The potential impacts of marine aquaculture operations on the environment are reviewed. The reported effects of suspended mussel farms on the benthic environment are examined and the potential impacts discussed. A framework to assess the impacts of suspended mussel farms is presented. The use of simulation models to predict the impact of fish farm wastes on the benthic environment is discussed and the mathematical theory supporting such models is presented. The applicability of these models to mussel farming is discussed and the data required to undertake such modelling identified. The effect of increased sedimentation on the macrobenthic community, physical structure and biogeochemistry of the surficial sediment around three suspended mussel farms are examined. At one site, the benthic community was subjected to bulk sedimentation, organic enrichment and reduced macrobenthic infaunal diversity. Elevated levels of organic carbon were recorded close to the farm. At the remaining two sites, benthic impacts were less clear and not demonstrably due to the mussel farms. The settling velocity of mussel faeces and pseudofaeces was required to enable modelling of particles ejected from the farm sites. An experiment was devised to measure this parameter.- The settling velocity of mussel faeces (~0.5 cms-I ) was less than pseudofaeces (~1 cms-I ). Differences in these settling velocities were attributed to the organic content and particle size of the excreted matter. The particle tracking model DEPOMOD (Cromey et at., 2000a) was used as a platform from which to develop a simulation model predicting the benthic impact of suspended mussel farms. Parameters within the model were modified to be represent a mussel farming scenario. Data from the three sites surveyed were applied to the model. Although the model results compared favourably with the field data, the model tended to overestimate the benthic impact as measured by the Infaunal Trophic Index. The results of the model are discussed and improvements and further experiments are identified.

Certain organophosphorus compounds have the ability to induce a delayed neuropathic condition in sensitive species termed organophosphorus compound-induced delayed neurotoxicity (OPIDN). Esteratic changes associated with OPIDN have been successfully modeled in vitro. The physical characteristics of lesion development in OPIDN including the mode of nerve cell death, cytotoxic initiator and effector molecules, and cytoskeletal involvement have received little in vitro investigation. This dissertation evaluated the mode of cell death (apoptosis versus oncotic-necrosis), and cell cycle, cytoskeletal, nuclear, and mitochondrial alterations induced by OP compounds in SH-SY5Y cultures, an in vitro human neuroblastoma model. The distribution of in vivo neural degeneration in white Leghorn hen models was also assessed as a prelude to validating the mode of OP compound-induced in vivo neural cell death. These endpoints were evaluated by utilizing flow cytometry, spectrophotometry, gel electrophoresis, immunohistochemistry, light, and electron microscopy. Initial data gathered on culture parameters revealed that the mitotic status, basal rates of cell death, and total culture density were dependent on the condition of the media and the initial seeding density. Subsequent in vitro investigations used standardized culture conditions with OP compounds (diisopropylphosphorofluoridate (DFP), paraoxon, parathion, phenyl saligenin phosphate (PSP), tri-ortho-tolyl phosphate (TOTP), and triphenyl phosphite (TPPi); 1uM - 1mM). These studies revealed that OP compounds altered the cell cycle phase, decreased the amount of intracellular f-actin, altered the mitochondrial membrane potential, and induced caspase-3 activation and nuclear partitioning characteristic of apoptosis. The amount of change in these parameters was strongly dependent on the OP compound, the length of incubation time, and the presence of modulators of cytotoxicity such as phenylmethylsulfonyl fluoride (PMSF), carbachol, Ac-DEVD-CHO, Ac-IETD-CHO, and cyclosporin A. Preliminary in vivo experiments designed to validate in vitro results revealed neural degeneration involving fibers, terminals, and cell soma in spinal cord and brain tissue of PSP- and TPPi- exposed hens. The distribution and magnitude of these changes were contingent on the OP compound and length of time post-exposure. Subsequent experiments designed to evaluate the mode of cell death in these tissues revealed little evidence of either necrosis or apoptosis. These results, therefore, did not support or refute in vitro observations. Many OP compound-induced subcellular alterations have been demonstrated in our in vitro SH-SY5Y neuroblastoma model. Even though the mode of cell death observed in SH-SY5Y cells was not validated in in vivo experiments, in vitro observations nonetheless provide stimulating areas to further research the mechanisms of OPIDN and OP compound-induced cell death. / Ph. D.

