Seamounts are often typified by highly rich and diverse communities of predominantly large suspension feeding organisms such as gorgonian and antipatharian corals, which are often the focus of seamount research. By comparison few studies have focused on the more enigmatic but no less important infauna. The study of Senghor Seamount, which is located near to the Cape Verde Archipelago in the NE Atlantic, sought to address this knowledge gap and provides the very first quantitative and systematic analysis of a seamount macrofaunal community. In addition to the investigation of seamount macrobenthic community characteristics, the response of the community to a range of environmental variables was also determined. In particular, the potential effect of topography-flow interactions upon the macrobenthic community was investigated. In order to achieve these objectives a Multicorer (MUC) was used to quantitatively sample four transects on the seamount from summit (~100 m) to base (~3300 m) depths. There were a number of key findings. The hydrodynamic regime was found to be particularly complex and was a result of a number of interacting flow components. This was found to alter sediment characteristics and may have also resulted in an alteration of the downward particulate organic carbon flux. Consequently, inter-transect variation of community characteristics was observed at some depth ranges. Depth, and the environmental variables which covary with this gradient, was also found to dominantly structure the community on Senghor Seamount. However, any explanation for the variation of community characteristics on the seamount may be highly multivariate and further biological and environmental observations would be required to adequately resolve these patterns.

Prolific growth of Ulva lactuca L. in some marine environments into which sewage is discharged causes many problems. An understanding of the reasons for this growth is required so that it can be controlled or prevented. The thesis is concerned with tackling this problem and also investigating whether Ulva lactuca can be used as an indicator organism for pollution. Prior to studies on growth of Ulva in polluted conditions, its pattern of life-history and mode of growth had to be elucidated. These findings led to the development of suitable laboratory culture facilities and development of a technique for studying growth by use of excised discs of thallus tissue. Laboratory culture was based upon the use of Erdschreiber medium and growth measured by percentage increase in area after two weeks in culture. Laboratory nutrient bioassays using growth rate measurements were used to determine the effects of likely growth rate stimulating substances found in sewage, including three nitrogen forms, (nitrate-N, nitrite-N and ammonium-N), orthophosphate, acetate, adenine and kinetin, and sewage-contaminated mud itself. Only ammonium-nitrogen within the range 0.4 to 7.8 mg dm -3, and sewage-contaminated mud, were found to significantly stimulate the growth rate of Ulva above that of Erdschreiber control medium. Further growth rate assessments were made with samples of field seawater collected at points throughout two sewage-polluted harbours, Poole in Dorset with an Ulva problem, and Langstone in Hampshire at present without a problem. The results obtained were correlated with the concentrations of nutrients in the water samples, and with results of the earlier artificially enriched seawater experiments. Ammoniumnitrogen was confirmed to be the only compound in field water which significantly stimulated growth of Ulva over that obtained with the control medium. The regions where prolific growth of Ulva occurred in Poole Harbour were the only areas which had field water with ammonium-nitrogen levels elevated to the range &aown in laboratory studies to cause significantly higher growth rates of Ulva discs. Water from Langstone Harbour although sewage-polluted did not stimulate growth of Ulva discs and water analysis revealed. ammonium- nitrogen levels below those determined as growth stimulatory. The ability of Ulva to act as a test organism for a range of toxic substances including industrial/domestic sewage sludge, detergent, copper, zinc, lead, cadmium and mercury was studied. Graded growth responses were obtained for these components, and toxic levels of them were found to be similar to those for other macro-algae. Ammonium-nitrogen was thus found to be the factor responsible for prolific growth of Ulva in the field. In order to prevent or minimise nuisance caused by enhanced Ulva growth it is recommended that the level of ammonium-nitrogen is kept below 0.3 mg dm -3 in seawater at all times. Because of specificity of response to a siaagle compound it is concluded that Ulva cannot be used as a general pollution indicator species, but its prolific growth in the field certainly indicates elevated ammonium-nitrogen levels.

