Vibrio parahaemolyticus is a Gram-negative, halophilic pathogen that occurs naturally in coastal and estuarine environments. This human pathogen is frequently isolated from a variety of seafood, particular oysters, and is the leading cause of gastroenteritis associated with seafood consumption. Several outbreaks of V. parahaemolyticus infections linked to consumption of raw oysters have been documented. Contamination of oysters with V. parahaemolyticus is a concern for public health. This study investigated the efficacy of high pressure processing (HPP) in inactivating V. parahaemolyticus in raw Pacific oysters (Crassostrea gigas) and identified a process condition capable of achieving greater than 3.52-log reductions of V. parahaemolyticus in raw oysters for commercial application. Raw Pacific oysters were inoculated with a clinical strain of V. parahaemolyticus 10293 (O1:K56) to levels of 10⁴⁻⁵ cells per gram and processed at 293 MPa (43K PSI) for 90, 120, 150, 180 and 210 s. Populations of V. parahaemolyticus in oysters after processes were analyzed with the 5-tube most probable number (MPN) method. A minimum HPP of 293 MPa for 120 s at groundwater temperature (8±1 °C) was identified capable of achieving greater than 3.52-log reductions of V. parahaemolyticus in Pacific oysters. The HPP (293 MPa for 120 s at 8±1 °C) was validated at a commercial scale according to the FDA's National Shellfish Sanitation Program Post Harvest Processing (PHP) Validation/Verification Interim Guidance for Vibrio vulnificus and Vibrio parahaemolyticus. Negative results obtained by the MPN method were confirmed with a multiplex PCR detecting genes encoding thermolabile hemolysin (tl), thermostable direct hemolysin (tdh) and TDH-related hemolysin (trh). Oysters processed at 293 MPa for 120 sec had a shelf life of 6-8 days when stored at 5 °C or 16-18 days when stored in ice. This validated HPP was accepted by the FDA as a post harvest process to eliminate V. parahaemolyticus in raw oysters. / Graduation date: 2012

As the global energy crisis continues to have an impact on developing countries such as South Africa, stakeholders form an increasingly significant role especially around the concerns of development and the impact on the environment. Environmental conflicts have risen to the forefront in many areas in South Africa. Environmental conflicts fall under public disputes, which often occur as a result of human needs. This study is an attempt to explore the environmental conflict surrounding the proposed Nuclear Power station at Thyspunt, Oyster Bay in the Eastern Cape. Stakeholders are an integral part of environmental conflicts, and analyzing interests of stakeholders is vital in understanding environmental conflicts. This explorative study, seeks explore and to describe the interests of homeowners who are one of the key stakeholders involved the environmental conflict at Thyspunt, Oyster Bay in the Eastern Cape. The homeowners are represented by the St Francis Residents/ Ratepayers Association. The researcher conducted extensive face-face interviews with these homeowners. The organizations official documents, minutes of their meetings, letters to the media and various publications in which homeowners expressed their feelings were also made use of by the researcher in order to triangulate findings, as well as for data collection methods. The major themes were constructed from the study include: Security, Trust, Power and the various sources thereof, as well as a need for self-actualization based on values, and a final theme of the positive functions of conflict. The challenges facing the homeowners in terms of human security and environmental impact of the nuclear development are highlighted. Further recommendations for a more in-depth study are also made.

