An attempt was made to compare the rates of primary productivity and of microheterotrophic activity in th waters of Swansea Bay. In order to do this, primary productivity was measured by the 14C fixation method, and chlorophyll a content of the water was used as a measure of phytoplankton biomass. Estimations of microheterotrophic activity and of microbiol biomass were based on the measurement of rates of glucose uptake and of ATP in the water after detailed examination of the applicability of these methods. Estimation of ATP was based on the measurement, in a scintillation counter, of the light produced by a cell-free fire-fly bioluminescence system. Several variants of this method were tried. The one finally adopted was based on the method of Stanley and Williams (1969) and was capable of estimating 2.4 ng ATP per litre seawater. The values found in the seawater samples ranged from 2 to 300 ng per litre. Rates of glucose uptake were estimated by measuring rates of uptake of added 3H-glucose of high specific activity coupled with measurements of the concentration of glucose naturally present on the water samples. It was shown that, under the incubation conditions used, rate of 3H-glucose uptake was linear with time and proportional to the quality of unsterilized seawater present. From these estimations, values for the turnover time of glucose were obtained. These were 1-2 days in May/June, 3-9 days in April/May and about 30 days in August. In order to obtain absolute rates of glucose metabolism it was necessary to measure the concentration of the glucose naturally present in the seawater. Several methods of doing this were tried and the one finally adopted was based on the fluorimetric enzymatic assay of Hicks and Carey (1968). In this glucose is coupled with the enzymes hexokinase, glucose-6-phosphate dehydrogenase and diaphorase with the dyeresazurin so that the dye is reduced to the highly fluorescent resarufin. After some difficulties this method was applied successfully to measurements of glucose in the waters of Swansea Bay. Values ranged from 1-80ug/l. Using these values, and the rates of H-glucose uptake measured in the same samples, rates of glucose uptake were estimated at 0.004 to 0.98og glucose/l/hour. During June to October, 1977, samples were taken at intervals from Mumbles Pier and 3 miles off-shore in Swansea Bay. Using these samples, rates of primary productivity and of microheterotrophic activity were measured together with the ATP, glucose and chlorophyll a content of the water. Certain trends in these parameters with time were distinguished and are discussed. There is some evidence that suggests that rate of glucose uptake may be determined by the glucose content of the water and that, this in turn, may be determined by rate of primary productivity. Rates of glucose metabolism were, however, low in comparison with rates of primary productivity. In terms of carbon flux glucose uptake was generally less than 1% of carbon fixation by photosynthesis. It is concluded that measurement of glucose uptake may be an inadequate indicator of total microheterophic activity.

Computer programs are developed to model the process of longshore current generation by sea waves in the region of a harbour using the finite element method. Wave behaviour is modelled using a solution of the medium-depth wave equation due to Berkhoff. Reflection, refraction and diffraction effects are encompassed. A non-reflecting boundary condition is developed for use on the artificial boundaries. The radiation stress theory of Longuet Higgins is applied in conjunction with a limiting ratio wave breaking criterion to obtain forcing terms for use in the shallow water equations. A generalisation of the radiation stress theory is attempted. The influence of the eddy viscosity and bottom friction terms used in the shallow water equations on the longshore currents is investigated. The computer programs are verified by comparison of the longshore current patterns generated in the region of a harbour when an oblique angle of wave incidence is used with the patterns from a physical model. Very good qualitative agreement is found. The influence of modifications to the eddy viscosity term on the current pattern is analysed. Wave oscillations found in the wave program solution are shown to be caused by partial wave reflection due to changes in the water depth. It is found necessary to refine the finite element mesh when the wave program is used in large models with a short wavelength. The partial reflected waves are found to have major effects on the expected eddy circulation when wavelengths long relative to the model are used. Circulation cells are generated when an angle of wave incidence normal to the shoreline is used. Longshore variations in water depth cause the radiation stress imbalances which result in the circulation patterns.

