Dissertations / Theses on the topic 'Sydney rock oyster'

This thesis provides the first comprehensive assessment of the economic viability of Australia's Sydney rock oyster industry and forms the bases for future policy and industry management recommendations. In the four separate studies of the thesis, the socio-economic profile of the industry, the market price formation dynamics within Australia's oyster market, efficiency and productivity levels and the potential impact of climate change and market dynamics on the industry's future revenue were investigated. Findings of this project suggest, for example, that market dynamics may pose a greater thread to the future development of this industry than direct effect from climate change.

A direct enrichment procedure has been developed for selectively recovering low numbers of Campylobacter jejuni and Campylobacter coli from oyster tissue. This procedure makes use of a selective enrichment step, using a broth medium composed of 2% proteose peptone, 1% yeast extract, 0.2% potassium L-aspartate, 0.25% sodium chloride as basal medium (PYA broth)plus 0.2% bacteriological charcoal, polymyxin (5000 IU/ litre), cefoperazone(30 mg/litre), trimethoprim (10 mg/litre), cycloheximide (50 mg/litre), sodium pyruvate (0.25g/litre), sodium metabisulphate (0.25g/litre) and ferrous sulphate (0.25g/litre). In this study the procedure has been used to study the occurrence of thermophilic campylobacters in Sydney rock oysters. Seventy nine samples were screened during the winter months of April to July in 1985. Approximately 8% of the samples contained C.jejuni and 6% of the samples were positive for C.coli. The survival of C.jejuni and C.coli in the Sydney rock oyster was also investigated and results discussed. In contaminated shell stock stored at 20 and 30 degrees Centigrade, C.jejuni and C.coli survived for periods varying from 2 to 9 days. The failure of the organism to multiply in oyster tissue at any of these temperatures studied is an important phenomenon.
Master of Science (Hons)

Estuarine acidification, caused by disturbance of acid sulfate soils (ASS), is a recurrent problem in eastern Australia. Affected waters are characterised by low pH and elevated concentrations of metals, principally aluminium and iron. The effects of acid and elevated metal concentrations associated with ASS, on adult Sydney rock oysters, have not been previously investigated. This study tested links between ASS-affected drainage, subsequent estuarine acidification and Sydney rock oyster production problems on the Hastings and Manning Rivers, mid north coast New South Wales. The primary objective of this thesis was to establish if estuarine acidification causes mortality and slow growth in individual Sydney rock oysters by exposing oysters to low pH, iron and aluminium using field and laboratory experiments. Water quality data showed that estuarine acidification was spatially extensive in the Hastings and Manning Rivers following heavy rainfall and was due to mineral acids originating from drained or excavated ASS. Estuarine acidification regularly affected areas used for Sydney rock oyster production following heavy rainfall. Field experiments showed that Sydney rock oyster mortality rates were significantly higher at sites exposed to ASS-affected waters compared to locations that were isolated from ASS-affected waters. Oyster mortality increased with the time of exposure and smaller oysters (mean weight = 5 g) experienced significantly higher mortality relative to larger oysters (mean weight = 29 g). This was caused by acid-induced shell degradation resulting in perforation of the smaller oysters??? under-developed shells. Additionally, Sydney rock oyster growth rates were dramatically reduced at sites exposed to ASS-affected waters and the overall mean condition index of oysters at ASS-affected field sites was significantly lower than the overall mean condition index of oysters at non-impacted sites. Findings from laboratory experiments showed that ASS-affected water alters oyster valve movements and significantly reduces oyster feeding rates at pH 5.5. Acidic treatments (pH 5.1) containing 7.64 mg L-1 of aluminium or ASS-affected water caused changes in the mantle and gill soft tissues following short-term exposure. Degenerative effects described in oysters in this study were also due to iron contained in ASS-affected waters. Iron precipitates accumulated on the shell, gills and mantle and were observed in the stomach, intestine, digestive tubules and rectum. This study concluded that Sydney rock oysters are unable to tolerate acidic conditions caused by ASS outflows and cannot be viably cultivated in acid-prone areas of the estuary.

