Les foraminifères benthiques sont largement utilisés en océanographie comme bio-indicateurs paléoclimatiques et paléoenvironnementaux du fait de leur présence dans tous les milieux marins, leur sensibilité aux changements environnementaux et leur grande capacité de fossilisation. Néanmoins, leur utilisation nécessite une connaissance approfondie de leur écologie et des paramètres contrôlant leur distribution. Si les connaissances sur l’écologie des foraminifères benthiques sont de plus en plus complètes, elles demeurent très sporadiques dans la zone arctique, système complexe caractérisé par des interactions multiples entre l'atmosphère, l'océan et la cryosphère, pourtant au coeur du changement climatique global. L'amplification polaire du changement climatique conduit les régions des hautes latitudes à se réchauffer près de deux fois plus vite que les régions tempérées. Dans ce contexte, cette thèse s'attache à mieux comprendre l'écologie des foraminifères benthiques vivants dans plusieurs régions arctiques et définir l'importance du contrôle des paramètres environnementaux sur les faunes tels que les propriétés des masses d'eau, la productivité primaire et le flux de matière organique ainsi que la dynamique de la glace de mer. Les foraminifères benthiques vivants ont été analysés dans les premiers centimètres de sédiment de 21 carottes d’interfaces prélevées dans trois régions arctiques durant les étés 2014 et 2015 : la mer de Barents, la baie de Baffin et la mer de Chukchi. Ces trois régions présentent des particularités en termes de couvert de banquise, de circulation des masses d’eau ou de dynamique de la production primaire. Nos résultats montrent que ces facteurs influencent la distribution des foraminifères benthiques. Le flux de matière organique qui résulte de la forte productivité primaire printanière aux abords des fronts polaires hydrographiques, des bordures de glace de mer (zones marginales de glace) et dans la polynie des eaux du nord (baie de Baffin) impacte la densité et la diversité des faunes et favorise le développement de certaines espèces. Nonionellina labradorica dans les eaux arctiques froides et Cassidulina neoteretis associée aux eaux atlantiques répondent aux apports de matière organique fraîche tandis que Melonis barleeanus s’accommode des milieux riches en matière organique plus dégradée. Dans les environnements oligotrophes plus profonds, Oridorsalis tenerus est une espèce ubiquiste. Cette espèce est associée à Cibicidoides wuellerstorfi sur la marge ouest de la mer de Barents et Ioanella tumidula dans le bassin plus profond au nord de la mer de Chukchi. Les propriétés physiques et chimiques des masses d’eau contraignent également la distribution faunistique. En baie de Baffin et sur le plateau de la mer de Chukchi, les eaux corrosives engendrent la dissolution des carbonates, favorisant la dominance des espèces agglutinées. Les études menées dans le cadre de cette thèse permettent de calibrer l'outil foraminifère benthique dans l'actuel et d'affiner leur utilisation en tant que proxy paléoclimatique et paléoenvironnemental en Arctique. Enfin, une étude préliminaire sur les foraminifères benthiques fossiles de trois carottes de la mer de Barents a permis de montrer les variations des conditions paléoenvironnementales au cours des deux derniers siècles. / Benthic foraminifera are widely used in oceanography as paleoclimate and paleoenvironmental bio-indicators due to their presence in all marine environments, their sensitivity to environmental changes and their great capacity to fossilize. However, the use of benthic foraminifera as paleoenvironmental proxies requires a good knowledge of the ecological conditions and the parameters controlling species distribution. Although knowledges about the ecology of benthic foraminifera are improving, they remain sporadic in Arctic area, a complex ecosystem characterized by multiple interactions between the atmosphere, the ocean and the cryosphere and particularly sensitive to change and vulnerable to global warming. Temperatures in the Arctic have risen twice as fast as the global average over the past decades, a phenomenon that has been dubbed the “polar amplification of global warming”. In this context, this thesis aims at better understanding the ecology of living benthic foraminifera in Arctic regions and at defining the importance of environmental controls on fauna such as water mass properties, primary productivity, organic matter flux as well as sea-ice dynamics. Living benthic foraminifera were identified in the first centimetres of 21 surface sediment cores collected in three Arctic areas during summer in 2014 and 2015: Baffin Bay and the Barents and Chukchi Seas. These three regions present specific characteristics in terms of sea-ice cover, water mass circulation or primary productivity. Our results suggest that these factors influence the distribution of benthic foraminifera. The flux of organic matter resulting from primary productivity intensified during spring and summer periods near hydrographic polar fronts, sea-ice edges (marginal ice zones) and in the north water polynya (Baffin Bay) increases the fauna’s densities and diversity and favours the development of specific species. Nonionellina labradorica in cold Arctic waters and Cassidulina neoteretis associated with Atlantic waters respond to fresh supply of organic matter while Melonis barleeanus is found in environment rich in degraded organic matter. In deeper oligotrophic environments, Oridorsalis tenerus is a ubiquitous species associated with Cibicidoides wuellerstorfi on the west continental margin of Barents Sea and Ioanella tumidula in the deeper basin in the north of the Chukchi Sea. Physical and chemical water mass properties also affect the distribution of living benthic foraminifera. In the Baffin Bay and the continental shelf of the Chukchi Sea, corrosive waters lead to carbonate dissolution, favouring the dominance of agglutinated species. This thesis hence contributes to calibrate the benthic foraminifera to their environment and to improve their application as paleoclimate and paleoenvironmental proxies in the Arctic. Finally, a preliminary study about fossil benthic foraminifera in three cores of Barents Sea allowed to show variations of environmental conditions during the last two centuries.