In 1999, the officials of the Nigerian and Sao Tome & Principe’s governments embarked upon delineating their maritime boundary. They discovered that the two nations’ maritime boundary overlapped as a result of establishing their Exclusive Economic Zone; and this area of overlap was found to have enormous hydrocarbon and non-hydrocarbon resources. Several meetings and negotiations ensured and the area of overlap designated a joint development zone. The aim of the research is to evaluate the viability and effectiveness of implementing the recently published Transboundary Waters Assessment Programme-Large Marine Ecosystem indicators to the Nigeria-Sao Tome & Principe Joint Development Zone-an area of sub-Large Marine Ecosystem scale- given the characteristics of the zone and particularly the extent of Illegal, Unregulated, and Unreported fishing around the area. An interview and questionnaire survey was conducted on some selected stakeholders where initial findings revealed a clear lack of information exchange among critical stakeholders, inadequate attention to living resource exploitation in a joint development designated to cover both living and non-living resources, lack of a coherent mechanism to tackle issues of Illegal, Unreported and Unregulated fishing practices among others and most importantly lack of or ignorance on the use and employment of indicators for marine ecosystem assessment as encouraged by scientists. Results from the survey were further compared and evaluated against international best practices where recommendations emerged. This provided insights and lessons upon further evaluations from examples of successful application of use and deployment of indicators for marine resource assessment especially in joint development context for the research area that are capable of being applicable elsewhere in similar scenarios. Feedback and comments were later obtained upon the initial analysis from the main stakeholders responsible for the sustainable management of the Joint Development Zone’s fishery resources. This was then integrated into the research which provided critical insights and key lessons on the use and employment of indicators as well as on the current management arrangements in place for the sustainable management of the Joint Development Zone’s fishery resources.

The Caspian Sea is the world's largest closed body of water, and it has a number of unique features, not least, the considerable fluctuations in water level during the 20th century. This water level dropped by 3 m from 1929 to 1977, increased rapidly by 2.6 m during thetwo decades following, and from 1995 a slow rate of change continues. It is likely that the underlying causes of these water level changes are the human activities in the Caspian Sea Basin but literature shows that climate change also had a significant effect. Moreover, these sea level changes occur in a region with a high intrinsic level of seismic activity due to its tectonic setting. Since the sea level fluctuations represent very large scale changes in the loading of the Earth's crust, it seems likely that they are responsible for aspects of the overall seismicity. This is analogous to the problem of Reservoir Induced Seismicity, although even the largest reservoirs are tiny compared to the Caspian Sea. The research reviews the available data to create a reliable database of seismic events in the desired timeframe and location. It was observed that there was a correlation between the Caspian Sea level fluctuations and changes in regional seismicity. Further analysis indicated changes in the b-value of the Gutenberg-Richter Relationship that had an inverse correlation with water level fluctuations, demonstrating that RIS effects are significant. Through statistical examination of the earthquakes listed in the catalogue, the research attempted to find events which could possibly be induced earthquakes. Another large scale effect of the Caspian Sea level changes is investigated on its coasts where the beach profiles were affected by these changes. This sea is a unique laboratory for studies related to sea level rise and several studies have been performed by other researchers on the northern and western Caspian Sea coast. The southern coast, however, has not been adequately explored, thus this research aimed to investigate this part of the coastline. Three field surveys were made along 700 km of the southern coast. In addition to shore sediment sampling, land forms were mapped. Also, deep sediments were sampled by divers along profiles at right angles to the coast at 5 depths up to a depth of 10 m, and hydrographic profiles were surveyed. Laboratory tests were performed on the collected sediment samples. Several classifications were generated based on different factors, and finally, the southern Caspian Sea coast was classified into four categories with respect to their behaviour in response to sea level change. This study investigates the cause and two large scale impacts of the changing water level in the Caspian Sea, and provides a database for future studies. The result can be applied to predict future problems if the water level of the Caspian Sea continues to show considerable changes.

No description available.

