Na bacia do Arroio Chuí, localizada na região sul da Planície Costeira do Rio Grande do Sul no município de Santa Vitória do Palmar, geralmente nas margens constituídas de barrancas, são encontrados grande quantidade de fósseis de mamíferos integrantes da megafauna pleistocênica. Os estudos até então realizados tinham escopo basicamente na identificação taxonômica dos fósseis e os aspectos biológicos e ecológicos dessa fauna. No presente trabalho, foi elaborado um banco de dados contendo informações relativas às assembleias fossilíferas do Arroio Chuí, tafonomia e a distribuição espacial no sistema de coordenadas da superfície verdadeira terrestre, em um ambiente de Sistema de Informações Geográficas (SIG). A base de dados foi elaborada a partir do acervo analisado do museu Coronel Tancredo Fernandes de Mello, gerando tabelas de dados contendo informações sobre o material fossilifero, georreferenciando os sítios contendo fósseis e desenvolvendo análises estatísticas. A localização precisa das ocorrências de fósseis permitiu a observação de sua distribuição espacial, o que constituiu uma ferramenta na avaliação paleogeográfica da região e permitiu gerar subsídios que auxiliaram para colaborar na compreensão da evolução geológica da porção sul da planície costeira. / In the Chuí Creek basin, located in the southern Coastal Plain of Rio Grande do Sul state, in the Santa Vitoria do Palmar county, usually in the banks, great number of fossils of mammals of the Pleistocene megafauna is found. The studies developed so far focused on the taxonomic identification and biological and ecological aspects of this fauna. In the present work a database containing informations regarding the fossil assemblages of Chuí Creek, taphonomy and spatial distribution in the true Earth surface coordinate system, was elaborated in a Geograpgic Information System (SIG) environment. The database was elaborated from the collection of Coronel Tancredo Fernandes de Mello museum, producing data tables with informations regarding the fossil material, georeferencing the fossil sites and generating statistical analyses. The precise location of the fossils showed their spatial distribution, which turned out to be a tool for evaluate the regional paleogeography and aided to understand the geological evolution of the southern portion of the coastal plain.

Orientador: Prof. Dr. Charles Morphy D. Santos / Coorientadora: Profa. Dra. Mirian Liza Alves Foranceli Pacheco / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Evolução e Diversidade, Santo André, 2018. / A presente tese teve por objetivo contribuir para o conhecimento a respeito da megafauna do Cenozóico do continente Americano. O foco do trabalho foi o estudo da megafauna pleistocênica da América do Sul, para correlações paleobiogeográficas e paleoecológicas, e da superordem Xenarthra, para considerações sobre ecomorfologia. Para as análises ecomorfológicas, foi considerado um contexto geocronológico e geográfico mais amplo, incluindo nas análises espécimes tanto do Neógeno quanto do Quaternário da América do Sul e do Norte. Foram descritas novas ocorrências de fósseis de mamíferos de grande porte ¿ tais como preguiças gigantes, gliptodontes, gonfotérios, tigres-dente-de-sabre e ursídeos ¿ para o estado do Mato Grosso do Sul. As considerações paleobiogeográficas consitiram em uma tentativa de correlação da paleofauna do Pleistoceno da Serra da Bodoquena com outras regiões da América do Sul. Além disso, uma nova ocorrência de filhote fossilizado de Nothrotherium maquinense é reportada para o estado de São Paulo com posterior datação radiométrica e análise de isótopos de carbono. O segundo ponto abordado nesta tese incluiu estudos ecomorfológicos em Xenarthra fósseis e atuais com base no formato do úmero. Para este fim, foi aplicado o método de morfometria geométrica bidimensional e tridimensional. Os resultados obtidos mostram que a Serra da Bodoquena apresenta maior similaridade taxonômica com a Região Intertropical Brasileira, devendo, portanto, ser incluída neste contexto paleobiogeográfico. Também verificou-se a ocorrência de um segundo táxon de Nothrotheriinae e de Ursidae em território brasileiro, além de um terceiro táxon de Scelidotheriinae. Os resultados sobre N. maquinense no estado de São Paulo indicam que a espécie estava presente na região por volta dos 13 mil anos antes do presente, e que se alimentava de plantas C3, indicando a possibilidade da presença de ambientes mais úmidos na região. Do ponto de visto ecomorfológico, foi verificado que o