No description available.

This study sought to determine whether tributyltin (TBT), a toxic environmental contaminant now banned from use in antifoulant paints, could have contributed to ecological degradation in shallow lakes. Anthropogenic stresses have often led to changes in ecological structure and functioning within such waterbodies, with catastrophic loss of submerged macrophytes a common phenomenon. An area that has experienced intense TBT contamination and widespread macrophyte loss, is the Broads, a popular inland navigable waterway in E. England. Development of an online SPE-LC-MSn analytical method enabled identification and quantification of contemporary organic antifoul biocides in water and sediment samples. This contemporary analysis improved understanding of the transport mechanisms that would have been responsible for dilution and dispersion of TBT. Within the River Bure study area, a distinct antifoul biocide contamination gradient was observed, that related to the level and type of boating activity. Most significantly, biocide transportation has led to areas not directly exposed to boating activity, but in hydrological connection, to become contaminated. The recent ecological histories of contaminated lakes was reconstucted using multi-proxy palaeoecological analytical techniques on cores collected using a new wide-diameter corer. Data from the radiometrically-dated cores indicated that at least twenty years of continuous TBT pollution occurred in the Broads, against a backgound of eutrophication. The pre-TBT period was characterised by presence of macrophyte remains with abundant plant-associated diatoms, cladocera and invertebrates, which switched to predominantly planktonic assemblages after initial detection of TBT. Environmental concentrations of TBT present during its active usage in antifoulant paints, would have adversely affected functionally important aquatic organisms, as indicated by ecotoxicological test data. The spatio-temporal assessment of contamination, combined with a palaeoecological approach, has been successful in reconstructing relative toxicant exposure and patterns of ecological change in the Broads. This methodology could be applied to the study of other persistent pollutants.

The world ocean can broadly be split into two regimes, the shallow shelf seas up to a few hundred metres deep and the deep open ocean which is typically 4-5 km deep. These two regimes are separated by a narrow region of steep topography. This steep topography acts to limit the exchange to those processes that break the assumptions of geostrophy. This exchange, however, is important on both a local and global scale. The shelf seas are an important source of dense water masses, ventilating the deep ocean, control of the flux of mid-depth open ocean heat to glacial fronts, supply of nutrients from the open ocean to sustain enhanced productivity on the shelf, and export of the carbon drawn-down by this productivity into the deep ocean. This problem will be explored through two themes, one exploring the role of the bolus transport and one exploring an integral framework. The bolus transport is de ned as the transport as a result of co-variances in layer thickness and layer velocity. This has previously been extensively applied for the atmosphere and the action of eddies in the Southern Ocean. Here the bolus transport driven by the action of the internal tide near the shelf edge is considered. First we consider a sinusoidal internal wave on the interface of a two well mixed layer ocean. This leads to a theoretical scaling for the bolus transport of (ca2)=(2hi) in the same direction as the propagation of the wave. The bolus transport was then calculated for eight moorings across four locations. For the surface layer these transports were in the range 1.09 to 0.1 m2s 1 and for the bottom layer were in the range 1.06 to 0.04 m2s 1. These observational estimates compare favourably with the estimates from the theory, with the theory within 40% of the observed values. This bolus transport is balanced locally by a time-mean velocity of equal magnitude but directed off shelf in both layers. The Walin Framework is an integral framework describing the rate at which water crosses density surfaces. This is used to diagnose the formation, or destruction, rate of water within density classes across the European Shelf, bounded by the 200m isobath, the southern limit of the Celtic Sea and the Norwegian Coast. This formation rate makes the largest contribution to the exchange across the shelf edge. This reveals three distinct regimes: an off-shelf transport in the lightest classes of 0.5 Sv, an on-shelf transport in the middle density classes of 1.5 Sv, and an off shelf transport in the densest classes of 1 Sv. Mapping these along the shelf edge indicates that much of the shelf does not reach the lightest classes so only the intermediate and dense regime is applicable. The lightest regime primarily exists along the southern section of the Norwegian Trench. This implies two circulations: a down-welling circulation of 1 Sv across much of the European Shelf and an across shelf transport of 0.5 Sv, on-shelf across much of the shelf edge balanced by an off shelf transport in the Norwegian Trench. This down-welling circulation is similar to previous estimates of the total transport across the European Shelf Break.

