O bioma Cerrado ocupa aproximadamente 20% do território brasileiro e dos seus 207 milhões de hectares, 14 são ocupados com agricultura (grãos) e 50 por pastagens cultivadas. Dessa forma, o conhecimento da dinâmica da matéria orgânica (MOS) e da agregação do solo com o emprego de diferentes usos da terra e manejos agrícolas após a conversão do sistema nativo é de extrema importância para o desenvolvimento socioeconômico e, principalmente, ambiental da região no que se refere à sustentabilidade dos sistemas produtivos. O objetivo desta pesquisa foi avaliar as alterações nos os estoques de C e N, assim como a agregação, o fracionamento da MOS, a origem do C e N (delta13C e delta15N) e as propriedades microbiológicas do solo. O estudo foi realizado em um Latossolo vermelho distrófico de textura argilosa (50-70% de argila) no município de Rio Verde (GO) (\'17GRAUS\'39\'07\'\'S e \'51GRAUS\'06\'49\'\'O). As áreas consistiram de um sistema nativo de fitofisionomia Cerradão (CE), uma pastagem de baixa produtividade com 20 anos (PA-20), um sistema plantio convencional com 29 anos (SPC-29) e quatro sistemas plantio direto com 3(SPD-3), 7(SPD-7), 10(SPD-10) e 15(SPD-15) anos de uso. As amostras de solo (0-5, 5-10, 10-20, 20-30 e 30-40cm) foram coletadas em julho de 2006 (época seca) e fevereiro de 2007 (época chuvosa). Os estoques de C do solo, além de comparados entre as áreas de estudo, também foram comparados aos resultados obtidos nos mesmos locais em um estudo anterior realizado há 3 anos (2004). A densidade foi inferior e o teor e estoque de C do solo (0-40 cm) superior nas áreas sob CE, SPD-15 e SPD-10 (exceto a densidade) em relação às demais áreas. No período médio de 3 anos não houve diferenças estatísticas entre os estoques de C, enquanto a densidade do solo elevou-se significativamente nas áreas SPC-29 e SPD-7. As áreas sob SPD apresentaram taxa média de acúmulo de C anual no solo estimada em 1.17 Mg ha-1. Esses resultados sugeriram que a prática do SPD nas áreas verificadas, precedido por nove anos de cultivo sob SPC, levou aproximadamente dez anos para o restabelecimento do estoque de C semelhante à condição sob vegetação original do Cerrado. Foi verificada elevada agregação do solo, semelhante nas épocas seca e chuvosa, com predominância de agregados >2,00mm em todas as áreas e camadas de solo avaliadas. No CE e na PA-20 foram observados os maiores DMP e quantidades de agregados >2,00mm, sendo que os sistemas de plantio afetaram negativamente essas variáveis. Nos sistemas agrícolas, os SPD tiveram os maiores valores DMP e agregados > 2,00mm em comparação ao SPC-29 na camada 0-5cm de solo. Quanto a quantidade de MOS leve livre e aos teores de C e N nas classes de agregados do solo, o CE e o SPD-15 em comparação as demais áreas indicaram maiores valores, com intermediários no SPD-10 (exceto N). Os teores de C, principalmente na classe de agregado >0,25mm (0-5 cm), o DMP e estoque de C (0-20cm) apresentaram correlação significativamente positiva. Dessa forma, as observações referentes ao C e a agregação do solo indicaram que a preservação e a manutenção da classe de agregados >0,25 mm foram processos fundamentais para os maiores níveis de C observados no CE, SPD-10 e SPD-15. E a quantidade de MOS leve livre verificada, componente responsável pela manutenção dos agregados, concordam com a correlação observada. Na área PA-20, mesmo com elevada agregação do solo, provavelmente pela baixa produtividade da gramínea não houve disponibilidade suficiente de C (via MOS) para a manutenção das classes de agregados, acarretando no menor estoque de C em relação as demais áreas (exceto ao SPC-29). A mesma insuficiência de MOS ocorreu na área SPC-29, mas nesse caso devido ao revolvimento do solo que acelerou a oxidação da MOS, visto que o aporte de resíduos culturais na área é semelhante as sob SPD, por utilizarem a mesma sucessão de culturas. No CE os valores mais negativos de delta13C observados em relação a PA-20 representam a predominância de plantas de ciclo fotossintético C3. E o mesmo padrão significativo de enriquecimento de delta13C e delta15N no solo em profundidade ocorreu devido à mineralização da MOS, exceto nos valores de delta13C na PA-20 provavelmente a gradativa substituição da MOS original. Os menores valores de delta15N no Cerrado podem estar indicando maior fixação biológica de N em relação à pastagem. Da MOS original do CE, 83% foi substituída na área PA-20 e apesar da elevada substituição, demonstra que baixa produtividade da gramínea pode ter influenciado no menor estoque de C da área em relação ao CE. Não foram verificadas diferenças nos valores de delta13C e delta15N entre as classes de agregados em cada área de pesquisa. Os valores de C e N microbiano (Cmic e Nmic), assim como as relações com os teores de C e N totais, e o qCO2 foram influenciados pelas estações sazonais, sendo maiores na época chuvosa, exceto para o qCO2. Menores valores de qCO2 na época chuvosa refletiram maior eficiência de imobilização de C na biomassa microbiana. Para as áreas sob uso da terra, os maiores valores de Cmic e Nmic foram observados na PA-20 e os menores no SPC-29. Esses resultados indicaram melhores condições ao desenvolvimento microbiano na PA-20 provavelmente ao cultivo da gramínea, a excreção dos animais e a reforma da área (dezembro/2007). A adoção do SPD foi importante fator no aumento do Cmic e Nmic em relação ao SPC, possivelmente ao não revolvimento do solo e aporte de resíduos e superfície, que com o tempo de implantação adaptou a biomassa microbiana a uma nova condição. O Cmic e o Nmic indicaram alterações nas áreas implantadas em relação ao Cerrado e apontou maior equilíbrio da microbiota nessa área / The Savannah biome occupies 20% of the Brazilian territory, approximately, and of their 207 million hectares, 14 are taken by agriculture (grains productions) and 50 for farming (cultivated pastures). In that way, the knowledge of soil organic matter (SOM) dynamics and the soil aggregation with the different uses and agricultural handlings after the conversion of the native system is very important for the socioeconomic development, environmental preservation and the sustainability of the productive systems. Therefore, the objective of this research was to evaluate the alterations of C and N stocks, the aggregation, the SOM fractionation, the origin of C and N (delta13C e delta15N) - and the microbiological properties of the soil. The study was accomplished in a Oxisol (clayey Red Dystrophic Latosol) with 50-70% of clay in the municipal district of Rio Verde (Goias state, Brazil) (\'17GRAUS\'39\'07\'\'S and \'51GRAUS\'06\'49\'\'W). The areas consisted of a native system of Savannah (CE) phytophysionomy (Cerradão), a pasture of low productivity with 20 years (PA -20), a conventional till with 29 years (SPC -29) and four no-till