A direct enrichment procedure has been developed for selectively recovering low numbers of Campylobacter jejuni and Campylobacter coli from oyster tissue. This procedure makes use of a selective enrichment step, using a broth medium composed of 2% proteose peptone, 1% yeast extract, 0.2% potassium L-aspartate, 0.25% sodium chloride as basal medium (PYA broth)plus 0.2% bacteriological charcoal, polymyxin (5000 IU/ litre), cefoperazone(30 mg/litre), trimethoprim (10 mg/litre), cycloheximide (50 mg/litre), sodium pyruvate (0.25g/litre), sodium metabisulphate (0.25g/litre) and ferrous sulphate (0.25g/litre). In this study the procedure has been used to study the occurrence of thermophilic campylobacters in Sydney rock oysters. Seventy nine samples were screened during the winter months of April to July in 1985. Approximately 8% of the samples contained C.jejuni and 6% of the samples were positive for C.coli. The survival of C.jejuni and C.coli in the Sydney rock oyster was also investigated and results discussed. In contaminated shell stock stored at 20 and 30 degrees Centigrade, C.jejuni and C.coli survived for periods varying from 2 to 9 days. The failure of the organism to multiply in oyster tissue at any of these temperatures studied is an important phenomenon.

Genetic variation is the resource animal breeders exploit in stock improvement programs. Both the process of selection and husbandry practices employed in aquaculture will erode genetic variation levels overtime, hence the critical resource can be lost and this may compromise future genetic gains in breeding programs. The amount of genetic variation in five lines of Sydney Rock Oyster (SRO) that had been selected for QX (Queensland unknown) disease resistance were examined and compared with that in a wild reference population using seven specific SRO microsatellite loci. The five selected lines had significantly lower levels of genetic diversity than did the wild reference population with allelic diversity declining approximately 80%, but impacts on heterozygosity per locus were less severe. Significant deficiencies in heterozygotes were detected at six of the seven loci in both mass selected lines and the wild reference population. Against this trend however, a significant excess of heterozygotes was recorded at three loci Sgo9, Sgo14 and Sgo21 in three QX disease resistant lines (#2, #5 and #13). All populations were significantly genetic differentiated from each other based on pairwise FST values. A neighbour joining tree based on DA genetic distances showed a clear separation between all culture and wild populations. Results of this study show clearly, that the impacts of the stock improvement program for SRO has significantly eroded natural levels of genetic variation in the culture lines. This could compromise long-term genetic gains and affect sustainability of the SRO breeding program over the long-term.

There has been a continuous decline in both the production and general performance of the SRO in NSW estuaries over the past three decades. The relationship of this decline to both environmental and oyster-density related factors are assessed in this thesis. This question has been examined at different scales: a large scale that compares two different estuaries (Clyde and Shoalhaven Rivers, southern NSW); a regional scale that encompasses variations within an estuary and, at a lease scale that examines processes pertaining to individual or small groups of oysters. Levels of inorganic nutrients were in general very low potentially limiting primary production. The limiting nutrient was nitrogen or phosphorus depending on whether long term conditions were dry or wet, respectively. Only during rain events, through the input of terrestrial material, were conditions favourable for fast rates of primary production. Carbon and nitrogen isotope analysis has demonstrated that both external material and local resuspension of the benthos constitute a major proportion of the SRO diet. The uptake of the various food sources also varied considerably depending on local environmental conditions. Increases in SRO growth were strongly correlated to increases in temperature with a low temperature cut-off at ~13°C. Growth also appeared to reduce considerably when salinities lower than ~15ppt persisted for the order of a month. These factors may alter growth through changes in filtration rates. These processes were modelled in a coupled hydrodynamic-NPO (Nitrogen-Phytoplankton-Oyster) model of the Clyde River. This demonstrated that primary production was more affected by estuarine dynamics and nutrient concentrations than oyster uptake. At the current levels of oyster densities, primary production by itself could not account for the observed oyster growth, however growth became realistic with observed levels of POC added to the model. A set of environmental indices were used to complement the model and to assess the sustainability of the culture system. The combined indices indicated that while the ecological carrying capacity of the Clyde was exceeded the production capacity at an estuarine scale was not. On the lease scale, density experiments showed that while growth was not reduced as a result of current stocking densities, the condition index was significantly affected.

