Thesis (M.S.)--Rutgers University, 2008. / "Graduate Program in Ecology and Evolution." Includes bibliographical references (p. 73-77).

The Dona and Roberts Bay watershed comprises one of the five major watersheds in Sarasota County, Florida. It is connected to the Gulf of Mexico via Venice Inlet. Like many estuaries in the Florida, significant modifications have been made to the drainage basins, principally to the main tributaries. The system has undergone several anthropogenic modifications to enhance water management efforts. Creeks that comprise fresh water input into the system have been dammed in order to inhibit the upstream flow of salt water during the dry season. They are also deepened or lengthened to allow for better drainage. In addition, biogenic activity has also had morphological effects on the system. There are numerous oyster bars, and mangrove forests that impose obstruction to the tidal and river flows. This has resulted in a highly complicated estuary system in terms of flow velocities and sedimentation patterns. The objectives of this study are to quantify the sediment characteristics and deposition-erosion trends and their relationship to flow patterns and other natural and anthropogenic factors within the system. A detailed sedimentary analysis was conducted based on 149 surface sediment samples and 29 drill cores. Spatial distribution of the sediment properties is quite complex, controlled by several interactive factors including; local sediment supply, intensity of the hydrodynamic processes, distribution of oyster bars and mangrove islands, and artificial structures. Sedimentation and erosion is significantly influenced by flood events. In some locations, such as the mouth of the fluvial channels, or the confluence of two creeks, the core data suggest that rapid sedimentation, driven by flood events, is responsible for the development of some of the large shoals. A 2-D depth-averaged circulation model was established for the study area. Many of the natural structures and artificial modifications to the watershed system are incorporated into the model. A close relationship between the flow intensity and sediment characteristics, and therefore, sedimentation-erosion tendency is identified. Remotely sensed data is also incorporated into the study in order to gain an understanding of the development of the estuary system over a ten-year period. Data suggests that the maturation of biogenic organisms that inhabit the system coincides with the development of complex sedimentation patterns.

Heavy metals present in high concentrations in aquatic habitats are bioaccumulated within the tissues of intertidal organisms. The chemical analyses of animal tissues and sediments provide an indication of bioavailability of heavy metals in the environment. Monitoring of the coastal pollution using organisms is widely practiced all over the world.Chemical analysis of the tissues of Pacific oyster, Crassostrea gigas, and river sediments were used in this study to monitor the environmental concentrations, of cadmium, copper, lead and zinc of shallow coastal areas near to the river mouths of Mahurangi, Awaruku, Waiake, Taiorahi and Wairau. All of these river mouths are situated along the northeastern coast of Auckland. Each month, during the period of November 2002 to October 2003, three replicate samples of oysters, and sediments were collected from each of the river mouths for analysis. Three additional replicate samples of oysters were collected separately, in each month in order to calculate the condition index of oysters. Oyster tissues and sediments were analysed with Inductively Coupled Atomic Plasma Emission Spectrometer to detect the concentration levels of cadmium, copper, lead and zinc.The highest level of copper and zinc concentrations in the oyster tissues was observed in the river mouth of Wairau. Wairau river mouth receives water from heavily urbanised and industrialised catchments. A higher concentration of cadmium was observed in the oysters of the river mouth of Mahurangi than in the oysters in the other sites. The reason for this difference could be due to the heavy use of cadmium contaminated fertilizers at the pasture lands situated around the Mahurangi estuary. Therefore, the relationship between the land use of the catchments and the degree of pollution of the estuarine habitats could be established from the data obtained from this study. Higher concentrations of heavy metals were found in the sediments of Waiake, Taiorahi and Wairau compared to the sediments of Mahurangi and Awaruku. Significantly higher level of copper was observed in the sediments of Awaruku. However no clear co-relation was found between heavy metal concentration in oysters and in sediments. Variations of the condition of oysters were closely related to seasonal changes of the life cycle of the oysters. No clear relationship was found between the condition of the oysters and the heavy metal concentration of the river mouth habitats.This study provides evidence that Pacific oysters are good organisms to use as bioindicators of environmental heavy metal levels in shallow coastal waters. The results of this study suggest a clear relationship between the heavy metal concentration in river waters and the land use of the catchment areas of those rivers. The results may be useful in management strategies of the northeastern coastal areas of Auckland.

Thesis (Ph. D.)--University of New South Wales, 2003. / Also available online.

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed May 30, 2008; title from title screen. Includes bibliographical references (p. 62-66).