Perceived conflicts between piscivorous birds and commercial freshwater fisheries are common, and such a perception exists at Loch Leven, a wetland of international importance for nature conservation and a famous commercial brown trout Salmo trutta fishery, where Great Cormorants Phalacrocorax carbo have been shot in large numbers. This thesis describes the foraging behaviour of cormorants wintering on Loch Leven. It summarises changes in wintering numbers over a 32 year period, and reviews data on fish populations, fish stocking rates, angling catches and angling effort in order to seek evidence of detrimental impacts of cormorants on the fishery, and beneficial effects of large-scale cormorant shooting. Finally, this thesis considers turnover within the wintering cormorant population, and its implications for cormorant control. Cormorants spent most of the time roosting, and a single peak of feeding activity occurred early in the morning. Compared to early or late winter, cormorants showed higher foraging activity during mid-winter. Both solitary feeding and flock feeding were recorded, with flock feeding predominating. Solitary feeding was distributed over a wide area. The intensity of flock feeding was less evenly distributed, with 36% of grid squares not used. Overall, 78% of flock feeding activity took place in 23% of grid squares and 59% took place in 13% of grid squares. The best predictor of both solitary feeding and flock feeding intensity of use was mean water depth. Mean water depth was also the best predictor of winter brown trout distribution, although winter brown trout distribution was not a predictor of either solitary feeding or flock feeding intensity of use.

Five species of sea turtle are known to nest on the north and east coast beaches of Trinidad, West Indies. In descending order of abundance: the leatherback (Dermochelys coriacea), the hawksbill (Eretmochelys imbricata), the green (Chelonia mydas), the olive ridley (Lepidochelys olivacea) and the loggerhead (Caretta caretta). This thesis investigates a number of aspects of the ecology and conservation of the sea turtles nesting and foraging on the north coast. Prior to this project, little research had been carried out on the north coast region, largely due to the difficulties of accessing the nesting beaches. The main aims of the project include making reliable estimates of the annual nesting population size of each species, to identify the main threats to the turtles at various life stages, and to make recommendations on how best to conserve the sea turtles in Trinidad. Overall, this thesis offers an up-to-date overview of the status of the sea turtle populations nesting on the north coast of Trinidad. The results presented here highlight Trinidad’s importance as a region for turtles, especially for nesting leatherbacks, foraging greens and nesting and foraging hawksbills. This study will be useful in assisting the Trinidadian Government to meet their obligations under the Biodiversity Convention, and in facilitating the assessment of the remaining leatherbacks in the Atlantic. Recommendations are made for future conservation and management.

Experiments were carried out to identify the environmental factors influencing survival during emersion with the aim of suggesting modifications to present transit conditions in order to minimise physiological stress, thus improving scallop condition and survival. Results showed that increasing the emersion temperature from 5 to 20oC caused a reduction in maximum survival time of 62%. Similarly, reduction in relative humidity, from 95 to 70% saturation, resulted in 27% reduction in maximum survival time. Scallops exposed to a fine sea-water mist showed a 13% improvement in survival and the survival of scallops tested in December was 67% better than those tested in July. This seasonal effect appeared to be correlated with tissue glycogen concentrations which decreased by 29% over the same period. Maximum survival of any emersed scallop was 166 hours, although the animals were not in an edible condition after this time. Experimental factors which were found not to influence survival directly were packing orientation, enforced shell-valve closure and hypertoxic conditions (˜100% oxygen). These results implicated aspects of energy metabolism as the primary causes of scallop death during emersion and therefore this area was investigated in more detail. Further work showed that, heart rate had a positive linear relationship with temperature until ˜19oC. Thereafter, heart rate became irregular and uncoordinated, suggesting that poorer survival at high temperature is caused by loss of physiological integration and difficulty in meeting increased metabolic demands. The oxygen consumption rate of Pecten maximus in air is reduced to only 50% of the aquatic rate within 8 hours of emersion. This decline in respiration rate continued and was typically between 25 and 30% of the aquatic oxygen consumption rate after 60 hours in air. In addition, heart rate, haemolymph PO2, haemolymph pH and mantle cavity fluid PO2 and pH all decreased during emersion, implying that respiratory and circulatory systems were deteriorating.

