No description available.

Thesis (Ph. D.)--University of Auckland, 1990. / Includes bibliographical references.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. / Includes bibliographical references.

Ocean acidification (OA) together with other anthropogenic perturbations is projected to dramatically alter marine environments over the coming centuries. The vast majority of marine species reproduce by freely spawning sperm directly into the water column, where fertilisation can then either be external or a female can draw sperm into a burrow, brooding chamber or onto her external surface. Hence, sperm are now being released into rapidly changing seawater conditions. In this thesis, I firstly assess what is currently known on the potential for OA and other anthropogenic stressors to influence freely spawned sperm in marine invertebrate taxa. I then present a series of experimental chapters investigating the influence of OA, as a single stressor or in conjunction with a second stressor, copper, on sperm function, physiology and competitive fertilisation performance in a range of invertebrate taxa. My research demonstrates that sperm are vulnerable to the projected changes in seawater carbonate chemistry under OA, with responses observed at all biological levels from sperm physiology, swimming performance, fertilisation ecology and sperm competitiveness. In a multi-stressor experiment on polychaete gametes and larvae, I provide empirical evidence that changes to seawater pH under OA can alter the susceptibility of early life stages including sperm, to the common coastal pollutant copper. Sperm DNA damage increased by 150 % and larval survivorship was reduced by 44 % in combined exposures, than when exposed to copper alone. As a single stressor OA also acted to significantly reduce Arenicola marina sperm swimming speeds and fertilisation success. This work was followed up with a mechanistic investigation of A. marina sperm swimming performance under OA conditions. I found that the length of time between spawning and fertilisation can strongly influence the impact of OA on sperm performance. Key fitness-related aspects of sperm functioning declined after several hours under OA conditions, and these declines could not be explained by changes in sperm ATP content, oxygen consumption or viability. In a final set of experiments, I ran a set of paired competitive fertilisation trials in the sea urchin, Paracentrotus lividus. In addition to reducing fundamental sperm performance parameters, OA conditions affected competitive interactions between males during fertilisation, with potential implications for the proportion of offspring contributed by each male under the new conditions. This work suggests that the ‘best’ males currently may not be the most competitive under OA. Overall this body of work reveals a series of significant changes to sperm performance under OA that might act to perturb sperm functioning in future oceans.

Orientadores: Gisela de Aragão Umbuzeiro, Guilherme Ribeiro Lotufo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-22T02:19:34Z (GMT). No. of bitstreams: 1 Artal_MarianaColetty_M.pdf: 1329770 bytes, checksum: e43efcef07526606b4d54de36469576e (MD5) Previous issue date: 2013 / Resumo: A produção e uso de corantes representam números relevantes no mundo e no Brasil. Efeitos ecotoxicológicos desses compostos, especialmente frente a organismos estuarinos e marinhos são ainda pouco explorados. Neste estudo avaliou-se a toxicidade dos azo corantes C.I. Disperse Red 1 e C.I. Disperse Red 13 para o copépodo estuarino Nitokra sp. avaliando efeitos adversos como a imobilidade e o sucesso de eclosão dos ovos antes e após tratamento fotoeletroquímico. Os corantes Disperse Red 1 e Disperse Red 13 apresentaram toxicidade para o teste de imobilidade com concentração efetiva CE50(96h) de 0,3 a 2,1 mg.L-1 (n=4) e 1,5 mg.L-1 (n=2), respectivamente. As concentrações que causaram efeitos adversos na taxa de eclosão de ovos foram maiores ou próximas à CE50 de imobilidade, demonstrando que esse endpoint não foi mais sensível como esperado. Testes realizados após o tratamento fotoeletroquímico dos mesmos corantes mostraram que a toxicidade tanto no teste de imobilidade quando no teste de sucesso de eclosão de ovos foi reduzida. Esse tratamento mostra-se promissor para o tratamento desses compostos, porém, cabe ressaltar que a utilização de sal para o tratamento é interferente e causa toxicidade quando descartado ou disposto em ambientes de água doce / Abstract: Production and use of dyes represent relevant numbers in the world and in Brazil. Ecotoxicological effects of these compounds, especially to estuarine and marine organisms are unknown. This study evaluated the toxicity of the azo dye CI Disperse Red 1 and CI Disperse Red 13 to an estuarine copepod Nitokra sp. evaluating adverse effects measured as immobility and egg hatching success before and after photoelectrochemical treatment. Both dyes Disperse Red 1 and Disperse Red 13 were toxic with immobility effective concentration EC50 (96h) in the range of 0.3 to 2.1 mg.L-1 (n= 4) and 1.5 mg.L-1 (n= 2), respectively. The concentrations that caused adverse effects on the success of eggs hatching were higher or close to the EC50 immobility, demonstrating that this is not the most sensitive endpoint as expected. Tests performed after photoelectrochemical treatment showed that the toxicity of both tests was reduced. This treatment shows promise for the treatment of these compounds, however, it is worth noting that the use of salt for treatment is interfering and cause toxicity when discarded or disposed of in freshwater environments / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

