Ao largo da costa oeste da Am´erica do Sul o sistema de ressurg^encia costeira apresenta uma excepcional produtividade, um resultado da alta efici^encia do ecossistema biol´ogico em converter a produ¸c~ao prim´aria em biomassa. Esses processos qu´?micobiol ´ogicos s~ao fortemente modulados pelo ambiente f´?sico da regi~ao. Por exemplo, durante eventos do El-Ni~no a produtividade pesqueira ´e fortemente prejudicada em resposta a uma inibi¸c~ao da ressurg^encia costeira. Apesar disso ser um fato j´a bastante conhecido desde ´epocas pr´e-colombianas, muita d´uvida ainda persiste sobre o mecanismo pelo qual o sistema costeiro ´e afetado por esses fen^omenos de grande escala. O presente trabalho foi realizado com o objetivo de se contribuir com esse conhecimento, estudando como ocorreram as mudan¸cas do sistema durante recentes eventos El Ni~no, principalmente na escala intrasazonal. Nessa investiga¸c~ao foram utilizadas diferentes metodologias de an´alise de dados para identificar a natureza dos for¸cantes de oscila¸c~oes significativas observadas durante o El Ni~no 1997-1998. Tamb´em foi investigado se essas oscila¸c~oes foram for¸cadas remotamente e se propagaram como ondas aprisionadas na costa; quais foram suas propriedades espaciais e sua propaga¸c~ao longo da costa. A primeira parte do trabalho consiste na an´alise da variabilidade temporal e a caracteriza¸c~ao das flutua¸c~oes de baixa freq¨u^encia ocorridas durante eventos El Ni~no. Essa an´alise faz uso do espectro de ondeleta aplicado a s´eries temporais longas de dados do n´?vel do mar de esta¸c~oes costeiras distribu´?das ao longo da costa sul do Equador, costa do Peru e costa norte do Chile. O espectro de ondeleta cruzada e o espectro da coer^encia foram usados para avaliar a import^ancia relativa das for¸cantes remota e local das varia¸c~oes do n´?vel do mar associadas com os efeitos do El Ni~no 1997-1998. Na segunda parte, as flutua¸c~oes for¸cadas remotamente foram comparadas com modelos lineares simples e o modelo de Brink e Chapman (1987) para se obter as propriedades das ondas aprisionadas na costa durante o El Ni~no Extraordin ´ario (1997-1998). Uma importante conclus~ao dessas an´alises foi a constata¸c~ao de que variabilidades intrasazonais ao largo da costa do Peru durante esse El Ni~no foi, em parte significativa, o resultado da atua¸c~ao de for¸cantes remotas e locais, associadas com ondas equatoriais incidindo na Costa Oeste da Am´erica do Sul e com o efeito do vento, respectivamente. / Off the western coast of South America, the coastal upwelling system presents an exceptional productivity, a result of the high efficiency of the biological ecosystem in converting the primary production into biomass. These chemical and biological processes are strongly modulated by the physical environment. For instance, during El Ni~no events the fishery productivity is strongly impaired in response to an inhibition of the coastal upwelling. In spite of this fact be widely known since pre-Colombian times, much doubts still persist about the mechanism by means of which the coastal system is affected by the large scale phenomena. The present work was idealized with the intention of contributing for this knowledge, studying how occurred the changes in the system during recent El Ni~no events, with emphasis on the intraseasonal scale. In this investigation, different methodologies of data analysis were used to identify the nature of the forcing which produced significant oscillations observed during the El Ni~no 1997-1998. Also, it was investigated if these oscillations were remotely forced and propagated along the coast as coastal trapped waves; what were their spatial and propagation properties. The first part of the work consists of an analysis of the temporal variability and the characterization of the low-frequency fluctuations occurred during the El Ni~no events. This analysis uses the wavelet spectrum applied to time series of sea level data collected off southern Equador, Peru and northern Chile. The cross wavelet spectrum and coherence spectrum were used to evaluate the relative importance of local and remote forcing of the sea level, associated with effects of the 1997-1998 El Ni~no. In the second part, the fluctuations remotely forced wer compared with results of simple linear models and with the model of Brink and Chapman (1987), in order to obtain the coastal trapped waves properties during that extraordinary El Ni~no event. One important conclusion of these analyses was the confirmation that the intraseasonal variability observed offo Peru during the 1997-1998 El Ni~no was, in part, the result of remote and local forcing, associated with equatorial waves and the wind effect, respectively.

