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Tritium is a by-product of civil nuclear reactors, military nuclear applications, fusion programmes and radiopharmaceutical production. It commonly occurs, though not exclusively, as tritiated water (HTO) or organically-bound tritium (OBT) in the environment but may exist as other forms in nuclear-related construction and fabrication materials. During the lifetime of nuclear sites (especially those involving heavy water) tritium becomes variably incorporated into the fabric of the buildings. When nuclear decommissioning works and environmental assessments are undertaken it is necessary to accurately evaluate tritium activities in a wide range of materials prior to any waste sentencing. Of the various materials comprising UK radioactive wastes, concrete and metal account for approximately 20% of the total weight of low level waste (LLW) and 12% and 35% of the total weight of intermediate level waste (ILW). Proper sampling and storage of samples are significant factors in achieving accurate tritium activities. The degree of loss of 3H and cross-contamination can be significantly reduced by storing samples in an air/water tight container in a freezer (-18°C). The potential for tritium contamination is dependent on the 3H form. Most 3H loss originates from tritiated water which is easily exchanged with atmospheric hydrogen in the form of water vapour at room temperature. However, the loss of more strongly bound 3H, produced in-situ in materials by neutron activation, is not significant even at room temperature. Such tritium is tightly retained in materials and does not readily exchange with water or diffuse. In nuclear reactor environments tritium may be produced via several neutron-induced reactions, 2H(n,g)3H, 6Li(n,a)3H, 10B(n,2a)3H and ternary fission (fission yield <0.01%). It may also exist as tritiated water (HTO) that is able to migrate readily and can adsorb onto various construction materials such as structural concrete. In such locations it exists as a weakly-bound form that can be lost at ambient temperatures. Bioshield concretes present a special case and systematic analysis of a sequence of sub-samples taken from a bioshield core (from UKAEA Winfrith) has identified a strongly-bound form of 3H in addition to the weakly bound form. The strongly bound 3H in concrete is held more strongly in mineral lattices and requires a temperature of >850°C to achieve quantitative recovery. This more strongly retained tritium originates from neutron capture of trace lithium (6Li and potentially 10B) distributed throughout minerals in the concrete. The highest proportion of strongly bound 3H was observed in the core sections closest to the core. Weakly bound tritium is associated with water loss from hydrated mineral components. Tritium is retained in metals by absorption by free water, hydrated surface oxidation layer, H ingress into bulk metal and also as lattice-bound tritium produced via in-situ neutron activation. Away from the possible influence of neutrons, the main 3H contamination to metals arises from absorption and diffusion via atmospheric exposure to the HTO. Here contamination is mainly confined to the metal surface layer. The tritium penetration rate into metal surfaces is controlled by the metal type and its surface condition. Where metals are exposed to a significant neutron flux and contain 6Li, 7Li and 10B then in situ 3H production will occur which may propagate beyond the surface layer. In such cases tritium may exist in two forms namely a weakly bound HTO form and a non-HTO strongly bound form. The HTO form is readily lost at moderate temperatures (~120°C) whereas the non-HTO requires up to 850°C for complete extraction.