To aid the commercialisation of triploid technology for Sydney rock oysters (Succostreu glomerafa) in NSW, triploids and diploids were evaluated for growth, mortality and meat condition on commercial oyster farms throughout the state. After 2% years, triploids were on average 30.7% heavier and 8.6% larger in shell height than same parent diploids. Mortality of triploids was significantly lower (p < 0.01) or not significantly different @ > 0.05) from that of diploids at 12 of the 13 sites. Average cumulative mortality after 2% years across the 13 sites was 28% for diploids compared to only 16% for triploids. Performance of triploids over diploids varied considerably between sites. Wild-caught diploids had lower growth rates and higher mortality than both diploid and triploid hatchery stock.

This project examined the effects on genetic diversity of oysters by hatchery techniques and selective breeding. The edible oyster industry in Australia comprises of two main species: Crassostrea gigas and Saccostrea glomerata, which are produced by hatcheries or natural spatfall, respectively. This study examined the levels of genetic diversity as a result of unintentional selection in C. gigas, and as a result of intentional selection (a selective breeding program to increase meat weight) in S. glomerata. This study has implications for aquaculture species worldwide as it examines the levels of genetic diversity in introduced (eg C. gigas) and a previously declining, native (S. glomerata) species, which comprise two of the main groups of species utilised for aquaculture. The oyster aquaculture industry in Tasmania is based on Pacific oysters, C. gigas, and derived from imports of Japanese oysters made some 40 years ago. Fears were held that introduction and subsequent domestication had eroded the genetic diversity. As the industry wished to embark on selective breeding programs, a genetic audit of the hatchery stocks was required. Four Australian established (ie non-hatchery produced) populations, and two of Japanese populations that originally imported, were analysed to determine the amount of genetic diversity present. Three different genetic techniques were employed - allozyme electrophoresis, microsatellite DNA and mitochondrial DNA RFLP (restriction fragment length polymorphism) analyses. Using 17 allozyme loci, three hatchery and four naturalised populations of Crassostrea gigas (Thunberg) in Australia were compared with one another and with two endemic Japanese populations. All populations showed a high degree of genetic variability. The percent of polymorphic loci ranged from an average of 70.6% (hatcheries) through 73.5% (naturalised and Japan). Mean observed heterozygosities ranged from 0.267 (naturalised) through 0.285 (hatcheries) to 0.291 (Japan). Mean numbers of alleles per locus ranged from 3.0 (hatcheries) through 3.3 (naturalised) to 3.5 (Japan). Most loci and populations showed good fits to Hardy-Weinberg expectations; the few significant exceptions were heterozygote deficiencies. Tests of allele frequency differentiation among the nine populations revealed that 11 of the 16 variable loci showed significant (a reduced to 0.05/16 = 0.0031) inter-population heterogeneity after both x 2 . and GsT analysis (Table 2.5). Four loci — GDA, 6PGDH, PEPS-I and PROT-2 — were non-significant for both analyses, and EST-D was significant for x2 analysis (P < 0.001), but not after Bonferroni correction for GsT analysis (P = 0.004). Five populations (BEA, BRI, DUN, SMI, SEN) conformed to Hardy-Weinberg equilibrium for all loci. A few populations and loci did not conform (after Bonferroni correction, using a = 0.0031): HIR (AK, DIA, PGI), NSW (PEPS-2), PIT (DIA), and SWA (DIA) (data not shown). All the non-conforming samples showed heterozygote deficiencies, which were significant in two cases: HR (DIA: x2 = 35.67, P < 0.001; D — 0.314, P < 0.001); and SWA (DIA: X2 79.04, P = 0.001, D = - 0.397, P < 0.001). Allele-frequency differences among populations were minor, although sometimes statistically significant: only about 1% of the allele frequency variation could be attributed to among-population differences. The levels of homozygous excess observed in this study were lower than that previously reported for this species, but may be due to the same reasons such as gel scoring errors, null alleles, selection, inbreeding, population admixture or sampling error. Four microsatellite loci (consisting of two dinucleotide, one tetranucleotide and one tetranucleotide/dinucleotide motifs) were used to analyse the populations. Primers were designed on clone sequence containing at least five repeats of a microsatellite motif. Ten sets of primers were trialled but only four sets had variability levels useful for population genetics analyses, as the others had between 23-34 alleles or were monomorphic. High levels of genetic variability were observed (mean polymorphism = 0.889, mean heterozygosity = 0.188). Tests of allele frequency differentiation among the nine populations revealed that three of the four variable loci showed significant (a reduced to 0.05/4 = 0.0125) inter-population heterogeneity after x2 analysis and Gsr analysis — cmrCgl 7, BV59 and cmrCg61. The amount of differentiation among the populations was, however, small. Across