Nearshore hypoxia within the Northern California Current (NCC) system is a seasonal phenomenon caused by coastal upwelling and occurs mainly during late-summer and early fall. The effects of low oxygen levels on fish and invertebrate communities, particularly during early-life history stages, however, are poorly known for this area. I investigated the effects of hypoxia on the density, community structure, vertical and horizontal distribution of fish larvae and juveniles, as well as body condition of juveniles, along the central Oregon and Washington coasts during the summers of 2008 - 2011. During this sampling period, bottom dissolved oxygen (DO) values ranged from 0.49 to 9.85 ml l�����, and the number of hypoxic (e.g., < 1.4 ml l�����) stations sampled was low compared to 2002 and 2006 (only 54 sampling stations for the ichthyoplankton study out of 493, and only 12 stations out of 90 for the benthic juvenile study). From the ichthyoplankton study, I found that the overall density of fish larvae increased as bottom-DO values increased; however, the effect on individual species density was limited. Between 44.65 ��N and 46.00 ��N (~Florence, OR ��� Astoria, OR), fish larvae altered their vertical distribution when bottom-DO was low by rising in shallower water layers. From the benthic juvenile study, I found that English sole (Parophrys vetulus), butter sole (Isopsetta isolepis), speckled sanddab (Citharichthys stigmaeus) and Pacific sanddab (Citharichthys sordidus) dominated the catch with annual variation in abundances. Species composition, abundance and length had strong relationships with depth. Species abundance for English sole (< 75 mm), speckled sanddab (<100 mm) and Pacific sanddab also increased with increased bottom-DO. However, the body condition of butter sole (< 75 mm) and of large speckled sanddab (���100 mm) increased with decreased bottom-DO. Overall my research elucidates important patterns of larval and juvenile fish distribution within the NCC during summer. In both studies I have found a limited effect of DO on abundance, distribution and community assemblages. Variables other than DO, such as depth, season and location, dominated the explained variance of the intervening multivariate and univariate analysis. However, due to the paucity of samples during hypoxic events, continued monitoring of nearshore larval and juvenile species over varying hypoxic conditions is necessary for understanding the impact of hypoxia on these communities and subsequent adult populations. / Graduation date: 2013

Tropical cyclones (TCs) often change intensity as they move over mesoscale oceanic features, as a function of the oceanic mixed layer (OML) thermal response (cooling) to the storm's wind stress. For example, observational evidence indicates that TCs in the Gulf of Mexico rapidly weaken over cyclonic cold core eddies (CCEs) where the cooling response is enhanced, and they rapidly intensify over anticyclonic warm features such as the Loop Current (LC) and Warm Core Eddies (WCEs) where OML cooling is reduced. Understanding this contrasting thermal response has important implications for oceanic feedback to TCs' intensity in forecasting models. Based on numerical experimentation and data acquired during hurricanes Katrina and Rita, this dissertation delineates the contrasting velocity and thermal response to TCs in mesoscale oceanic eddies. Observational evidence and model results indicate that, during the forced stage, the wind-driven horizontal current divergence under the storm's eye is affected by the underlying geostrophic circulation. Upwelling (downwelling) regimes develop when the wind stress vector is with (against) the geostrophic OML velocity vector. During the relaxation stage, background geostrophic circulations modulate vertical dispersion of OML near-inertial energy. The near-inertial velocity response is subsequently shifted toward more sub-inertial frequencies inside WCEs, where rapid vertical dispersion prevents accumulation of kinetic energy in the OML that reduces vertical shears and layer cooling. By contrast, near-inertial oscillations are vertically trapped in OMLs inside CCEs that increases vertical shears and entrainment. Estimates of downward vertical radiation of near-inertial wave energies were significantly stronger in the LC bulge (12.1X10 super -2 W m super -2) compared to that in CCEs (1.8X10 super -2 W m super -2). The rotational and translation properties of the geostrophic eddies have an important impact on the internal wave wake produced by TCs. More near-inertial kinetic energy is horizontally trapped in more rapidly rotating eddies. This response enhances vertical shear development and mixing. Moreover, the upper ocean temperature anomaly and near-inertial oscillations induced by TCs are transported by the westward-propagating geostrophic eddies. From a broader perspective, coupled models must capture oceanic features to reproduce the differentiated TC-induced OML cooling to improve intensity forecasting.