Les otolithes sont des pièces calcifiées de l’oreille interne des Ostéichtyens impliquées dans les fonctions d’audition et d’équilibration. Leur morphologie est utilisée comme indicateur de divers processus ou propriétés écologiques. Cette application nécessite d’identifier les facteurs endogènes et exogènes agissant simultanément comme sources de variation. Cette thèse porte sur la détection et la quantification des contributions relatives de l’asymétrie directionnelle et du régime alimentaire à la variation morphologique des otolithes à l’échelle intra-populationnelle. Une asymétrie directionnelle entre les otolithes droit et gauche est montrée chez les poissons plats, l’otolithe le plus long et large étant toujours du côté aveugle, contrairement aux espèces de poissons ronds pour lesquels l’asymétrie est moindre. Cependant, l’asymétrie n’excède pas 18% d’amplitude suggérant une canalisation de la symétrie de forme d’origine évolutive. Une corrélation entre le régime alimentaire et la forme des otolithes est détectée chez 4 espèces de poissons in situ. La composition du régime contribue plus fortement à la variabilité morphologique que la quantité ingérée et impacte la forme des otolithes à la fois globalement et localement. Une étude expérimentale sur le bar commun (Dicentrarchus labrax) montre que la composition du régime alimentaire en acides gras essentiels au stade larvaire affecte la morphogenèse des otolithes pendant le stade juvénile sans affecter la croissance somatique des individus. Ceci suggère un effet direct et non indirect via la croissance somatique. Cet effet disparait aux stades ultérieurs ce qui évoque une canalisation de la morphologie des otolithes. / Otoliths are calcified structures located in Osteichthyes’ inner ear that are involved in audition and balance. Their morphology is used as an indicator of various ecological processes or properties. This application requires identifying the endogenous and exogenous factors that act simultaneously as sources of shape variation. This thesis aims at detecting and quantifying the relative contributions of directional asymmetry and diet to otolith shape variation at the intra-population level. Directional asymmetry between left and right otoliths was found in flat-fishes, the blind-side otolith being always longer and larger, whereas it was negligible in round-fishes. However, asymmetry amplitude never exceeded 18%, which suggests evolutionary canalization of otolith shape symmetry. A correlation between global diet and otolith was detected in 4 species studied in situ. Diet composition contributed more than food amount to morphological variation and affected otolith shape both globally and locally. An experimental study on sea bass (Dicentrarchus larbrax) showed that diet composition in terms of essential polyunsaturated fatty acids at larval stage affects otolith morphogenesis during juvenile stage without impacting on individuals’ somatic growth. This result suggests a direct effect of diet on otolith shape and not an indirect one through the somatic-otolith growth relationship. This effect disappeared at later stages, morphogenetic trajectories converging back to a similar shape, which suggests ontogenetic canalization of otolith shape.

La population de lieu noir (Pollachius virens) de mer du Nord a une importance économique élevée pour les pêcheries européennes. Depuis une dizaine d’années, l’abondance du lieu noir a décliné, alors que le merlu (Merluccius merluccius), qui était peu pêché dans cette zone, a vu son abondance fortement augmenter. Ce travail se concentre sur la nature des interactions écologiques entre le lieu noir et le merlu en Mer du Nord afin de déterminer si la récente émergence du merlu dans cette zone pourrait expliquer, au moins en partie, le récent déclin du stock de lieu noir. Les résultats obtenus lors de ce travail de recherche ont permis de valider l’hypothèse de compétition entre le lieu noir et le merlu. De plus, cette étude a révélé un impact potentiellement négatif de l’augmentation du merlu sur la biomasse de lieu noir. L’émergence du merlu en mer du Nord doit donc être sérieusement prise en compte dans les avis scientifiques supportant les décisions de gestion encadrant la pêche du lieu noir, mais aussi des autres espèces de mer du Nord que l’émergence du merlu est susceptible d’affecter. Finalement, ce travail fournit donc les premières bases écologiques nécessaires à une investigation plus détaillée des conséquences de l’émergence du merlu dans un écosystème hautement exploité tel que la mer du Nord. / North Sea saithe (Pollachius virens) has high economic value for European fisheries. In recent years, North Sea saithe abundance has decreased, while abundance of hake (Merluccius merluccius), which was rarely fished in the North Sea, has increased dramatically in the area. This work investigate the nature of the ecological interactions between saithe and hake in the North Sea, in order to understand if recent hake emergence in this area could explain, at least partially, the recent decline of the saithe stock. The results obtained during this research suggested competitive interactions between saithe and hake predators in the area. In addition, this investigation revealed potential negative effects of hake emergence in the North Sea on the resident saithe stock. Therefore, hake emergence in the North Sea must be taken into account when managing commercial species fisheries, the sustainability of which may be threatened by this up-coming predator. Finally, the results obtained within this PhD research thesis highlight the importance of hake as an up-coming predator and competitor in the North Sea, and provide the necessary basis for further investigations of hake potential ecological and economic function in this exploited ecosystem.