<I>Emiliania huxleyi</I> is the most abundant coccolithophore in the World's oceans today. These organisms have the ability to calcify and photosynthesise, and may represent an important oceanic sink for dissolved inorganic carbon. As a result, they have the potential to influence the oceanic carbon cycle. It has been proposed that calcification may improve carbon acquisition under CO<SUB>2</SUB> <SUB>(aqueous)</SUB> limiting conditions, but may involve high Ca<SUP>2+</SUP> transport costs. In this thesis, results presented show that calcification increases in <I>E. huxleyi</I> (strain L) in response to low phosphorus and/or nitrate, high external pH, and high dissolved inorganic carbon. This information was used to produce calcifying and non-calcifying cells of the same strain allowing comparisons, which avoided the genetic and psychological differences between strains. Calcification correlated with an increase in photosynthetic efficiency (Φ><SUB>PSII</SUB>), relative electron transport rate (REF<SUB>PSII</SUB>) and the proportion of photons captured and converted to chemical energy (qP). The mechanisms underlying these correlations are unknown, but may involve the H<SUP>+</SUP> produced during calcification being used to supply an internal CO<SUB>2</SUB> source. High calcifying cells were found to have a lower internal pH than low-calcifying cells, and were able to take up HCO<SUB>3</SUB><SUP>-</SUP>. This may influence CO<SUB>2</SUB> availability within the cell, or nutrient requirements and assimilation. Results from X-ray microanalysis and Electron Energy Loss Spectroscopy indicate that the endomembrane system may provide an efficient pathway for Ca<SUP>2+</SUP> transport to the coccolith vesicle. Potentially, this avoids transport of Ca<SUP>2+</SUP> against a concentration gradient, and resolves what was thought to be one of the major cost-aspects of calcification. The most likely advantage of calcification is that it may allow low levels of photosynthesis to occur efficiently, thus increasing survival time during co-limitation by CO<SUB>2</SUB>, phosphorous and/or nitrate. Calcification may enable the cell to reduce the nutrient requirements for photosynthesis, or allow internal nutrient recycling.

No description available.

A numerical model for tidal water movements, which is based on the shallow water equations, has been set up in this study. The shallow water equations are solved using the explicit finite difference method and the study area is divided into relatively rough grid meshes in the initial stage of this study. After the model has been justified and can be operated steadily, the computational area is refined. On the basis of the initial tidal model mentioned above, a further developed tidal model, in which the shallow water equations is solved using a well-known alternating direction implicit method, is programmed. The model is operated with a staggered grid system which allows the ADI numerical scheme to be operated and the two dimensional difference equations to be reduced into one dimensional equations, which can be solved simply, even in an implicit numerical scheme. Tidal water elevation, tidal current velocity field and the tidal water flow pattern can be produced by the model. When the tidal model is running and provides the velocity field of the tidal currents, an advective-diffusion equation is introduced into the model in order that the model can predict the water diffusion and dispersion processes for a water-borne effluent concentration, i.e. salinity, in the study area. The model combining the shallow water and advective diffusion equations becomes the framework of the water quality model. The tidal model is also used to produce tidally-induced Eulerian residual currents for the area of interest by introducing a time filter sub-programme into the model, since residual current significantly affect transport processes in coastal areas, which are important in controlling the water quality in the study area. The model is applied to a real embayment, Swansea Bay, with real bathymetry. The relevant results obtained by the numerical model have been compared to the real data collected from the same computing area, and the results are encouraging showing some of the numerical results in good agreement with the real data.

A seasonal study measuring N<SUB>2</SUB> fixation, primary production and biomass of <I>Trichodesmium </I>spp. was conducted on a monthly basis for over two years at the Bermuda Atlantic Time-series Study (BATS) site. Due to seasonal changes in hydrography and meteorology, the BATS site offers a unique opportunity to study the environmental factors regulating N<SUB>2</SUB> fixation by <I>Trichodesmium</I>. Nitrogen fixation was measured using the <SUP>15</SUP>N<SUB>2</SUB> technique and the acetylene reduction assay simultaneously. The geometric mean of the molar ratio between the two techniques was 3:1 but varied by a factor of 40. Measurements of <SUP>15</SUP>N<SUB>2</SUB> incorporation was conducted on single colonies and appeared to be the more sensitive method. Rates of N<SUB>2</SUB> fixation per colony ranged from 0.01-17 ng Ncol<SUP>-1</SUP> H<SUP>-1</SUP>. Nitrogen fixation rates were compared to primary production, incorporation of organic and inorganic nitrogen and the iron content of the colonies. The seasonal pattern of N<SUB>2</SUB> fixation was highly correlated to aeolian dust deposition data collected from the AEROCE tower in Bermuda. Single trichomes of <I>Trichodesmium</I> spp. were enumerated and found to develop at the nutricline. Peak abundance of trichomes preceded maximal abundance of colonies in the surface waters at the BATS site in later summer and fall. An annual integrated N<SUB>2</SUB> fixation rate, from the upper 140 m of the water column, was 0.024 mol N m<SUP>-2</SUP> y<SUP>-1</SUP> using an average <I>in situ</I> depth profile of colony distribution, enumerated trichomes and corrected for the effect of reduced light on the rate of N<SUB>2</SUB> fixation. High rates of ectoenzyme activity associated with <I>Trichodesmium </I>colonies showed that the cyanobacteria are also important in regenerated production. The primary environmental factors regulating N<SUB>2</SUB> fixation by <I>Trichodesmium</I> appeared in the following sequence throughout the year: nitrate intrusion during vertical mixing of the water column, increased surface seawater temperature, low wind speed causing stratification and atmospheric deposition of iron. The annual contribution of N<SUB>2</SUB> fixation by <I>Trichodesmium </I>spp. to new production was of the same order or magnitude as recent refined model estimates for the North Atlantic Ocean.