The Arctic and North Atlantic underwent significant climactic changes since the Last Glacial Maximum (25,000 years before present (1950 AD); ka BP), but offsets in the timing of events between the two regions are poorly constrained due to age model uncertainties that arise from changing radiocarbon reservoir ages. Here, we use a relatively high-resolution, multi-proxy stable isotope and sedimentologic dataset from Eastern Fram Strait (ODP Leg 162 Site 986) marine sediments to constrain the timing of Svalbard/Barents Sea Ice Sheet decay and infer deglacial reservoir ages over the last 30 ka. We use magnetic susceptibility, inorganic and organic carbon, foraminiferal assemblage counts, planktonic foraminiferal isotopes, and iceberg-rafted debris proxies to infer glaciomarine and paleoclimactic processes in Eastern Fram Strait. Significant negative Neogloboquadrina pachyderma (sinistral) δ18O episodes from background levels at 18.8 ka (-3.0 /) and 20.4 ka (-0.8 /) (on a radiocarbon-based age model) are shown to indicate meltwater discharge events from the Svalbard/Barents Sea Ice Sheet during the early glacial termination (21-14.7 ka). To allow for direct comparison between the timing of Eastern Fram Strait meltwater events and North Atlantic climate changes, the ODP Site 986 age model is correlated to the well-dated Greenland Ice Sheet Project 2 (GISP2) ice core δ18O record. The refined age model suggests that 16.0 and 18.1 ka are more realistic estimates for the meltwater events, inferring surface ocean reservoir age shifts of 1750 ± 1050 years in Eastern Fram Strait during the early glacial termination. Trends in reservoir ages throughout the last deglaciation mirror Nordic Sea deep ocean circulation changes and previously reported trends in the sub-polar North Atlantic; however, reservoir ages appear to be greater in Eastern Fram Strait. We hypothesize that processes affecting the distribution of reservoir ages in the North Atlantic and Arctic (e.g. sea ice cover, meltwater input, and ocean circulation) may have resulted in larger reservoir ages in polar regimes than in sub-polar ones during the last deglaciation, analogous to contemporary distributions. In contrast to previous radiocarbon age model-based studies in the Nordic Seas that predict a significant meltwater event at ~19 ka, these findings show that rapid Svalbard/Barents Sea Ice Sheet decay began at 16 ka and suggest that uncertainty on the order of thousands of years may exist in previous paleoclimate studies with radiocarbon-based age models from the deglacial Nordic Seas and Arctic.