úmero de Xenarthra é funcionalmente informativo, sendo possível distinguir indivíduos adaptados para modos de vida arborícolas, semiarborícolas, ambulatoriais e escavadores. Adicionalmente, foi contastado a influência do tamanho sobre o formato do úmero. / The present thesis aimed to contribute to the knowledge about the Cenozoic Megafauna from the American continent. The focus was on both the Pleistocene Megafauna from South America, regarding paleobiogeographical correlations, and on the superorder Xenarthra, regarding considerations on ecomorphology. A broader geochronological and geographic context was considered to the ecomorphological analyses, including both Neogene and Quaternary specimens from South America and North America. The paleobiogeographical considerations were an attempt to correlate the Pleistocene paleofauna from Serra da Bodoquena to other South American regions. In addition, new occurrences of large mammal fossils ¿ such as giant sloths, glyptodonts, gomphotheres, felines and ursines ¿ were described for the state of the Mato Grosso do Sul. Additionally, a new occurrence of fossil cub identified as Nothrotherium maquinense was reported to the state of São Paulo. Dating and stable isotopes analyses were conduced. The second point addressed in this thesis includes ecomorphological studies on extant and extinct Xenarthrans based on the humerus shape. For this purpose, the bidimensional and tridimensional geometric morphometrics method were applied. The results showed that the Serra da Bodoquena presents greater taxonomic similarity to Brazilian Intertropical Region. Therefore, Mato Grosso do Sul should be included in this paleobiogeographical context. Additionally, the occurrence of a second Nothrotheriinae and Ursidae taxa, and a third Scelidotheriinae taxa was reported to Brazilian territory. The results on N. maquinense point out that such species was present in the region around 13 kya and it fed on C3 plants. This fact indicates the possibility of the presence of wetter environments in that region during late Pleistocene. From the ecomorphological point of view, it was verified that the Xenarthra humerus is functionally informative, being possible to distinguish individuals adapted to arboreal, semiarboreal, ambulatory and digger habitus. The influence of size on the humerus shape has been verified as well.

The number of mammals species belonging to the Pleistocene megafauna (animals with more than 44 kg) registered for Sergipe state is still low compared with other states from Brazilian Intertropical Region (BIR). In this study, fossils found in fossiliferous outcrops (Tanks) in the Charco and São José Farm (municipality of Poço Redondo, Sergipe) and Elefante Farm (município de Gararu, Sergipe) localities were analysed. This study described fossils of taxa already registered for the state, like Eremotherium laurillardi, Notiomastodon platensis, Smilodon populator, Mylodontidae and Toxodontinae, besides registering for the first time Xenorhinotherium bahiense, increasing the number of taxa known in Sergipe. Besides the description of fossils, this study also provided absolute dating and isotopes analyses for E. laurillardi e N. platensis from São José Farm (Poço Redondo, Sergipe) tank, contributing for the knowledge about the chronology of this species in BIR, their paleodiets and the environment where they lived during the final Pleistocene. The results showed that the mastodont N. platensis occurred between 12.125 and 19.594 cal yr BP and exhibited a grazer diet (d13C = -1.1 to 1.3 ), while the giant sloth E. laurillardi lived between 11.084 and 13.581 cal yr BP, with a mixed feeder diet (C3/C4 plants; values ratio d13C = -7.7 to -3.3 ). The d18O values of N. platensis ranged between 31.1 to 34.7 , while the values of E. laurillardi ranged between 27.7 to 29.7 , but in both cases the species where inhabiting an environment with high temperatures. The compilation of the data available for this species in this region allows the conclusion that neither species did exhibit differences in its diet through the last thousand of years of the final Pleistocene, which suggests that the vegetational composition of this locality did not vary during this period. / A quantidade de espécies de mamíferos pertencentes à megafauna (indivíduos com mais de 44 kg) Pleistocênica registradas para o estado de Sergipe ainda é baixa quando comparada com outros estados da Região Intertopical Brasileira - RIB. No presente trabalho foram analisados fósseis encontrados em afloramentos