In the first part of this thesis an overview is given of methods available for the analysis of nanomolar nitrate and phosphate in seawater before going on to describe in more detail a system built in our laboratory comprising liquid waveguide capillary cells connected to a conventional segmented-flow autoanalyser. This approach is suitable for routine field measurements of nitrate and phosphate and achieves detection limits of < 1 nM phosphate and nitrate. Investigations were conducted into interferences of silicate and arsenate with the analysis of nanomolar concentrations of SRP, the effect of sample filtration on the measurement of nanomolar nitrate + nitrite and SRP concentrations, and the stability of samples during storage are described. Arsenate interference scaled linearly with phosphate concentrations of up to 50 nM, resulting in an overestimation of SRP concentrations of 4.6 ± 1.4% for an assumed arsenate concentration of 20 nM. The interference effect of added Si(OH)4 on the measured SRP signal is small at the dissolved silicon concentrations typically found in oligotrophic waters. Filtration of surface seawater samples resulted in a decrease in concentration of 1.7 – 2.7 nM (±0.5 nM) SRP, and a small decrease in nitrate concentrations which was within the precision of the method (±0.6 nM). A stability study indicated that storage of very low concentration nutrient samples in the dark at 4°C for less than 24 h resulted in no statistically significant changes in nutrient concentrations. The second half of this thesis presents a dataset from aerosols collected at the Cape Verde Atmospheric Observatory (CVAO) between July 2007 and July 2008 and collected during a research cruise in the (sub-) tropical North Atlantic Ocean in January 2008. Total acid digestion followed by ICP-MS analysis reveals that the total elemental composition of the dust is close to average crustal composition and shows a high degree of consistency. Based on elemental composition data alone, dust collected on the cruise appears similar to dust collected at the CVAO. Zn and Pb are elevated above crustal values indicating an anthropogenic source, but show an association with periods of high mineral dust concentration. Ultrapure water leaches of dust samples combined with analysis for nutrients and trace metals show a picture of atmospheric concentrations of soluble trace metals and nutrients throughout the year in the study region. Estimated dry deposition fluxes for Fe, and inorganic N and P show a marked difference between summer and winter, with higher Fe and P deposition during winter when mineral dust concentrations are at their greatest, while N inputs are more constant throughout the year. Relative to Redfield ratios, atmospheric inputs are greatly enriched in Fe relative to N and P.

To achieve long-term planning and whole-ecosystem management of the oceans requires data on the extent of human impacts and the wider availability of data on human activities. This study, which aimed to provide the first detailed assessment of the extent of human activities in the deep North East Atlantic, OSPAR Maritime Area, revealed that during 2005 bottom-trawl fisheries affected an area of seafloor at least one order of magnitude greater than all the other the activities in the study combined. It was also found that identifying data sources, access to data and data quality presented significant barriers to implementing whole-ecosystem management and governance in the North East Atlantic. Additional work, in the North West Atlantic, to investigate the availability of data on human activities and to identify examples of best practice, revealed similar problems to those encountered in the North East Atlantic. Legal and policy frameworks and reporting requirements for human activities in the North East Atlantic were reviewed and recommendations made. This study identified access to fisheries’ vessel-monitoring data (VMS) and data quality as particular problems. Currently the location of bottom-trawling can only be identified by analysis of these data. This information is vital for ecosystem management. Current European Commission legislation, regarding access to environmental data and more specifically fisheries data, were discussed and the responses to applications made to European Member States for VMS data were analyzed. The results revealed a variety of interpretations of the Regulation. While the ecosystem approach is incorporated into many conventions and agreements, its implementation is not straightforward. For whole-ecosystem governance and management of the oceans, it is necessary to move beyond the traditional sector-based, piecemeal approaches. To do so requires significant improvements in availability and management of human-activities data and a shift in thinking towards a more integrated approach.

No description available.

