identifying the mechanisms that caused theses variations. The study is based on the geochemical analyses of major, minor, and trace elements of sediments from the northeastern Pacific, by combining ICP-MS and XRF scans measurements. These measurements allowed distinguishing the effect of biologic productivity and oceanic ventilation on sediment oxygenation. I was able to highlight the predominant impact of the productivity off the Baja California Margin (23°N), which varied in phase with the high northern Atlantic temperature across the past 120,000 years. Moreover, oceanic ventilation did play an important role off the Papagayo Gulf (12°N), because of the advection of water mass coming from the high northern and southern latitudes. OMS intensity in the northeastern Pacific could thus be influenced by changes in the atmospheric and oceanic circulation, in relation to high northern and southern latitudes climates.

Le Système d’Upwelling Péruvien (PUS) et la Zone à Oxygène minimum (OMZ) qui y est associée font partie des régions les plus marquées par les variations climatiques de type El Niño Southern Oscillation (ENSO), tant à l’échelle interannuelle qu’à l’échelle décennale. Or, peu d’enregistrements de l’impact de l’ENSO sur cette zone géographique atteignent ces résolutions temporelles, malgré des conditions propices à la conservation de dépôts sédimentaires laminés.Nous avons analysé ces archives sédimentaires à l’échelle de la lamine et en utilisant des marqueurs sédimentologiques, micro paléontologiques et géochimiques afin de retracer les variations de tous les paramètres susceptibles de répondre aux changements climatiques(précipitations, productivité, dénitrification, températures océaniques de surface). Cette approche nous a permis de disposer d’un enregistrement complet des conditions environnementales dans l’OMZ du Pérou à des échelles pluri-annuelle à multidécennale, ce qui est inégalé sur des périodes au-delà du dernier millénaire. Nous avons ainsi pu mettre en évidence une forte empreinte de la circulation de Walker sur le PUS. Cet impact est modulé par les régions extra tropicales de l’hémisphère Nord, en particulier par l’Oscillation Nord-Atlantique (NAO) à l’échelle multidécennale, par la circulation thermohaline à l’échelle centennale et par l’Anticyclone Sibérien à l’échelle millénaire. / The Peruvian Upwelling System (PUS) and the corresponding Oxygen Minimum Zone (OMZ) are part of the regions where the imprint of climatic variations due to El Niño Southern Oscillation (ENSO) at the interannual and multidecadal timescales is the strongest. However,only a few records of ENSO-like climatic variability reach such short timescales in thisgeographical area, despite prevailing conditions favorable to the preservation of laminatedsediments. We analyzed these sedimentary archives at the scale of the lamination, using sedimentology, micropaleontology and geochemistry. The aim was to trace variations in all parameters responding to climatic changes (rainfall, productivity, denitrification, sea surfacetemperatures). This approach has provided a full record of environmental conditions in thePeruvian OMZ at multiannual and multidecadal timescales for the first time on time intervals exceeding the last millennium. We thus evidenced a strong imprint of the Walker circulation on the PUS. This impact is paced by the extratropical northern hemisphere, especially by the North Atlantic Oscillation (NAO) at the multidecadal timescale, by the thermohaline circulation at the centennial timescale and by the Siberian High at the millennial timescale.