all loci, only 4% of the genetic variation could be attributed to differences among populations. No population conformed to Hardy-Weinberg equilibrium for all loci. Where populations did not conform to Hardy-Weinberg equilibrium, a significant excess of homozygotes was observed. Although null alleles have been previously reported for the loci used in this study null alleles do not appear to explain the heterozygote deficiencies observed in this study, based on analysis by the NullTest program (W. Amos, pers. comm.) as the frequency of the proposed null alleles seems too high. Unbiased (Nei, 1978) genetic distances over the four loci were estimated between all pair-wise combinations of populations. All pair-wise population distances are very small (Nei D<0.03). However, the standard errors of the distances are large (ranging to 0.0295±0.0867 between the SWA/BEA/BRI/HIR/PIT/NSW/SMI/SEN and DUN clusters), indicating that the groupings, based on only four loci, are not statistically meaningful. There were no significant changes of genetic diversity between the populations. Overall, the use of microsatellites confirmed the results of the allozyme study of these populations. - the introduction of oysters from Japan to Tasmania, and their subsequent domestication, have not substantially eroded the genetic basis of the Tasmanian stock. Very little variation was found using mitochondrial DNA (mtDNA) RFLP analysis using 12 restriction enzymes in one hatchery and one endemic population. The mtDNA fragment used was found to contain two conserved genes explaining the lack of variability observed. The technical limitations and lack of knowledge of the oyster mtDNA genome made this approach inappropriate for population genetics analysis. However, the identification of the proximity of the 16srRNA, and COIII genes observed in this study gives further insight into the mtDNA gene order of C. gigas. Together with previous findings of the mtDNA RE site map (Oohara and Mori, 1989), the location of the cytochrome b gene . (Li and Hedgecock, 1998), this study demonstrates a block of COIII, 16srRNA and cytochrome b mtDNA genes —a combination unique to bivalves. Two generations of a selected breeding line for increased whole weight (using mass selection) and unselected group of the Sydney rock oyster Saccostrea glomerata were examined using allozyme electrophoresis (a total of 14 loci analysed). Genetic variability levels were determined for each group - all were high and similar to one another (mean percentage polymorphic, 66.7, mean observed heterozygosity, 0.222; mean number of alleles, 2.5). Genotype frequencies at all loci in all groups conformed to Hardy-Weinberg equilibrium, except for the ESTD-2 locus in the second generation (P<0.001), which had a large and significant excess of homozygotes (Selander index D = -0.451, P<0.001). Thus significant allele frequency differences were observed at seven loci between control and second generation, at eight loci between second and third generation, and at only one locus for control and third generation. This suggests that the second generation sample is responsible for most of the heterogeneity observed. Despite the difference between actual and estimated broodstock numbers, the expected numbers of alleles of the second and third generations of the selected breeding line were very close to the observed numbers in all cases, suggesting that random genetic drift (sampling variation) alone was the cause of allelic variation between the groups. The results of this allozyme survey indicate that the selective breeding for increased whole weight has not substantially eroded levels of genetic variation. There are high levels of genetic variation present in the control group and in the two generations of the selected breeding line. The limited, but statistically significant, heterogeneity between the second generation and other samples appears to be due to a sampling artifact; it is likely to be biologically unimportant. The type of selective breeding program used (mass selection) aided the retention of genetic diversity across the generations sampled. By using oysters from 4 different areas and using large numbers of oysters for spawning helped to achieve the levels of genetic diversity observed. In summary, this study has not only substantially broadened the base of knowledge in the two oysters species investigated, but also shown that intentional (in the form of selective breeding) and unintentional (in the form of introduction and subsequent domestication) selection of aquaculture species need not result in major allele loss. Without major allele loss an aquaculture species then has the potential for successful selective breeding for desired traits; as the genetic diversity and hence likelihood of finding particular gene(s) of interest have not been diminished significantly, and has every chance of success. That the two commercially important edible oyster species (introduced and native) in this study have not shown a large magnitude of genetic diversity loss despite either introduction, naturalisation and domestication, or selective breeding serves as a encouraging example to the oyster industries and researchers involved as well as those in other countries and indeed other aquaculture species.