No description available.

The low frequency flow dynamics of the N.W. Aegean Sea, are investigated using a barotropic shelf circulation model, and by analysis of data from current meters deployed in Thermaikos Gulf. The performance of Groves (1955) and Lanczos-cosine filters is assessed to provide optimal low-pass filtering for the current meter records. The Lanczos-cosine filter is found to be the most effective in the present study. Time series and spectral analysis are applied to the filtered current meter records and to concurrent meteorological data. The results of these analyses show significant inputs of low frequency energy at periods of 2-4 days, 6-8 days and 20-26 days. An anomalous energy band exists that is uncorrelated with the wind and which is absent from one current meter record. The results from a depth-integrated momentum balance suggest that these bands are related to direct meteorological forcing. The 2-4 day band is related to 3-dimensional coastal water processes. The 6-8 day band is described in terms of internal Kelvin waves and the 20-26 day band is related to continental shelf waves. The anomalous band with 11-13 day period is associated with freshwater forcing from rivers. The low frequency shelf circulation of the Aegean Sea is modelled analytically. Solutions to the two-dimensional vorticity equation written in terms of stream functions are sought within a circular basin with exponential cross-shelf topography. The dispersion relations for the propagation of free waves is given. Introduction of the ageostrophic approximation allows solution to the wind-forced vorticity equation wherein, parameter separation leads to a wave equation soluble by the method of characteristics. The separation parameter is determined from the associated Sturm-Liouville equation. The damped wave problem is also solved. The model predicts the propagation of continental shelf waves, with periods of 20-26 days around the Aegean Sea.

The shallow water equations have been solved numerically using the Galerkin finite element method. Flow problems which can be classified as one-dimensional and two-dimensional are investigated. Two differing types of integration procedure (Gaussian Quadrature scheme and a mixed quadrature scheme involving both Gaussian Quadrature and Simpson's Rule) are examined to determine the most efficient way of obtaining the finite element solutions. The mixed quadrature scheme is shown to be a faster but less accurate process than the Gaussian scheme. The numerical results from the one-dimensional models are initially tested by comparison with the known analytic solutions for a straight channel and a wedge-shaped channel. Solutions from numerical models show good agreement with the analytic solutions. The one-dimensional models are also used to simulate the M<SUB>2</SUB> tide in the Bristol Channel. The results are in good agreement with observed field data. The two-dimensional models are tested against analytic solutions for a straight canal and an open coastal embayment with a variety of bottom topographies. The numerical results are in good agreement with the analytic solutions. Finite element solutions are found for real situations, in particular the area around Lundy Island within the Bristol Channel and in the Bristol Channel itself. The numerical solutions are compared with the observed field data. The two-dimensional numerical models produce solutions which are in good agreement with observed field data. An analysis of the eddy formation around Lundy Island shows that these features, which were first observed in satellite imagery, are predicted by the two-dimensional numerical models. Coriolis force is shown to be important in the formation of the island wake. The one-dimensional numerical models are less successful in predicting the observed field data than the two-dimensional numerical models but the former are very efficient in terms of computer time and also provide a good prediction of water levels and elevation phase lags.

Laboratory and in situ studies have been made of compressional wave sound velocity and attenuation in water-saturated non-cohesive sediments. A broadband acoustic system (25 kHz to 450 kHz) has been developed for laboratory use. Using this arrangement, information relating to sound velocity, attenuation, and the frequency dependence of attenuation has been obtained from sand sized sedimentary material (with mean sizes ranging from 0.09 mm to 1.33 mm), at various stages of sediment compaction. Particle shape and size distribution statistics have been determined for the sediment samples used in the investigation. Statistical analysis of the data has shown that sample porosity and sediment mean grain size are the sedimentological variables most significantly related to the sound velocity. Attenuation has been shown to be predominantly related to sediment grain size, sample porosity, and overall grain surface area. The frequency (f) dependence of attenuation (a) has been shown to vary in the equation, a = Kfn with n ranging from less than 0.5 to better than 1.0. This variation in the frequency exponent is discussed with respect to the sedimentological characteristics of the samples. The development of an acoustic system for use in the field is described; this has enabled in situ measurements of sound velocity and attenuation to be carried out in medium and fine grained beach sands (over the frequency range 15 kHz to 70 kHz). The results obtained from the field study are compared with empirically derived predictions, based on the analysis of the laboratory data. Finally, the interrelationships between the sedimentological and acoustic characteristics of the sediment samples are incorporated into prediction equations, using the acoustic parameters as independent variables. This approach has demonstrated, for material in the sand size range, the potential of improved delineation of sediment type using compressional wave data obtained in the field.