fossilíferos (do tipo tanque) nas localidades Fazenda Charco e Fazenda São José (município de Poço Redondo, Sergipe) e na Fazenda Elefante (município de Gararu, Sergipe). Este estudo descreveu novas peças de taxa já conhecidos para o estado como, por exemplo, Eremotherium laurillardi, Notiomastodon platensis, Smilodon populator, Mylodontidae e Toxodontinae, além de fazer o primeiro registro de Xenorhinotherium bahiense, aumentando o número de taxa conhecidos em Sergipe. Além da descrição e registro de fósseis, o presente estudo também forneceu datações absolutas e análises isotópicas para fósseis das espécies E. laurillardi e N. platensis, provenientes da Fazenda São José (Poço Redondo, Sergipe), contribuindo para o conhecimento sobre a cronologia destes megamamíferos na RIB, além de caracterizar suas paleodietas e o ambiente no qual viveram durante o Pleistoceno final. Os resultados indicaram que N. platensis ocorreu entre 12.125 até 19.594 cal yr BP, apresentando uma dieta pastadora (d13C = -1.1 a 1.3 ), enquanto E. laurillardi ocorreu entre 11.084 até 13.581 cal yr BP, com dieta generalista (plantas C3/C4; d13C= -7.7 a -3.3 ). Os valores de d18O de N. platensis variaram entre 31.1 to 34.7 , enquanto os valores de E. laurillardi variaram de 27.7 to 29.7 , demonstrando que ambas as espécies habitam um local com altas temperaturas. A partir da reunião dos dados existentes para estas espécies nesta região, conclui-se que estas permaneceram com a mesma dieta ao longo dos últimos milhares de anos do Pleistoceno final, permitindo a interpretação de que a composição vegetacional da localidade também não variou durante este período.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Numerous studies of paleo-environmental reconstruction (vegetation and climate) have been carried out in southern, southeastern, and central Brazil, based on the pollen deposited in lacustrine and peatbog sediments. Such studies are scarce in the Brazilian Northeast, however. Studies of this type permit the development of inferences on the ecological processes affecting local plant and animal communities. The present study aimed to understand the paleo-environmental dynamics of a tank-type fossil outcrop in the municipality of Jaguarari, part of the Senhor do Bonfim micro-region in central-western Bahia state, located within the Caatinga biome. Fossils of neopleistocene mammals were collected, together with samples of soil and plants for isotopic analyses (13C). Six mammalian taxa were identified: Eremotherium laurillardi, Notiomastodon platensis, Toxodontinae, Felidae, Panochthus greslebini, and Equus (Amerhippus) neogeus. The paleo-environmental interpretation of the ecological characteristics of these taxa indicated that this assemblage was found with a predominantly open environment, associated with areas of denser habitat. The isotopic analysis indicated that the vegetation of the area has been stable up to the present day, with no exchange of C3 to C4 at the study sites. The presence of charcoal fragments at different depths in the soil indicates the occurrence of wildfires throughout the Holocene, possibly as a consequence of a relatively much drier climate. The wildfires may have been anthropogenic, given that the evidence was found in association with vestiges of ancient human populations. The dynamics of the vegetation observed at the site to the depth excavated indicated a predominance of arboreal vegetation since approximately 15,000 BP, finally returning to a more humid climate similar to that of the present day. The vegetation of the study region may not have suffered major modifications of the vegetation during the drier periods of the mid-Holocene, with forest formations predominating. During excavations, the need for a patrimonial education program was perceived, in order to promote measures for the conservation of paleontological sites, together with the local population of Lajedo II village. The results of this initiative indicated that this approach is a useful tool for the generation of information on natural patrimony, basic concepts of conservation, the legal basis for this process and the possible sanctions that enforce it, as well as contributing to the development of new knowledge and perspectives in the local community. / Estudos de reconstrução paleoambiental (vegetação e clima) são mais abundantes nas regiões Sul, Sudeste e Central do Brasil utilizando pólen depositado em sedimentos lacustres e turfeiras. Por outro lado, na região Nordeste, trabalhos análogos são mais