Le système du Courant de Californie (CCS) est l'un des grands systèmes d'upwelling de bord est de la planète, caractérisés par un régime saisonnier de vents qui provoque des remontées d'eaux profondes (upwelling côtier), riches en nutriments, favorisant une forte activité biologique. À long terme, l'écosystème du CCS révèle des alternances de dominance de communautés marines, encore inexpliquées. L'objet de cette thèse est de comprendre l'effet de la variabilité pluriannuelle des vents sur la structure et le fonctionnement des premiers maillons trophiques de l'écosystème du CCS à partir d'études de processus reposant sur une approche numérique. Une première étude a permis de montrer que l'upwelling côtier et le transport côte-large ont une variabilité à basse fréquence fortement corrélée à celle de la tension de vent parallèle à la côte et au mode North Pacific Gyre Oscillation (NPGO), mis en évidence récemment et connu pour capturer une part de la variabilité à basse fréquence des vents d'upwelling et de la chlorophylle dans le CCS. Une étude fine de ces vents a permis de mettre en évidence une relation forte entre leur variabilité saisonnière et le mode NPGO, avec une modulation temporelle du déclenchement de la saison d'upwelling du CCS. L'impact d'un tel déphasage de l'upwelling sur un écosystème planctonique a pu ensuite être testé. À la côte, l'écosystème répond directement à un scénario d'upwelling précoce par une productivité plus forte. Au large, les incidences sur l'écosystème s'opèrent via les processus de transport côte-large. L'effet sur le zooplancton est plus prononcé que sur le phytoplancton et est susceptible d'affecter les niveaux trophiques supérieurs.

Carbon dioxide (CO2) is an important greenhouse gas, and the atmospheric concentration of CO2 has increased by more than 100 ppm since prior to the industrial revolution.  The global oceans are considered an important sink of atmospheric CO2, since approximately one third of the anthropogenic emissions are absorbed by the oceans. To be able to model the global carbon cycle and the future climate, it is important to have knowledge of the processes controlling the air-sea exchange of CO2. In this thesis, measurements as well as a model is used in order to increase the knowledge of the exchange processes. The air-sea flux of CO2 is estimated from high frequency measurements using three methods; one empirical method, and two methods with a solid theoretical foundation. The methods are modified to be applicable for various atmospheric stratifications, and the agreement between methods is good in average. A new parameterization of the transfer velocity (the rate of transfer across the air-sea interface), is implemented in a Baltic Sea model. The new parameterization includes also the mechanism of water-side convection. The impact of including the new parameterization is relatively small due to feedback processes in the model. The new parameterization is however more representative for flux calculations using in-situ measurement or remote sensing products. When removing the feedback to the model, the monthly average flux increases by up to 20% in some months, compared to when water-side convection is not included. The Baltic Sea carbon budget was estimated using the Baltic Sea model, and the Baltic Sea was found to be a net sink of CO2. This is consistent with some previous studies, while contradictory to others. The dissimilarity between studies indicates the difficulty in estimating the carbon budget mainly due to variations of the CO2 uptake/release in time and space. Local variations not captured by the model, such as coastal upwelling, give uncertainties to the model. Coastal upwelling can alter the uptake/release of CO2 in a region by up to 250%. If upwelling would be included in the model, the Baltic Sea might be considered a smaller sink of CO2.

This doctoral thesis deals with the biogeochemical processes taking place in estuarine systems known as 'rias', located at the NW of the Iberian Peninsula. Its realization has been possible thanks to financial support from the JAE-Program of the Spanish Council for Scientific Research (CSIC) co-funded by the European Social Fund (ESF), and the ‘INTERESANTE' project, funded by the CICYT. Additionally, it is a contribution to the Spanish LOICZ program (Land-Ocean Interactions in the Coastal Zone). An oceanographic characterization of the Northern Galician Rias is presented in Chapter 2. This chapter also involves an extensive analysis of summer upwelling and downwelling processes, winter shelf-water upwelling, and poleward intrusion in the northern Galician shelf. Chapter 3 deals with the fluvial contributions to the Northern Galician Rias, including the quantification of major and minor chemical elements (nutrient salts, trace elements) in the dissolved and particulate matter, chlorophyll-a, DIN, PON, DOC, POC and C/N ratio. In Chapter 4 the sediment-water fluxes of nutrients in a ria coastal systems are discussed. Fluxes driven by molecular diffusion and advective transport across sediment-water interfaces during tidal flooding for the Northern Galician Rias are calculated. Chapter 5 focuses on the hydrological, chemical and biological interactions in the Northern Galician Rias, exemplified by the case of the Ria of Barqueiro, identifying their oceanographic periods in relation to nutrient availability, primary production, phytoplankton biomass, taxonomic composition and hydrographic patterns.