To aid the commercialisation of triploid technology for Sydney rock oysters (Saccostrea glomerata) in NSW, triploids and diploids were evaluated for growth, mortality and meat condition on commercial oyster farms throughout the state. After 21/2 years, triploids were on average 30.7% heavier and 8.6% larger in shell height than same parent diploids. Mortality of triploids was significantly lower (p < 0.01) or not significantly different (p > 0.05) from that of diploids at 12 of the 13 sites. Average cumulative mortality after 21/2 years across the 13 sites was 28% for diploids compared to only 16% for triploids. Performance of triploids over diploids varied considerably between sites. Wild-caught diploids had lower growth rates and higher mortality than both diploid and triploid hatchery stock. At seven sites where oysters were exposed to the parasite Mikrocytos roughleyi (cause of "winter mortality"), triploid Sydney rock oysters survived the disease better than diploids. Cumulative mortality of diploids during the second winter/spring at these sites was 35% compared to only 12.2% for triploids. Meat condition of diploids and triploids varied between the five sites throughout NSW. Over the final year on leases, ploidy, month and the ploidy*month interaction had a significant effect on meat condition at all sites except for ploidy at the southern, Lake Pambula site. From March to December (autumn to the first month of summer) condition indices of triploids were greater, or not significantly different from those of diploids at all sites. Triploid Sydney rock oysters were susceptible to brown discolouration of the gonad surface. Discolouration occurred in localised areas of the gonad and was not correlated to condition index except for triploids at Lake Pambula. As discolouration was less noticeable during cooler months of the year, it coincided with the generally superior condition of triploids relative to diploids during winter and spring, so that triploids remain a viable winter crop for farmers throughout NSW. After two years, an experiment in Port Stephens showed triploid oysters from two initial size grades were heavier and larger than equivalent size grades of same parent diploids (p <0.05). Initial size grade had a significant effect on final mean whole weight and shell height for both ploidy types (r) < 0.05). There was no significant difference in the final percentage triploidy between small and large grade triploids. A large proportion of diploid/triploid mosaicism was detected in adult triploid oysters. To determine if improvements in growth of a selected oyster line (L2) were additive to the faster growth of triploids, the performance of diploid and triploid selected and control oysters (four oyster lines) was compared. After a grow-out period of 21 months both mean whole weights and shell heights were in the order: L2 triploids > control triploids > L2 diploids > control diploids. A significant (p < 0.05) site* line interaction effect on whole weights and shell heights was detected. Growth improvements from selective breeding and triploidy were found to be additive with L2 triploids being 63% heavier than control diploids after 21 months grow-out. In this experiment, the type of oyster had no effect on final condition index, percent cavity volume, percent shell weight or cumulative mortality. Both diploid and triploid selected oysters had significantly (p < 0.05) higher whole weight to shell height ratios than diploid and triploid control oysters. Triploid Sydney rock oysters were shown to outperform diploids throughout NSW in terms of growth, survival and meat condition. The demand for both diploid and triploid Sydney rock oyster spat is now increasing and the demonstrated ability to combine the growth advantages of triploidy with selective breeding will no doubt increase the demand for hatchery spat further. However, commercial uptake of triploid technology will rely on overcoming the problems of early larval and spat mortality of hatchery reared Sydney rock oysters to ensure continuity of supply to farmers.