A goal of the U.S. Environmental Protection Agency is to develop protocols applicable to coral reefs to distinguish between the effects of local water quality and those associated with regional to global environmental change. One test case is the current-dominated southeast coast of Florida where the Delray Outfall delivers 30 million gallons per day (114,000 cubic meters per day) of secondary-treated sewage into the ocean. Five study sites were established at depths between 15 and 18 m, and at distances between 1 and 18 km distance from the outfall, where the Stony Coral Rapid Bioassessment Protocol (RBP) was conducted to determine coral cover and selected other parameters. During sampling, 29 surface sediment samples were collected that I analyzed with respect to sediment texture, foraminiferal assemblages, and sediment constituents. Most samples were characterized by fine sands with <2% mud. A total of 77 genera of foraminifers were identified, averaging 28 genera per sample. Abundances of foraminiferal shells varied among samples by more than an order of magnitude (83 to 1010 shells per g sediment). The Foraminifera in Reef Assessment and Monitoring (FORAM) Index was calculated from the foraminiferal data, yielding values of 3 or more for all sites, with 26 of the 29 test sites yielding values >4, indicating that water quality should support coral growth. Sediment constituent analyses revealed that the sediments were overwhelmingly dominated by unidentifiable fragments (60%), with molluscan debris second (20%), and calcareous algae third (4.5%); larger foraminiferal shells and coral fragments together made up < 5.5%. The resulting sediment constituent (SEDCON) Index was consistently <2, indicating that erosional processes dominate over sediment production along the sampled shelf area. Results provided by the FORAM and SEDCON indices are consistent with results for stony coral based on the RBP. Stony coral cover was low at all sites, <2%, indicating that coral occurs in the area but neither dominates the benthos nor builds reefs. No relationship was observed between any parameter and distance from the Delray Outfall. However, both the RBP and FORAM Index indicated poorest conditions at the Horseshoe site, suggesting unidentified stressors in that vicinity.

The "Mystery Interval" (17.5-14.5 ka) is an unusual time period of abrupt global climate change during the late glacial between Heinrich event 1 and the Bølling-Allerød warm period (~17.5-14.5 ka). This period was characterized by extreme cooling in the North Atlantic region, warming in Antarctica, the rise of atmospheric greenhouse gases, and a variety of hydrologic changes around the globe, all of which may have stemmed from Heinrich event 1 and the possible collapse of the Atlantic?s meridional overturning circulation. A distinctive and unique gray clay layer was deposited in Cariaco Basin, Venezuela, within this time period, which has no apparent counterpart in the basin?s sediment record for at least the last full glacial-interglacial cycle. One hypothesis for the origin of the gray layer is that the initial pulse of deglacial sea level rise over the shallow Unare Platform, south of the basin, caused remobilization and rapid emplacement of previously deposited shelf sediments. However, analysis of the timing and extent of sea level rise as well as evidence from radiocarbon ages and a comparison of the organic content of gray layer sediments and known turbidites in the basin does not support this hypothesis. The alternative hypothesis, that the gray layer is related to increased fluvial discharge from local rivers as a result of elevated regional rainfall, is supported by a number of lines of evidence. The bulk sediment elemental content measured by scanning X-ray fluorescence (XRF) (this study) and clay mineralogy (Yu, 1996) support input of local river sediments. Coccolith abundances (Mertens et al., 2009), sea surface salinity (SSS) estimates and foraminiferal Ba/Ca analysis (this study) are also consistent with freshening of surface waters caused by elevated river runoff. This implies increased rainfall in the region which is corroborated by elemental and mineralogical ratios that point to increased precipitation and chemical weathering. Average terrigenous grain size and terrigenous fluxes are also in line with modern rainy season data. Despite prior suggestions that the Cariaco Basin region should be dry due to a southward-shifted Inter-tropical Convergence Zone (ITCZ) during cool periods in the North Atlantic, such as the Mystery Interval, data presented in this thesis suggest elevated rainfall and fluvial input related to deposition of the gray layer. Multiple lines of proxy evidence indicate that Cariaco Basin may have been characterized by a drier climate in the first part of the Mystery Interval but then shifted to a wetter climate in the second part, after ~16.5 ka, which might resolve this apparent conflict. The change to wetter conditions is most likely due to a northward shift in the position of the ITCZ, possibly due to warming tropical North Atlantic sea surface temperatures (SSTs) and/or extreme North Atlantic seasonality. Comparison of the Cariaco Basin climate records to climate observations from around the globe reveal a similar shift in climatic conditions around the same time, suggesting that the Mystery Interval may actually have been a two-phase event. Although many of the climatic observations from around the world can be explained by a shift from a southerly position of the ITCZ within the first part of the Mystery Interval to a more northerly position during the later part of the interval, many regions are not directly affected by the ITCZ and other complicating factors may play a role in the rapid climate changes observed globally.