Dans cette thèse, nous nous sommes consacrés au problème d'interaction d'échelles selon deux angles distincts : d'une part une approche globale et grande échelle du système climatique qui nous a permis d'étudier la modulation basse fréquence d'ENSO, d'autre part une démarche plus locale au cours de laquelle nous avons étudié plus particulièrement la dynamique du Pacifique tropical est et du système de courants de Humboldt au large du Pérou. La première partie a été motivée par une approche relativement récente dans la communauté des climatologues. Il s'agit de la question cruciale de la variabilité basse fréquence d'ENSO, et de la possibilité que celle-ci puisse émerger " simplement " du système climatique tropical, sans action extérieure qu'elle soit stochastique ou en lien avec la variabilité des plus hautes latitudesDans ce contexte particulier, il est alors question de mécanismes nonlinéaires pour expliquer comment la stabilité d'ENSO peut être influencée par la variabilité climatique. Ceci a servi d'hypothèse de travail pour l'ensemble de cette thèse. Nous avons ainsi abordé la possibilité qu'ENSO pouvait être rectifié sur des échelles de temps longues (interdécennales) par la modulation de la nonlinéarité elle-même. Pour cela, nous avons utilisé des méthodes mathématiques originales qui nous ont permis d'une part de détecter des changements brusques (statistiquement significatifs) de l'état moyen du Pacifique tropical et d'autre part d'accéder à un proxy de la nonlinéarité intégrée dans le système tropical. En combinant ces deux démarches, nous avons pu mettre en évidence une boucle de rétroaction auto entretenue sur des échelles de temps longues qui serait pilotée par des mécanismes nonlinéaires qui auraient la capacité de faire interférer diverses échelles temporelles et ainsi de transférer l'énergie des basses fréquences (état moyen du pacifique tropical) vers les hautes fréquences (oscillation australe) et vice-versa. Dans la seconde partie de cette thèse nous nous sommes focalisés sur la modélisation climatique du Pacifique tropical oriental. En effet, cette région, pourtant au cœur des préoccupations de la communauté scientifique en raison de son écosystème parmi les plus productifs de la planète, reste mal connue du point de vue des processus océanographiques et climatiques. En particulier, les modèles climatiques globaux présentent des biais importants dans cette région en terme d'état climatologique moyen. Nous avons testé, dans une approche de modélisation haute résolution, différentes sources possibles de ces biais : les caractéristiques bathymétriques des îles Galápagos (mal représentées dans les modèles globaux) capables de par leur position équatoriale de modifier la circulation régionale moyenne et donc le bilan thermodynamique; ou alors les processus associés aux mélanges turbulents (et par extension les processus nonlinéaires) à l'aide d'un modèle régional. Pour ce faire, nous avons procédé à des expériences de sensibilité qui nous ont permis d'une part de relativiser le rôle de l'archipel des Galápagos comme source de biais et d'autre part de mettre en exergue le rôle de la variabilité intra-saisonnière dans la rectification de l'état moyen du Pacifique tropical est.