Within Australia, the Sydney rock oyster (SRO) is cultivated mainly in New South Wales and Southern Queensland. Their cultivation is now threatened by many biotic and abiotic stressors such as QX (Queensland Unknown), winter mortality, temperature and salinity variation due to rainfall. Changing environmental conditions influence the oyster's immune system along with the presence of pathogens and virulence. The microbiome also fluctuates with biotic and abiotic changes, but sometimes the relationship between host, environment and pathogens is not visible. Therefore, I have used SRO as a model to better understand their genetics and microbiomes in this thesis study. The aims of this research were to distinguish cultivated oysters from wild oysters and their inbreeding potential using molecular markers; to assess the transfer of microbiome communities in cultivated and wild oysters and their microbial composition differences; and to determine the level of salinity stressing the growth and survival rates of SRO. Two molecular markers, exon-primed intron-crossing (EPIC) primer pair markers, were developed and used to distinguish cultivated from wild oysters and to measure their inbreeding potential. By using the genome of Saccostrea glomerata as a reference, I therefore designed and examined 3 EPIC primer pairs for SRO. Another experiment was performed on oyster rearing in aquariums to assess if microbiome communities in cultivated and wild oysters can transfer from oyster to oyster and to determine the microbial composition differences in oysters during 3 experimental periods: microbiota of cultured SRO, microbiota of wild SRO, and microbiota of SRO in a mixed period of rearing. Two bioassay experiments were carried out to determine the level of salinity stressing the growth and survival rates of SRO.

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.

This study of settlement, nursery and growing techniques for Sydney rock oysters, Saccostrea commercialis, and Pacific oysters, Crassostrea gigas, was aimed at developing and evaluating production systems for juvenile oysters (spat). Settlement, retention (spat retained within nursery units from settlement or stocking to harvest), survival and growth of juvenile wild and hatchery produced oysters were assessed in relation to systems design and management at sites in New South Wales (NSVV), Australia.

