The ability of a species to show plasticity throughout its range is suggested to be significant to the survival, maintenance, and expansion of populations. In the Southern Ocean, plastic traits may have enabled resilience since the onset of cooling, and given species the capacity to exploit empty niches after the retreat of ice in interglacial periods. Phenotypic plasticity has rarely been investigated in Southern Ocean invertebrates however, and the cold stenothermal environment, which prevails, has often been considered homogenous in its selection on fauna. Previous ecological studies have often pooled together material collected within predetermined biogeographic regions to overcome the limitations of sampling difficulties. Subtle differences between environments may however, be forcing ecological divergence in species, with possible implications for speciation processes. This thesis investigates the phenotypic plasticity and reproduction among populations of the small shallow-water brooding bivalve Lissarca miliaris over its Antarctic range, and of deep-sea protobranch bivalves Yoldiella ecaudata, Y. sabrina, and Y. valettei from contrasting benthic regions. The reproductive studies of L. miliaris revealed a previously unknown hermaphrodite trait, maximising the reproductive efficiency in a short-lived species where the female’s capacity to brood its young is limited. Reproduction is also described for the first time in deep-sea Antarctic protobranch bivalves and demonstrates lecithotrophic larval development. Additionally, Y. valettei shows evidence of simultaneous hermaphroditism, which may increase the likelihood of successful reproduction in low population densities. Phenotypic plasticity is observed among populations of bivalves, irrespective of geographical proximity, and with no latitudinal trends, but subtle differences in the environment. Significant differences in morphology and growth rates are identified among populations, and reproductive plasticity identified in L. miliaris and Y. sabrina. Increasing atmospheric temperature is also measured to show an effect on the ecophysiology of intertidal populations of L. miliaris at Signy Island over the past 40 years, with increasing growth rates at the cost of smaller offspring and pressure from endolithic algal decay.

No description available.

The anomuran sub-family Lithodinae comprises a great diversity of morphological and ecological forms, whose global radiation has not been specifically addressed since the modern syntheses of plate tectonics, oceanography, species theory and cladistic systematics. The focus of this thesis was to investigate the origin and radiations of the deep-sea Lithodinae as a case study for interchanges between deep and shallow oceans in mobile benthic fauna. Molecular sequences were obtained from six genes (for 47 species belonging to 10 genera of Lithodidae) and different aspects of morphology were examined in order to identify nested monophyletic groups based on shared, derived characteristics. The hypothesis that lineage-specific temperature tolerances influence the distribution of deep- and shallow-water groups was tested by examining habitat alongside phylogeny. Lithodid ancestors are likely to have had a north Pacific, shallow-water distribution and planktotrophic larvae. Some shallow-water populations of Lithodidae are tied to locations north of 30°N because of the restricted thermal tolerance of pelagic larval stages; however, life-history changes allowed the subfamily Lithodinae to expand through the global deep sea, where they are now living at the frontier of their lower temperature threshold in the Southern Ocean. Phylogenies indicate the importance of large-scale dispersals within deep-sea groups, linked to the cold deep-water currents that connect the major oceans. The subfamily Lithodinae includes examples of at least two genera in which diverse morphologies have arisen within the deep ocean in the absence of discernable barriers to gene flow. Adult migration and larval dispersal partially explain the widespread occurrence of the Lithodidae, but this does not indicate that lithodids roam the ocean depths unconstrained by physical or chemical conditions. Climate change throughout the Cenozoic has substantially altered the marine environment and shaped the distribution and radiation of the extant Lithodidae. In the forthcoming years, measurable changes in ocean temperature, ocean currents and benthic habitat will affect the distribution of the lithodids and the communities they live in, as they have in the past.