escassos. A partir deste tipo de estudo é possível inferir sobre os processos ecológicos associados às comunidades vegetais e animais. Neste trabalho buscou-se entender a dinâmica paleoambiental ocorrida em um afloramento fossilífero do tipo tanque localizado no município de Jaguarari, o qual faz parte da Microrregião de Senhor do Bonfim Centro-Oeste da Bahia, em domínio de Caatinga. Para tanto, coletou-se fósseis de mamíferos neopleistocênicos; solo e plantas para análises isotópicas (13C). A fauna identificada é composta por 6 taxa: Eremotherium laurillardi; Notiomastodon platensis; Toxodontinae; Felidae; Panochthus greslebini; Equus (Amerhippus) neogeus. Interpretações paleoambientais das características ecológicas dos taxa sugerem que este conjunto faunístico estava associado há um ambiente com predomínio de áreas abertas em associação com fisionomias mais fechadas. Os resultados isotópicos apontam para estabilidade vegetacional na região até o presente, sem troca de vegetação C3 para C4 nos locais estudados. A presença de fragmentos de carvão soterrados em várias profundidades do solo sugere a ocorrência de paleoincêndios durante todo o Holoceno, com a possível influência de um clima mais seco para a região. Estes incêndios podem ser de natureza antrópica, já que foram encontrados alguns vestígios de ocupação de populações antigas na região. A dinâmica da vegetação observada para Jaguarari, até a profundidade de solo estudada, sugere tendência a uma vegetação arbórea dominante, desde aproximadamente 15.000 anos AP. com retorno a um clima mais úmido e provavelmente similar ao atual. A região estudada, possivelmente, não sofreu modificação acentuada na vegetação no médio Holoceno, quando do estabelecimento de períodos mais secos, permanecendo com áreas de vegetação de floresta. Durante os trabalhos de escavação dos fósseis, sentiu-se a necessidade de desenvolver um trabalho de Educação Patrimonial junto à população do povoado de Lajedo II, para subsidiar ações de conservação dos sítios paleontológicos. Os resultados mostraram que esta ferramenta é um instrumento capaz de fornecer informações sobre patrimônio, noções de conservação, leis que normatizam estas práticas, as sanções legais previstas, como também, proporcionar a construção de novos conceitos e uma aprendizagem significativa na comunidade alvo.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Crustacea is mentioned as a dominant group in almost all continental shelf environments around the Brazilian coast and the taxonomic group with more studies. However, the carcinofauna of some Brazilian shelfs are poorly known, such as Sergipe state. The aim of this study is contribute for the knowledge of Crustacea, components of benthic megafauna from continental shelf of Sergipe and understand how populations communities vary spatially and temporally. The crustaceans were collected with otter trawl in two different seasonal periods, 18 stations between 36°32'W 10°36'S e 37°05’W 11°21’S distributed in 6 transects and in 10, 20 and 30 m isobaths, for a total of 72 stations sampled, between the years 1999 and 2000. Environmental parameters from water and sediment were collect in each station. In laboratory, the organisms were identified to species level and analyzed in terms of richness, abundance and biomass, and the community in terms of diversity indices, equitativity, frequency of occurrence and relative importance indices. The Crustacea was represented by 62749 individuals, distributed in 71 taxa, 199.97 kg of biomass and 77.81km² of density. The collected organisms are representatives of 2 orders, 4 infraorders, 25 families, 46 genus and 64 species. Brachyura presented the greatest number of taxa with 39, followed by Caridea with 12, Dendrobranchiata with 9, Anomura with 7, Stomatopoda with 2 and Achelata with 1. The community was abundant and displayed considerable richness; however, diversity and equitability were low, showing the dominance of the species X. kroyeri, N. schmitti, L. schmitti, F. schmitti and C. ornatus. The fauna varied in space and time and the main abiotic parameters that explain these variations were depth, temperature and the bottom type, especially coarser sediments with high levels of sand and gravel. Six species of Crustacea were recorded for the first time from Sergipe continental shelf, 3 Brachyura (Allactaea lithostrota, Coryrhynchus riisei e Ericerodes minusculus), 2 Caridea (Alpheus armillatus, A. cf. packardii e A. intrisecus) e 1 Stomatopoda (Squilla brasiliensis). / Os crustáceos são citados