Emiliania huxleyi is a ubiquitous coccolithophore present throughout the global ocean and capable of forming large blooms with significant effects on the global carbon cycle. Developing our understanding of E. huxleyi ecology is necessary in order to better quantify E. huxleyi’s role in the present carbon cycle, and to predict its role in the future carbon cycle under climate change scenarios. Major gaps in the understanding of E. huxleyi ecology were addressed using (1) controlled mesocosm experiments in June 2008 in Raunefjord, Norway, to map population genetics of E. huxleyi blooms in relation to ecological pressures (viruses and rapid growth), (2) biogeographic sampling of nannoplankton (2 - 20 μm) in the SO, including E. huxleyi, to determine ecological pressures on E. huxleyi blooms in situ (environmental gradients), and (3) controlled iron (Fe) addition bioassay experiments in the SO to establish the role of Fe gradients in the nannoplankton community relative to the phytoplankton community. During the mesocosm experiments, 279 individual E. huxleyi cells were isolated to establish clonal cultures, of which 143 were successfully genotyped using 5 microsatellite molecular markers. Both high gene diversity and two distinct genotypic populations were detected over the bloom time series and are strong evidence for a large reservoir of genetic variability within the E. huxleyi species concept, which may translate into phenotypic plasticity, such as differing levels of viral resistance. In the SO, the spatial and temporal biogeography of the three most numerous mineralizing nannoplankton groups, the coccolithophore E. huxleyi, the smaller (<20 μm) species of the diatom genus Fragilariopsis, and chrysophytes of the genus Tetraparma were defined using scanning electron microscopy (SEM) analysis in conjunction with an array of biological, physical, and chemical variables during two successive cruises to the Scotia Sea. Multivariate statistical analyses were used to identify the most influential environmental variables controlling mineralizing nannoplankton biogeography. Sea surface temperature (SST) and salinity were identified as primary variables and removed from the analysis, leaving frontal boundaries, macronutrient, and dFe concentrations significantly associated with a northern E. huxleyi-dominated community (group I; higher nutrients) and a southern Tetraparma- and Fragilariopsisdominated community (group II; lower nutrients). Estimates of biomass indicated that the Scotia Sea mineralizing nannoplankton community formed a substantial part (on average 13%) of the total phytoplankton community. The results of bioassay Fe incubations indicated a response in medium and large diatoms and E. huxleyi, and a number of microplankton (20 – 200 μm) diatom species. Overall, the work contributes substantially to our understanding of the molecular population structure, extent of phenotypic plasticity, and environmental parameters affecting the key phytoplankton E. huxleyi.

Coccolithophores are a unique group of calcifying phytoplankton that dominate pelagic biogenic calcification and facilitate carbon export. Changes in coccolithophore calcite production through changes in their abundance, species distribution or cellular calcification could affect the oceanic carbon cycle. Ocean acidification, global warming and future changes in nutrient and light conditions might affect coccolithophore populations. This study investigated the relationships between coccolithophore distribution and calcification and environmental factors, between the North Sea and the Arctic Ocean and in the Southern Ocean. Large gradients in carbonate chemistry and other variables provided insights into coccolithophore response to concurrent changes in the future ocean. Freshwater inputs and biological processes were driving the carbonate chemistry changes in the surface waters of the North Sea, the Norwegian Sea and the Svalbard Arctic region. Even though biological processes seemed to play a major role in shaping the saturation state (calcite) and pH of these regions, the carbonate chemistry of the freshwater sources (Baltic Sea, sea-ice melt, riverine input/ terrestrial runoff) was also important and had accentuated the effects of biological activity. A multivariate approach showed that changes in pH and mixed layer irradiance explained most of the variation in coccolithophore distribution and community composition between the North Sea and Svalbard. Differences between the Svalbard population (dominated by the family Papposphaeraceae) and those from other regions were mostly explained by pH, whereas mixed layer irradiance explained most of the variation between the North Sea, Norwegian Sea and Arctic water assemblages. Estimates of cell specific calcification rates showed that species composition can considerably affect community calcification. At Drake Passage, the coccolithophore community was dominated by Emiliania huxleyi B/C. Diversity and abundance were highest in the Subantarctic and Polar Frontal Zones, respectively, where temperature and mixed layer irradiance were high. Community and cell specific calcification, as well as coccolith production rates, showed an overall decreasing trend towards Antarctica and were correlated with the strong latitudinal gradients in temperature and calcite and anti-correlated with nutrient concentrations. Additionally, coccolith production rates and cell specific calcification were also correlated with mixed layer irradiance. Coccolithophore calcification rates at Svalbard and at Drake Passage were low compared to other oceanic regions. At Svalbard, the low calcification rates were the result of very low abundances of species that have both a low (e.g. Papposphaeraceae) and high (e.g. Coccolithus pelagicus) calcite content. At Drake Passage low calcification rates were the result of low to moderate abundances of E. huxleyi B/C, which has a low calcite content. The results of this study suggest that changes in future pelagic calcite production may result from physiological changes acting on single species and/or from shifts in the species composition of coccolithophore assemblages, as well as poleward biome migrations induced by ocean acidification, sea surface warming and stratification.

