Cold seep ecosystems in the deep sea are fuelled by chemosynthetic processes based on methane emission to the sediment surface from gas hydrate disassociation, methanogenesis or thermogenic processes. While cold seep ecosystems have been studied in the last three decades worldwide, little is known about New Zealand’s cold seep habitats and associated fauna. A joint German-New Zealand cruise to the Hikurangi Margin in early 2007 enabled biological and sediment sampling to investigate the biological and sedimentological relationships and variability of seeps and their faunal diversity. Multi-disciplinary approaches were employed that included Xray radiography, stratigraphic descriptions, lebensspuren traces analysis, sediment grain size analysis, determination of total organic content, carbonate content and its stable isotopic composition, and analysis of benthic invertebrate assemblages of seep habitats. The results of this study revealed three distinctive habitats and associated fauna based on the sediment characteristics and faunal type. Habitat 1 includes all sites pertaining to Omakere Ridge, a seep-related habitat comprised of layers of very poorly sorted, sandy silt, shell hash and bands of methane-derived authigenic aragonitic carbonate nodules with low total organic content (TOC). Due to the characteristics of the sediments and death assemblages of molluscs, it is inferred that Habitat 1 methane seepage is actively diffusive, waning or dormant. Habitat 2 describes sites that are either non-seep or relic and applies to those at Bear’s Paw and Kaka. Habitat 2 constituted of shell hash overlain with very poorly sandy silt, and low carbonates content and low to medium TOC. Habitat 3 describes non-seep related habitats, and includes all sites of the Wairarapa region and one reference site from Kaka also falls into this category. Sediments for Habitat 3 constituted poorly sorted silt with high TOC and low carbonate content which can be explained by their close proximity to land and converging sea currents. The mineral components of the background siliciclastic sediments for all sites studied originated in the Tertiary mudstone of the East Coast Basin. The characteristics of seep habitats of the Hikurangi Margin were comparable to that of the Northern Hemisphere modern seep counterparts, although the abundance and distributions of seep fauna were low. Results from this research have enhanced our understanding on the spatial and variability of methane fluxes and their affects on the duration of cold seep ecosystems, especially for New Zealand. However, more such studies are essential to increase our understanding of seep sediments and explain disturbance-sediment-benthic invertebrate interactions.

No description available.

Cold seep-carbonates are the microbially mediated by-products of the anaerobic oxidation of methane (AOM) at seafloor cold seeps, and are widespread about modern continental margins and in the geologic record. Some modern and Miocene examples of cold seep-carbonates from the East Coast Basin, North Island, New Zealand have been analysed in this study, to characterise and determine their carbonate fabrics, elemental and mineralogical composition, and stable δ18O and δ13C isotope signatures, so as to provide insights into the diagenetic changes associated with the lithification and burial of seep-carbonates. The ancient samples were collected from the onshore middle Miocene Tauwhareparae (TWP) seep deposit, while the modern samples were obtained from the National Institute of Water and Atmosphere (NIWA) Cruise TAN0616 (November 2006) from Ritchie Ridge, offshore Hikurangi Margin. A paragenetic sequence of diagenetic events involving early aragonitic phases, followed by late calcitic phases is defined for the seep-carbonates. This sequence likely has relevance for understanding the fluid-cement histories of seep-carbonates more widely. Two main carbonate mineralogies occur in each of the sample groups - modern samples are aragonitic or dolomitic, while the ancient ones consist dominantly of either aragonite or calcite. Thus, aragonite common to both sample groups, and is interpreted to represent the initial primary carbonate precipitate in hydrocarbon seep provinces under specific fluid flux and local pore-water chemistry conditions. Aragonite morphologies range from microcrystalline carbonate ('micarb'), to acicular aragonites that may form botryoids or spherulites. Dolomite occurs in those modern samples which appear to constitute exhumed remnants of a former subsurface 'seep plumbing system', and so are strictly not true seabed 'seep-carbonates', but instead are part of the larger hydrocarbon seep province. Calcite in the ancient samples is either a product of alteration and neomorphic transformation of aragonite, or derives from late stage cementation from burial fluids. As a result of their formation processes, the calcites are generally recrystallised and have equant or 'cellular' textures. Stable δ13C and δ18O isotope cross-plots reveal a large spread of values for the sample groups. Ancient samples range from δ13C -8 to -50 PDB and δ18O -5.5 to +2 PDB. Modern samples have δ13C values from -6 to -41 PDB and δ18O values ranging from +2.6 to +6.7 PDB. The δ13C values suggest the majority of the methane that formed these seep-carbonates is of thermogenic origin, although some mixing from other carbon sources may have occurred. The positive δ18O signatures are suggestive of carbonate formation during dissociation of gas hydrates, while the negative values possibly indicate that some of the formation fluids were warmer than normal in the 17 - 30 C range.