areas with 3 (SPD -3), 7 (SPD -7), 10 (SPD -10) and 15 (SPD -15) years of use. The soil samples from different depths (0-5, 5-10, 10-20, 20-30 and 30-40cm) were collected in July of 2006 (dry seasonal) and February of 2007 (rainy seasonal). The soil C stock, besides having compared among the study areas, its were also compared to the results obtained at the same places in a study accomplished previously, 3 years ago (2004). The C content and stock were higher (0-40cm) in the areas under CE, SPD-15 and SPD-10 and the bulk soil was lower in relation to the other areas. In the medium period of 3 years (2004 to 2007) there were not statistical differences among the storage of C, while the bulk soil were increased significantly in the areas SPC-29 and SPD-7. The areas under SPD showed medium rate of annual C accumulation in the soil valued to as 1.17 Mg ha-1. Those results suggested that the practice of SPD in the verified areas, preceded by 9 years of cultivation under SPC system, it took approximately ten years for the re-establishment of the C stock similar to the original vegetation (CE). Similar aggregation of the soil was verified in the dry and rainy seasons, with predominance of aggregates > 2.00mm in all areas and soil layers evaluated. In CE and in the PA-20 the largest mean weighed diameters (MWD) and amounts of aggregates were observed > 2,00mm, and the till systems affected negatively that variables. In the different agricultural systems, SPD had the largest values MWD and aggregates > 2.00mm in comparison with SPC-29 in the layer 0-5cm of soil. In relation to light free fraction from SOM and C and N in the soil aggregates, CE and SPD-15 in comparison to other areas indicated larger values, with intermediate SPD-10 (except N). The C content, mainly in the aggregate class > 0,25mm (layer 0-5cm of soil), DMP and C stock C (0-20cm) showed positive correlation. In that way, the observations regarding C and the soil aggregation showed that the preservation and the maintenance of the aggregates class > 0.25mm were fundamental processes to the largest levels of C observed in CE, SPD-10 and SPD-15 systems. The amount of light free fraction verified, responsible component for the maintenance soil aggregates, is in agree with the observed correlation. In the PA-20 area, even with high soil aggregation, probably for the low productivity of the grassy, there was not enough readiness of C (through SOM) for the maintenance of the aggregates classes, resulting in the smallest storage of C in relationship the other areas (except to SPC -29). The same deficiency of SOM happened in the area SPC-29, but in that case due to the rotation of the soil that accelerated the oxidation of the SOM, because the contribution of cultural residues in the area is similar to SPD, because these use the same cultures succession. The more negative values of delta13C observed in CE is due by the higher predominance of plants with C3 photosynthetic cycle. The same significant pattern of enrichment of delta13C and delta15N happened in the depth of the soil due to the SOM mineralization, with exception of the delta13C values in the PA-20 systems, due probably by the gradual substitution of the original SOM in the 20 years of CE transfer to PA-20 systems. The smallest delta15N values in CE system can be indicating larger N biological fixation in relation to the pasture. Of the original SOM of CE, 83% was exchange in the PA-20 area and in spite of the high exchange, the lowers productivity of the grassy might have influenced in the smallest C stock in the PA-20 to CE system. Differences were not verified in the values of delta13C e delta15N among the soil aggregates classes in each researched area. The microbial C e N values (Cmic and Nmic), as well as the relationship with the C e N contents and the qCO2 were influenced by the seasonal stations, being C e N larger and the qCO2 smaller at the rainy seasonal. The smaller qCO2 values in the rainy seasonal reflect the largest efficiency of C immobilization in the microbial biomass. The largest values of Cmic and Nmic were observed in the PA-20 and the smallest in SPC -29. Those results indicated better conditions to the microbial development in the PA-20 probably due to the grassy cultivation, the animal excretion and the reform of the area (December /2007). The adoption of SPD was an important factor in the Cmic and Nmic increase in relation to SPC, possibly due to the non soil rotation, the contribution of vegetables residues on the soil surface and- better microbial biomass adapted to the new condition of NT implantation. The Cmic and Nmic indicated alterations in the new areas implanted in relation to the CE and it pointed larger balance of the microbiota in CE system

[pt] Neste estudo foram determinadas as concentrações de Se e Hg, no tecido hepático, muscular e renal, de 70 golfinhos de cinco espécies diferentes (Tursiops truncatus, Stenella frontalis, Steno bredanensis, Sotalia guianensis e Pontoporia blainvillei) e uma espécie de ave marinha (Sula leucogaster), encontrados mortos, durante os anos de 2001 e 2013, na Costa Centro-Norte fluminense. A fim de identificar o processo de bioacumulação e biomagnificação, foram determinadas as concentrações de Se e Hg no fígado e no músculo de cinco espécies de peixe (Trichiurus lepturus, Micropogonias furnieri, Mugil liza, Sardinella brasiliensis, Scomber japonicus) e um cefalópode (Loligo plei). Para auxiliar no estudo dos níveis de Se e Hg, também foram avaliados os valores dos isótopos estáveis Delta 13C e Delta 15N no músculo de todas as espécies envolvidas. As concentrações mais elevadas de mercúrio e selênio foram observadas no fígado dos golfinhos, que apresentaram valores entre 11,2 e 684 mg kg elevado a potência negativa 1 para o Hg e entre 10,2 e 111 mg kg elevado a potência negativa 1 para Se. No músculo foram observadas concentrações mais baixas de Se e Hg nos golfinhos, apresentando concentrações de Hg que variaram entre 1,8 a 9,8 mg kg elevado a potência negativa 1, e de Se que variaram entre 1,9 a 2,3 mg kg elevado a potência negativa 1. A concentração de Hg no rim variou de 1,5 a 22 mg kg elevado a potência negativa 1 e de Se entre 7,6 a 12 mg kg elevado a potência negativa 1 nos golfinhos. Entre as presas, as concentrações mais elevadas de Hg e Se foram observadas no fígado, o mercúrio variou entre 0,3 e 1,6 mg kg elevado a potência negativa 1 e o selênio entre 6,6 e 40,4 mg elevado a potência negativa 1. As concentrações de Hg muscular ficaram entre 0,45 e 0,046 mg kg elevado a potência negativa 1 e de Se muscular entre 2,3 e 1,4 mg kg elevado a potência negativa 1 nas presas. Os golfinhos apresentaram maior enriquecimento de nitrogênio com valores médios entre 14,0 e 17,5 por mil. Para os isótopos estáveis de carbono, os valores médios variaram entre