For well over a century a great deal of effort has been expended into investigation of how polychaetes capture their food but there has been a relative lack of attention paid to the processing of ingested material in the various forms and functioning of the anterior gut in errant polychaetes. The principal focus of this study was the examination of the functional anatomy of the anterior digestive tracts from three families of polychaetes; the Arenicolidae; sedentary detritivores, the Nereidae; errant omnivores and the Nephtyidae; errant carnivores. Comparisons were made with the already well-studied gut anatomy and particularly the pharyngeal anatomy of Arenicola marina, so as to establish a baseline for the other families of polychaetes. Particular attention was focused on the method of pharyngeal stabilisation in relation to food capture and processing. It is universally accepted that ‘coelomic pressure’ has been the primary factor in the eversion of the pharynx and proboscis in polychaete worms. This study challenges this hypothesis. This was done with the use of micro-dissection in anaesthetised polychaetes, electro-stimulation, modern light microscopy methods and novel application of micro-computed x-ray tomography. Investigations using scanning electron microscopy with freeze dried and freeze fractured specimens have revealed a very unusual interlacing muscle fibre pattern, in the Nephtys pharynx. This suggests that specialised pharyngeal muscles, and particularly a newly named muscle, the ventral coelomic muscle (VCM), in Nephtys, may be a primary mover of proboscis eversion rather than as a consequence of an increase in coelomic pressure. To date, only one other study has recognised this muscle, describing it as a ‘ventral retensor’ that possibly aided in the retraction of the extruded pharynx. The VCM has its origin in the ventral pharynx; it is connected to the anterior intestine, and inserted into the ventral body wall from segment 40-45. This, at least, suggests a stabilising muscle for the pharynx and proximal intestine. The present study’s observations suggest that this muscle is in fact a major player in a primarily muscular driving force for proboscis extrusion. These findings strongly suggest that coelomic pressure increases, associated with proboscis extrusion, are secondary factors in proboscis extrusion in the Nephtyidae. In the Nereidae, it would appear, that the combined action of the powerful longitudinal and circular muscles, together with the firm integrity of the outer body wall, are important players in the muscular extrusion of the pharynx and jaws. Associated increases in coelomic pressure are possibly a secondary effect and linked more with burrowing and body movement and hydrostatic support. In errant polychaetes with relatively short straight guts the anterior sections of the gut should be expected to play an important role in food processing, especially as examination of the intestines of many species, especially Nephtyidae, have revealed many of them to be empty.

The Central Indian Ridge (CIR) between 18° and 21°S shows significant morphological variation at a relatively constant spreading rate (between 47 and 51mmyr-1). High resolution TOBI sidescan sonar data (cruise CD127) and multibeam bathymetry data (Magofond 2 cruise), complemented by regional geophysical and geochemical datasets, provide an important opportunity to examine the processes controlling morphological and volcano-tectonic variations along the CIR. The CIR is situated on an elevated plateau formed from a temporally persistent and robust melt supply to the ridge axis. Analysis of the data shows that the fracture zones have a significant structural control on along-axis morphology and melt supply, partitioning the ridge into three morphologically defined regions. The central region (Region B) bounded by two of the fracture zones, contains segments which show rifted axial morphologies characteristic of slow-spreading ridges. Regions A and C show patterns of variable volcanic robustness along-axis associated with the supply and availability of melt to the ridge. Tectonic analysis correlates with inter- and intra-segment trends in morphology and volcanic structure, further highlighting regions of robust or deficient melt supply. Strong relationships are also revealed between the tectonic parameters of fault length, spacing and density along-axis. Finite difference analysis is used to model the Non-Transform Discontinuities along the CIR and Mid-Atlantic Ridge to understand patterns of strain within their interiors. The results indicate the presence of a damage zone ahead of a propagating segment tip, providing increased crustal permeability and a greater potential for hosting hydrothermal circulation. Analysis of geochemical data along the CIR identifies five hydrothermal plume signatures, three of which are coincident with the locations of NTDs in the study area, correlating with the findings of the numerical analysis. A detailed model of the CIR demonstrates that thermal variation influenced by ridge structure can produce significant variations in morphology and volcano-tectonic distribution at a constant spreading rate.

Orientador: Fabio Augusto / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T17:02:04Z (GMT). No. of bitstreams: 1 Oliveira_AnaMariade_D.pdf: 4464249 bytes, checksum: e1dcc40236e7dd94aa43a41c09928e8d (MD5) Previous issue date: 2005 / Doutorado / Quimica Analitica / Doutor em Ciências

