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No description available.

No description available.

No description available.

Coccolithophores (Haptophytes) are abundantly distributed throughout the global oceans. Emifionia huxleyi frequently blooms in the upper stratified oligotrophic and neritic depths from sub-polar to tropical latitudes and is central to carbon and sulphur biogeochemical cycling studies. E. huxleyi's biosynthesis of long chain (C31-C39) unsaturated lipids have been a biomarker for phytoplankton algae in palaeoenvironments. Here a signature fatty acid profile is presented to identify taxa and growth stage in bloom studies. Fatty acids are essential for normal cell function, and beneficial for hyperlipidaemia, suppression of hypertension, protection against renal heart failure, cardiovascular and inflammatory diseases, and cancer. The world's rapidly dwindling fish are the main natural source of o m ega~3 oils and many species may not be recoverable. At least 28% of the world's fish are over exploited or depleted and 52% fully exploited. Growing consumer omega-3 demand is driving alternative source studies with marine algae at the forefront. Through the examination of 48 stra ins of E. huxleyi, commercially valuable n-3 PUFAs have been reported in proportions of up to 70 mol% of total fatty acids in warm water strains. High cellular population densities and increased abundances of n-3 l C-PUFAs in response to phosphate enrichment give E. huxleyi potential use as a commercial organism for biotechnological applications. During laboratory based infection trials with coccolithovirus isolate 86 {EhV-86J long chain bases (lCBs) associated with structurally novel sphingolipids have been correlated with the composition of seven coccol ithovirus isolates, leading this investigation to support theories of viral trans dominant manipulation of the host E. huxley; for the increased fitness of the pathogen. By increasing the infection period and suppressing programmed cell death mechanisms the coccolithovirus is able to increase the number of progeny, and by utilising the outer plasma membrane of the host as a viral envelope, extensively increasing their titre within the water-column for future rounds of infection. These lCSs have been identified in phytoplankton blooms in the Western English Channel, making them possible chemotaxonomic biomarkers for termination of phytoplankton blooms by Phycodnaviridae members. Unlike other viruses, coccolithoviruses infects multiple stra ins of phytoplankton. A susceptibility study here involving 78 host strains demonstrated a prolific regulator of this vastly omnipresent alga. Finally, Transmission Electron Microscopy presents morphological features of nine coccolithoviruses that were previously unknown.

"I would put my money on one fundamental principle ... all life evolves by the differential survival of replicating entities" (Richard Dawkins) This study is aimed towards understanding the complexity in unicellular eukaryotic phytoplankton populations. For my research work I have chosen Tetraselmis (Prasinophyceae) as the test organism. Prasinophycean algae are considered as ancestors of all green algae and embryophytic land plants. Tetraselmis is a key transition organism in the phylogeny of green algae. The taxonomy and phylogeny of the genus was investigated using morphological, ultrastructural, flow cytometry and molecular cladistics analysis. Partial 18s rDNA sequences from fresh material and from gene bank were analysed. In this process a new species of Tetraselmis (T. indica) from salt pans of Goa, India has been reported. The high structural and molecular divergence observed in this species pointed towards the evolution in function, hence, T. indica was chosen as the test organism. T. indica inhabits the highly dynamic salt pan ecosystem and survives in wide fluctuations of salinity and environmental parameters. Studies at cellular level, where changes in cell physiology, biochemistry and optical properties were studied as a means of evaluating their function and response to alteration in the environment were carried out. Experiments suggested the existence of structural, physiological and metabolic differentiation in Tetraselmis as indicated by flow cytometric studies, differential absorption spectras and staining patterns. Further it was observed that an incipient differentiation exists in otherwise identical cells giving rise to a heterogenous population whose components exhibit differential survival and behaviour, which work in association for the existence of population. Investigation of the biology of a single cell and its lineage helped in deciphering the consequences and implications of heterogeneity and complexity in this unicellular eukaryote. To study how component cells of a heterogenous population achieve their own behaviour, the hierarchy of subcomponents within these component cells was explored. Studies suggested that the fate of different components is set at a very early stage of cell division and hence the division products of a single cell exhibit ultrastructural and metabolic differences. To consider the social interactions, naturally associated bacteria were inoculated with the axenic cultures of cells and the differential and marked influence of each bacterium on its growth dynamics was observed. This study highlights that interrogating the complete web of individual and social interactions is of importance in understanding the functionality and regulation of unicellular life.

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Inter-tidal macro-algae communities often exhibit consistent broad vertical distribution patterns of species. The factors that set the distribution limits of these patterns have long intrigued marine ecologists, and several hypotheses have been proposed to explain this phenomenon; however, no general conclusion has yet been drawn. Of all the factors limiting the occurence and development of photosynthetic organisms in aquatic environments, light is the most crucial and variable, and its role in the zonation of intertidal macro-algae is an unresolved issue. This thesis addresses the problem of whether the characteristics of the underwater light field available to intertidal macro-algae could influence species distribution. Semi-diurnal in situ measurements of the underwater light field were carried out at three sites on the south-west coast of England (United Kingdom)); the Hamble Estuary, Southampton Water and Swanage Bay. The tide is shown to significantly affect the water optical properties, and the tidal range and water transparency combine to produce important intensity and spectral fluctuations of the underwater light field available to intertidal macro-algae. To circumvent the limitations of in situ field studies a mathematical model was developed to investigate the effect of tidal features on the availability of underwater light to intertidal macro-algae across the compete tidal cycle. The results reveal the importance of the range and phase of the tide, and identify two significant zones within the intertidal zone which might depict where certain macro-algae flourish. Finally, the effect of vertical height of "transplanted" macro-algae in the intertidal zone and their pigment content was studies in situ. The results of this study were inconclusive but produce the foundation for future work. This study demonstrated that intertidal macro-algae are subjected to major intensity and spectral fluctuations in underwater irradiance, and there are two major zones within the intertidal zone which could potentially affect the zonation of some species.