Estimates of vertical fluxes of nitrate (JN) into the subsurface chlorophyll maximum from the bottom mixed layer were made in a variety of hydrological regimes over the Celtic Sea in 2003 and 2005. Over a topographically flat shelf JN varied with the spring-neap tidal cycle (1.1 (neap) – 2.8 (spring) mmol m-2 day-1), driven by changes in barotropic shear generated vertical diffusivities (Kz) at the base of the thermocline. Further increases in nitrate fluxes were possible through small shear perturbations. JN is further enhanced over topographic features, such as banks on the shelf or the shelf break, by the generation and dissipation of lee waves. The strength of mixing driven by the lee waves also varies with the spring-neap cycle, with higher Kz at the base of the thermocline occurring around spring tide, compared to neap tide, associated with the greater occurrence of short period internal waves. Over banks vertical nitrate fluxes varied between 2.9 (neap) – 15.7 (spring) mmol N m-2 day-1 and over the shelf break estimated vertical nitrate fluxes were 4 (neap) –15 (spring) mmol m-2 day-1. These fluxes are capable of supporting new production of 207 mg C m-2 day-1 over the Celtic Sea shelf, which over the summer stratified period is potentially greater than the new production taking place in the spring bloom. Enhanced production of 1200 mg C m-2 day-1 is supportable over regions of the shelf affected by the generation of lee waves over banks. This equated to a 4% increase in new production within the SCM over the Celtic Sea shelf. 31% of new production in the Celtic Sea was associated with the shelf break, where 660 mg C m-2 day-1 could be supported in the shelf break region.

The aim of this study was to improve our understanding of the marine iron cycle using a newly implemented technique to measure dissolved iron in seawater. The setting up of a flow-injection analyser with chemiluminescence detection (FIACL) for Fe(II) proved to be non-trivial. Extensive work was undertaken to solve problems relating to our limited level of understanding of the CL reaction, and the variable behaviour of the resins prepared to preconcentrate iron. An analyser for Fe(II)+(III) was optimised, and careful assessment of data demonstrated the high quality of the information interpreted in this study, from the Celtic Sea shelf edge (Northeast Atlantic), and from the North Scotia Ridge (Southern Ocean). The distribution of iron at the Celtic Sea shelf edge was examined, and was used to provide a conceptual framework for future studies. Dissolved Fe (< 0.4 µm) concentrations were measured in samples from nine vertical profiles taken across the continental slope (160 – 2950 m water depth). Dissolved iron concentrations varied between 0.2 and 5.4 nM, and the resulting detailed section showed evidence of a range of processes influencing the iron distributions. The presence of elevated levels of dissolved Fe near the seafloor was consistent with release of Fe from in situ particulate organic matter remineralisation at two upper slope stations, and possibly of pore water release upon resuspension on shelf. Lateral transport of dissolved iron was evident in an intermediate nepheloid layer and its advection along an isopycnal. Surface waters at the shelf break also showed evidence of vertical mixing of deeper iron-rich waters. The data also suggest some degree of stabilisation of relatively high concentrations of iron, presumably through ligand association or as colloids. The possibility of iron limitation of phytoplankton at the shelf edge was not ruled out despite obvious depletion of nitrate. This study supports the view that export of dissolved iron laterally to the ocean’s interior from shelf and coastal zones may have important implications for the global budget of oceanic iron. A set of surface samples collected on a survey between the Falkland Islands and South Georgia were analysed for total dissolvable iron. Results suggested a source of benthic iron near South Georgia. A shift in photo-physiology of phytoplankton towards South Georgia was probably influenced by the transition from iron-limited to iron-replete populations. These results therefore strongly support the hypothesis that South Georgia may be a "pulse-point" of iron to high-nutrient low-chlorophyll waters.

Deep-sea hydrothermal vents and cold seeps are remarkable for their spectacular megaand macrofauna, many of which appear to have a high level of endemism to these chemosynthetic environments. It is not clear whether the patterns of biodiversity, faunal zonation and biogeography documented in these size categories, are also present in the meiofauna. This thesis examines the diversity and density patterns of the meiofauna (with particular reference to nematodes) in quantitative samples collected from: Bathymodiolus mussel beds in a deep-sea hydrothermal vent field on the East Pacific Rise; Bathymodiolus mussel beds at an Atlantic methane seep site; an Atlantic hydrothermal vent sediment mound and a reference non-chemosynthetic sediment site on the Mid-Atlantic Ridge. Results suggested that deep-water chemosynthetic substrata will generally harbour assemblages exhibiting lower diversity and elevated dominance. The densities of meiobenthos appeared to vary in accordance with the presence of macrofauna. From the study of the meiobenthos of hydrothermal vent mussel beds spanning 27 degrees of latitude on the EPR, the nematodes share the same, if not a larger biogeographical province as the macrofauna. From comparison of data collected from the vent mussel beds and the Atlantic methane seep mussel bed, it was evident that the species composition of the nematode assemblage was completely different. Density levels and major taxa composition were very similar as a result of similar local factors acting within the mussel beds. Based on a comparison of data collected from all mussel bed samples and the hydrothermal sediment core, it was evident that the nematode assemblages were significantly different. Factors determining all the observed differences are discussed.