menos 16,8 e menos 15,5 por mil nos cetáceos. A razão isotópica entre as presas varou entre 8,3 e 13,5 por mil para o Delta 15N e entre menos 18,3 a menos 11,9 para o Delta 13C. Foi observado poder de biomagnificação positivo para o mercúrio nas espécies S. guianenis (log [Hg] = menos 0,031 mais 0,195 asterisco Delta 15 N; r igual a 0,719; p menor 0,001) e S. frontalis (log [Hg] igual a menos 0,15 mais 0,21 asterisco Delta 15 N; r igual 0,68; p menor que 0,0001), sendo possível concluir que a biomagnificação do Hg é efetiva na região estudada. / [en] This study determined the concentrations of Se and Hg in the liver, muscle and kidney tissue, of 70 dolphins from five different species (Tursiops truncatus, Stenella frontalis, Steno bredanensis, Sotalia guianensis and Pontoporia blainvillei) and a species of seabird (Sula leucogaster), found dead during 2001 and 2013 on the North-Central Coast of the State of Rio de Janeiro. In order to identify the bioaccumulation and biomagnification processes, the concentrations of Se and Hg in the liver and muscle of five species of fish (Trichiurus lepturus, Micropogonias furnieri, Mugil liza, Sardinella brasiliensis, Scomber japonicus) and a cephalopods (Loligo plei) were determined. To assist in the study of Se and Hg, Delta 13 C and Delta 15 N stable isotopes in the muscle of all investigated were also evaluated species involved. The highest concentrations of mercury and selenium were observed in dolphin liver, which presented values between 11.2 and 684 mg kg elevated to negative power 1 for Hg and between 10.2 and 111.3 mg kg elevated to negative power 1 for Se. In muscle lower concentrations of Se and Hg were observed for these species, showing Hg concentrations ranging from 1.8 to 9.8 mg Kg elevated to negative power 1, while Se ranged from 1.9 to 2.3 mg kg elevated to negative power 1. Hg concentrations in the kidney varied from 1.5 to 22.0 mg kg elevated to negative power 1 and Se between 7.6 to 12.2 mg kg elevated to negative power 1 in dolphins. Among the prey, higher concentrations of Hg and Se were observed in liver, mercury varied from 0.28 to 1.6 mg kg elevated to negative power 1 and selenium between 6.6 and 40.4 mg kg elevated to negative power 1. Hg muscle concentrations were between 0.45 and 0.046 mg kg elevated to negative power 1 and muscle Se between 2.3 and 1.4 mg kg elevated to negative power 1 in the prey. Dolphins show higher nitrogen enrichment with mean values between 14.0 and 17.5 per thousand. For the stable carbon isotopes, the mean values ranged between less 16.8 and less 15.5 per thousand in cetaceans. The isotopic ratio of the prey ranged between 8.3 and 13.5 per thousand for Delta 15N and between less 18.3 and less 11.9 for Delta 13C. Positive biomagnification power was observed for mercury to species S. guianenis (log [Hg] equal less 0.031 more 0.195 asterisk Delta 15N; r equal 0.719; p less than 0.001) and S. frontalis (log [Hg] equal less 0.15 more 0.21 asterisk Delta 15N; r 10 equal 0.68; p less than 0.0001), and indicating that the biomagnification of Hg is effective in the region studied.

L’Âge du Bronze est un moment de changement pour les groupes humains en Italie : les attestations archéologiques montrent comment les nouvelles pratiques agricoles, le système d’élevage et le développement de nouvelles activités économiques sont diffusés différemment selon les régions, conformément à l’environnement et aux facteurs sociaux. L’étude des stratégies de subsistance et des comportements socio-économiques à travers l’analyse des patrons alimentaires en Italie, pendant l’Âge du Bronze est donc proposée. L’enjeu est de comprendre comment les habitudes alimentaires reflètent ces transformations et d’analyser l’introduction et consommation de nouvelles ressources végétales et animales. Sur la base d’une approche diachronique et géographique, l’évolution des habitudes alimentaires à travers les analyses des isotopes stables dans le collagène des os humains et animaux est présentée. L’étude se concentre sur dix sites datant de 2300-930 av. J.-C. L’analyse au niveau géographique témoigne d’une diète plus variée dans le Nord et le Centre de l’Italie par rapport au Sud. Concernant l’analyse diachronique, une homogénéité des ressources consommées à l’Âge du Bronze Ancien est remarquée. Pour l’Âge du Bronze Moyen et Final l’émergence de régimes alimentaires basés sur de nouvelles plantes est mise en évidence. Cette période se présente donc comme un moment de rupture et de transition. L’introduction de nouvelles ressources et la diffusion de céréales contribuent à mettre en évidence les dynamiques des échanges culturels qui ont caractérisé les communautés à l’Âge du Bronze, même si l’environnement et les variations climatiques ne doivent pas être négligées. / The Bronze Age is characterised by significant changes in human groups organisation and activities. In Italy, archaeological evidences show that new agricultural practices, livestock farming and new economic activities were introduced. All these aspects evolved differently, depending on geographical areas, local environment and social factors. The study of subsistence strategies and socio-economic behaviours through the analysis of dietary patterns in Italy during the Bronze Age is presented. Main scopes are to delineate Italian society’s food choices and to analyse the introduction of new resources. Stable isotopes analyses contained in collagen of human and animal bone has been performed. A diachronic and geographic approach is presented. The analysis focuses on ten Italian sites dating from ca. 2300 to 930 BC, presenting both diachronic and geographic comparison. The geographic analysis shows a more varied diet in the North and Central Italy, compared to the Southern areas. Concerning the diachronic analysis, data highlight the homogeneity of the resources consumed during the Early Bronze Age. For both Middle and Late Bronze Ages, the introduction of new plants in the diet is evident. Thus, Middle Bronze Age represents a pivotal moment in protohistoric societies, as a phase of rupture and transition. The consumption of different food resources and new cereals diffusion processes contribute to highlight the importance of contacts and cultural exchanges. These relationships had a significant influence on Italian communities during the Bronze Age, including food habits, although the environment and the climatic oscillations of this period cannot be neglected. / L'età del Bronzo è una fase della Protostoria caratterizzata in Italia da importanti cambiamenti per i gruppi umani. Le evidenze archeologiche suggeriscono l'introduzione di nuove pratiche agricole e sistemi di allevamento, a cui si associa la sviluppo di attività di rilevanza a livello economico (e.g. metallugia), e una maggiore organizzazione della società che