Agência Nacional do Petróleo / O presente estudo aborda a caracterização geológica em termos estruturais e estratigráficos do sistema petrolífero responsável pela ocorrência de exsudações de óleos encontradas sobre o embasamento cristalino na região limítrofe entre as bacias de Almada e Jequitinhonha. A partir das amostras de óleo coletadas no campo, foram feitas análises geoquímicas (Isótopos e biomarcadores) que permitiram definir duas famílias de óleo: (a) Família I, com altas proporções de esteranos C28, predominância do terpanos tricíclico C23 e proporções elevadas do Hopano C29, características de óleos gerados em ambiente marinho carbonático, provavelmente de idade albiana a turoniana; e (b) Família II, com valores δ13C de -26,8, e presença marcante de gamacerano, que sugere uma rocha geradora formada em um ambiente hipersalino, característico do Aptiano. A interpretação das linhas sísmicas possibilitou a definição de um sistema de migração, para os óleos analisados, da rocha geradora até a superfície. O arcabouço estrutural sugere um processo de migração das falhas do rifte para os altos estruturais ao longo de um sistema de falhas NW-SE, encontradas na região associada às zonas de transferência de Ilhéus. A ausência de um selo efetivo favoreceu a migração do óleo até a superfície. A interpretação geológica integrada à caracterização geoquímica dos óleos indica a existência de sistemas petrolíferos ativos e sugere o controle estrutural na distribuição das exsudações de óleo. Adicionalmente, se fez uma caracterização faciológica, palinológica e geoquímica (%COT, RI, %S, isótopos de carbono e biomarcadores) dos sedimentos aflorantes entre as cidades de Ilhéus e Una, que foram associados neste estudo à Formação Rio Doce. A partir da correlação dos afloramentos estudados observa-se que os mesmos representariam a porção mais superior da Formação Rio Doce depositada no Mioceno, segundo as análises palinológicas. Esta deposição ocorreu dentro de uma progressiva tendência de raseamento, no contexto de um trato de sistema de mar alto, onde teriam-se desenvolvido espessos pacotes de folhelhos sílticos de água rasa, intercalados com barras arenosas em um contexto estuarino. / The following study, presents the geologic characterization from the structural and stratigraphic point of view of the petroleum system, found out on top of the basement located in the boundaries region of the Almada and Jequitinhonha basins. Taking as an starting point the oil samples gathered during the field phase, the geochemical analysis (Isotopes and biomarkers) were done, allowing the identification of two oil families: The first family, with high portions of steranes C28, predominance of the C23 tricycle and high portions of C29 hopane, which characterized a carbonate marine environment to source rock and most probably Albian to Turonian age. The second family, with δ13C -26.8, and the imminent presence of gammacerane, which suggest a source rock generated in a hypersaline environment, commonly found in the Aptian. The interpretation done with the seismic lines facilitated the definition of a source rock migration system to reach the surface. The structural framework suggests a migrating process associated to the rift faults going to higher structures throughout a fault system NW-SE, found out in the region associated to the Ilhéus transference zones; the absence of an effective seal permitted the oil migration till reach the surface. The integral interpretations with the geochemical characterization of the oil indicate the presence of active petroleum system which suggests structural controls in the oil seeps. Furthermore, the current study addresses the faciologic, palynological and geochemical characterization (%TOC, IR, %S, isotopes and biomarkers) of sedimentary rocks cropping out in the Rio Doce formation between Ilhéus and Una cities. As from the correlation of the section study it is observed that these are represented at the higher portion of the Rio Doce formation, deposited in Miocene, also supported by the palynologic analysis. The deposition occurred inside a progressive trend of shallow upgrade, in the context of a highstand systems tract, where thick packages of argillaceous shale, intercalated with sand bars in an estuarine context