como grupo dominante em quase todos os ambientes de plataforma ao longo do litoral brasileiro, sendo também o grupo com maior volume de trabalhos realizados. No entanto, algumas plataformas brasileiras ainda têm sua carcinofauna precariamente desconhecida, como é o caso de Sergipe. Nesse sentido, esse trabalho visa contribuir para o conhecimento dos Crustacea, componentes da megafauna bêntica, da plataforma continental de Sergipe, bem como entender como as populações que compõe essa comunidade se distribuem espacial e temporalmente ao longo da plataforma. Os crustáceos foram coletados a partir de arrastos duplos com rede de arrasto pesqueiro em quatro campanhas amostrais entre 1999 e 2000, em 18 estações entre 36°32'W 10°36'S e 37°05’W 11°21’S distribuídas em seis transectos, nas isóbatas de 10, 20 e 30 m, totalizando 72 estações amostradas. Também foram coletados os parâmetros ambientais da água e do sedimento para cada estação. Os organismos foram identificados até o nível de espécie, utilizando literatura taxonômica específica, e analisados em termos de riqueza, abundância e biomassa e, a comunidade foi analisada a partir dos índices de diversidade, equitatividade, frequência de ocorrência e índice de importância relativa. A fauna de Crustacea esteve representada por 62749 indivíduos distribuídos em 71 táxons que somaram 199.97 kg de biomassa úmida e uma densidade de 77.81 ind./km². Os organismos coletados são representantes de 2 ordens, 4 infraordens, 25 famílias, 46 gêneros e 64 espécies. Dos grupos principais de Crustacea, Brachyura apresentou maior número de táxons com 39, seguido de Caridea com 12, Dendrobranchiata com 9, Anomura com 7, Stomatopoda com 2 e Achelata com 1. A comunidade estudada foi abundante e com uma riqueza considerável, mas a diversidade e equitatividade da fauna foram baixas, evidenciando a dominância das espécies X. kroyeri, N. schmitti, L. schmitti, F. schmitti e C. ornatus para a fauna de Crustacea da plataforma continental. A fauna variou em função do tempo e do espaço e os principais parâmetros abióticos que explicaram essas variações foram a profundidade, a temperatura e o tipo de fundo, principalmente os sedimentos mais grossos com altos teores de areia e cascalho. Dentre os Crustacea identificados, foram registrados pela primeira vez para a plataforma continental de Sergipe seis espécies, sendo 3 Brachyura (Allactaea lithostrota, Coryrhynchus riisei e Ericerodes minusculus), 2 Caridea (A. cf. packardii e A. intrisecus) e 1 Stomatopoda (Squilla brasiliensis).

Substantial hunting pressure and habitat destruction caused by oil extraction has critically endangered the Amazonian manatee in Ecuador. The current population status is unknown because an effective method to observe them in the wild has yet to be developed. This study explored whether the Amazonian manatee persists or has been extirpated in the eastern Ecuadorian Amazon utilizing side-scan sonar to increase odds of detection. Spatial differences in probability of detection were quantified if manatees were observed. The level of chemical contamination was determined and compared spatially and temporally against historical data. Data were collected using opportunistic transect surveys and grab sampling of surface water in Yasuni National Park, Lagartococha, and Cuyabeno Wildlife Reserve. Surveys confirmed that the manatee population is extant. Manatees were encountered more often in Cuyabeno Wildlife Reserve than in Lagartococha and Yasuni. Side-scan sonar detected more manatees than previously reported in 1996-1999. Side-scan sonar is a viable method for detection of manatees in the Ecuadorian Amazon system and resulted in greater detection as a function of effort. All future population studies should incorporate side-scan sonar. Lead, arsenic, mercury, polynuclear aromatic hydrocarbons [PAHs], and volatile organic compounds [VOCs] were not detected in the waters of the study region. High total petroleum hydrocarbon [TPH] levels were measured in 7 samples from Yasuni National Park. The concentrations of TPH were higher in Yasuni National Park than in Lagartococha and Cuyabeno. TPHs were detected only in the study region with a recent oil spill; there was no evidence that TPHs were higher near oil production wells and pipelines. The concentrations of TPH were significantly different than those measured in 1998 (z =3.01710, p=0.0026). A dedicated study should be performed to develop a protocol for monitoring persistent oil contaminants in the Ecuadorian Amazon and determine their sink.