Coastal marine environments are important for biodiversity and ecosystem services; however human pressure on coastal ecosystems has increased markedly over the last several decades. In order to determine the state of coastal environments apex predators, in particularly seabirds, can be used to monitor these habitats. At the population level monitoring multiple populations of a species can be investigated to identify potential drivers of population changes. However, as many apex predators are long-lived with a low reproductive output there can be a time-lag before detecting changes in population abundance reflecting adverse environmental conditions. Therefore, instead traits which reflect environmental conditions during the breeding season may be useful in monitoring habitats over shorter time frames. Of several widespread seabird species associated with the coastal environment across the region of interest of south-west Scotland and Northern Ireland, the herring gull Larus argentatus was found to show the greatest potential as a monitoring species. Spatial variation in herring gull colony growth rate was observed across the region, potentially driven by the availability of local intertidal and terrestrial resources. I therefore investigate several herring gull traits from multiple colonies to determine whether these alternative traits can effectively be used to monitor the coastal marine environment. In particular I am interested in three features of these traits: (i) do they show spatial variation in the selected colonies across the region of interest; (ii) are these traits sensitive to local environmental conditions reflecting local resource availability and (iii) do the traits relate to a short- and long-term measure of the gulls' demography. Spatial variation between colonies was observed in all selected traits associated with eggs, the extent of marine and terrestrial resources consumed and with the gulls' foraging behaviour; albeit to differing extents. Firstly, I investigate the resource use of herring gulls as food resources are often an important limiting factor in seabird colonies. The resource use of gulls was estimated via two techniques, pellets and stable isotope analysis of chick feathers, which gave comparable results. Colonies located in sheltered coastlines, with more favourable intertidal habitats, were found to forage more on marine items; whilst colonies located nearer built-up areas foraged to a greater extent on terrestrial items. The resources the gulls predominantly consumed were found to influence their demography, with greater breeding success in colonies which consumed a higher proportion of marine resources. Traits associated with the herring gull's eggs showed different sensitivities to local conditions. Both egg colour and volume were found to be influenced by the ambient temperature prior to laying; with larger eggs and less brown eggs in colonies associated with higher ambient temperatures. In colonies with higher local SST and chlorophyll a concentrations, eggs were found to have greater maculation. Egg colour was also found to relate to the gulls' overall breeding success in 2014, with higher final brood sizes in colonies where eggs were less brown in colouration. Finally, investigating the gulls' foraging behaviours, nest attendance was higher in colonies with a higher amount of built-up area within the foraging range; and, during 2013, in colonies closer to farmland. In colonies with higher local SST and chlorophyll a concentrations, provisioning rates were higher and trip durations shorter; whilst provisioning rates were also higher in colonies located in areas of high wave fetch, along more exposed coastlines. Of the foraging behaviours trip duration was found to relate to the gulls overall breeding success; with shorter trip durations in colonies with higher breeding success. These results highlight that herring gull traits are sensitive to local environmental conditions during the breeding season, especially egg maculation, the extent of marine resources the gulls consume and the three foraging behaviours; and therefore may be effective in monitoring the coastal environment. In addition, it suggests that average egg colour, the extent of marine resources the gulls consume and trip duration of a colony, are useful in reflecting environmental conditions as well as reflecting the gulls' demography relating in breeding success. Investigating herring gull traits from multiple colonies, which reflect environmental conditions over shorter time periods than colony GR, may therefore be useful in monitoring the coastal environment. In addition, they may help establish why this species has experienced contrasting colony GR in recent years; leading it to be categorised as a red-listed bird on conservation concern in the UK.