The New Zealand fur seal (Arctocephalus forsteri) is the most abundant fur seal species in the Australian-New Zealand region. Approximately 85 % of Australia’s population of New Zealand fur seals reside in the state of South Australia. As a result of their abundance and size, it has been estimated that the New Zealand fur seal population in South Australia consumes the greatest biomass of resources of all marine mammal and seabird species. However, despite the importance of New Zealand fur seals as top predators, our understanding of their foraging ecology in South Australia is limited. In order to better understand the habitat utilized and the diet of New Zealand fur seals, this study explores the foraging ecology of lactating seals from four primary colonies in South Australia, which account for ~ 78 % of the Australian population. These colonies are Cape Gantheaume (36о04’S, 137о27’E) and Cape du Couedic (36о03’S, 136о42’E) on Kangaroo Island; North Neptune Island (35о13’S, 136о03’E) and Liguanea Island (34о59’S, 135о37’E). I start this study by assessing the seasonal variation in foraging location and dive behaviour of lactating New Zealand fur seals from Cape Gantheaume. 18 seals were fitted with satellite transmitters and time depth recorders (TDRs). The presence of thermoclines (derived from TDRs), were used as a surrogate measure of upwelling activity in continental shelf habitats. During the austral autumn 80 % of lactating fur seals foraged on the continental shelf (114 ± 44 km from the colony), in a region associated with a seasonal coastal upwelling system, the Bonney upwelling. In contrast, during winter months seals predominantly foraged in oceanic waters (62 %), in a region associated with the Subtropical Front (460 ± 138 km from the colony). Results suggested that lactating New Zealand fur seals shift their foraging location from continental shelf to oceanic habitats, in response to a seasonal decline in continental shelf productivity, attributed to the cessation of the Bonney upwelling in autumn. To study inter-colony differences in foraging locations, 21 New Zealand fur seals were satellite tracked from four colonies within close proximity (46 km – 200km apart). Seals initiated foraging trips on a colony-specific bearing (Cape Gantheaume 141 ± 33º, Cape du Couedic 186 ± 12º, North Neptune Island 200 ± 23º and Liguanea Island 234 ± 69º), and recorded little overlap between colony-specific foraging areas. The distribution of colony-specific foraging grounds appeared to be influenced by the proximity of colonies to predictable local upwelling features, as well as a distant oceanic frontal zone, the Subtropical Front. Foraging site fidelity and route-choice was further assessed by comparing site fidelity between continental shelf and oceanic habitats. Data from 31 lactating females, satellite tracked over 107 consecutive foraging trips indicated that females foraging on the continental shelf recorded a significantly greater overlap in foraging area between consecutive foraging routes, when compared to females that foraged in oceanic waters (55.9 ± 20.4 % and 13.4 ± 7.6 %, respectively). Findings suggest that seals learn the direction of travel to a predictable foraging region, and initiate a foraging trip on that bearing. However, actual foraging routes are likely to be influenced by a number of factors including previous foraging trip experience and prey encounter rate, which is related to prey density and the spatial scale of the patch exploited. The final chapter integrates scat analysis with milk fatty acid (FA) analysis to investigate dietary differences between continental shelf and oceanic waters. Milk FA composition was determined for 29 satellite-tracked fur seals, that were known to forage in either shelf or oceanic habitats. Based on FA compositions, I predicted the likelihood that milk samples collected at random (n = 131) represented individual seals having foraged either on the continental shelf or in distant oceanic waters. FA analysis and satellite tracking results contrasted with scat analyses, from which only 6 % of scats by frequency of occurrence contained prey remains from oceanic waters. The results suggest that scats were biased toward females foraging on the continental shelf. This study highlights the importance of two predictable ocean features utilised by New Zealand fur seals; (1) a nearby and seasonally predictable coastal upwelling system, the Bonney upwelling and; (2) a distant but permanent oceanic front, the Subtropical Front. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1347312 / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Studies, 2008