Agência Nacional do Petróleo / O presente estudo aborda a caracterização geológica em termos estruturais e estratigráficos do sistema petrolífero responsável pela ocorrência de exsudações de óleos encontradas sobre o embasamento cristalino na região limítrofe entre as bacias de Almada e Jequitinhonha. A partir das amostras de óleo coletadas no campo, foram feitas análises geoquímicas (Isótopos e biomarcadores) que permitiram definir duas famílias de óleo: (a) Família I, com altas proporções de esteranos C28, predominância do terpanos tricíclico C23 e proporções elevadas do Hopano C29, características de óleos gerados em ambiente marinho carbonático, provavelmente de idade albiana a turoniana; e (b) Família II, com valores δ13C de -26,8, e presença marcante de gamacerano, que sugere uma rocha geradora formada em um ambiente hipersalino, característico do Aptiano. A interpretação das linhas sísmicas possibilitou a definição de um sistema de migração, para os óleos analisados, da rocha geradora até a superfície. O arcabouço estrutural sugere um processo de migração das falhas do rifte para os altos estruturais ao longo de um sistema de falhas NW-SE, encontradas na região associada às zonas de transferência de Ilhéus. A ausência de um selo efetivo favoreceu a migração do óleo até a superfície. A interpretação geológica integrada à caracterização geoquímica dos óleos indica a existência de sistemas petrolíferos ativos e sugere o controle estrutural na distribuição das exsudações de óleo. Adicionalmente, se fez uma caracterização faciológica, palinológica e geoquímica (%COT, RI, %S, isótopos de carbono e biomarcadores) dos sedimentos aflorantes entre as cidades de Ilhéus e Una, que foram associados neste estudo à Formação Rio Doce. A partir da correlação dos afloramentos estudados observa-se que os mesmos representariam a porção mais superior da Formação Rio Doce depositada no Mioceno, segundo as análises palinológicas. Esta deposição ocorreu dentro de uma progressiva tendência de raseamento, no contexto de um trato de sistema de mar alto, onde teriam-se desenvolvido espessos pacotes de folhelhos sílticos de água rasa, intercalados com barras arenosas em um contexto estuarino. / The following study, presents the geologic characterization from the structural and stratigraphic point of view of the petroleum system, found out on top of the basement located in the boundaries region of the Almada and Jequitinhonha basins. Taking as an starting point the oil samples gathered during the field phase, the geochemical analysis (Isotopes and biomarkers) were done, allowing the identification of two oil families: The first family, with high portions of steranes C28, predominance of the C23 tricycle and high portions of C29 hopane, which characterized a carbonate marine environment to source rock and most probably Albian to Turonian age. The second family, with δ13C -26.8, and the imminent presence of gammacerane, which suggest a source rock generated in a hypersaline environment, commonly found in the Aptian. The interpretation done with the seismic lines facilitated the definition of a source rock migration system to reach the surface. The structural framework suggests a migrating process associated to the rift faults going to higher structures throughout a fault system NW-SE, found out in the region associated to the Ilhéus transference zones; the absence of an effective seal permitted the oil migration till reach the surface. The integral interpretations with the geochemical characterization of the oil indicate the presence of active petroleum system which suggests structural controls in the oil seeps. Furthermore, the current study addresses the faciologic, palynological and geochemical characterization (%TOC, IR, %S, isotopes and biomarkers) of sedimentary rocks cropping out in the Rio Doce formation between Ilhéus and Una cities. As from the correlation of the section study it is observed that these are represented at the higher portion of the Rio Doce formation, deposited in Miocene, also supported by the palynologic analysis. The deposition occurred inside a progressive trend of shallow upgrade, in the context of a highstand systems tract, where thick packages of argillaceous shale, intercalated with sand bars in an estuarine context