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Haiqiang Chen, Animal & Food Sciences. Includes bibliographical references.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Os coliformes termotolerantes tÃm sido descritos como um dos melhores indicadores de contaminaÃÃo de ambientes aquÃticos por resÃduos humanos, sendo amplamente utilizado como parÃmetro para classificaÃÃo de Ãreas onde se cultiva ou extrai ostras. Dentre os membros deste grupo, a Escherichia coli se destaca como uma espÃcie potencialmente patogÃnica, representando risco para a saÃde pÃblica quando associada ao consumo de moluscos bivalves crus ou parcialmente cozidos. Entretanto, pouco à sabido sobre a colonizaÃÃo nos tecidos desses moluscos e/ou distribuiÃÃo dessas bactÃrias entÃricas. O presente estudo teve como objetivos:(i) quantificar coliformes termotolerantes do fluido corporal e dos sÃtios anatÃmicos, separadamente;(ii) isolar e identificar E. coli de amostras de ostras comercializadas in natura na Praia do Futuro, Fortaleza-CearÃ;(iii) avaliar o perfil de virulÃncia e resistÃncia a antimicrobianos dos isolados de E. coli. Foram realizadas dez coletas no perÃodo de fevereiro a abril de 2012, sendo analisadas dez ostras por coleta, divididas em um fluido corporal (lÃquido intervalvar) e dois sÃtios anatÃmicos (mÃsculo e trato gastrointestinal). Os resultados apontaram trÃs amostras com contagens de coliformes acima do limite estabelecido pela legislaÃÃo n 12 de 2001 da ANVISA, tendo o lÃquido intervalvar apresentado o NMP mais elevado em seis amostras. Das 137 cepas de E. coli isoladas, verificou-se maior incidÃncia de resistÃncia à tetraciclina e oxitetraciclina (19%), com variaÃÃo do Ãndice de MÃltipla ResistÃncia (MAR) entre 0,250 e 0,625. Observou-se ainda a presenÃa de cepas produtoras de enzimas beta-lactamases de espectro estendido, porÃm nenhuma das cepas testadas apresentou produÃÃo de biofilme. A elevada frequÃncia de resistÃncia à oxitetraciclina sugere uma pressÃo seletiva sobre a microbiota do ecossistema manguezal, que pode ser afetada diretamente pela atividade de carcinicultura, praticada na regiÃo prÃxima à cidade de ParnaÃba, localizada no Estado do PiauÃ, de onde as ostras sÃo extraÃdas. AlÃm disso, a presenÃa de mÃltipla resistÃncia aos antimicrobianos observada pode ser indicativa de risco para os consumidores de ostra in natura. / Fecal coliforms have been described as one of the best indicators of pollution in the aquatic environments by human wastes, and it is widely used as a parameter for classifying areas where oysters are farmed or extracted. Among Enterobacteriaceae members, E. coli stands out as potential pathogenic specie, representing risk for public healthy when associated with consumption of raw or undercooked bivalves. However, little is known about this colonization in the bivalve tissues and/or distribution of these enteric bacteria. The objective of the present study was to: (i) quantify fecal coliforms from body fluid and anatomical sites, separately; (ii) isolate and identify E. coli in oysters commercialized in natura in Praia do Futuro beach, Fortaleza-CearÃ; (iii) evaluate the virulence profile and resistance to antimicrobial agents of E. coli isolates. The study covered ten samples, from February to April 2012, by analyzing twelve oysters for sample, divided into a body fluid (intervalvar liquor) and two anatomical sites (mantle and gastrointestinal tract). Fecal coliforms concentration was higher than allowed by legislation n 12/2001 of ANVISA in three samples, and intervalvar liquor presented higher MPN in six samples. Out of 137 E. coli strains isolated, 19% was resistant to both tetracycline and oxytetracycline, and MAR ranged from 0,250 to 0,625. It is further noted producing expended spectrum beta lactamases strains, however none showed biofilm production. The major frequency resistance to oxytetracycline suggests a selective pressure to mangrove ecosystem microbiota that could be directly affected by farming shrimp activity, practiced in a region next to ParnaÃba city, located in Piauà state, where oysters are extracted. In addition, the presence of multiple resistance can be a risk for in natura oyster consumers.