The Middle Eocene (37 to 49 million years ago, Ma) was characterised by warmer global temperatures and higher atmospheric carbon dioxide (pCO2) levels than today with only small/non-existant icesheets. Because predicted pCO2 levels for the coming century have not been seen on Earth since at least ~40 Ma thus, the primary objective of this thesis is to improve our understanding of the nature, timing and consequences of carbon perturbations in the Middle Eocene between 39 and 43 Ma. In Chapter 3, a new (instrument specific) methodology for measuring Mg/Ca in foraminiferal calcite is developed to enable the simultaneous measurement of additional trace elements indicative of foraminiferal test contamination. This new methodology enables Mg/Ca data to be screened more efficiently for contamination and increases confidence in palaeoceanographic reconstructions based on the Mg/Ca palaeotemperature proxy. In Chapter 4, new foraminiferal stable isotope records (~5 kyr resolution) from Demerara Rise in the equatorial Atlantic are generated to test the hypothesis that the onset of continental ice sheets in the Northern Hemisphere occurred at ~41.6 Ma in the Middle Eocene, 30 million years earlier than previously thought. The new data herein, indicate that if continental ice sheets were present, they were small and easily accommodated on Antarctica with no need to invoke storage of ice in the Northern Hemisphere. The dearth of appropriate Middle Eocene sedimentary sections on which to work means that a well calibrated timescale for this interval remains to be produced. In Chapters 5 and 6, this problem is addressed using Middle Eocene sediments recovered from the Blake Nose plateau in the western North Atlantic. A new high resolution magnetic stratigraphy and new quantitative foraminiferal biostratigraphic counts were developed between 39.5 and 42.0 Ma, which allows re-assessment and refinement of previous magnetostratigraphic and biostratigraphic interpretations. This provides excellent age control for these sediments and new calibrations to the Geomagnetic Polarity Time Scale (GPTS). In Chapter 7, the first high-resolution quantitative planktic foraminiferal assemblage counts were developed for the global warming event the Middle Eocene Climatic Optimum (MECO) between ~39.5 and 41.5 Ma. New biotic records show that the MECO was accompanied by significant biotic shifts that suggest a shift from warm, oligotrophic surface waters to warmer, more productive surface waters during the MECO.

The magnitudes and pathways of sand transport in Chioggia Inlet, southern Venice Lagoon, and the resulting morphological evolution have been investigated. Bathymetric analysis has established that there is a net export of sediment from the southern Lagoon Basin, and that significant morphodynamic changes in the barrier-inlet system have taken place. The total loss of sediment from the lagoon was evaluated as 125,770 m3/a, 10% of which is estimated to be sand. In addition, the presence of an ebb-tidal delta, extending from the mouth of Chioggia Inlet, as well as two subaqueous spits, were identified. The ebb-tidal delta annual growth was estimated as 50,000 m3/a, suggesting the existence of an additional source of sand for the delta, in addition to the Lagoon. The pathways and provenance of sand in transport were determined through seabed sampling and mineralogical analysis. Three predominant sources were identified: sand eroded from the tidal flats in the Southern Basin; a northelrly littoral drift of quartz-rich sand supplied by the Adige and Brenta rivers, to the south of the Chioggia Inlet; and a southerly littoral drift of carbonate-rich renourishment sand from Pellestrina, to the north of the Inlet. The nature and magnitude of transport through the inlet was investigated through direct measurements and modelling. It was found that the export of sand through the inlet is bed grain size dependant, ebb dominant and mostly in the bottom 1 m of the water column. The shape of the profile of concentration is well reproduced by the Rouse parameter, and thresholds for motion are between those derived by Van Rijn (1993) and by Amos et al. (2010b) for the Venetian inlets. Modelling results suggest that present export rates are 40% lower than those evaluated from longterm bathymetry changes. Volumetric and modelling estimates of drift along the shores adjacent to the Inlet indicate that the main contribution to the inlet features is littoral drift, with a longshore transport rate of 118,000 m3/a, from the south, and 91,000 m3/a, from the north. A conceptual sand budget for Chioggia Inlet was proposed. Littoral drift was found to be dominant over transport through the Inlet; thus, it is suggested that although the overall budget of sand in Chioggia Inlet is still negative, a small import of sand is starting to take place. Furthermore, the contribution of Chioggia Inlet to the net export of sand from the lagoon, based on present net budget estimates was calculated as 15%.