During the course of this programme of work, two related studies were carried out in collaboration with colleagues in the Division of Ecology & Evolutionary Biology. Together with Hussein Jen-Jan, we explored some hidden costs of an aggressive, proactive life style by examining respiratory function in relation to coping strategy in common carp (chapter 6).  Morphometric analysis of the fine structure of the gills was used to estimate respiratory area and histological analysis of sections through the gill filaments was used to measure the extent to which the secondary lamellae were obscured by epithelial cells. There was a significant relationship between risk-taking phenotype and both the size of the respiratory surface and the extent to which this is exposed as opposed to covered with epithelial cells. Risk-taking fish had larger and more exposed respiratory surfaces than did risk-avoiding fish, with fish with intermediate risk-taking phenotype having intermediate scores. These differences are interpreted as an adaptation to the known high resting metabolic rate of risk-taking fish (Chapter 6).  Together with Priyadarshini, we look at social interactions and growth in relation to risk-taking phenotype in goldfish. Within the social groups, though most goldfish showed no aggressive behaviour, some of the fish attacked their companions at least once per minute of observation and some individuals showed as many as 8 attacks per minute. These levels are surprisingly high for what is usually seen as a non-aggressive species. In groups comprising 3 goldfish of each risk-taking category, the risk-avoiding fish showed relatively little aggression. Overall, fish that showed any aggression within social groups gained preferential access to a restricted food supply (Chapter 6).  There were no differences in weight, length or condition between risk-taking and risk-avoiding goldfish at the point of initial screening, but by the end of the experiment the risk-avoiding fish held in groups with other risk-avoiders had gained less weight and had strikingly lower condition factors compared to the other categories of fish (i.e. all risk-avoiders and risk-takers held in mixed groups). It is suggested that some sort of social facilitation of fear keeps levels of stress high in groups composed entirely of risk-avoiding fish (Chapter 6).  The implications of all these results are considered in a final general discussion (Chapter 7).

Le corps humain est composé de plusieurs milliards de cellules neuronales, lesquelles ont un impact primordial sur les systèmes vitaux. En effet, le système nerveux, étant lui-même un système vital du corps humain, effectue de nombreuses fonctions afin de voir au bon fonctionnement des autres systèmes du corps, tels que le système cardiovasculaire, le système digestif, le système musculaire et bien d’autres. Plusieurs maladies neurodégénératives telles que l’Alzheimer et la maladie de Creutzfeldt-Jakob, affectent les cellules nerveuses du corps et occasionnent la perte de différentes fonctions causant une diminution du bien-être et pouvant mener à la mort. La hausse du nombre d’individus atteint de maladies neurodégénératives observée au fils des ans nous montre l’importance de comprendre les phénomènes moléculaires qui se produisent lors des mécanismes de dégénérescence axonale dans les neurones. Lors de ma maîtrise dans le laboratoire du professeur Richard Blouin, j’ai étudié l’impact d’une augmentation intracellulaire de calcium sur la protéine dual leucine zipper kinase (DLK) en utilisant un modèle cellulaire humain, les SH-SY5Y. J’ai pu démontrer que l’entrée de calcium dans la cellule avait un impact sur la quantité de protéine DLK présente dans celles-ci. En effet, j’ai pu observer une diminution de la quantité de DLK dans les cellules suite à une entrée de calcium, un phénomène exclusivement calcium-dépendant. À l’aide d’inhibiteurs pharmacologiques, j’ai pu montrer l’implication, des calpaïnes, des protéases calcium-dépendantes reconnues pour leur rôle dans la dégénérescence axonale. Les essais in vitro montrent que DLK est une cible spécifique des calpaïnes.

Social interactions and aggression among salmonid fish are known to induce stress responses, particularly in subordinate fish, and the physiological effects of these stress responses have implications for fish in both aquaculture and natural environments. The physiological responses exhibited by subordinate fish (i.e. those fish that are low ranking in a social hierarchy) vary depending on the nature and extent of the social interaction and can also be influenced by environmental factors. Artificial environments - typically aquaria - generally elicit a larger stress response in the subordinate fish due to the fish being held in close confinement. The present study has clearly demonstrated that the physiological responses to social interaction and the formation of dominance hierarchies in rainbow trout and brown trough are affected by the environment of the fish e.g. whether the environment is artificial or natural, and stable or subject to fluctuations. In an artificial environment, the present study has confirmed that the effects of the social stress encountered by subordinate fish include decreases in growth rate and condition and increases in plasma cortisol but has also demonstrated decreases in the ability to secrete further cortisol and increases in the standard metabolic rate of subordinates. In a semi-natural environment these physiological consequences of subordinance were seen to be reduced; indeed with the presence of environmental perturbations no physiological differences were noted between dominant and subordinate fish. Finally the present study also investigated the role of cortisol in chloride cell proliferation and the determination of social status and concluded that cortisol appears to play a mineralocorticoid role in the proliferation of chloride cells and may also influence the outcome of social interactions.