>Magister Scientiae - MSc / Marine invertebrate associated (MIA) bacteria are an important source of bioactive secondary metabolites with the potential to address the current anti-microbial resistance crisis experienced globally. Secondary metabolites (SM) have historically yielded several compounds with pharmaceutical applications such as anti-viral, anti-microbial, anti-cancer, anti-inflammatory and anti-parasitic. This study aimed to use bioassay and genomic approaches in the identification of MIA bacteria isolated from South African marine invertebrates as a source of bioactive compounds and the characterisation of the produced SMs using analytical techniques. A total of 23 MIA bacteria were cultured under different conditions (one strain many compounds approach (OSMAC)) to evaluate their ability to produce anti-microbial compounds against a panel of indicator strains namely Escherichia coli 1699, Bacillus cereus ATCC10702, Pseudomonas putida ATCC12633, Mycobacterium aurum A+, Staphylococcus epidermidis ATCC14990, Aspergillus fumigatus MRC and Candida albicans NIOH.

Thesis (Ph.D.) - University of St Andrews, April 2006.

This work is focused on characterising and evaluating the intensity and selectivity of the marine fauna during the Tr/J mass extinction and recovery of the ecosystem in different localities throughout Pangaea. To address this, four localities were studied: St. Audrie’s Bay, Larne and Pinhay Bay in the UK, and Portezuelo Providencia in Chile. From each locality, samples were taken at approximately 1m intervals throughout the Tr/J sections. Species abundance per sample was estimated and each species was classified according to autoecological information derived from the literature. In order to assess changes in the structure and composition of the assemblages, NMDS and beta diversity index were performed, dominance and richness were estimated and the data were tested against five rank abundance (RAD) models. Ecospace modelling was used to estimate the loss in ecological diversity. Measures of the body size of bivalves and ichno-parameters were recorded on each section. Through the UK sections, the richness, dominance and the composition rate shifted abruptly during the extinction event. A geometric model shows the best fit during extinction events and, in contrast, a log-normal model best fits the pre-extinction and recovery event. The body size of the bivalves did not decrease during the Tr/J, while the coverage, richness and body size of ichnofossils increased during the recovery. The Chile Tr/J section records low richness, but the ecological complexity and richness decreases through the interval and composition records high turnover, while the dominance increases. The results indicate that the Tr/J disruption changed species composition in a relatively short time period, which decreased the ecological functionality of the invertebrate marine assemblage. In spatial terms, the UK fauna show a clear response to the extinction effect, but the diversity response of the Chilean assemblage is not clear at all, which may be related to taphonomical bias. Alternatively, this work analysed stage-by-stage occupation of ecospace of 3181 genera recorded from Sepkoski`s compendium for the marine fauna from the Late Permian to Early Jurassic. The ecospace can be represented as a combination of the three axes of tiering, motility and feeding, each divided into six subcategories. From the Cambrian to Recent, ecospace utilisation has tripled, however the trend through the Phanerozoic remains unclear. This result indicates that from the Guadalupian to Sinemurian the number of modes of life did not increase significantly, but the ecospace packing does. There was a significant positive correlation between abundance of predators and both infaunalisation and motility. However, the ecospace utilisation decreased 35% and 16% at the end of Permian and Triassic, respectively. During the extinction events, non-motile animals, organisms with little physiological control of biocalcification and the epifaunal forms, were heavily affected. This indicates that the mass extinction had a particular ecological effect on the biota and is an important episode of ecological changes due to ecological selectivity. Parallel, the appearance of adaptations to new trophic niches during the Triassic, like durophagy, presumably increased predation pressure and drove the increase in benthic infaunalisation. This series of adaptation could be potentially associated with the Marine Mesozoic Revolution.