This study is an investigation of the timing of extinction of late Pleistocene, large bodied mammalian herbivores (megafauna) and of the environment in which they lived. The demise of the megafauna near the end of the Pleistocene remains unexplained. Owing to potential human involvement in the extinctions, archaeologists have been particularly concerned to understand the causes for faunal losses. Our current lack of understanding of the timing and the causes of the extinctions in North America may result from a deficiency in understanding the histories of each individual species of extinct animal on a local level. Detailed regional chronologies of fauna are necessary for comparison with paleoenvironmental and archaeological data to help sort out causes for extinction. The Willamette Valley of western Oregon has long been noted for finds of megafauna, though records have not been synthesized since the early 20th century and these materials have remained largely unstudied. In this thesis, I first create a catalog of extinct megafauna recovered from the Willamette Valley. Next, using material from the northern valley, I employ AMS radiocarbon dating, stable isotope δ¹³C and δ¹⁵N analyses, and gross inferences based on the dietary specializations and habitat preferences of taxa in order to reconstruct environments and to develop a local chronology of events that is then arrayed against archaeological and paleoenvironmental data. The results of this study indicate that megafaunal populations in the northern Willamette Valley were contemporaneous with the earliest known human populations of the Pacific Northwest, as well as later populations associated with the Clovis Paleoindian Horizon. Consistent with the overkill hypothesis, radiocarbon ages span the length of the Clovis window, but no ages are younger than Clovis. Moreover, all radiocarbon ages are older than or contemporaneous to the onset of the Younger Dryas Stadial. No age ranges fall exclusively within the Younger Dryas. Comparison of megafaunal ages and paleoenvironmental records support the view that climate change contributed to local animal population declines. Prior to ~13,000 cal BP, the Willamette Valley was an open environment; herbivores mainly consumed C₃ vegetation. The timing of the loss of megafauna coincides with increased forested conditions as indicated by regional paleoenvironmental reconstruction. As the timing of megafaunal decline correlates with Clovis, the onset of the Younger Dryas, and increased forested conditions, it is not possible with the data currently available to distinguish the cause of extinction in the Willamette Valley. The age ranges of the fauna coupled with taphonomic and geologic context indicate that the fauna are autochthonous to the Willamette Valley; they do not represent ice rafted carcasses or isolated skeletal elements transported from elsewhere during late Pleistocene glacial outburst floods.

Cette thèse participe à accroitre les connaissances sur les facteurs régissant la structures des communautés benthiques de la Grande Vasière (GV) du Golfe de Gascogne. Une attention particulière a été portée au rôle du chalutage de fond, dont l’intensité a été estimée à l’aide des données VMS. A l’échelle de la GV, nos résultats suggèrent que le chalutage de fond serait le principal moteur de structuration du mégabenthos (> 10 mm). Cependant, cette hypothèse n’a pu être formellement démontrée en raison de la co-variation entre l’activité de pêche et certaines caractéristiques environnementales. Par conséquent, les travaux ont été poursuivis sur une zone restreinte de la GV, choisie de manière à minimiser les variations dans l’habitat, tout en conservant un large gradient d’intensité de chalutageNous avons ainsi observé des modifications saisonnières et temporaires de la structure des communautés méga et macro-benthiques (>1 mm) en lien avec le chalutage. Ils proviendraient essentiellement d’une disponibilité alimentaire accrue pour les prédateurs-charognards de la mégafaune et de modifications des caractéristiques sédimentaires pour la macrofaune. En revanche, l’étude de la diversité fonctionnelle montre que ces changements n’ont que des répercussions mineures sur le fonctionnement de l’écosystème. Nos conclusions suggèrent que l’écosystème benthique de la GV a probablement été façonné par plusieurs décennies de pêche intensive et qu’il est actuellement adapté à des perturbations anthropiques chroniques / This PhD thesis aims at increasing the knowledge on factors influencing the benthic community structures of the « Grande Vasière » (GV) of the Bay of Biscay. Particular attention has been paid to the role of bottom trawling whose intensity has been estimated using VMS data. At the scale of the GV, our results suggest that bottom-trawling is the main driver of the megabenthic community structure (> 10mm). However, this hypothesis has not been formally demonstrated due to the co-variations between the trawling intensity and certain environmental characteristics. Hence, works continued on a restricted part of the GV that displayed minimal variations of environmental characteristics while exhibiting a wide gradient of trawling intensityResults suggest that bottom-trawling induces seasonnal and transient modifications on the mega and macrobenthic (> 1mm) communities. These changes could be due to an increase of food availability for the megabenthic predator-scavengers and to changes of sedimentary characteristics for macrofauna. However, investigation about functional diversity showed that these changes did not have major consequences on ecosystem functioning. We concluded that decades of bottom trawling may have shaped the benthic ecosystem of the GV and that it is currently adapted to frequent disruptions.

