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

University of Technology, Sydney. Faculty of Science. / The suitability of the Sydney rock oyster (Saccostrea commercialis) as a monitor of heavy metal contamination in estuarine and coastal waters was assessed. Case study I examined the influence of body size (ie: soft tissue dry weight) on the tissue concentrations of Cu, Zn, and Fe. Sampling was replicated both spatially and temporally in order to determine whether the size-metal relationship for these elements varied with geographical location (ie: differing levels of environmental contamination) or season. All oysters were collected from 'wild' populations in the HawkesburyfNepean estuary. Least-squares regression analysis indicated that Cu concentrations were independent of body size at all times. Analysis of covariance (ANCOVA) showed that this relationship did not change with either geographical location or season. Size-metal relalionships for Zn indicated that concentrations for this element varied from being independent of size to being size-dependent with proportionally greater concentrations present in the larger individuals. Yet lests for homogeneily of slopes (ANCOVA) showed that no differences in regression coefficients occurred with geographical location or season. Iron concentrations were size-dependent with proportionally greater concentrations in the smaller individuals. ANCOVA revealed that homogeneity of slopes with geographical location occurred only on two of the four sampling occasions. Further examination of data revealed that the size·range of the individuals sampled may be important in determining size-metal relationship for iron. Case Study II examined the concentrations of Cu and Zn in S. commercialis deployed into the Georges River/Botany Bay and the Port Stephens estuaries. The influence of tissue assimilation/loss on metal concenlralions was also examined. Organisms of a homogenous genetic stock, of a similar size and age, and transplanted to a similar lidal height were utilized. As all organisms were of a similar size and age at the time of their deployment any differences in size during sampling were attributed to growth. Results indicated that tissue loss (ie: 'degrowth') not accompanied by a similar loss of metal resulted in an increase in metal concentrations. The assimilation of new tissue at a greater rate than metal accumulation (ie: 'dilution') resulted in decreased metal concentrations. From these relationships it was apparent that measures must be taken to reduce, account for, or eliminate the effects of growth in bivalve monitoring programs. Unless this problem is addressed, metal concentration values in S. commercialis are likely to give an inaccurate estimation of the level of environmenlal contamination and confound attempts to isolate pollution point sources.

University of Technology, Sydney. Faculty of Science. / The suitability of the Sydney rock oyster (Saccostrea commercialis) as a monitor of heavy metal contamination in estuarine and coastal waters was assessed. Case study I examined the influence of body size (ie: soft tissue dry weight) on the tissue concentrations of Cu, Zn, and Fe. Sampling was replicated both spatially and temporally in order to determine whether the size-metal relationship for these elements varied with geographical location (ie: differing levels of environmental contamination) or season. All oysters were collected from 'wild' populations in the HawkesburyfNepean estuary. Least-squares regression analysis indicated that Cu concentrations were independent of body size at all times. Analysis of covariance (ANCOVA) showed that this relationship did not change with either geographical location or season. Size-metal relalionships for Zn indicated that concentrations for this element varied from being independent of size to being size-dependent with proportionally greater concentrations present in the larger individuals. Yet lests for homogeneily of slopes (ANCOVA) showed that no differences in regression coefficients occurred with geographical location or season. Iron concentrations were size-dependent with proportionally greater concentrations in the smaller individuals. ANCOVA revealed that homogeneity of slopes with geographical location occurred only on two of the four sampling occasions. Further examination of data revealed that the size·range of the individuals sampled may be important in determining size-metal relationship for iron. Case Study II examined the concentrations of Cu and Zn in S. commercialis deployed into the Georges River/Botany Bay and the Port Stephens estuaries. The influence of tissue assimilation/loss on metal concenlralions was also examined. Organisms of a homogenous genetic stock, of a similar size and age, and transplanted to a similar lidal height were utilized. As all organisms were of a similar size and age at the time of their deployment any differences in size during sampling were attributed to growth. Results indicated that tissue loss (ie: 'degrowth') not accompanied by a similar loss of metal resulted in an increase in metal concentrations. The assimilation of new tissue at a greater rate than metal accumulation (ie: 'dilution') resulted in decreased metal concentrations. From these relationships it was apparent that measures must be taken to reduce, account for, or eliminate the effects of growth in bivalve monitoring programs. Unless this problem is addressed, metal concentration values in S. commercialis are likely to give an inaccurate estimation of the level of environmenlal contamination and confound attempts to isolate pollution point sources.

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Bibliography: leaves 194-210.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references.

Thesis (M.S.)--University of North Carolina at Wilmington, 2004. / Includes bibliographical references (leaves : 68-75).

Thesis (Ph. D.)--University of Hong Kong, 1978.

Aerobic heterotrophic bacteria associated with oyster larvae feed algae Isochrysis galbana, Monochrysis lutheri and Pseudoisochrysis paradoxa were isolated and enumerated. The bacterial numbers ranged from 7.8x10³ to 3.9x10⁶ CFU per ml. The bacteria associated with Pseudoisochrysis sp. were identified and the majority of isolates belonged to genera Leucothrix (51%). Also present were members of Pseudomonas III sp. (19.1%), atypical Moraxella sp. (16.8%), Moraxella sp. (7.2%) and Flavobacterium sp. (5.9%). The growth of bacteria on marine agar was fastidious and took four days to form visible colonies. None of the bacterial isolates grew in buffered salt broth in which the algae had been grown. Marine broth supplemented with 0.1% beef extract best supported the growth of the isolates, while ferric citrate (3x10⁻⁴ M) supported their growth in buffered salt broth. The role of algae as a solid support for bacteria was investigated by studying the attachment of bacteria on glass slides suspended in the growth medium. The percent of Leucothrix sp. attached to the slide was 2.1-3.0%. This was four to six times greater than that of Staphylococcus (0.5%), an organism well known for its commensal growth on skin and mucus membranes of man and animal. Hydrophobic attraction, which is thought to play an important role in the orientation of bacteria to solid surfaces, was studied by measuring the adsorption of bacteria on hydrocarbons introduced to a bacterial suspension. Leucothrix sp. exhibited the strongest affinity, whereas Flavobacterium sp. and Pseudomonas sp. adsorbed the least. An attempt to obtain an axenic culture of algae by antibiotic treatment was unsuccessful due to the detrimental effect of antibiotics to both algae and bacteria. / Graduation date: 1982

Thesis (M. Phil.)--University of Hong Kong, 1979.

abstract / Biological Sciences / Doctoral / Doctor of Philosophy