The close proximity of net-pen salmon farms and wild Pacific salmon stocks in British Columbia (BC) is an incentive for precautionary management of the environmentally and economically damaging parasites known as sea lice. Bivalves cultured as part of an integrated multi-trophic aquaculture (IMTA) system may contribute natural, preventative louse control through the ingestion of planktonic sea lice larvae. A field trial was conducted to test sea lice mitigation by bivalves at a commercial Atlantic salmon (Salmo salar) farm in BC using Pacific oysters (Crassostrea gigas). Oysters were cultured in trays around one end of the farm and at a reference site approximately 150 m away from August 2013 until August 2014. Parasitic and planktonic sea lice (Lepeophtheirus salmonis and Caligus clemensi) were monitored before and during oyster deployment, beginning in December 2012. Parasite abundance peaked in January 2013 (6.5 lice/fish, >85% C. clemensi), and the following year in February 2014 (3.3 lice/fish, >80% L. salmonis). Larval density within cages peaked in January, both in 2013 (1.28 larvae/m3) and 2014 (0.96 larvae/m3). Parasite abundance was significantly correlated with both surface salinity (r2= 0.28, p=0.04) and sea lice larval density (r2= 0.65, p=0.01). Observed densities were significantly lower (t=3.41, p=0.009) than those calculated for the site based on water temperature and salinity, the number of adult female lice present, and the approximate number of fish. Sea lice mitigation by oysters was assessed by comparing monthly sea lice larval densities inside bivalve and non-bivalve fish cages, and by analyzing preserved oyster digestive tracts from January 2014 (when larval densities were highest) for presence of L. salmonis DNA using PCR. Using these methods, no significant evidence of sea lice mitigation was detected. Oyster growth was monitored by measuring whole wet weight, soft tissue wet, dry, and ash-free dry weight, and shell length, width, and height approximately every four months. Oysters were sampled equally across different sides of the farm and at the reference site (~150 m away from the farm) at three depths: 1, 3, and 6 m. All seven measurements increased significantly over time. Effects of side and depth varied by growth parameter; in general, oysters at 1 and 3 m were significantly larger than those at 6 m, and oysters cultured at the reference site were either significantly smaller or the same size as those cultured around the farm. Oysters from select sides were consistently, significantly larger than those from other sides and from the reference site. Overall, the findings suggest that sea lice larvae quickly dispersed away from the farm after hatching and were not significantly impacted by bivalve presence around the fish cages. Bivalves grew significantly larger over time and size was significantly impacted by both depth and side of the fish cage. While no evidence of larval sea lice reduction/ingestion by cultured bivalves was detected, this study provides information on all sea lice stages present throughout an Atlantic salmon production cycle, as well as the first detailed growth analysis of Pacific oysters cultured alongside farmed Atlantic salmon in BC. / Graduate / 0792 / byrneaa@gmail.com

Whole oysters were processed under a series of pressures from 30,000 to 45,000 psi at different holding times (0, 1, and 2 min) and then stored at <4°C, for 27 d. During the shelf-life study, the quality of oysters was determined by measuring pH, moisture content, and microbial counts including aerobic, anaerobic bacteria and coliform. Descriptive testing was also performed by a trained panel. The pH of high pressure process (HPP) samples decreased slightly from 6.3 to 5.7 during storage while the control dropped to pH 4.4. Moisture content of the control decreased slightly while HPP samples increased slightly. Pressure treatment did not significantly inhibit lipase activity during the shelf-life study. HPP reduced initial microbial load by approximately 2-3 logs and counts remained at a reduced level through the storage study. Descriptive tests showed that HPP treated oysters received higher quality scores than the control during the storage trial. Whole oysters were shucked under pressure of 35,000 psi, 2 min. After shucking, oyster meats were water packed in plastic containers and repressureized. Tests were performed at 45,000 psi, 30 s and 50,000 psi (0 holding time, 10 s). All samples were stored at <40C for 25 d. During the shelf-life study, oyster quality was determined by measuring pH, moisture content, protease, and microbial counts including aerobic, anaerobic bacteria and coliform. The pH of HPP samples decreased slightly from 6.5 to 5.7 during storage while the control I, hand-shucked oysters, dropped to pH 4.3. Pressure treatment seemed to increase protease activity during the shelf-life study. HPP reduced initial microbial load by approximately 2-3 logs and inhibited microbial growth during storage. / Graduation date: 2001

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1978. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 29-30. / B.S.