mostrano al loro interno una strutturazione e gerarchizzazione più marcata: questi aspetti presentano tendenze differenti secondo l'area geografica, in seguito alle caratteristiche ambientali locali e fattori di tipo sociale. Questo lavoro propone lo studio delle strategie di sussistenza e delle tendenze socio-economiche attraverso l'analisi dell'alimentazione. Gli obiettivi sono comprendere come le transformazioni che si manifestano a livello socio-economico si riflettono nella dieta, delineare le tendenze alimentari considerando anche gli aspetti biologici e analizzare il consump di nuove risorse. Lo studio è stato effetuato attraverso l'analisi degli isotopi stabili contenuti nel collagene delle ossa di resti umani e animali. Sono stati selezionati 10 siti della penisola italiana datati tra 2300-930 BC: prendendo in considerazione altri siti disponibili in letteratura, l'analisi è avvenuto applicando un approccio di tipo geografico e cronologico. L'analisi geografica ha messo in evidenza come il Nord e il Centro Italia presentino dei pattern alimentari variegati, contrariamente à quanto si rileva per il Sud Italia. L'analisi cronologica mostra come nel Bronzo Antico si noti una maggior omogeneità nel tipo di risorse consumate, differentemente all'età del Bronzo Medio e Rencete-Finale, dove l'introduzione di nuovi cereali nella dieta,come il miglio, risultaevidente. Questo studio, quindi, mostra come nel Bronzo Antico rappresenti un momento critico, di transizione, per i gruppi umani protostorici. Il consumo di risorse differenti e il processo di diffusione di nuovi cereali sottolinea l'importanza dei contatti e degli scambi culturali tra le diverse comunità. Queste relazioni cominciano ad avere un'influenza rilevante durante l'età del Bronzo, anche a livello di abitudini alimentari, sebbene non possano essere ignorate le caratteristiche ambientali locali e le oscillazioni climatiche di questo periodo.

Os locais de estudo estão situados no PETAR – Parque Estadual Turístico do Alto Ribeira e PEI – Parque Estadual Intervales, na região do sudeste do Brasil. A área é caracterizada pela presença de vegetação nativa de Floresta Atlântica e dois lagos naturais conhecidos por Lagoa Grande E Lagoa Vermelha, onde foram coletados três testemunhos sedimentares. Análises químicas (C, N, mineralogia), isotópicas (12C, 13C e 14C) e biológicas (palinologia) foram usadas nesse estudo para entender a história da paleovegetação da região durante o Pleistoceno tardio e o Holoceno, assim como suas relações com as mudanças climáticas. Amostras de solo foram coletadas a partir de trincheiras e tradagens em dez locais sob vegetação de floresta natural no PETAR e no PEI. Os dados isotópicos (δ13C) da matéria orgânica do solo em dois pontos do PETAR mostraram valores de δ13C mais enriquecidos ( -17,1%0 e -20,1%0) nas camadas mais profundas, indicando a presença de uma vegetação menos densa que a atual, com uma provável mistura de plantas C3, e C4, no período de ~30.000 a 16.000 anos AP, sugerindo a presença de um clima mais seco. De ~16.000 anos AP até o presente um empobrecimento isotópico significativo (até -28,3 %0) foi observado em todos os locais, indicativo de expansão da floresta, provavelmente associada à presença de um clima mais úmido que no período anterior. Os dados isotópicos (δ13C) dos solos de PEI indicam a presença de vegetação de floresta desde ~14.000 anos AP, exceto em um local (SAI) onde valores de δ13C mais enriquecidos (-21,8 %0) foram observados, relacionados provavelmente à mistura de plantas C3 e C4 e/ou à presença de uma vegetação de floresta menos densa em ~14.000 anos AP. A partir dos resultados da matéria orgânica sedimentar do testemunho da Lagoa Grande foi verificado que as condições ambientais foram relativamente estáveis durante os últimos 1000 anos, caracterizados pela presença de plantas C3, e fitoplâncton, sugerindo condições climáticas úmidas e que o lago provavelmente não se apresentou seco durante o último milênio. Condições ambientais para a Lagoa Vermelha também foram relativamente estáveis durante os últimos 4500 anos, caracterizadas pela presença significativa de plantas C3 na matéria orgânica sedimentar indicando condições climáticas úmidas. Mudanças na composição da vegetação foram registradas pela palinologia durante o período de ~1400 a 1100 anos AP, relacionadas a presença de um provável clima frio que o atual. / The study sites are in the PETAR - Parque Estadual Turístico do Alto Ribeira and PEI - Parque Estadual Intervales, in the southeastern region of Brazil. The area is characterized by the presence of the native vegetation of Atlantic forest and two natural lakes called LAgoa Grande and Lagoa Vermelha, where three sediment cores were collected. Chemical (C, N and mineralogy), isotope (12C, 13C and 14C), and biological (pollen analyses) tools were used in the study to understand the palaeovegetation history of the region during the late Pleistocene and Holocene and its relation to climate changes. Soils samples were collected from trenches and by drilling at five locations under natural forest vegetation in the PETAR and PEI study sites.The isotope data (δ13C)collected in soil at two locations in the PETAR area showed much more enriched δ13C values ( -17,1%0 and -20,1%0)in the deeper horizons, indicating the presence of a less dense vegetation than the present modern day, with a probable mixture of C3 and C4 plants, in the period of ~30.000 to ~16.000 years BP. This pattern suggested the presence of a drier climate. From ~16.000 years BP to the present, a significant isotopic depletion (up to -28,3 %0)was observed in all sites indicating an expansion of the forest, probable associated to the presence of a more humid climate than the previous period. The isotope results (δ13C) collected at the PEI soils indicated the presence of forest vegetation since ~14.000 years BP, except in one location (SAI), where more enriched δ13C values (-21,8 %0) were observed probable related to mixture of C3 e C4 plants, and/or a presence of a less dense forest vegetation around ~14.000 years BP. From the results of the sediment organic matter compositions of LAgoa Grande, it was verified that the environmental conditions were relatively stable during the last 1000 years, characterized by the presence of C3 plants and phytoplankton, suggesting humid climaticconditions and the lake probable wasn't dry during the last millennium. Environmental conditions for the Lagoa Vermelha were also relatively stable during the last 4500 years, characterized by the significant presence of C3 plants in the sediment organic matter indicating humid climatic conditions. The changes in vegetation composition recorded by palynology during the period of ~1400 to 1100 years BP can be related to existence of a probable colder climate than today.