Research Doctorate - Doctor of Philosophy (PhD)
Tolerance to heavy metal pollution has been described in many living organisms exposed to heavy metals at sublethal levels. Organisms living in metal contaminated sites have to develop physiological processes to respond to metal exposure to ensure survival and reproduction. The organisms may respond to this challenge through physiological acclimation or adaptation (the selection of resistant genotypes). This thesis was focused on the influence of prior metal exposure history on metal tolerance in Sydney rock oyster, Saccostrea glomerata in NSW, Australia. The thesis explored both physiological acclimation and possible adaptation to metal stress. To determine the level of metal contamination among estuaries in NSW and indicate the most relevant metals for further experimental studies, multivariate statistical techniques such as principle component analysis (PCA) and factor analysis (FA), and ecological risk indices including contamination factor (C_f), degree of contamination (C_d) and pollution loading index (PLI) were employed. Using accumulated metals in tissues of the oysters growing wild and farmed in NSW, these analyses identified locations both low and elevated in metals and identified metals most responsible for driving differences among locations.. The results indicated that most of polluted estuaries were located in the Central region of NSW, having impacts from large urban and industrial conurbation, while the unpolluted estuaries were located in the Northern / Southern region within the major regional waterways with low urban activity. The most elevated metals among NSW estuaries were cadmium, copper, lead and zinc. To investigate possible adaptation, the influence of metal exposure history on metal tolerance in the Sydney rock oyster (Saccostrea glomerata) offspring was investigated. The oysters were sampled from ten NSW estuaries such as Clyde River, Hastings River, Hunter River, Manning River, Nambucca, North Haven, Port Stephens, Port Kembla, Swansea Channels, and Wallis Lake which have a gradient in metal exposure history based on the results of multivariate analysis (PCA/FA) and ecological indices (C_f, C_d and PLI) of metals accumulated to adult oysters. Embryos were prepared under laboratory conditions by fertilizing sperm from ten males and oocytes from ten females within estuary using a strip spawning technique. The embryos were then exposed to sublethal concentrations of 2.5-40 μg/l, copper and 7.5-120 μg/l zinc for 48 h. The median effective concentration (EC₅₀) was determined as the metal concentration that caused 50% abnormal D-veliger larvae development.. The EC₅₀ values for copper were not significantly different among estuaries. Interestingly, a strong positive correlation between EC₅₀ and tissue metal concentration was found for zinc (R² = 0.835, p<0.000), but not for copper. Locations with higher environmental Zn exposures had more tolerant offspring. Such a finding suggests adaptation to Zn exposure (the selection of resistant genotypes) or a physiological acclimation effect mediated via maternal transfer. The full-length genomic sequence of S. glomerata, metallothionein (sgMT) was cloned and characterized. The sgMT sequence was composed of two metal responsive elements (MRE), one TATA box, one activator protein-1 (AP-1), three coding exons (28, 117, 80 bp), and two introns (115, 393 bp). The coding exons encoding a protein of 74 amino acids, with 9 cysteine motifs (Cys-X-Cys), cysteine-rich (28%), high lysine content (13.5%) and no aromatic amino acid residues. The phylogenetic analysis of sgMT protein sequence revealed that the sgMT was classified into the MT isoform I. Sequencing of full length of MT mRNA and MT genomic DNA allowed the identification of an intron-exon boundary and the development of the quantitative real time polymerase chain reaction (qRT-PCR). The qRT-PCR revealed that tissue-specific MT gene expression in S. glomerata was expressed highest in the digestive gland; significantly higher than gills, mantle, adductor muscle and gonad. The digestive gland was selected as a target tissue for a further examination of S. glomerata MT gene expression. Physiological acclimation to metals was also investigated by comparing adult oysters with a past history of metal exposure to oysters with no past history of metal exposure (both from the same gene pool) and examining their responses to subsequent metal challenges. Specifically, the experiment involved examining the influence of prior metal exposure history in wild Sydney rock oyster (Saccostrea glomerata) on metal accumulation, MT mRNA expression, glutathione peroxidase (GPx) and superoxide dismutase (SOD) upon subsequent cadmium, copper and zinc exposure. Oysters were sampled from seven locations in Hunter River such as Fullerton Cove, Kooragang Dykes, Windmill, South Arm Bridge, Fern bay, Fullerton St Stockton and Stockton Bridge. The results of multivariate analysis (PCA/FA) and ecological indices (C_f and C_d) of metal accumulation in the oyster tissue from seven locations elucidated that Windmill was the most contaminated with metals, while Fern Bay was the lowest. Copper and zinc were the most elevated metals with 3.71 and 2.51 times higher than NSW background, thus these metals were selected as metal candidates for metal exposure experiment. Cadmium was included as a positive control. Windmill(high past metal exposure history) and Fern Bay( negligible past metal exposure history)oysters were exposed to 20 and 200 μg/l of cadmium, 50 and 500 μg/l of copper and 200 and 2000 μg/l of zinc for 14 days. After exposure, MT mRNA expression, GPx and SOD activities were measured in digestive glands. The two-way ANOVA results revealed that Windmill oysters activated MT mRNA expression significantly higher than Fern bay oysters after exposure to 200 μg/l Cd, F(2, 22) = 10.35, p = 0.0007 and 2000 μg/l Zn, F(2, 21) = 24.28, p < 0.0001. The GPx activity was not significantly different between those oysters. The SOD activity showed significant interaction effects for copper with F(2, 21) = 10.91, p = 0.0006, indicating that Windmill oysters produced SOD activity significantly higher than Fern bay oysters after 50 μg/l Cu exposure. Significant interaction was also found for zinc with F(2, 24) = 7.27, p = 0.0034, where Fern bay oysters produced SOD higher than Windmill oysters after 200 μg/l Zn exposure, while Windmill oysters produced SOD higher than Fern bay oysters after 2000 μg/l Zn exposure. Thus prior exposure to metals can result in an upregulated compensatory response upon subsequent exposure to metals indicative of acclimation. Both acclimation, and potentially adaptation, are mechanisms responsible for the observed tolerance to metals in the Sydney Rock Oyster.