Scottish harmful phytoplankton monitoring programmes, and previous research studies, have shown that the saxitoxin producing (Group I) and, recently, the non saxitoxin producing (Group III) ribotypes of A. tamarense are present in Scottish waters, co-occurring in some locations. Shellfish toxcity events may have been in decline in recent years, possibly due to increasing presence of the benign Group III ribotypes. This thesis investigated the interactions between these two A. tamarense ribotypes. To study these morphologically identicle organisms a fluorescence in situ hybridization-flow cytometry (FISH-FC) based method of cell identification and enumeration was developed, allowing, for the first time, Group I and Group III A. tamarense strains to be studied in co-culture. In isolation, toxin production of the Group I strain was elevated under P limitation as well as at low temperature and short light (spring) conditions. In co-culture a competitive interaction between Group I and Group III ribotypes was clear, with growth rates, maximum cell densities and total toxicity per cell showing marked changes compared to monocultures. Both strains showed a preference for the intermediate temperatures of 15 and 18 °C. Yet despite this, strain differences did occur. The Group III strain out-competed the Group I strain, having a higher biomass and maximum specific growth rate across most of the temperatures studied. The Group III strain also appeared to be able take up and utilise P more effectively that the Group I strain. Mathematical modelling revealed that the observed growth patterns (i.e. dominance of the Group III strain) in mixed culture was not solely due to more efficient nutrient uptake but, additional interaction(s) such as allelopathy were also involved. Laboratory studies assessing a number of Scottish sediment samples identified the presence of Group I, Group III and hybrid cysts, highlighting the possibility that the more dominant ribotype may outbreed the other over time, if as the literature suggests, hybrid crosses fail to produce viable progeny.

La mise en place de l’approche écosystémique des pêches (AEP) requiert une amélioration de nos connaissances sur la complexité des écosystèmes. Comprendre la réaction de l’écosystème à des mesures de gestion est essentiel pour atteindre les objectifs de conservation. La modélisation écosystémique a amélioré nos connaissances sur le fonctionnement des écosystèmes et leurs interactions avec les usages du domaine maritime; et est de plus en plus utilisée pour évaluer l’impact de mesures de gestion. Le comportement de pêche des flottilles démersales françaises en Manche Orientale a été analysé. Les résultats montrent que les pêcheurs conservent leurs habitudes de pêches et que le trafic maritime peut impacter leurs décisions. Une analyse globale des résultats d’études menées au cours des trente dernières années démontre l’influence des habitudes et des espèces ciblées sur le comportement de pêche. L’exploration de la dynamique de l’écosystème a nécessité l’utilisation du modèle Atlantis, en focalisant sur deux espèces commerciales, la sole (Solea solea) et la plie (Pleuronectes platessa). L’importance des zones estuariennes est révélée, ainsi que le rôle joué par les rejets et par deux espèces clés, la morue (Gadus morhua) et le merlan (Merlangius merlangius). La sole et la plie ont peu d’influence sur le réseau trophique excepté sur la dynamique des invertébrés benthiques. Nous évaluons les conséquences de l’application de fermeture de zones et d’une réduction d’effort sur le comportement de pêche et l’écosystème et mettons en évidence un bénéfice de l’application combinée de ces mesures sur la biomasse des espèces commerciales et sur la valeur débarquée par unité d’effort. / The implementation of the ecosystem approach to fisheries management (EAFM) requires an enhancement of our knowledge of ecosystem complexity. Understanding the ecosystem reaction to management regulation is a key to achieve conservation objectives. Ecosystem modelling improves our knowledge on ecosystem functioning in interaction with human activities, and it is now widely used to evaluate management strategies. The fishers’ behaviour of the French demersal fisheries in the Eastern English Channel (EEC) has been investigated. Results showed that fishers tended to adhere to past annual fishing practices and maritime traffic may impact on fishing decision. A global analysis of the fisheries science literature during the last three decades evidenced the influence of tradition and species targeting in fishers’ behaviour. The exploration of ecosystem dynamics required the use of the ecosystem model Atlantis with a focus on two commercial flatfish species, sole (Solea solea) and plaice (Pleuronectes platessa). The importance of estuary areas and of nutrient inputs has been revealed as well as the role of discards and of two key species, cod (Gadus morhua) and whiting (Merlangius merlangius). Sole and plaice did not have a strong influence on the trophic network excepted on the benthic invertebrates’ dynamics. Finally, we investigated the consequences of area closure and effort reduction on fishers’ behaviour and the ecosystem impacted. We observed a noticeable benefit of combining area closure and effort reduction on the biomass of most commercial species and on the total value landed per unit effort.