Les roches mantelliques exposées sur le plancher océanique et/ou en contact avec l’atmosphère au niveau d’une ophiolite, sont en déséquilibre et s’altèrent, via les réactions de serpentinisation (i.e. d’hydratation et oxydo-réduction) et les réactions de carbonatation. Ces réactions d’altération jouent un rôle important dans les échanges chimiques entre la Terre profonde et les enveloppes externes, en particulier dans le cycle des volatils (C, H et O) via la minéralisation du CO2 atmosphérique, la production d’hydrogène et la formation d’hydrocarbures et de molécules prébiotiques. L’ophiolite d’Oman est un « laboratoire naturel » idéal pour étudier ces réactions depuis l’hydrothermalisme océanique jusqu’à l’altération continentale actuelle.Cette thèse présente les résultats d’une étude multi-technique et multi-échelle réalisée sur une série de péridotites serpentinisées et carbonatées échantillonnées sur deux sites, Wadi Dima et Batin (Massif de Wadi Tayin), considérés comme représentatifs des processus d’altération affectant l’ophiolite d’Oman. Ces travaux combinent caractérisations (micro-)structurales (EBSD, µ-tomographie), pétrographiques et minéralogiques (Raman, Cathodoluminescence, (3D-)XANES), et analyses géochimiques (EPMA, (LA)-ICPMS) et isotopiques (isotopes du O, C micro-bulk et in-situ).L’étude des harzburgites de Wadi Dima a permis d’identifier la succession des épisodes de serpentinisation et de carbonatation qui ont affecté les péridotites lors du refroidissement de la lithosphère jusqu’à la mise en place de l’Ophiolite d’Oman. La serpentinisation commence en domaine océanique (appauvrissement en REE, anomalie négative en Ce) durant le refroidissement initial de la lithosphère océanique et/ou au début du détachement intra-océanique à < 200-220°C, par la formation des veines de lizardite. Cette serpentinisation continue avec la formation de chrysotile au centre de la structure maillée, remplaçant l’olivine. Le dernier stade de serpentinisation a lieu simultanément au premier stade de carbonatation et engendre l’altération complète de la péridotite à < 100°C. Le système est contrôlé par des hétérogénéités locales (anomalies en Ce et variation de la composition isotopique en carbone). La carbonatation continue à < 50°C lors de la transition en domaine continental. Des veines de carbonates se forment par interaction avec des fluides issus des sédiments durant la convergence et avec des fluides de surface et de sub-surface durant l’altération actuelle de l’ophiolite. Ce processus marque le passage d’un régime hydrothermal océanique dont la chimie est dominée par la composition de la roche, à un régime hydrothermal continental dont la chimie est contrôlée par la composition du fluide dans des fractures. Paradoxalement, la structure initiale du manteau contrôle l’orientation et la distribution des veines de carbonate.Le site de Batin se distingue par sa structure complexe avec la présence de nombreux filons de gabbros et de pyroxénites et des évidences d’imprégnation magmatique. La serpentinisation y est marquée par la formation de textures atypiques en anneau ("fingerprint") caractérisées par des variations des teneurs en Fe-Mg et du redox à micro-échelle et par des compositions isotopiques en oxygène en déséquilibre. Ces caractéristiques sont interprétées comme résultant de déséquilibres locaux dans les processus de transport-nucléation-réaction pouvant être liés à plusieurs paramètres : forts gradients de température, redox, composition du fluide, et de perméabilité.Cette thèse apporte de nouvelles données vis-à-vis des relations temporelles et spatiales entre les réactions de serpentinisation et de carbonatation, les hétérogénéités chimiques à micro-échelle et l’impact de ces réactions d’altération sur les bilans globaux des volatils (C, H et O) en Oman. Elle met particulièrement en évidence la possibilité de stocker du CO2 et de produire de l’H2 simultanément lors de l’altération du plancher océanique. / Mantle rocks exposed in seafloor and/or directly in contact with atmosphere in ophiolite system are thermodynamically and chemically in disequilibrium. Mantle alteration is driven by serpentinization (ie, hydration and oxidation-reduction reactions) and carbonatization reactions. These reactions play an major role in the chemical exchanges between the deep mantle and the outer envelops, especially in the global mass budget of volatiles (C, H and O) via CO2 mineralization, hydrogen production and formation of hydrocarbons and prebiotic molecules. Oman ophiolite is an ideal "natural laboratory" for studying alteration reactions in mantle rocks from ocean hydrothermalism to modern continental weathering.This thesis presents the results of a multi-technical and multi-scale study on carbonate-hosted serpentinized peridotites in two sites, Wadi Dima and Batin (Wadi Tayin massif), considered representative of the alteration processes affecting the Oman ophiolite. This work combines (micro-) structural (EBSD, µ-tomography), petrographical (EPMA), mineralogical (Raman, Cathodoluminescence, (3D-)XANES), geochemical ((LA)-ICPMS) and isotopic studies (O, C in situ and micro-bulk).Studies in Wadi Dima harzburgites have highlighted successive episodes of serpentinization and carbonatization in Oman peridotites from oceanic lithosphere cooling to Oman Ophiolite emplacement. Serpentinization occurs in oceanic setting (REE depletion, negative Ce anomalies), probably during the onset of the oceanic lithosphere cooling and / or of the intra-oceanic detachment, at < 200-220°C, driven by the formation of lizardite veins constituting the mesh structure. Serpentinization continues at lower temperature with the formation of chrysotile in the center of the mesh structure, replacing olivine. The last stage of serpentinization is concurrent with early carbonatization and generates the complete peridotite alteration at < 100°C. In this rock-dominated system, fluid flow paths are controlled by nano-porosity (etch pits), by pore scale weakness and by local heterogeneity in permeability, generating local chemical heterogeneities (Ce anomalies variability and carbon isotope heterogeneity). Carbonatization continues at < 50°C during the transition in continental setting. Carbonate veins are formed during interaction with sediment-derived fluids during intra-oceanic detachment at the onset of obduction and with surface and sub-surface fluids during modern continental Ophiolite weathering. This process records the transition from oceanic diffuse-flow rock-dominated to cooler continental fluid-focused-flow fluid-dominated hydrothermal systems. Paradoxically, initial mantle structure controls orientation and distribution of carbonate veins.Batin site is distinguished by its complex structure with the presence of abundant gabbros and pyroxenites dikes, evidence of magmatic impregnation peridotites. Serpentinization is charcheterized by the formation of an uncommon texture in rings ("fingerprint") at the expense of olivine, marked by chemically variation in Fe-Mg and redox at microscale and by disequilibrium oxygen isotopic composition. These features are interpreted as resulting from local disequilibrium in the transport-nucleation-reaction processes that may be related to several parameters: high temperature gradient, redox, fluid composition, and permeability.This thesis brings new constraints on temporal and spatial relations between serpentinization and carbonatization reactions, on local chemical heterogeneities at micro-scale and on the global chemical budget of volatiles (C, H and O) in Oman peridotites. It has highlighted the possibility to store CO2 and producing H2 simultaneously during subseafloor alteration.