Marine phytoplankton are central to biogeochemical cycling within the ocean, driving enzyme catalysed redox reactions using a set of evolutionary conserved metabolic proteins. Data are presented from four cruises in the North Atlantic in both the sub-tropics (D326, winter 2008 and FeAST, summer 2008) and the high latitudes (D350, spring 2010 and D354, summer 2010). Optimisation of quantitative immunoblotting enabled detection of target photosynthetic proteins and resulted in a method which provided extraction efficiencies averaging 71% 12% and good reproducibility. Quantification of target proteins within natural marine communities, are combined with photophysiological measurements and biochemical data, to determine protein distribution patterns and suggest potential acclimation patterns in response to environmental forcing. Quantification of photosystem II (PSII) and Rubisco, was achieved from phytoplankton communities in the sub-tropical North Atlantic, in both surface waters and from the deep-chlorophyll maximum (DCM). Increased PSII abundance, relative to total protein, observed in samples from the DCM suggest that phytoplankton within the sub-tropical North Atlantic, photoacclimate to lower irradiance by increasing the abundance of PSII reaction centres. Data collected from the high latitude North Atlantic (HLNA) during spring and summer 2010 suggest that, during summer, primary productivity in the Irminger Basin was limited by iron (Fe) availability while co-limitation by Fe and nitrate was constraining phytoplankton growth in the Iceland Basin. The most significant inter-season difference in protein abundance was a decrease in Rubisco in summer. This decline was potentially attributed to a decrease in nitrate availability between spring and summer. Low PSII:Chl a ratios, coupled with depressed photosynthetic efficiency (Fv/Fm), were observed in the Irminger basin during summer, potentially as a result of larger antenna sizes and/or excess uncoupled Chl-binding proteins, in response to Fe limitation. Nutrient addition incubation experiments in the HLNA, during summer 2010, further supported the in situ data. In particular, the molecular level response of these communities to Fe addition was characterised by a marked increase in PSII:Chl a. Overall this thesis has enabled absolute quantification of key photosynthetic proteins from natural communities in the North Atlantic and has addressed potential environmental drivers for changes in protein abundance. Future quantification of key photosynthetic proteins, in natural communities, will provide applications in primary productivity estimates.

Despite its extreme environmental conditions, the deep sea harbours a unique and species-rich fauna of mostly unknown age and phylogeny. Pennatulids (Anthozoa: Octocorallia) are a group whose taxonomy and phylogenetic relationships remain poorly known and little studied, in spite of their abundance and ecological importance in softbottom communities. Phylogenetic analysis of a combination of partial ND2 and msh1 sequences produced well-supported phylogenetic relationships for representative deepsea (and shallow-water) pennatulids at familial, generic and specific taxonomic levels. Generally, molecular data were congruent with current classification and previous phylogenetic reconstructions of the O. Pennatulacea based on morphology. Discrepancies were evident concerning the finer details for some families and genera: this can be attributable to the high frequency of homoplasy in pennatulids where reversals in evolution have led to taxa that possess apomorphic character states that are analogous with plesiomorphic traits. Genetic analysis gave strong support that highly-derived taxa occur in both shallow and deep water and that many may have differentiated and dispersed from the deep sea to the shallows. The Renillidae, which is considered one of the most primitive shallow-water families, evolved recently from deep-water ancestors. Conversely, the bathyal Anthoptilidae was the most primitive of families, and although more evidence is required, pennatulids as a group may have originated in deep water. The systematics of the exclusively deep-sea genus Umbellula, which contains fortytwo species, remains unclear despite the repeated attempts of revision. Incorporating new morphological and distributional data from the examination of recently collected material, together with type specimens, genetic analysis, and a critical study of the literature, fifteen Umbellula species are here considered valid, including three new to science. Eight species lack sclerites in the autozooids, U. magniflora, U. encrinus, U. antarctica, U. carpenteri and Umbellula sp.1 n. sp. (quadrangular axes), and U. huxleyi and U. pellucida (round axes); and seven possess autozooid sclerites, U. thomsoni and U. hemigymna (quadrangular axes), and U. monocephalus, U. aciculifera, U. durissima, Umbellula sp.2 n. sp. and Umbellula sp.3 n. sp. (round axes). Biogeographic data and genetic evidence supported the hypothesis that species of Umbellula differentiated in the Indo-Pacific. Many radiated southwards to the Antarctic and later north into the Atlantic, E Pacific, Indian and Arctic oceans, occupying bathyal and abyssal depths. Other, older species that evolved via a separate evolutionary pathway, may have originated in the Indo-Pacific, and dispersed to the Subantarctic (U. sp.2 n. sp.) or Indian and Atlantic oceans (U. monocephalus). Further, morphological examination of Umbellula showed it adapted to the oligotrophic conditions of the deep sea by reducing the number but increasing the size of the autozooids, and in doing so, enlarged the food-catchment area; abyssal species have done so even more extremely.

No description available.