The removal of iron from the <0.45m fraction of Tamar River water on addition of both calcium chloride solution and sea water was studied using a continuous autoanalytical system. The addition of increasing concentrations of either calcium ions or sea water caused increased iron removal, but at all of the concentrations studied a fraction of iron was found to remain within the <0.45jim fraction (termed the residual or unreactive fraction). Storage time was shown to have a marked effect on the residual concentration. Kinetic analysis of the experimental results showed that when a residual fraction was taken into account, the data could be described by either a first or second order kinetic model. The first order model gave an approximately linear increase in rate constant with increasing concentrations of calcium ions or sea water, ranging from 1.02 xlO to 6.14x10 s for the addition of calcium ions and from 3.97 xlO to 6.95 xlO s for the addition of sea water. The second orderrate constant also showed an increase with increasing calcium concentration, from 3.95 xlO to 3.02 xlO 1 mol s . When the first and second order profiles were studied and the fit of the model to the experimental residual values was considered, the first order was shown to be a better descriptor of the observed removal of microcolloidal iron. A comparative study was made of iron removal under different conditions of simulated estuarine mixing, following the procedures of Fox & Wofsy {Geochim. Cosmochim. Acta, 1983, vol 47 p211), Mayer (Geochim. Cosmochim. Acta, 1982, vol 46 p2527), Hunter & Leonard (Geochim. Cosmochim. Acta, 1988, vol 52 pi 123) - all using 'discrete sampling during mixing and Duffy (PhD Thesis, University of Southampton) - using continuous sampling with more rapid mixing. Variations among the 'discrete' methods are small relative to those between them and the method of Duffy (1985) e.g. 65 % for the 'continuous' method as compared with 36%, at a salinity of 5, and the first order rate constant was seen to be about an order of magnitude greater for the'continuous'method e.g. 3.97 xlO s as compared with 1.97 xlO s , at a salinity of 5. Further experiments looking specifically at the effect of stirring rate on a 'discrete' sampling method concurred with these observations. In experiments carried out at a salinity of 8, the iron removal increased from 44% to 55% and the first order rate constant increased from 2.96 xlO to 3.58x10 s as a result of a relative increase in stirring rate from 1 to 5. The fact that the first order rate constant for iron removal varied with the energy of the system, even in the least energetic system studied, and that under all conditions the first order model provided the best descriptor of the observed process, showed that the mechanism of microcolloidal aggregation under all these conditions could not be accounted for by Brownian Motion. Shear must therefore be a significant factor and it was concluded that none of the systems studied could afford a test of kinetic order under conditions where Brownian Motion dominantly accounts for particle collisions. The experiments, however, are still of relevance to environmental conditions, since estuarine mixing is greatly influenced by turbulence due to tidal energy and wind stress. Phosphate behaviour was studied concurrently with that of iron and both the percentage removal and kinetic rate constants showed comparable dependence on calcium ion / sea water concentration, although the percentage phosphate removal was consistently lower than that observed for iron. Kinetic rate constants ranged from 0.0019 to 0.0179 s for the first order model and 0.29 xlO to 5.3 xlO' 1 mol" s for second order. When the removal profiles were studied and the fit of the first and second order models to the experimental residual values was considered, the first order model was again shown to be a better descriptor of the observed removal. Phosphate behaviour remained essentially unaffected by changes in experimental methodologies or stirring rate. The factor which most affected iron (stirring) had no major systematic effect on phosphate and therefore it must be concluded that the results indicate a co-removal of phosphate during iron colloid aggregation rather than removal of a common colloidal population containing both constituents.

Air bubbles in the ocean, naturally induced by breaking waves or artificially entrained by ships, remain in the water for different periods of time. Knowledge of the factors accounting for the differences in air bubble residence time (BRT) is essential for understanding processes of air sea-gas exchange as well as for the detection of underwater ship wakes in defence applications. Reasons for the differences in BRT have been found mainly with respect to physical and chemical properties of seawater, such as temperature, salinity and gas saturation level. The impact of biological factors on the behaviour of air bubbles in seawater has not previously been investigated. It is hypothesised that phytoplankton influence BRT through the production of dissolved organic material (DOM) and oxygen. Laboratory experiments were carried out in a seawater mesocosm tank system to investigate the influence of phytoplankton growth on the BRT of artificially injected air bubbles of a wide size range (10-1000 µm diameter) using both natural phytoplankton populations from Kiel Firth and phytoplankton monocultures. BRT was determined acoustically and several phytoplankton growth-related parameters (chlorophyll concentration, dissolved inorganic nutrients, dissolved organic carbon (DOC), oxygen saturation, bacteria numbers) as well as physico-chemical parameters (surface tension and viscosity) were monitored. BRT showed statistically significant covariation with oxygen saturation and chlorophyll a concentration during phytoplankton growth periods in the tank. Increases in BRT of a factor of > 2 were found during the chlorophyll maxima, provided that the water was sufficiently supersaturated with oxygen (~>110%). When the seawater was undersaturated with oxygen, BRT changed only marginally regardless of the chlorophyll a concentration. No clear relationship was evident between BRT and measurements of DOC, surface tension and viscosity. Investigations of the influence of dissolved oxygen on BRT through variation of oxygen saturation of deionised water showed that oxygen saturation alone has no apparent effect on BRT. The influence of phytoplankton on the rheological properties of an air/water interface was investigated in small scale experiments using different phytoplankton monocultures. An increase in surface shear viscosity was detected for only one of the four species of microalgae tested, Nitzschia closterium. Dependency of BRT on the combination of oxygen supersaturation and other phytoplankton growth-related parameters are discussed.