Orientador: Dirlei Antonio Berto / Resumo: Objetivou-se com este estudo avaliar a influência dos nucleotídeos (inosinato e guanilato dissódico) sobre o desempenho, peso relativo e turnover do 13C no intestino delgado, baço, fígado e pâncreas de leitões desmamados com idade média de 21 dias. Foram avaliados os seguintes tratamentos: dieta controle sem suplementação de nucleotídeos (Nu); dietas contendo 0,2% de Nu; 0,4% de Nu e 0,6% de Nu. No primeiro experimento 84 leitões desmamados (6,04 ± 0,25 kg) foram distribuídos em um delineamento experimental em blocos ao acaso com quatro tratamentos (níveis de Nu), sete repetições e três animais por unidade experimental, para avaliação do desempenho. No segundo experimento foram utilizados 87 leitões desmamados (6,03 ± 0,23 kg) em delineamento experimental em blocos ao acaso, com os mesmos tratamentos, sendo abatidos três leitões no dia do desmame (dia zero) e três leitões por tratamento nos dias 3, 5, 8, 12, 23, 35 e 49 após o desmame, para avaliar o turnover do 13C na mucosa e na parede intestinal (duodeno e jejuno), no baço, fígado e pâncreas, e o peso relativo do intestino delgado e do baço, fígado e pâncreas. No primeiro experimento não foi verificado efeito dos tratamentos (P > 0,05) nas variáveis de desempenho dos leitões no período de 21 a 36 dias de idade. No período de 21 a 48 dias de idade dos leitões houve efeito quadrático (P < 0,01) dos níveis de Nu no consumo diário de ração e ganho diário de peso. No período experimental total (21 a 55 dias de idade dos leitões... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study was conducted to evaluate effects of dietary supplementation of nucleotide (disodium 5´guanylate and disodium 5´inosinate) on the growth performance, relative weight and carbon turnover 13C of the small intestine, spleen, liver and pancreas of weaned piglets of 21 days of age. The treatments were dietary supplementation with 0% (control); 0.2%; 0.4% or 0.6% nucleotide of diet. In the first trial eighty-four weaned piglets (6.04 ± 0.25 kg average initial BW) were allotted to four dietary treatments (Nu levels) with seven pens per treatment and three pigs per pen, in a randomized complete block design to evaluate the performance. In the second trial eighty-seven weaned piglets (6.03 ± 0.23 kg average initial BW) were used in a randomized complete block design, with the same treatments, and on the day of weaning (day zero) were slaughtered three piglets and days 3, 5, 8, 12, 23, 35 and 49 after weaning, three pigs per treatment were slaughtered, to evaluate the effect of nucleotide on the turnover 13C in the mucosa and intestinal wall (duodenum and jejunum), spleen, liver and pancreas and relative weight of the small intestine and spleen, liver and pancreas. During the first period (21 to 36 days of age), no differences were detected on the performance. During the second period (21 to 48 days of age), a quadratic effect (P < 0.01) of the levels of nucleotide was verified on average daily feed intake and average daily weight gain. During the whole experimental period ... (Complete abstract click electronic access below) / Doutor

A conversão de florestas em pastagens e seu subseqüente abandono tem ocorrido por toda Amazônia, e embora exista muita pesquisa sobre as conseqüências desta mudança de cobertura do solo, ainda existem muitas perguntas sobre os processos biogeoquímicos associados a estas mudanças. Neste estudo, nós avaliamos os efeitos da mudança de cobertura sobre a respiração do solo em pastagens e florestas secundárias e intactas próximo de Rio Branco, Acre. Utilizou-se o método de câmaras dinâmicas associadas com analisador de gás por infravermelho. As folhas de gramíneas dentro dos anéis de medida nas pastagens foram responsáveis por cerca de 50% do fluxo durante a estação chuvosa, mas na estação seca, sua influência pode ser confundida com a variabilidade entre os anéis de medida. Os maiores fluxos de CO2 são observados em pastagens e não em florestas, mesmo se descontado o efeito das folhas em pastagens. As maiores amplitudes de variação sazonal também foi observada em pastagens. Devido aos maiores fluxos em pastagens, o fluxo anual de CO2 do solo para atmosfera foi 20% maior em pastagens em comparação com as florestas. A respiração heterotrófica é similar em pastagens e florestas secundárias e intactas, mostrando que a respiração autotrófica é responsável pelos altos fluxos de CO2 em pastagens . O ?13C do CO2 de origem heterotrófica em pastagem foi de -15‰, demonstrando que os microrganismos do solo se alimentam principalmente de matéria orgânica originado da pastagem. / Conversion of forest to cattle pastures and subsequent abandonment of those pastures is occurring throughout the Amazon Basin, but the biogeochemical consequences of this land cover change are not well understood. In this study we assess the effects of land-use change on soil respiration in pastures, secondary forests and mature forests near Rio Branco, Acre. Leaves inside the measurement chambers were responsible for about 50% of the pasture fluxes in the wet season, but in the dry season its influence was confounded with variability within replicates. The greatest CO2 fluxes are observed in pastures, which also presented the greatest amplitude of seasonal variation. Annual fluxes were 20% higher in pastures compared to forests. Heterotrophic respiration was similar in pasture and mature and secondary forests, indicating that autotrophic respiration is probably the main cause of higher fluxes in pastures. The ?13C of heterotrophic respired CO2 in pasture was -15‰, showing that microorganisms in pasture soil are feeding mostly on carbon from grasses and not from remaining forest carbon.