Converting energy from ocean waves is an exciting concept aimed at reducing our dependency on fossil fuels. Ocean energy devices must convert the large forces and relatively small movements from ocean waves into electrical power with a minimum carbon and energy intensity in order to be economically viable. The research herein focuses on the Oyster, a flap-type pitching wave energy converter developed by Aquamarine Power. A device that has the minimal carbon or energy intensity is not necessarily the most mechanically efficient. A commercially viable wave energy converter should have a competitive cost of energy and be as carbon negative as possible. In order to expedite the route to commercialisation, successive designs should iterate towards a minimum lifetime cost of energy. The sheer complexity of wave energy converter systems makes for a vast optimisation problem to determine the system parameters that exhibit the minimum carbon and energy intensities. This thesis presents a study of the oscillating flap-type wave energy converter to determine the trends between design parameters, total power output and carbon and energy throughput. The minimum carbon and energy intensities have been shown to be strongly dependent on minimising maintenance requirements. In order to determine the design criterion a range of flap widths and system pressures are investigated and their effect on component service lives assessed. The results are then converted to lifetime carbon and energy intensities for a direct comparison. To achieve this, fundamental research on the maintenance requirements of critical components such as the hinge bearings and hydraulic power system is required. A hydrodynamic model describes the dynamic response and links the system energy inputs to its modelled energy output. This work is intended to help guide developers of flap-type wave energy converters towards commercialisation. It enhances the understanding of the routes to failure and service life predictions, providing avenues to balance service lives to optimise maintenance and maximise uptime. This will assist in the development of more energy efficient wave energy converters over their lifetime. This information will better enable the marine energy sector to offset our fossil fuel dependence, ultimately reducing our impact on the environment and leading to a ‘greener’ future.

The Japanese oyster Crassostrea gigas is commercially grown in bays and estuaries of the Pacific Northwest. The oyster's complex, ciliated, plicate gill is responsible for removing particles from surrounding waters for ingestion. In order to determine how this is accomplished, structural interrelationships of gill components were investigated using scanning electron microscopy and light microscopy. Particle movement was observed directly on both isolated gill sections and intact gills. Feeding data were obtained by comparing initial to final concentration and size of algal particles in a Coulter counter.

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.

Cryopreservation of gametes is a valuable tool for the fast-growing aquaculture industry in New Zealand. In the present study, research was aimed to improve the cryopreservation of Pacific oyster (Crassostrea gigas) oocytes. For this, two main approaches were used: the modification of an existing published (standard) cryopreservation protocol for oyster oocytes and the modification of the oocytes themselves prior to cryopreservation. The objectives in the chapters of this thesis were: (a) determination of the cryobiological characteristics of oyster oocytes; (b) assessment and reduction of intracellular ice formation (IIF) in oocytes; and (c) modification of the lipid fraction (cholesterol and fatty acids) of oocytes prior to cryopreservation. Knowledge of the membrane permeability parameters in response to concentrations of water and ethylene glycol (EG), the influence of temperature upon these parameters, and the osmotic tolerance limits of oyster oocytes were used to develop computer models that simulated the cellular volume changes that oocytes underwent during EG addition and removal. The models predicted that when one part of EG was added in one step to one part of oocyte suspension and equilibrated for 20 min at 20 �C, similar volume changes in oocytes would be obtained, compared to a more complicated multi-step addition method. This method of addition resulted in similar post-thaw fertilization rates to those obtained by using the multi-step addition method, thus reducing oocyte handling. Cryomicroscopy was used to assess the effect of cooling rates and EG concentration on the temperature at which oocytes underwent IIF. It was found that IIF occurred at higher subzero temperatures when fast cooling rates were used (30 and 5 �C min⁻�) and at EG concentrations ranged between 0 and 15%. At a relatively slower cooling rate of 0.3 �C min⁻� and with 10% EG, which are the conditions employed in the standard cryopreservation protocol, no IIF occurred. The steps of the standard protocol that were more likely to cause oocyte damage were identified by evaluating the fertilization rate of oocytes at each step. Results showed that oocytes were most damaged by cooling them to -35 �C and followed by plunging them in liquid nitrogen. Contrary to what had been observed under the cryomicroscope, transmission electron microscopy (TEM) analysis revealed that all oocytes cryopreserved by the standard protocol contained cytoplasmic ice. In addition, it was also observed that oocytes were at two developmental stages when frozen (prophase and metaphase I). These observations prompted the development of alternative cooling programmes aimed to reduce intracellular ice. The effect of cooling rate, plunge temperature and time held at the plunge temperature were thus evaluated, based on post-thaw fertilization rate of oocytes. Overall, neither the cooling rate nor the holding time had an effect on oocyte fertility. However, the plunge temperature had an effect, where oocytes plunged at -60 �C had lower post-thaw fertilization rates than oocytes plunged at -35 �C. Through the slowing of the cooling rate, lengthening of the holding time and lowering of the plunge temperature, it was possible to reduce the amount of ice in the cytoplasm. However, the reduction of intracellular ice did not improve the post-thaw fertilization rate of the oocytes; on the contrary, post-thaw fertilization decreased notoriously. From these results, it can be suggested that oyster oocytes are more likely to be damaged by exposure to high intra and extracellular solute concentration than IIF during cryopreservation. In an effort to modify the lipid content of oyster oocytes prior to cryopreservation and thus, making them more resistant during cryopreservation, oocytes were incubated in solutions that would add or remove cholesterol or in solutions rich in long chain fatty acids (EPA or DHA). Oocytes incubated in cholesterol-rich solutions showed a positive uptake of fluorescently labelled cholesterol and this effect was dose dependent. Nevertheless, this uptake did not improve the post-thaw fertilization rate nor did it increase the total cholesterol content of the oocytes. When oocytes were incubated in non-conjugated or conjugated EPA or DHA, no increase in the proportion of these fatty acids was identified in the fatty acid profiles of whole oocytes and no improvement of the post-thaw fertilization rate was recorded. Given that there was no uptake of fatty acids from the incubation media by the oocytes, a different approach was taken. This involved the supplementation of lipid-rich diets to the oyster broodstock during gametogenesis (cold-conditioning) and vitellogenesis (warm-conditioning). Despite results showing that lipid content and, indeed, fatty acid profile was altered through the diet, the results also showed that fresh oocytes from broodstock fed during cold-conditioning did not show any improvement in their fertilization rates, nor did they benefit from a lipid-rich diet during warm-conditioning. On the other hand, cryopreserved oocytes did have higher post-thaw fertilisation rates when broodstock were fed during cold-conditioning and, although no effect was found from feeding broodstock with either of the lipid-rich diets during warm-conditioning, trends indicated that a diet consisting of fresh microalgae or the commercial supplement Algamac would yield the highest post-thaw fertilization rates. This thesis has furthered the understanding of some of the factors that determine cryosurvival in oyster oocytes and has demonstrated that both physical and biological issues must be taken into consideration for cryopreservation. Specifically, the results in this thesis helped to modify an empirically developed cryopreservation protocol for Pacific oyster oocytes. In addition, the results also showed strong evidence of the survival of oyster oocytes to intracellular ice and highlighted the importance of supplying the broodstock with lipid-rich food during the periods of gamete formation and maturation in order to obtain oocytes that are more amenable to cryopreservation. These benefits could be of significant practical importance and may be extended for the development or refinement of cryopreservation protocols for other shellfish species of commercial importance to the aquaculture industry of New Zealand.