Zur SLC22-Genfamilie von Karnitin- und organischen Ionentransportern gehören u. a. auch die organischen Kationentransporter der Ratte rOCT1 und rOCT2 sowie deren humane Analoga. Diese funtionell bereits gut charakterisierten Proteine werden in verschiedenen Geweben exprimiert und transportieren endogene und pharmakologisch relevante Substanzen. Die Aufklärung des Transportmechanismus und der Regulation sind Gegenstand intensiver Forschungsbemühungen. In dieser Arbeit wurde durch elekrophysiologische Methoden, die modifiziert auch zur Messung von Membrankapazitäten und des Strom-Teilchen-Aufnahmeverhältnisses (CFR) eingesetzt wurden, der Effekt des ungeladenen, membranpermeablen SH-Gruppenregenz MMTS auf den in Xenopus laevis-Oozyten exprimierten rOCT1 untersucht. Durch MMTS kam es zu einer Aktivierung von substratinduzierten Strömen und Kapazitätsänderungen, einer unterschiedlichen Veränderung von Substrat- und Inhibitoraffinitäten sowie einer Zunahme der absoluten Oozytenmembrankapazität. Die CFR und die Spannungsabhängigkeit änderten sich nicht. An rOCT2 konnten teils gleich-, teils gegensinnige Veränderungen nach MMTS-Exposition gezeigt werden. Diese Phänomene können am ehesten durch eine Konformationsänderung der polyvalenten Substratbindungsregion, einen verstärken Membraneinbau der Transportermoleküle und eine gesteigerte Transportrate des Einzeltransporters erklärt werden. Durch die Untersuchung von Mutanten konnten die Cysteine 322 und 451 als essentiell für den MMTS-Effekt identifiziert werden. Die Daten deuten darauf hin, dass die Modifikation dieser Cysteine für die Effekte zwingend erforderlich ist. Möglicherweise ist aber ein Xenopus-eigenes Regulatorprotein an der Entstehung der Effekte beteiligt, welches in die entsprechenden Proteinregionen des rOCT1 eingreift. Mit der Identifikation von Cystein 451 konnte ein weiterer Beweis für die wichtige Bedeutung der 10. Transmembrandomäne erbracht werden. Mit dem Cystein 322 wurde eine weitere wichtige Aminosäure für die Funktion und möglicherweise auch die Regulation von rOCT1 identifiziert. / rOCT1 and rOCT2 are functionally well characterised members of the SLC22-transporter family. It includes carnitine and organic cation and anion transporters. OCTs are expressed in a variety of tissues and transport a number of drugs and endogenous substrates. Their transport mechanism and regulation are currently intensively being investigated. MMTS is an uncharged and membrane-permeable SH-reactive substance. Using electrophysiological methods the effect of MMTS on rOCT1 expressed in X. laevis-oocytes was investigated. These methods were modified to measure membrane capacitance and current-flux-ratios. MMTS-exposure induced an activation of substrate-induced currents and capacitance changes, a differing alteration of substrate and inhibitor affinities and an increase in the absolute oocyte membrane capacitance. The transport stoechiometry and voltage dependence were not influenced by MMTS exposure. Properties of rOCT2 were partially altered in the same and partially in the opposite way. The effects can most likely be explained by a conformational change of the polyvalent substrate binding region, an increased membrane insertion of OCT molecules and an increased substrate turnover number of the single transporter. Investigating mutants the cysteines 322 and 451 could be identified to be essential for the MMTS-effect. The data suggest that the modification of both cysteines is absolutely necessary to create the seen effects. However the participation of a Xenopus regulatory protein for the induction of the MMTS-effect interfering with the mentioned OCT regions must be taken into account. The identification of cysteine 451 proves once more the importance of the 10th TMD within the OCT family. Cyteins 322 might be another important amino acid for functional properties and the regulation of organic cation transporters.

No description available.