Interactions between deepwater sedimentary systems and growing coeval salt structures result in the development of unique morphological features. This thesis focuses on controls on the formation and development of these features in a deforming deepwater passive margin setting, offshore Angola. Using 3D seismic datasets and well data, the evolution of basin-bounding structures and infill history of a salt withdrawal mini-basin are investigated, focusing on fan lobe complexes and mass transport complexes (MTCs). Structural restoration, isopachs and sediment accumulation rate maps are used to describe the basin evolution, with rates of change of bed length of individual structures calculated using biostratigraphic data. Early sedimentation on the slope was dominated by erosional channel complexes (33.9 - 18.26 Ma). Subsequently, salt movement and a concomitant increase in the growth rate of the basin-bounding anticlines, led to the formation of MTCs (18.26 - 8.29 Ma). Two types of MTC are examined: 1. laterally extensive deposits which thin onto structures and were sourced from the contemporaneous shelf; 2. small-scale MTCs sourced from basin-bounding structures. As salt movement continued, the basin became largely enclosed and ponded fans developed (8.29 - 5.58 Ma). Four lobe complexes imaged in unprecedented detail are investigated, revealing systematic changes in sediment entry point, fan shape and orientation through time. Combining observations on spatial distribution of sedimentary systems with maps showing the rate of growth of structures within the mini-basin and observations of the variations in stratal relationships through time, the following can be concluded: • ponded fan deposition occurred during low growth rate intervals (rate of change of bed length < 10 mMa-1). The lobe complex shape resulted from their passive response to relict topography from preceding high rate of change of bed length periods, • regional MTC deposits respond passively to structural growth and relict topography, being preferentially deposited in bathymetric lows, whilst • channels and local MTCs respond actively to medium and high growth rate structures; channel pathways change in response to structures with bed length change rates > 15 mMa-1.

No description available.

The work presented in this thesis concerns the procuring of mops of the tidal streams in southern Start Bay, a region of particular interest as the existence of the shallow Skerries Bank results in considerable variation of the water depth in the area. The first step taken towards achieving this intention involves the accumulation, by sea-trials, of considerable sea-trial data. For this data (collected at different times and therefore different states of the tide) to be compared, empirical relationships are presented to allow all tidal stream results to be adjusted to refer to a chosen reference spring tidal range. Use is then made of these comparisons to deduce the approximate hydrodynamic equations describing the tidal flow over the region, taken as a whole. In the light of these equations, an argument against employing mathematical modelling as a means of obtaining the tidal stream maps in this particular region is put forward. Instead of mathematical modelling, a simple hydraulic model is used and it's predictive results are presented in cartographic form. The resulting maps are compared to sea-trial data and discussed. Finally, the results emanating from this work are summarized, conclusions drawn from them and some suggestions made for future work.

Chemosymbiotic invertebrates obtain nutrition from harbouring bacteria that oxidize reduced chemicals to produce energy for carbon fixation. This allows the animals to thrive in the extreme conditions of the deep sea, because the high concentrations of sulphide (thiotrophy) and methane (methanotrophy) at cold seeps and hydrothermal vents can be utilized by the symbiotic bacteria. This research investigates whether the key role of chemosymbiosis in shaping modern deep sea ecosystems can be traced through geological time, by using the stable isotope composition (δ13C, δ15N, δ34S) of organic matter in invertebrate shells. Shell-bound organic matter (SBOM) was isolated using various shell removal techniques, and method comparison suggests that the original isotopic signal is least affect by using EDTA or acetic acid. Multi-isotope analysis of SBOM obtained from (deep sea) molluscs and brachiopods confirms that the main types of chemosymbiosis can be differentiated from non-symbiotic heterotrophic nutritional strategies. In particular chemosymbiotic SBOM δ13C is characteristically depleted, with defined ranges for the presence of either methanotrophic or thiotrophic symbionts across environmental settings. In suspected thiotrophic taxa from ancient cold seeps, the preservation of this modern range (SBOM δ13C -35‰ to -29‰) is limited to young subfossil specimens, but the upper threshold is only exceeded in pre-Pliocene samples. Moreover, the protected intra-crystalline SBOM pool retains a distinct δ13C signal up to the Miocene, and available δ34S and δ15N data of intra-crystalline SBOM do not overlap between heterotrophy and thiotrophy. For methanotrophy (δ13C -65‰ to -36‰ at modern cold seeps) a residual δ13C biosignature does appear to be present in total SBOM from Miocene samples. This encouraging finding, together with the discovery of intra-crystalline original proteins in a fossil of Cretaceous age, suggests that future work on other well-preserved specimens could trace the evolution of chemosymbiosis deep into geological time.