No description available.

This research provides a new method to identify likely marine feeding grounds for migratory pelagic species that are problematic to directly study at sea. The method is based on stable isotope compositions of tissues that may be sampled without harming the target animals, and can be conducted retrospectively from tissue archives. The wild Atlantic salmon has been in steep decline throughout its native range over the past four decades, largely due to increases in marine mortality. This research investigated potential causes of this decline using stable isotope analysis of archived scale samples, taken from returning adult salmon over the past few decades. Investigations of UK scale holdings identified the River Frome and Northeast Coast Driftnet Fishery archives as the most available and useful, giving good spatial contrast and temporal coverage. After developing sampling and analytical protocols, carbon and nitrogen isotopic composition was measured in grilse (one-sea winter) and multi-sea winter (MSW) salmon scale samples taken from both archives over 23 and 14 years. Analyses were performed on the last marine growth season, giving a retrospective record of marine conditions experienced by each fish. Both isotopes are influenced by baseline environmental conditions, and climatic effects are found to exert strong controls on numbers of fish returning to both the Northeast Coast and River Frome populations. Trophic level and/or baseline nitrate effects are also found to influence returning abundance to these populations, although more strongly in the Frome. Yearly d13C values were correlated with median yearly sea surface temperature values for each degree of latitude and longitude across the North Atlantic, and maps produced of the correlation strengths. These maps suggest likely feeding grounds for each cohort within each population, with the River Frome grilse and MSW salmon respectively feeding near the shelf breaks of northeast and southwest Iceland. The Northeast Coast grilse and MSW salmon were, in contrast, feeding near the shelf breaks of the southern Norwegian Sea and the Bear Island Trench in the northern Norwegian Sea, respectively.

Most studies of deep-sea benthic fauna have concentrated on soft sediments with little sampling in rocky areas and even less on non-vent mid-ocean ridges and within submarine canyons, mainly as a result of difficulty accessing them. To assess the distribution and abundance of cold-water corals along an Axial Volcanic Ridges along the Mid-Atlantic ridge at 45oN 27oW, and within the Whittard Canyon along the Irish Margin video footage from the ROV Isis taken during a three scientific cruises was analysed. Samples were also taken to allow taxonomic and phylogentic work to be completed. Abundance of octocorals per 100 m transect were calculated and mapped using Arc GIS, with a maximum of 59 in the AVR compared to 855 within the Whittard Canyon. Thirty-one putative species were identified within the Whittard Canyon including some scleractinians, Eleven more than were found in along the AVR. Both locations indicated differences in coral assemblages dependent on substratum type with sedimented areas having increased occurrence of Pennatulidae and Chrysogorgiidae within the AVR and an increased abundance of Acanella and Radicipes upon sediment in comparison to rock within the Whittard Canyon. It is suggested that these differences in abundance and assemblage structure, both within and between the AVR and Whittard Canyon sites, reflects higher food availability as well as differences in substratum type on which coral larvae settle. Taxononomic investigations identified 4 new species from samples taken along the AVR, and are described within the thesis. Phylogenetic analysis of novel sequences obtained throughout this study, as well as published sequences, showed the presence of 3 clades A) Calcaxonia and some Alcyoniidae B) Holoaxonia and Pennatulacea C) some Alcyoniidae, Corallium and Paragorgia. When individual MSH1 and ND2 genes were combined the Pennatulacea separated out as a fourth clade. This was attributed to an increase in resolution when two or more genes are used for analysis. Results indicate that morphological taxonomy and molecular analysis are not in agreement and there is a requirement for some taxonomic revisions using molecular data to confirm species boundaries and help guide taxonomic decisions.