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2018-03-12T17:39:30Z No. of bitstreams: 1 Tese Manuel Moreira.pdf: 26683391 bytes, checksum: 22f4cca548ed444677c5428a580b351d (MD5) / Made available in DSpace on 2018-03-12T17:39:30Z (GMT). No. of bitstreams: 1 Tese Manuel Moreira.pdf: 26683391 bytes, checksum: 22f4cca548ed444677c5428a580b351d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A acumulação dos elementos-traço nos sedimentos desempenha um importante papel na ciclagem destes elementos nos ambientes marinhos, associado a variáveis formas de retenção no reservatório sedimentar, em diferentes escalas temporais. No presente estudo foi avaliado o fracionamento geoquímico de Fe, Mn, As, Cd, Co, Cr, Cu, Mo, Ni, Pb e Zn entre as frações solúveis em HCl, associada à pirita (FeS2) e associada à fração orgânica, como forma de elucidar os processos que determinam a acumulação destes elementos nos sedimentos da plataforma continental do Sistema de Ressurgência de Cabo Frio (SRCF) nos últimos 8.000 anos. Foi observado que o fracionamento dos elementos Fe, Mn, As, Cr, Ni, Pb e Zn apresenta uma maior proporção na fração solúvel em HCl nos três testemunhos sedimentares coletados ao longo da plataforma continental. O Cu em todas as estações apresentou uma maior proporção na fração da matéria orgânica. O Cd (plataforma interna) e o Pb (plataforma externa) apresentaram uma fração da matéria orgânica importante. O Mo apresentou uma fração pirítica mais importante. O fracionamento geoquímico demonstrou que as formas nas quais os elementos foram acumulados, indicam fortemente influência da diagênese sedimentar. As concentrações de Fe e de S pirítico não foram fatores limitantes no grau de piritização dos elementos-traço. A associação de elementos-traço, tanto à fração ligada à MO quanto à fração ligada à pirita, contribuiu para determinar a retenção de elementos nos sedimentos. Quanto mais intensos foram os processos de re-oxidação do ciclo do S (indicados pela assinatura isotópica da pirita, δ34S), maior foi o grau de piritização do Pb, ao contrário do encontrado para Fe, Cu e Mo, em áreas específicas da plataforma. A estabilização do nível do mar foi o principal evento paleo-oceanográfico determinando a variação vertical da acumulação nos últimos 8.000 anos cal AP, sendo que a variabilidade dos fluxos dos elementos estudados (em relação ao somatório das frações não-detríticas obtidas na extração sequencial) não tendeu a acompanhar a variabilidade do fracionamento geoquímico. Mesmo sob condições oxidantes da coluna d’água, pode ser encontrado um sinergismo da associação à MO e à pirita, contribuindo para determinar a retenção de elementos como Cd, Co, Cu, Mo e Pb nos sedimentos / The accumulation of trace elements in the sediments plays an important role in the cycling of these elements in marine environments, associated with different forms of retention in the sedimentary reservoir, at different time scales. In the present study, the geochemical fractionation of Fe, Mn, As, Cd, Co, Cr, Cu, Mo, Ni, Pb and Zn was evaluated between the fractions soluble in HCl, associated with pyrite (FeS2) and associated with the organic fraction, To elucidate the processes that determine the accumulation of these elements in sediments of the continental shelf of the Cabo Frio Upwelling System (CFUS) in the last 8,000 years. It was observed that the fractionation of the elements Fe, Mn, As, Cr, Ni, Pb and Zn presents a higher proportion in the soluble fraction in HCl in the three sediment cores collected along the continental shelf. Cu in all seasons presented a higher proportion in the fraction of organic matter. The Cd (inner shelf) and the Pb (outer shelf) presented a fraction of the important organic matter. Mo presented a more important pyritic fraction. Geochemical fractionation has shown that the forms in which the elements are being accumulated are strongly influenced by sedimentary diagenesis. The concentrations of Fe and S pyritic were not limiting factors in the degree of piritization of trace elements. The association of trace elements to the fraction bound to the MO and to the fraction bound to pyrite contributed to determine the retention of elements in the sediments. The more intense the S-cycle re-oxidation processes (indicated by the isotopic signature of pyrite, δ34S), the higher the Pb pyritization degree, as opposed to Fe, Cu and Mo, in specific areas of the shelf. The stabilization of the sea level was the main paleo-oceanographic event determining the vertical variation of the accumulation in the last 8,000 years BP. The variability of the fluxes of the elements studied (in relation to the sum of the non-detrital fractions obtained in the sequential extraction) did not tend to follow the variability of the geochemical fractionation. Even under oxidizing conditions of the water column, a synergism of the association with OM and pyrite can be found, contributing to determine the retention of elements such as Cd, Co, Cu, Mo and Pb in the sediments