The subject of this study was to investigate the species composition and spatial distribution pastern of iving (Rose Bengal stained) benthic foraminifera in sediment surface samples (0-1 cm) off the Southwestern Taiwan and Dongsha Atoll. The main objectives of this study was to document the living benthic foraminiferal assemblages off the Southwestern Taiwan and Dongsha Atoll and to examine their distribution in relation to environmental parameters. Four benthic foraminiferal biofacies were recognized within the substrate type in Dongsha Atoll: A1 (Fine-grained) is represented by Pseudomassilina spp. - Quinqueloculina parkeri, A2 (Fine-grained) is represented by Hauerina spp. - Pseudomassilina spp., B1 (Coarse-grained) is characterised by Calcarina spp. - Quinqueloculina spp., B2 (Coarse-grained) is characterised by Amphistegina spp. - Quinqueloculina spp. Sediment surface samples off the Southwestern Taiwan during May 2009 led to the identification of four assemblages. Assemblage A is characterised by Ammonia spp. - Bolivina spp., Assemblage B between is characterized by Asterorotalia spp. - Globobulimina spp., Assemblage C is represented by Cibicides spp. - Nummulites spp., Assemblage D is represented by Ammonia spp. - Cibicides spp. Sediment surface samples off the Southwestern Taiwan during Nov. 2009 led to the identification of three assemblages. Assemblage A is dominated by Ammonia spp. - Cibicides spp., Assemblage B is characterised by Ammonia spp. - Bolivina spp., Assemblage C is characterised by Asterorotalia spp. - Bolivina spp. Stained benthic foraminifera form Dongsha Atoll correlated with current wave, collected site, coarse fraction and TOC contents. Living benthic foraminifera off the Southwestern Taiwan seems not to be related with TOC contents and coarse fraction, the assemblages were found to be more related to tidal energy and lateral transport.

The Antarctic Intermediate Water (AAIW) plays an important role on controlling globally climatic change. Numbers of researchers attempted to discuss whether AAIW across the equator or notduring glacial- interglacial transitions. In this study, we analyzed Mg/Ca and £UREE/Ca on benthic foraminiferal species, Cibicidoides wuellerstorfi, from core MD052922C, which retrieved from western equatorial Pacific region, for revealing the long-term variations of Paleohydrology in intermediate water depths of tropical Pacific. Our evaluated results reveal that the Mg/Ca ratios ranging from 1.27 to 2.04 mmol/mol, and ranging between 2.2 and 3.2¢J when calculating into paleotemoeratures.Highest Mg/Ca can be observed in MIS 6. This finding implies that the present AAIW mean temperature is colder than glacials, and the present AAIW is well-ventilated than that in glacials.Higher £UREEs/Ca values are usually well correlated with old and poor ventilated water masses. In our record, higher £UREEs/Ca values are observed at MIS 5 impling that the intermediate depth water mass of the western tropical Pacific is poor ventilated when comparing to glacials.

Shallowing-upward meter-scale cycles (parasequences) consisting of megalodont-bearing limestones or clay levels at the bottom and fenestral limestones, breccias, stromatolites or vadose pisoids at the top constitute the basic working units of the Upper Triassic successions in the Central and Western Taurides. These cycles are mainly represented by subtidal through supratidal carbonate facies and known as Lofer cycles in the literature. The presence of breccias, mud cracks, dissolution vugs and vadose pisoids indicates subaerially exposed conditions at the top of the cycles. Shallowing-upward meter-scale cycles are interpreted as 4th and 5th order cycles in this study. Megalodont-bearing limestones of the subtidal zone are characterized by wackestones/packstones with abundant involutinids. However, involutinids are poorly represented in the intertidal-supratidal zone. To determine the relationship between cyclicity and foraminifers, the vertical variation of benthic foraminifer abundance has been analysed in the cycles. This analysis leads us to conclude that the foraminiferal abundance decreases from subtidal through supratidal zone. Furthermore, cluster analysis was performed in order to delineate the relation between the biofacies and foraminiferal associations. Micropaleontological analysis of the uppermost Triassic carbonates reveals the presence of restricted platform foraminiferal associations in the studied successions. Foraminiferal associations discovered in the samples belong to the Upper Norian (Sevatian)-Rhaetian Triasina hantkeni assemblage zone. Detailed examination of peritidal carbonates in the Central and Western Taurides against the studies, which claimed that the Dachstein-type platform carbonates are characterized by the transgressive models, should be explained by regressive models.