No description available.

As the biomass of jellyfish (medusae of the Scyphozoa and Hydrozoa) has risen in numerous locations worldwide, awareness of their potential to exert a controlling influence on marine ecosystems and hinder the recruitment of fish stocks has increased. Medusae are capable of intensive, size–selective, predation on zooplankton, which may alter the composition of the plankton community. Jellyfish are often found in dense layers, up to hundreds of metres thick, which can extend horizontally for hundreds of kilometres. Such aggregations may benefit specialist feeders, such as turtles, that rely upon jellyfish for food and those fish that are able to find refuge under the jellyfish umbrellas. Nonetheless, the predominance of jellyfish in pelagic ecosystems is not generally viewed as desirable; in fact, this situation has been portrayed as the result of pollution and overexploitation of otherwise productive seas. However, jellyfish are sensitive indicators of environmental change, and their populations appear to respond to climatic fluctuations, so jellyfish warrant study for their intrinsic ecosystem role particularly given present concerns over climate change. With growing acceptance that fishery management should take an holistic ‘ecosystem approach’, knowledge of the interactions between jellyfish, fisheries and climate may be vital in progression towards the goal of ecosystem–based sustainable management of fisheries. Unfortunately, due to their gelatinous nature, medusae are difficult to sample using conventional netting techniques and data on changes in distribution and abundance are consequently sparse. Recent studies have demonstrated that medusae can be detected acoustically and that this technique could provide a rapid and cost–effective estimate of their biomass and distribution. This thesis reports my endeavour to demonstrate the ecosystem role of medusae and to develop acoustic techniques to monitor their biomass. Through regession analyses, I link the abundance of medusae (Aurelia aurita, Cyanea lamarckii, and Cyanea capillata) in regions of the North Sea to climatic fluctuations, as quantified by the North Atlantic Oscillation Index, and show that medusae may be important indicators of regional ecosystem change. The mechanisms linking climatic fluctuations to ecosystem changes are explored via a correlative modelling approach using General Additive Models; I show that the mechanisms are location dependent and explainable in terms of direct, rapidly responding (intra–annual) influences (surface warming, river run–off, and wind–driven mixing and advection) and longer–term (interannual) oceanographic responses (changes in circulation currents i.e. the northward extent of the gulf stream and relative strength of inflow into the North Sea of the North Atlantic current, Continental Shelf Jet and Arctic waters). I present correlative evidence for a detrimental impact by Aurelia aurita on herring 0–group recruitment, once the influence of interannual change in herring spewing stock biomass on recruitment is factored out through modelling with a Ricker stock–recruitment relationship. Similarly, a commensal relationship between whiting and Cyanea spp. medusae is shown to improve North Sea whiting survival to the 1–group. In progress towards the automated acoustic identification of species, I have developed an in situ discrimination tool that can distinguish between echoes from: Aequorea aequorea; Chrysaora hysoscella; clupeid fish (sardine, anchovy and round herring); and horse mackerel/Cape hake. The technique relies upon characteristic differences in echo strength between frequencies, which are determined for each jellyfish species and finfish group using combined multifrequency acoustic and pelagic trawl samples. This method has facilitated the world’s first acoustic–based estimate of jellyfish biomass in the Namibian Benguela Sea. The 12.2 million tonnes of biomass of medusae (Aequorea aequorea and Chrysaora hysoscella) in the Namibian Benguela Sea was found to be greater than the combined biomass, 3.6 million tonnes, of commercially important fish (horse mackerel, Cape hake, sardines, anchovy, and round herring) in the same area. These results suggest that medusae may have an important role in the Benguela ecosystem that has previously been overlooked and that their biomass should be monitored.