Premise of research. The duration and intensity of flowering overlap among plants are the first determiners of the potential for pollinator-mediated plant-plant interactions. Yet, our ability to describe community-wide patterns of coflowering, and thus understand its impact on the structure of plant-pollinator communities, is limited. Methodology. We present a conceptual framework for how network theory can reveal structural properties that are ecologically relevant in diverse coflowering communities. Coflowering modules, in particular, may suggest that groups of species coflower more strongly (clustering) with each other than with other species (over-dispersion) in the community. Such a finding would indicate that competitive and facilitative interactions do not act alone but instead act simultaneously to mediate the assembly of coflowering communities. We illustrate our conceptual framework in four diverse coflowering communities in the serpentine seeps in northern California. Pivotal results. Our coflowering networks vary in size and degree but not in overall connectance, suggesting that both intrinsic community features (species richness) and ecological constraints (length of flowering season) play a role in mediating coflowering community structure (distribution of frequency and intensity of flowering overlap among plant species). We show, for the first time, that groups of species tend to coflower more strongly with each other than with other species in a community, supporting the idea that competition and facilitation are not mutually exclusive processes mediating coflowering community assembly. Our results show that the degree of modularity is not sensitive to the number of coflowering species within each community, suggesting that ecological factors may be more important in driving this pattern. Conclusions. Coflowering networks have the potential to advance our understanding of the causes and consequences of flowering overlap in diverse plant communities by revealing a more in-depth and novel characterization of coflowering community structure. Such characterization will allow for a better understanding of the importance of coflowering patterns in mediating the structure of plant-pollinator interactions.

Premise of the Study: There is growing interest in understanding plant–plant interactions via pollen transfer at the community level. Studies on the structure and spatial variability of pollen transfer networks have been valuable to this understanding. However, there is high variability in the intensity of sampling used to characterize pollen transfer interactions, which could influence network structure. To date, there is no knowledge of how sampling effort influences the richness of pollen on stigmas and thereby transfer interactions observed, nor how this may vary across species and study sites. Methods: We use rarefaction curves on 16 species to characterize the relationship between sampling effort (number of stigmas analyzed) and the richness of pollen transfer interactions recorded. We further assess variability in this relationship among species, plant community types, and sites within a single plant community. Key Results: We show high among-species variation in the amount of sampling required to sufficiently characterize interspecific pollen transfer. We further reveal variability in the sampling effort-interaction richness relationship among different plant communities and even for the same species growing in different sites. Conclusions: The wide heterogeneity in the sampling effort required to accurately characterize pollen transfer interactions observed has the potential to influence the characterization of pollen transfer dynamics. Thus, sampling completeness should be considered in future studies to avoid overestimation of modularity and specialization in pollen transfer networks that may bias the predicted causes and expected consequences of such processes for plant–plant interactions.

Marine geological surveys in Asköfjärden in the southern Stockholm Archipelago hasrevealed step like features in the sediments on the Baltic sea floor. The aim of this project is toanalyse the steps and possible formation processes from the survey data. The data used aretaken from the acoustic instruments multibeam echosunder and Chirp sonar sediment profiler.The multibeam reveal the seafloor topography and can detect water column features. TheChirp sonar produce sub-bottom profiles showing the sediments down to some tens of metersunderneath the sea floor. The multibeam data show multiple crescent shaped steps as well aselliptically shaped “pockmarks”. Water column data show what could be interpreted as seepsfrom the sea floor under these features. The sub bottom profile show deformation and fluidsignatures under the steps. Gas signatures and what could be other fluids are present. Theinterpretation concludes that the formation could be from either gas or groundwater seeps. Nodefinitive conclusions can be made from the data available for the present study, andapetrophysical or geochemical study of the study area cold provide further understanding ofthe formation of the steps.

No description available.