Experiments were carried out in fall and winter, 1990 and spring and summer, 1991 , to determine growth and mortality of juvenile Pacific oysters {Crassostrea gigas) in effluent from cultured coho salmon {Oncorhynchus kisutch) , and effluent from salmon in which the red macroalga Palmaria mollis was cultured. Ambient sea water from Yaquina Bay was used as a control. Juvenile Manila clams {Tapes japonica) were also tested in summer, to compare the growth response of clams with that of Pacific oysters. Measured growth parameters included: increase in mean individual live weight, specific growth rate (% increase of mean live weight per day) and mean individual organic (ash-free) weight. Temperature, chlorophyll a, phaeopigment, carbon and nitrogen concentrations and C/N ratio for all treatments were also recorded during spring and summer, 1991. The oysters grew significantly faster in effluent from salmon and salmon conditioned by macroalgae than in the control during the Fall Experiment (September 7- 0ctober 31, 1990). Mean water temperature was 13-16°C. Growth rates were significantly greater in oysters cultured in salmon effluent than in the control during the Winter Experiment (December 7, 1990-February 15, 1991). However, growth was very poor due to low water temperatures (7-10°C). Growth of oysters was significantly greater in the control than in effluent from salmon and salmon conditioned by macrolagae in the Spring Experiment (March 7-May 24, 1991). Mean water temperature was 12°C. In the Summer Experiments, (June 3-July 4 and July 19-August 17, 1991) growth of oysters was more rapid in treatments with macroalgae as compared to treatments without macroalgae Comparative experiments with juvenile Manila clams gave similar results. Percentage mortality for both oysters and clams ranged from 0 to 5% and was highest during winter and lowest during summer. Mean chlorophyll values ranged from 1 μg/1 in spring, 1991 to 11 μg/1 summer, 1991. / Graduation date: 1992