Malgré leur distance de la pression industrielle, les milieux marins austraux et antarctiques sont contaminés par des polluants globaux, tels que le mercure (Hg), par le transport atmosphérique et les courants océaniques. Jusqu'à présent, les voies de contamination du Hg dans l'Océan Austral restent peu connues, en particulier dans le secteur Indien, et de nouvelles études sont nécessaires pour élucider son devenir et son impact dans ces régions. Les oiseaux marins, en tant que prédateurs supérieurs des chaînes alimentaires marines, sont exposés à des concentrations élevées de méthylmercure (MeHg) via leur régime alimentaire. De plus, ils présentent des habitats de prédation contrastés dans les différents compartiments marins (en termes spatiaux et de profondeur). Par conséquent, ils sont considérés comme des bioindicateurs efficaces de la contamination par Hg et la bonne connaissance de leurs caractéristiques écologiques permet leur application comme traceurs du Hg dans des environnements éloignés, qui sont autrement difficiles à échantillonner. L'objectif principal de ce travail de doctorat est la caractérisation des voies d'exposition de MeHg accumulé par les oiseaux marins et l'identification des processus impliqués dans le cycle biogéochimique du Hg dans l'Océan Austral (des eaux antarctiques aux eaux subtropicales). L'approche méthodologique proposée consiste à combiner la composition isotopique du Hg et la spéciation du Hg dans les tissus d’espèces d’oiseaux marins de l'Océan Austral choisis précisément. Dans une première étape, une évaluation des signatures isotopiques de Hg spécifique de chaque tissu a été réalisée, notamment dans le sang et les plumes, car ceux-ci peuvent être échantillonnés de manière non létale. Chez les poussins, les deux tissus peuvent être utilisés efficacement et indifféremment comme bioindicateurs de la contamination locale en utilisant des isotopes du Hg, alors que chez les adultes, chaque tissu donne accès à une exposition temporelle différente : le sang à l'échelle récente (c'est-à-dire l'exposition pendant la période de reproduction) et les plumes à l'échelle annuelle, fournissant ainsi des informations isotopiques complémentaires aux différentes étapes du cycle annuel des oiseaux. Une deuxième partie a été axée sur l'exploration des sources de MeHg dans quatre espèces de manchots d’une même zone subantarctique, les îles de Crozet. Les populations ont été discriminées par leurs signatures isotopiques du Hg en fonction de leurs habitats de prédation et leurs mouvements latitudinaux, qui se trouvent être les facteurs principaux déterminant leur exposition à différentes sources de MeHg. Dans une troisième partie, les isotopes du Hg ont été étudiés dans deux modèles d'oiseaux (poussins de labbes et manchots adultes) sur une grande échelle latitudinale de l'Antarctique à la zone subtropicale. Les variations latitudinales des valeurs isotopiques du Hg (δ202Hg, Δ199Hg) semblent être influencées par une différente amplitude des processus photochimiques et d'autres voies biogéochimiques telles que la réduction du Hg, et les processus de méthylation / déméthylation, ainsi que les processus trophiques ou métaboliques. / Despite their distance from industrial pressure, marine southern and Antarctic environments are contaminated by worldwide distributed pollutants, such as mercury (Hg), through atmospheric transport and oceanic currents. So far, Hg contamination pathways in the Southern Ocean remains poorly understood, particularly in the Indian sector, and new studies are required to elucidate its fate and impact in these regions. Seabirds, as top predators of marine food webs, are exposed to elevated concentrations of biomagnified methylmercury (MeHg) via dietary intake and moreover, they forage in the different marine compartments both in spatial and depth terms. Therefore, they are considered as effective bioindicators of Hg environmental contamination and the good knowledge of their ecological characteristics permits their application for tracing Hg in such remote environments otherwise of difficult access. The main objective of this doctoral work is the characterization of the exposure pathways of the MeHg accumulated in model seabirds and the identification of the processes involved in the Hg biogeochemical cycle in the Southern Ocean (from Antarctic to subtropical waters). The proposed methodological approach consisted on the combination of Hg isotopic composition and Hg speciation in tissues of a precise selection of seabirds of the Southern Ocean. In a first step, the evaluation of tissue-specific Hg isotopic signatures was accomplished notably in blood and feathers, as they can be non-lethally sampled. In chicks, both tissues can be effectively and indifferently used for biomonitoring of local contamination using Hg isotopes, whereas in adults each tissue provides access to different temporal exposure : blood at recent scale (i.e. exposure during the breeding period) and feathers at annual scale, thus providing complementary isotopic information at the different stages of seabird annual cycle. A second part was focused on the exploration of MeHg sources in four penguin species within a same subantarctic location, the Crozet Islands. Hg isotopes effectively discriminated the four populations and species-specific foraging habitats and latitudinal movements were found the main factors determining their exposure to distinct environmental MeHg sources. In a third part, Hg isotopes were investigated in two ubiquitous seabird models (skua chicks and penguins) over a large a latitudinal scale from Antarctica to the subtropics. Latitudinal variations of Hg isotopic values (δ202Hg, Δ199Hg) appeared to be influenced by different extent of photochemical processes and other biogeochemical pathways such as Hg reduction, and methylation/demethylation processes, as well as trophic or metabolic processes.

Les écosystèmes marins côtiers subissent de nombreuses perturbations naturelles et anthropiques. Dans le contexte socio-économique actuel, mieux comprendre le fonctionnement et transfert des contaminants dans ces écosystèmes est primordial. L’étude du transfert de la matière organique et des contaminants aux interfaces, constitue un enjeu crucial. Les principaux objectifs sont de caractériser l’ichtyofaune des herbiers de posidonie et comprendre les relations trophiques ; d’établir les niveaux et variabilité spatiale de la contamination en éléments traces ETs et polluants organiques persistants POPs dans les compartiments de l’écosystème ; et d’identifier les sources et les processus influençant les niveaux de contamination le long du réseau trophique à Marseille et Hyères. La caractérisation du peuplement de poissons et des relations trophiques au sein de l’écosystème est nécessaire pour comprendre les niveaux de contamination. Chez les poissons, le phénomène de bioaccumulation des ETs est difficile à mettre en évidence, excepté pour le mercure. L’influence du régime alimentaire, taille et besoins physiologiques et métaboliques est manifeste. La grande stabilité et la rémanence des POPs leur confèrent des propriétés de bioconcentration et de bioamplification importantes. Les concentrations en contaminants mesurées, ainsi que la détection de pesticides toxiques interdits, attestent de la nécessité de considérer cette pollution avec attention, plus forte à Marseille. / The marine ecosystems undergo frequent disturbances. In the current socio-economic context characterized by intensive urban development and industrialization, it is of primordial importance for the management of the environment to achieve a better understanding of the functioning and the transfer of contaminants within these ecosystems. The study of the transfer of organic matter and contaminants to the interfaces is thus a crucial issue. The main objectives are to characterize the fish fauna and to determine the food webs; to establish the levels and patterns of spatial variability of contamination by trace elements TEs and persistent organic pollutants POPs; and to identify the sources and the processes having an influence on the levels of contamination throughout the food webs. The characterization of the fish populations and the trophic relations between the compartments of the ecosystem is necessary in order to understand the levels of contamination in TEs and POPs. For the fishes, it is difficult to provide evidence of the phenomenon of bioaccumulation of TEs, except for mercury, but the influence of diet, size and physiological and metabolic requirements is obvious. The great stability, liposolubility and persistence of the POPs confer on them significant bioconcentration and bioamplification capabilities. The concentrations in TEs and POPs recorded, and the detection of banned toxic pesticides, attest to the necessity of paying close attention to this pollution.