The purpose of this study is to investigate the Upper Tournaisian substage within the Carboniferous carbonate deposits of the Aladag Unit in the Hadim region (Central Taurides) based on foraminiferal diversity and to study the meter scale cyclicity in order to explain the sequence stratigraphic evolution of the carbonate succession. In this study, a 27.01 m thick stratigraphic section consisting of limestones and shales was measured and 89 samples, collected along this section, were analyzed. Micropaleontological analyses are based on benthic foraminifera. According to the benthic foraminiferal assemblages, two biozones were identified as Zone Ut1 and Zone Ut2 within the Upper Tournaisian. Zone Ut1 is characterized by a poor foraminiferal assemblage while the Zone Ut2 consists of a diverse Upper Tournaisian foraminiferal fauna. In order to construct a sequence stratigraphic framework and appreciate depositional environmental changes, microfacies studies were carried out. Seven microfacies types were recognized and depending on the stacking patterns of these microfacies types, two fundamental types of cycles, A and B, were identified. Through the measured section, twenty-five shallowing-upward meter scale cycles and two sequence boundaries were determined. Quantitative analysis of benthic foraminifera was used to demonstrate the biological response to cyclicity. Since foraminifers are very sensitive to sea level changes, the abundance of benthic foraminifera displays a good response to sedimentary cyclicity. In order to apply a worldwide sequence stratigraphic correlation, the sequence boundaries and the meter scale cycles of this study were compared with those described in South China and Western European platform and the Moscow Syneclise. An Early Tournaisian transgression was followed by a major fall in relative sea level during the Late Tournaisian. Two sequence boundaries recognized in the measured section correspond to global sea level falls in the Late Tournaisian.

The aim of this study is to designate paleontologic, biostratigraphic and sequence stratigraphic characteristics of the Permian-Triassic Boundary beds of the Bolkar Dagi Unit in the Hadim region (Central Taurides). For this purpose a 48,06m thick stratigraphic section, composed of limestone, siltstone and sandstone, was measured and 116 samples were analyzed through the Permian Ta

The Manatee River Watershed (Manatee County, FL) has experienced heavy anthropogenic development over the last 100 years and was relatively pristine previous to this development. The population growth within the watershed has surpassed the national trends and has doubled in the last 30 years. The heavy anthropogenic development has led to depletion in natural resources, nutrient loading, coastal erosion, and increased pollution. This study constructs records of sedimentological processes to compare the pre-development records to the past 100 years of anthropogenic development. The first portion of this study identifies specific changes in sedimentation attributed to anthropogenic activity in the Manatee River. Anthropogenic development has increased the input of terrigenous material into the river by as much as an order of magnitude (0.3-3.0 g/cm2/yr) over three periods; 1) the predevelopment period (1900-1941), 2) the agricultural development period (1941-1970's), and 3) the urban development period (1970's-2010). The second portion of this study examines records of heavy metal (As, Cu, Pb) enrichment in the Manatee River. There are areas in the Manatee River that currently have, or recently have had, concentrations of heavy metals above the EPA regional screening levels. Throughout all of the Manatee River sediment cores there has been a continuous increase in the concentration of arsenic (0.32-20.91 ppm), lead (0.35-35.79 ppm) and copper (1.49-49.55 ppm) from 1900-2010. The third portion of this study utilizes calcareous tests from benthic foraminifera (Ammonia beccarii) in the longest sediment core to determine the Mg/Ca, 18O/ 16O, and 13C/ 12C ratios as proxies for river water temperature, salinity and nutrient content. These proxies allow for the assessment of changes in rates and range of river water parameters from the pre-anthropogenic to the anthropogenic periods. A Manatee River temperature record, precipitation/evaporation record and nutrification record have been constructed for the last 450 years (1550-2009 CE). These records are necessary to inform and enhance future coastal resource management practices.