Les estuaires ont été soumis à une forte pression humaine qui a entraîné la présence de polluants dans leurs eaux et sédiments, par exemple les métaux traces. Les estuaires du Golfe de Gascogne n’en sont pas une exception et les estuaires d’Ibaizabal et de la Gironde sont bien connus pour avoir des concentrations élevées de métaux. Dans ce contexte, les programmes de surveillance de l’environnement se sont appuyés sur l’utilisation des moules et des huîtres comme espèces sentinelles, car les analyses chimiques et biologiques de leurs tissus permettent d’évaluer l’état général de santé de leur environnement. Dans le but d’acquérir une meilleure compréhension des interactions entre la bioaccumulation et des effets toxiques du cuivre (Cu) et de l’argent (Ag) dans les huîtres Crassostrea gigas, ainsi que l’influence de facteurs environnementaux, le présent travail présente une étude de terrain et trois expériences de laboratoire. Parmi les résultats obtenus, on peut souligner que : (I) même si les huîtres et les moules peuvent indiquer correctement l’état de santé des estuaires du Golfe de Gascogne, une accumulation clairement plus élevée de métaux se produit dans les huîtres que dans les moules, (II) la voie d’exposition (directe ou alimentaire)induit des réponses de différentes intensités dans les huîtres, (iii) la toxicité de l’Ag est renforcée par la présence accrue de Cu dans les huîtres et (IV) la salinité a un faible effet sur la toxicité des métaux dans les huîtres. / Estuaries have been subjected to a high human pressure which has led to the presence of pollutants in their waters and sediments including trace metals. The estuaries in the Bay of Biscay do not constitute an exception of this situation and the Ibaizabal and Gironde Estuaries are both very well known for having high metal concentrations in different compartments. In this context, environmental health monitoring programmes have relied on the use of mussels and oysters as sentinel organisms because chemical and biological analyses of their tissues allow assessing the general health status of their surrounding environment. The present work aims at acquiring a deeper understanding of the interactions between bioaccumulation and the toxic effects of copper (Cu) and silver (Ag) in oysters Crassostrea gigas, as well as the effects that environmental factors may have on them, For this, one field study and three laboratory experiments have been carried out. Among the most relevant results obtained it can be highlighted that: (I) both oysters and mussels are useful to properly indicate the health status of estuaries of the Bay of Biscay, yet higher accumulation of metals occurs in oysters than in mussels, (II) the intake pathway (watercolumn and/or food) induces different response intensities in oysters (III) the toxicity of Ag is enhanced in the presence of Cu in oysters and (IV) salinity has a low effect on the toxicity of both metals in oysters.

Two species of oviparous oysters, Crassostrea virginica (Gmelin, 1790), the Eastern oyster, and Crassostrea gigas (Thunbert, 1793), the Japanese oyster, were introduced into Tomales Bay, California, for commercial purposes. Because these oysters do not propagate in Tomales Bay, new shipments of adult oysters or oyster spat must be periodically sent from the east coast of the United States or from Japan. It is the purpose of this study to compare the seasonal gonadal changes which occur in the two species of adult oysters in Tomales Bay with one another, and to compare them with the seasonal gonadal changes which occur in the same species of oysters in other regions. The differences in gonadal changes will be related to variances in environmental conditions and to specific or racial characteristics. The introduction of oysters into a new environment is valuable for both commercial and scientific reasons. Although it has long been known that C. virginica and C. gigas do not propagate in Tomales Bay, no one has ever done a detailed study of their reproductive cycle or the seasonal histological changes in their gonads. This study, therefore, extends the knowledge concerning an oyster's reaction and adaptation to its new environment.

Vibrio vulnificus is a foodborne bacterial pathogen associated with raw oyster consumption. Shellfish depuration for 48 hours is a dynamic process where coliform bacteria are purged; however, this process is ineffective against V. vulnificus. The current study investigated the use of prolonged two-week depuration on V. vulnificus populations in Gulf Coast oysters. The study evaluated the impact of prolonged depuration on V. vulnificus fatty acid profile change and the ability to survive in simulated gastric fluid. Oyster depuration in seawater (10 or 22oC, 14 days) reduced V. vulnificus counts, but not to non-detectable level, indicating close ecological relationship between the pathogen and mollusk. Greatest V. vulnificus count reductions were seen in 12 ppt 10°C seawater (2.7 log10 CFU/g) and in 20 ppt 22°C seawater (2.8 logs). Mesophilic vibrios dominated the overall microflora of freshly harvested oysters, while refrigeration selected for psychrotrophic bacteria. Depuration at 22°C retained dominance of mesophilic vibrios, including pathogenic species. Although aerobic plate counts were lower in 22°C depurated oysters (5.0 logs vs 6.0 logs), depuration at 10°C had little to no advantage over 22°C in terms of vibrio population reduction. Use of prolonged depuration remains economically questionable since this method failed to completely eliminate V. vulnificus. Starved V. vulnificus behavior in artificial seawater showed that low temperature (4oC) and high seawater salinity (35 ppt) contributed to pathogen population reduction. Starved V. vulnificus did not adjust membrane fluidity to storage temperature within the investigated time frame. However, a significant fatty acid switch from C18:1w7c to C18:1w6c by double bond relocation was observed. The relocation was faster at ambient temperatures compared to refrigerated temperatures. The majority of V. vulnificus foodborne infections occur during warm summer months. Vibrio vulnificus ATCC 27562 was significantly less resistant (3.7 min D-value) to simulated gastric fluid (pH 4.0) after 7-day storage at 4oC compared to the control (7.8 min D-value). Therefore, greater gastric fluid sensitivity of the pathogen may occur in winter-harvested oysters and may partially explain the low number of winter outbreaks.