Au niveau des fonds océaniques, souvent considérés comme des déserts aux conditions de vie extrêmes, des oasis luxuriants de vie existent pourtant. Les sources hydrothermales et les suintements froids, principalement localisés au niveau des dorsales océaniques et des marges continentales, vont permettre le développement de communautés microbiennes et animales très particulières. Le Bassin de Guaymas, situé dans le Golfe de Californie (Mexique) présente la particularité de regrouper à la fois une zone de sources hydrothermales et une zone de suintements froids, situées à une soixantaine de kilomètres l’une de l’autre, et toutes deux recouvertes par une épaisse couche sédimentaire. Ces deux zones sont également colonisées par des étendues de bivalves, des buissons de vers tubicoles ainsi que de tapis microbiens blancs ou colorés comparables. Afin de mieux comprendre le fonctionnement global de ces deux types d’écosystèmes et notamment le rôle structurant des communautés microbiennes sédimentaires sur la répartition des différents assemblages de surface, les travaux entrepris dans cette thèse se proposaient d’étudier les communautés microbiennes sédimentaires associés à la zone de suintements froids (Marge de Sonora) et la zone de sources hydrothermales (Southern Trough) du Bassin de Guaymas. Pour cela, la diversité des communautés microbiennes (Bacteria et Archaea) de différents habitats caractérisés par une faune et des profils géochimiques particuliers, a été étudiée grâce à l’utilisation d’une technique de séquençage haut-débit, le pyroséquençage par la technique du 454, combinée à d’autres techniques comme le FISH ou la PCR quantitative. Cette étude a permis de déterminer que la structure et la diversité des communautés microbiennes dans ces sédiments étaient très spécifiques de ces environnements. Par ailleurs, les colonisateurs présents en surface des sédiments reflétaient des profils géochimiques et des communautés microbiennes très différentes au sein des sédiments. Dans les sédiments colonisés par les tapis microbiens, riches en méthane, les communautés microbiennes dominantes (ANME, Deltaproteobacteria…) utiliseraient notamment les émissions de méthane des couches sédimentaires profondes et produiraient d'importantes concentrations de sulfures, nécessaires à l’installation des communautés microbiennes thiotrophes de surface formant les tapis. Ces fortes concentrations en sulfure excluraient en revanche les communautés animales de ce périmètre. A contrario, dans les sédiments présentant de faibles concentrations en méthane et en sulfure, permettant l'installation d’assemblages faunistiques variés, les communautés microbiennes méthanotrophes anaérobies et productrices de sulfure étaient minoritaires. L'activité et le métabolisme de ces colonisateurs de surface pourraient par ailleurs permettre le développement des lignées microbiennes détectées dans ces habitats (MBG-D, Chloroflexi…). L'analyse des larges jeux de données obtenus au cours de cette étude nous a donc permis de mettre en évidence un système dynamique complexe fonctionnant en équilibre entre les communautés microbiennes sédimentaires, les organismes colonisant la surface du sédiment et la composition géochimique des eaux interstitielles. / Whereas the deep-sea environment is often considered to be a desert, hydrothermal vents andcold seeps provide “oases” of biological activity on the ocean floor. Vent and seep ecosystems support complex food webs based on microbial chemoautotrophic primary production. These hydrothermal vent and cold seeps ecosystems both release hydrocarbon- and sulfide-rich fluids,fueling various surface assemblages such as mat-forming giant bacteria or symbiont-bearinginvertebrates (e.g. bivalves, tubeworms). In the Guaymas Basin, the nearby presence at a few tens of kilometers of cold seeps and hydrothermal vents coupled with comparable sedimentary settings and depths offer a unique opportunity to assess and compare the microbial community composition of these ecosystems. Tobetter understand their overall functioning, we studied sedimentary microbial communities associated with cold seep and hydrothermal vent areas in the Guaymas Basin. The diversity of microbial communities inhabiting sediments was studied using high throughput sequencing (454pyrosequencing), combined with complementary approaches, such as FISH and quantitative PCR. This study reveals that sediments found in the Guaymas Basin were colonized by microbial communities typically found in these types of ecosystems. Our results revealed a high similarity between microbial communities composition associated with the cold seep and hydrothermal vent areas as a probable consequence of the sedimentary context. Nonetheless, thermophilic and hyperthermophilic lineages (e.g.: Thermodesulfobacteria, Desulfurococcales, etc) were exclusively identified in hydrothermally influenced sediments highlighting the strong influence of temperature gradients and other hydrothermally-related factors on microbial community composition. Furthermore, sediments populated by different surface assemblages show distinct porewater geochemistry features and are associated with distinct microbial communities. Indeed, in the sediments underlying microbial mats characterized by high methane porewater concentrations,microbial communities were dominated by anaerobic methane oxidizers (ANME), known to produce sulfide which provides high fluxes of sulfide to the seafloor. In contrast, sediment associated microbial communities underlying faunal assemblages were characterized by a lower biomass and lower methane porewater concentrations in sediments, limiting porewater sulfide concentrations. Without elevated and toxic sulfide concentrations, faunal assemblages can colonize the surface. Together, geochemical and microbial surveys indicate that porewater methane concentrations play an important role in the microbial community structure and subsequently in the establishment of the surface colonizers. Furthermore, presence and activity of the surface colonizers influence the underlying microbial communities probably because of modification of energy source availabilities. Finally, the existence of similar microbial populations between the two ecosystems also raises the question of their dispersal mechanisms. Our results support the hypothesis of a potential continuity among deep-sea ecosystems. In absence of physical borders, environmental conditions (temperature, specific compounds associated withhydrothermal fluids) might select specific and highly adapted microorganisms from the pool of microorganisms dispersed globally across the seafloor.