La Béringie, un vaste territoire qui s’étend de la Sibérie orientale au Territoire du Yukon, est perçue comme le point d’entrée des populations humaines en Amérique. A la fin du Pléistocène, ce territoire déglacé aurait constitué un refuge aux premières populations préhistoriques se dispersant hors d’Asie. Selon les données génétiques et paléo-génétiques, la Béringie fut occupée au cours du Dernier Maximum Glaciaire (19 000-23 000 cal BP, années calibrées Before Present) par une population humaine qui demeura génétiquement isolée durant près de 8000 à 9000 ans, donnant ainsi naissance à la lignée des Natifs Américains qui allaient se disperser, plus tard, au sud des masses glaciaires nordaméricaines et jusqu’en Amérique du Sud. Cette « Beringian standstill hypothesis », toutefois, ne trouva aucun soutien dans le registre archéologique : en Sibérie orientale, le plus ancien site est daté à 32 000 cal BP, tandis qu’en Alaska et au Yukon, la présence humaine ne remonte pas au-delà de 14 000 cal BP. Dans les années 70-80’s, le site des Grottes du Poisson-Bleu (Yukon) livra des outils en pierre et des ossements supposés modifiés par les humains, enfouis dans un dépôt loessique pléistocène ; les découvertes encouragèrent les archéologues J. Cinq-Mars et R. Morlan à évoquer l’hypothèse d’une occupation humaine sporadique dans le nord du Yukon entre 11 000 et 30 000 cal BP environ. La nature anthropogénique des échantillons osseux soumis aux datations radiocarbones ainsi que l’intégrité de la stratigraphie furent toutefois remises en question par une majorité d’archéologues. La présente dissertation propose une analyse archéozoologique et taphonomique rigoureuse et systématique des assemblages fauniques de mammifères des Grottes I et II dans le but d’appréhender les facteurs responsables de l’accumulation et de la modification du matériel osseux. De nouvelles datations radiocarbones effectuées par le laboratoire Oxford Radiocarbon Accelerator Unit sur des ossements portant des traces indéniablement culturelles permettent une datation précise de l’occupation humaine du site. Les résultats illustrent plusieurs traces de découpe sur des os de cheval, caribou, wapiti et possiblement bison et mouflon, tandis que des ossements de mammouth pourraient avoir été collectés pour l’industrie osseuse. Les nouvelles datations AMS suggèrent que les Grottes du Poisson-Bleu étaient occupées de façon sporadique entre 12 000 et 24 000 cal BP, soit pendant et après le Dernier Maximum Glaciaire. Le site offre ainsi un soutien archéologique à l’hypothèse de l’isolation génétique des populations béringiennes à l’origine des premières dispersions en Amérique. L’histoire taphonomique des Grottes du Poisson-Bleu rejoint celle des sites karstiques béringiens qui illustrent des occupations interspécifiques alternées entre carnivores et des fréquentations humaines de courte durée pour des activités de chasse. En outre, les altérations anthropiques sur des os de cheval des Grottes I et II ravivent le débat sur les extinctions de la mégafaune à la fin du Pléistocène (ca. 14 000 cal BP). Le site souligne l’incomplétude du registre archéologique et invite à multiplier les efforts de recherche en Béringie si l’on veut être à même de comprendre la préhistoire du peuplement des Amériques. / Beringia, a vast landscape stretching from eastern Siberia to the Yukon Territory, is thought to be the initial entry point of humans into North and South America. At the end of the Pleistocene, this unglaciated region constituted a refugium for the first prehistoric populations dispersing out of Asia. According to genetic and palaeogenetic data, Beringia was occupied during the Last Glacial Maximum (19 000-23 000 cal BP, calibrated years before present) by a human population that remained genetically isolated for about 8000 to 9000 years, leading to the divergence of the Native American lineage that would eventually disperse south of the ice-sheets into North and South America. The « Beringian standstill hypothesis » is not well supported in the archaeological record, however: in eastern Siberia, the oldest archaeological site is dated to 32 000 cal BP while in Alaska and the Yukon, evidence for a human presence doesn’t exceed 14 000 cal BP. Excavated in the 70s-80s, the Bluefish Caves site (Yukon) yielded stone tools and bone remains thought to have been culturally modified, buried in a Pleistocene loess deposit; the discovery encouraged archaeologists J. Cinq-Mars and R. Morlan to propose that humans occupied the caves sporadically between about 11 000 and 30 000 cal BP. The anthropogenic nature of the bone samples submitted for radiocarbon analysis and the