Les explorations scientifiques menées depuis une quarantaine d’années ont permis d'identifier la diversité et la complexité des processus géologiques et géochimiques conduisant à la concentration des métaux dans les grands fonds océaniques. Les dépôts métallifères riches en hydroxydes de Fer et de Manganèse, tels que les encroûtements hydrogénétiques et hydrothermaux et les nodules polymétalliques, présentent des enrichissements variés en éléments d'intérêts économiques tels que le Ni, Cu, Co, Te, Pt et les Terres Rares. Bien que la minéralogie et la géochimie de ces dépôts aient été largement étudiées dans la littérature, les sources de métaux restent encore mal déterminées. Par conséquent, comprendre la géochimie de ces dépôts implique d’une part, de connaître les processus participant à leur genèse, et d’autre part d’avoir de meilleures connaissances sur les sources impliquées (par ex. flux continental et hydrothermal) et leur importance dans les grands cycles biogéochimiques des métaux dans les océans. Afin d’apporter de nouveaux éléments de réponse, notre approche a consisté à utiliser les compositions isotopiques des métaux comme traceurs biogéochimiques. Ce projet est structuré autour de deux hypothèses, (1) le développement et l’utilisation d’un nouveau outil géochimique que sont les isotopes du Ni pour tracer les sources et les processus d’enrichissements en métaux dans les dépôts métallifères océaniques ; (2) la combinaison de plusieurs systèmes isotopiques tels que Fe, Pb, Cu et Zn (et Ni) dans les encroûtements de fer-manganèse comme proxy de la composition isotopique de l’eau de mer profonde. Après avoir développé une méthode d’analyse des isotopes du Ni par MC-ICP-MS et estimé la variabilité isotopique du Ni dans les systèmes naturels par la caractérisation des grands réservoirs terrestres, nous avons évalué expérimentalement le fractionnementisotopique du Ni lors de son adsorption sur les oxyhydroxydes de Fe et Mn comme analogue à ce qui pourrait se produire dans les dépôts de Fe-Mn naturels. Les résultats indiquent que lors de l’adsorption du Ni, la phase solide est enrichie en isotopes légers par rapport à la solution avec des facteurs de fractionnement (Δ60/58Nimin/sol) variant de -1 ‰ pour la birnessite, -0.9 ‰ pour la goethite et -0.4 ‰ pour la ferrihydrite. A partir de ces résultats et d’autres études récentes, nous avons pu appuyer l’hypothèse selon laquelle d’un point de vue global la variabilité isotopique du Ni dans les dépôts métallifères océaniques riches en Fe et Mn s’explique par des processus d’enrichissement et de formation lors de l’incorporation des métaux dans les phases minérales de Fe et Mn plutôt que par des variations des compositions isotopiques des sources. Ainsi les encroûtements hydrogénétiques formés lentement à partir de l’eau de mer ne montrent pas de fractionnement isotopique du Ni, tandis que les dépôts hydrothermaux formés par des processus rapides liés aux apports hydrothermaux montrent des fractionnements du Ni plus importants. Puis, afin d’évaluer la possibilité d’utiliser les signatures isotopiques du Ni comme nouveaux traceurs paléocéanographiques, nous avons mené une étude comparative sur des encroûtements collectés dans le Pacifique Nord (proche de Hawaii) et le Pacifique Sud (proche de Tahiti). Dans ce contexte, les ncroûtements de fer-manganèse formés par précipitation très lente de l’ordre de quelques mm/Ma entre 1500 et 3000 m de profondeur, fournissent un enregistrement de plusieurs millions d’années des métaux dissous dans l’eau de mer. Après avoir réalisé une étude minéralogique et géochimique (éléments majeurs et traces) et calibré les taux de croissance des encroûtements, nous avons mesuré pour la première fois les compositions isotopiques du Ni, Fe, Zn, Cu et Pb sur la même série temporelle. / Scientific explorations implemented for around forty years allow to identifying the diversity and the complexity of geological and geochemical processes conducting to metals concentration on the deep seafloor. Fe- and Mn-rich metalliferous deposits such as hydrogenetic and hydrothermal ferromanganese (Fe-Mn) crusts and polymetallic nodules, present various enrichment in elements of economic interests like Ni, Cu, Co, Te, Pt and Rare Earth Elements. Although the mineralogy and geochemistry of these deposits have been largely studied in the literature, metal sources remain poorly determined. Accordingly, understanding the geochemistry of these deposits implies to know which processes are involved in their formation but also to have a better knowledge of the sources (e.g. the continental and hydrothermal fluxes) and their importance in the global oceanic metal biogeochemical cycles. In order to fill this gap, our approach consisted in using metal stable isotope compositions as biogeochemical tracers. This project is organized around two hypotheses, (1) development and utilization of a new geochemical tool, namely Ni isotopes, for tracing metal enrichment sources and processes in oceanic metalliferous deposits; (2) combination of several isotope systematics such as Fe, Pb, Cu, Zn (and Ni) in Fe-Mn crusts as proxies of the deep seawater isotope composition. Upon developing an analytical method for measuring Ni isotopes by MC-ICP-MS and estimating the Ni isotopes variability in natural systems through the characterization of terrestrial reservoirs, we experimentally evaluated Ni isotope fractionation during adsorption on Fe- and Mn-oxyhydroxides since similar processes may potentially occur in natural Fe-Mn deposits. Results indicate that after Ni adsorption, the solid phase is enriched in light Ni isotopes relatively to the solution with fractionation factors (Δ60/58Nimin/sol) varying from -1 ‰ for birnessite, -0.9 ‰ for goethite and -0.4 ‰ for ferrihydrite. These results, and other recent studies, strengthen our hypothesis according to which Ni isotopes variability in Fe- and Mn-rich metalliferous deposits can be explained by enrichment and formation processes during metal incorporation in Fe and Mn mineral phases rather than variations in the isotopic composition of the sources. Thus, hydrogenetic Fe-Mn crusts formed slowly from seawater dissolved metals do not show significant Ni isotope fractionation, whereas hydrothermal deposits formed by relatively rapid processes as a result of hydrothermal inputs exhibit important Ni isotope fractionation.