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-04-18T16:35:25Z No. of bitstreams: 1 Manuel_Fernando_Botero_2013.pdf: 3479801 bytes, checksum: bf039bb1ede70e046e8c2d699bf99bbd (MD5) / Made available in DSpace on 2017-04-18T16:35:25Z (GMT). No. of bitstreams: 1 Manuel_Fernando_Botero_2013.pdf: 3479801 bytes, checksum: bf039bb1ede70e046e8c2d699bf99bbd (MD5) / Coordenação de Aperfeiçoamento de Pessoal Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências- Geoquímica, Niterói, RJ / Os oceanos exportam o CO2 atmosférico para o fundo na forma de carbono orgânico particulado (COP) através da sedimentação de partículas planctônicas: detrito, fitoplâncton e pelotas fecais (PF). Em Cabo frio, sudeste da costa Brasileira, os eventos de ressurgência da ACAS ricas em nutrientes possibilitam o aumento na produtividade de comunidades fito e zooplanctônicas, COP e PFs. As PFs exportam carbono (C) para o fundo marinho e seu aporte para o fluxo de COP é variável, afetado pela natureza da rede trófica e a remineralização na coluna de água. O estudo do fluxo de COP é realizado mediante armadilhas de sedimentação que coletam partículas em intervalos pré-programados na parte externa da plataforma continental de Cabo Frio. Um fator de interferência no cálculo de COP é o zooplâncton ou swimmer (SW) que entra ativamente nas armadilhas de sedimentos através da migração vertical, causando uma superestimação no fluxo de partículas. As coletas de SWs e PFs foram realizadas com duas armadilhas de sedimentação em 50 e 100 m de profundidade, equipadas com 13 garrafas coletoras. Os intervalos de coleta foram de 5-7 dias por garrafa durante outono e inverno de 2011 e verão 2012. O material coletado nas garrafas foi passado através de peneiras de 1 mm e 500 μm de malha para separar os SWs. As PFs foram triadas a partir de uma aliquota da amostra peneirada. Os SWs e PFs foram separados, classificados e seu teor de C foi analisado. O fluxo de COP foi entre 0,2 e 4,4 mg C m-2 dia-1 sendo superior durante o verão, épocas de maior produtividade primária, produto de uma maior intrusão da ACAS na camada fótica. Os SWs representaram 63-94 % do C coletado na armadilha e foram constituídos principalmente por copépodos e pterópodos. O fluxo da maioria dos grupos de SWs aumentou no verão, produto de uma maior disponibilidade de alimento e diminuíram com a profundidade. O fluxo de C de PFs representou uma média de 1,5 % do fluxo de COP na maioria dos intervalos o que sugere a predominância de processos de remineralização na coluna d‟água. As variáveis medidas, não explicam os aumentos de PF em dois intervalos do inverno (até 56 % do COP), portanto se verifica uma alta dinâmica física das massas d‟água no ponto de coleta do sistema de ressurgência de Cabo Frio. A alta presença de SWs e o baixo fluxo de PFs descrevem uma área de baixa produtividade e altos processos de remineralização / The oceans export atmospheric CO2 to deep in the form of particulate organic carbon (POC) through the sedimentation of planktonic particles: detritus, phytoplankton and fecal pellets (FP). At Cabo Frio, southeast of Brazil margin coast, upwelling events of rich nutrients waters from South Atlantic Central Water (SACW) allow an increase in productivity of phyto and zooplankton communities, POC and FPs. The FPs can export carbon (C) to depth and their contribution to the POC flux is variable and is affected by the configuration of the food chain and remineralization in the water column. The study of the POC flux its made by sedimentation traps, that collect particles in pre-programmed time intervals on the outer continental shelf of Cabo Frio. The swimmers (SW) are zooplankton that interference on POC flux calculation. The SWs enter actively into the sediment traps through vertical migration, causing an overestimation of particle flux. The sampling of FPs and SWs were performed with two sediment traps with 13 sampler bottles at 50 and 100 m depth. The sampling intervals were 5-7 days per bottle during fall and winter of 2011 and summer of 2012. The collected material in the bottles was sieved with 1 mm and 500 μm sieves to separate SWS. The FPs were picked from an aliquot of the sieved sample. SWs and PFs were separated, sorted and their C content was analyzed. The POC flux oscillated between 0.2 and 4,4 mg C m-2 day-1 being higher during the summer, this is a season with higher primary production due to a higher frequency of intrusions of SAWC in the photic layer. The SWs accounted for 63-94 % of C collected in the trap and were composed mainly of copepods and pteropods. The flux of most groups of SWs increased during summer product of mayor food availability and decrease with depth. The C flux of PFs represents an average of 1.5 % of COP in the most of intervals, which suggests predominance of remineralization processes in the water column. The measured variables did not explain the increase of FPs in two intervals of winter (45-56 % of POC), therefore there is a high physical dynamics of water masses at the collection point in the Cabo Frio upwelling system. The high presence of SWs and low flux of PFs and POC describes an area of with low productivity and high remineralization processes