stratigraphic integrity of the site didn’t convince the scientific community, however. The current dissertation proposes a rigorous archaeozoological and taphonomic analysis of the mammal bone assemblages of Caves I and II in order to identify the agents responsible for the accumulation and modification of the bone material. The results show several cut marks on bone specimens belonging to horse, caribou, wapiti and possibly bison and Dall sheep, while mammoth skeletal remains may have been collected for bone industry. New radiocarbon dates obtained by an Oxford laboratory (Oxford Radiocarbon Accelerator Unit) on bone bearing indisputable evidence of cultural modification allow the precise dating of the human occupation at the site. The AMS dates suggest that the Bluefish Caves were occupied sporadically between 12 000 to 24 000 cal BP, i.e., during and after the Last Glacial Maximum. The site, therefore, offers archaeological support for the Beringian standstill hypothesis. The taphonomic history of the Bluefish Caves, as well as other Beringian karstic sites, shows use of the caves by various carnivores and short-term human occupations for hunting activities. Moreover, cultural modifications on horse bone from Caves I and II enhance the debate surrounding the megafaunal extinctions at the end of the Pleistocene (ca. 14 000 cal BP). The site underlines the incompleteness of the archaeological record and invites us to expand research efforts in Beringia if we are to understand the prehistory of the first people of the Americas.

Ce travail de thèse s'insère dans une démarche globale d'acquisition des connaissances sur la tortue verte (Chelonia mydas) dans l'océan Indien occidental et ce afin de disposer d'éléments scientifiques essentiels à la mise en place d'une gestion cohérente et efficace de cette espèce menacée. Dans un premier temps, appliquant différentes modèles statistiques, ce travail a visé à établir des données de référence sur l'abondance des tortues vertes femelles en reproduction et les tendances sur le long terme des principales populations. Dans un second temps, il a consisté à déterminer la structure génétique et les relations qui existent entre les différentes populations de cette espèce. Enfin, la conservation des tortues marines étant étroitement liée aux pressions extérieures, ce travail a tenté dans un troisième temps de caractériser les pressions anthropiques qu'elles subissent, et notamment celles liées à la pêche. L'ensemble de ces résultats a permis de réaliser des avancées majeures dans la connaissance de la biologie et de l'écologie de la tortue verte et de disposer d'une vision régionale fiable de l'état de conservation de cette espèce dans l'océan Indien occidental. Leur compilation a ainsi permis d'identifier des zones régionales prioritaires de protection mais aussi des sites de vigilance plus spécifiques comme celui d'Europa. Enfin cette synthèse met en lumière les priorités de recherche et les approches scientifiques à favoriser à l'avenir pour améliorer les connaissances et affiner les priorités de conservation non seulement des tortues marines, mais aussi de la mégafaune marine en général. / This thesis is a comprehensive work aiming to improve scientific knowledge on the green turtle (Chelonia mydas) in order to provide key scientific evidences needed for the implementation of coherent and effective management measures to protect at the Western Indian Ocean scale this threatened species. In a first step, this work aimed to established baseline data on the abundance of green turtles nesting females and long term trends of some key nesting populations of the region by applying different modelling methods. In a second step, this work determined the regional genetic structure of this species and the relationships that exists between the different populations. Finally, the conservation of marine turtles being closely dependant to external pressures, this work tried to characterize theanthropogenic pressures they face, more specifically those related to fishing activities. All these results allowed unraveling some key gaps on the biology and ecology of the green turtle in the region and led to a global vision of the conservation status of this species in the Western Indian Ocean. The compilation of the results enabled the identification of regional priority areas for protection, but also some more specific threatened sites such as Europa. Finally, this synthesis shedslight on research priorities and scientific approaches to be promote in the future to unlock other keyscientific issues and refine conservation priorities, not only of marine turtles, but also of marine megafauna as a whole.