Ocean acidification (OA) and warming represent two of the greatest challenges of the 21st century, and understanding how they will influence whole ecosystems and their functionality is crucial for effective management. My goal was to determine how climate change affects species and community assemblages by investigating both direct (physiological responses), and indirect (species interactions) effects. In Chapter 2, a metaanalysis was presented that suggested there are 'winners' and 'losers' in climate change, alongside some predictable trait-based variation in sensitivity/resilience that can be attributed to taxonomic groups and/or life stages. Importantly, it was also demonstrated that the combination of OA and warming generally interacted synergistically. In the first experiment (Chapter 3), aquarium-based mesocosms (also used in Chapters 4 and 5) were used to demonstrate that OA and warming not only directly alter species (individual) physiological performance, but also their predator-prey dynamics due to the reduction of prey quality. It was found that the reduced prey quality was sufficient enough to prevent the predator from being able to initiate compensatory feeding, and they subsequently exhibited tissue loss. This highlights the need to simultaneously consider the inclusion of those species that are trophically linked. In Chapter 4, the role of the predator in eliciting non-consumptive effects (i.e. foraging-refuge trade-off) was additionally considered. The results suggest that future ocean acidification and warming govern the diminishing energy budget of consumers, which requires them to be less risk adverse, but ultimately more susceptible to predation themselves. As a consequence, the strength of non-consumptive effects appear to reduce as energy reserves are exhausted, and the behavioural choices of the organisms become driven instead by the need to reduce starvation risk. In Chapter 5, the effects of OA and warming on a biodiversity-ecosystem functioning relationship were tested. In general, it was found that increased biodiversity appeared to either promote or at least sustain ecosystem multi-functionality (i.e. the positive functioning of the ecosystem, across several ecosystem processes). However, when the temperature was elevated it was no longer possible to sustain this multi-functionality due to a shift towards heterotrophy, resulting in trade-offs between ecosystem processes. In Chapter 6, the longer-term consequence of OA were considered, and an in-situ CO2 seep site was used to empirically link the energetic consequences of the individual to the contemporary demographic processes of the population. The results suggest that ocean acidification is driving individual and population level changes that will alter eco-evolutionary trajectories. Moreover, the results also suggest that the altered population demographics will leads to greater levels of short-term genetic drift that is predicted to oppose adaptation. Overall, these results illustrate how the effects of future OA and warming are likely to have important individual-, population-, community- and ecosystem-level consequences, with further interactions between these levels of biological hierarchy. Achieving a more holistic understanding of these response is imperative for the adaptation and management of climate change.

Previous investigations into wave induced mass transport have been restricted to two spatial dimensions, and, in view of the assumption of high frequency oscillations, the rotation of the earth neglected. Following a brief discussion of existing two-dimensional theories, fundamental ideas of wave induced mass transport are developed for a three-dimensional region. The analysis is separately considered for high and low frequency oscillations, between which are found significant differences. These concepts are then employed to determine the mass transport beneath doubly modulated gravity waves (high frequency oscillations) and tidal oscillations (low frequency oscillations). The predictions furnish a possible explanation of the occurrence of off-shore sand bars and the movement of bottom sediment in shallow ocean regions. A further consideration included is an assessment of the ability of edge waves on sloping continental shelves to transport loose coastal material, and for high frequency oscillations a seaward movement is deduced. The subsequent section of the work considers the formulation of a two-dimensional model for mass transport in turbulent conditions, and with varying distributions of eddy viscosity, the resulting transports are calculated. The final chapter, although not directly concerned with mass transport phenomena, is regarded as being relevant to the thesis. It is devoted to a generalisation of the boundary layer technique as a means of introducing bottom friction into gravity wave models. The method is found to predict an attenuation with time consistent with the well known approach via the Navier-Stokes equations, and seems well suited as a tool to be further exploited. -

In this thesis the Recent sediments deposited in the vicinity of Gibraltar Point on the Lincolnshire coast are described and the factors influencing their texture, composition and structure are discussed. The first part of the thesis deals with the aim and nature of the investigation, and the geographical setting of the area studied. The physiography of the area and its general evolution over the past two centuries are then described in detail. It is shown that the area can be sub-divided into a number of physiographically distinct environments and sub-environments of deposition. The Sediments which characterise these are described with emphasis on the significance of their grain size frequency distributions. The sedimentary structures are described and their origins discussed, and the compositions of the sand fractions (greater than 0.62 m.m.) are presented along with the results of a brief study of the mineralogy of the deposits. The latter part of the thesis is concerned with a general discussion of the dynamics of the sedimentation and an interpretation of the stratigraphy of the deposits studied.