Naturally occurring sedimentation is an important habitat-structuring factor. Increased sedimentation through anthropogenic actions can result in adverse effects to organisms and communities. With industrial activities moving further offshore, new habitats and organisms are affected. Particular in the North-East Atlantic, anthropogenic activities including oil and gas exploration and trawling have been recognised as major hazards to organisms that are sensitive to sedimentation. Sessile filter-feeders, such as sponges, provide vital functions to benthic habitats in many ecosystems and are believed to be adversely affected by turbid waters and settling particles. This project aimed to investigate the effects of sedimentation events from natural and anthropogenic sources on three different sponge species from contrasting habitats, Suberites ficus (shallow water, high sedimentation rates), Sycon ciliatum (shallow water, low sedimentation rates) and Phakellia ventilabrum (deep water, low sedimentation rates). The responses of the three species to increased concentrations of sediment were assessed on a physiological and a transcriptional level. Exposure to drill cuttings from oil exploration was investigated in Sycon ciliatum and Phakellia ventilabrum. It was shown that contrary to the expectations, respiration rates of all investigated sponges were not affected by sedimentation. However, on a molecular level the genes of the stress protein heat shock protein (hsp70) and the enzyme nitric oxide synthase (nos) were significantly regulated during exposure to sediment. Surprisingly, the expression pattern of hsp70 and nos was not consistent between the sponge species. Hsp70 transcription did not change in Suberites ficus, it was down-regulated in Sycon ciliatum and up-regulated in Phakellia ventilabrum. The expression of nos was down-regulated in Suberites ficus and up-regulated in Sycon ciliatum and Phakellia ventilabrum. Stress reaction seemed to be specific to each sponge species and might be dependent on the exposure to sedimentation that naturally occurs in their habitat.

No description available.

No description available.

This thesis uses data collected between 2007 and 2010 in an intensive, effort-based visual monitoring survey in southwest Cornwall, UK. The survey was carried out from a strategic watchpoint overlooking a regionally unique seabed feature, the Runnelstone Reef, which has previously been identified as key site for all three of the study’s target species: harbour porpoise Phocoena phocoena, basking shark Cetorhinus maximus and Balearic shearwater Puffinus mauretanicus. The location of the survey site is perceived as a productive, coastal marine ‘hotspot’ by local wildlife observers, eco-tour companies, conservation bodies and commercial fishermen. The aim of the study was to use a multidisciplinary approach to investigate the drivers behind the increased abundance and diversity of mega-vertebrates at the site. A wide range of environmental data, from fine-scale bathymetry to remote-sensed oceanographic data, were utilised in an attempt understand the potential interactions between the target species and the environment at a variety of scales. Although the target species have very different ecologies and each represent a different taxonomic Class; they each face significant threats throughout their range due to human impacts and are all listed as species of conservation concern on a number of UK, European and International Directives and Conventions. Therefore, improving our understanding of their distribution and highlighting interactions between the animals and their environment is an important objective, both for science and conservation. Harbour porpoise sightings showed significant fine scale temporal clustering associated with tidal flow, as well as spatial clustering around parts of the survey area with steepest seafloor slopes. The timing and location of highest porpoise densities coincided with tidal-topographically controlled hydrodynamic features identified using fine-scale current profile data (ADCP). The sightings and acoustic monitoring (C-POD) data both showed a high amount of temporal variability at seasonal, daily and hourly scales, highlighting the complex nature of the fine scale animal-environment interactions. Daily patterns in basking shark sightings data were investigated as a function of physical environmental covariates, with particular focus on the effect of meso-scale thermal fronts. In line with previous national scale studies of the species, shark sightings were significantly affected by sea surface temperature (SST) and there was evidence for a change in seasonal abundance compared to the long-term pattern. In addition, the variance of SST over the preceding weeks was identified as being a key predictor of the abundance of sharks in the survey area. Surprisingly, there was not a significant effect of the presence, persistence or thermal gradient strength of fronts on daily shark sightings. The implications of this result are discussed with reference to results of previous studies and the focus of marine protected area policy in the UK. The broad scale spatio-temporal analyses of Balearic shearwater sightings data from the UK, Ireland and France indicate that the birds continue to be recorded in significant numbers throughout areas previously considered to be at the northernmost extent of their range. Record counts of passing birds were recorded off southwest UK in the last two years, along with unprecedented aggregations in bays along the Brittany coast, comprising approximately 20 % of the estimated global population. The data presented provide much-needed quantitative information on the at-sea distribution and behaviour of this Critically Endangered species during the interbreeding period, and support earlier studies suggesting a northwards shift in their migratory distribution.