University of Technology, Sydney, 2001.
The study of place was often divided between the spatial interests of geographers and local historians intent on constructing heroic lineages. In the period of accelerated globalization however, discrete discourses on time and space are no longer tenable. Histories of place engage the transdisciplinary approach of recent scholarship in understanding the complexities and fluidity of the world in which we live. Places are constructed out of the enmeshing of the material, social and cultural. The reasons why people migrate both within and to particular places are also critical to the ongoing perceptions of that place, and the dynamics by which local communities operate within global networks. This thesis is an historical study of a recent sewage ocean outfall dispute between residents and the local council at Emerald Beach, in the Coffs Harbour region of New South Wales' Mid-North Coast. Alongside documentary sources, it uses oral testimony to examine the factors that contributed to people's understanding of their place, and the processes that resulted in the public contestation over that place. It argues that the positions taken in the sewage dispute cannot simply be perceived as a function of individual residents' responses within a bounded local context, but were a result of the complex processes of internal migration to the region since colonisation, and especially since the 1970s, that brought competing visions for the same place. In exploring the historical traces of the dispute, the thesis examines the first wave of non-Aboriginal migration to the coastal hinterland before turning attention to the second intensive wave of migration in the postwar period. Attention shifted away from the hinterland to the coast, and the chapters examine competing uses for the coast as local born residents, tourists and the influx of new settlers from the 1970s brought diverse dreams for the warm North Coast. In particular, the sewage conflict that grew into the direct-action protests at Emerald Beach provides clear insights into the flows of migration and settlement that led to the particular mix of people who fought for their divergent conceptions of place as critical to their lifestyle and residency. Without examining historical representations of places and events, conflict situations such as the sewage dispute at Emerald Beach cannot be fully illuminated. By demonstrating the force of internal migration on perceptions of, and contestation within place, this thesis provides one framework from which other places might be investigated.

Estuaries are the 'door mat' of human activity on land. They are also highly valued by the community. The New South Wales (NSW) oyster industry is Australia's oldest farming enterprise, dating back to the pre-European settlement era and as a consequence has social and cultural significance. Oyster farmers have developed generations of understanding and professional and intimate observation of the subtleties and frailties of NSW estuaries, cultivating their shells on a daily basis. The key motivation for this study is that the NSW oyster industry is a risk indicator of sustainable coastal catchment policy and practice. The studies are based on the overarching hypothesis that the economic, social, cultural, human health and environmental sustainability objectives of the NSW oyster industry require a historically- and scientifically-based risk analysis framework for selecting, managing and cultivating oyster farming areas. A review identified that it was vulnerable because of the lack of protection and planning for oyster growing areas. The aim of this thesis is to demonstrate that policies based on a risk analysis framework optimise outcomes for strategic management of the NSW oyster industry where risk is defined in terms of the effect of uncertainties on the industry's economic, social, cultural, human health and environmental sustainability objectives. The results demonstrate that a risk-based framework is effective in developing policy in strategic management of the NSW oyster industry and reducing uncertainty for the industry's economic, social, cultural, human health and environmental sustainability objectives. New approaches to improving profitability and durability and reducing risk to the NSW oyster industry objectives have been implemented as policy outcomes and industry practices as a result of this approach. Research and governance issues and the establishment of a management framework that fosters strategic policy development based on sound science using risk analysis and priority setting are all important steps on the ladder of estuarine ecosystem conservation and recovery. The policy outcomes that have been implemented in NSW as a result of a risk-based strategic approach are practical, tactical and goal oriented with the oyster industry recognised up-front in land use planning to address the consequences of potential impacts from ongoing rapid coastal urbanisation. A key element is the NSW Oyster Industry Sustainable Aquaculture Strategy.

Research Doctorate - Doctor of Philosophy (PhD)
Insulin-like growth factors (IGFs) play crucial roles in regulating growth, development and metabolism in animals. IGFs are complexed with specific binding proteins known as IGF binding proteins (IGFBPs), which modulate, either stimulate or inhibit, the action of IGFs. Most of the current literature on oyster biology focuses on reproductive cycle and growth patterns as well as their relationship with their ambient environmental conditions. Compared with vertebrates, little is known about the biology of IGFBPs and the molecular mechanisms involved in the regulation of growth in invertebrates, particularly molluscs. To fill this knowledge gap, both the cDNA and genomic DNA sequences of the IGFBP-5 and IGFBP-7 homologues were cloned from the Sydney rock oyster (SRO), Saccostrea glomerata. The spatial and temporal mRNA expression patterns, single nucleotide polymorphisms (SNPs) and their consequent haplotypes of these two genes as well as their transcriptional responses to fasting and hypoxia were investigated to decipher their potential roles in the regulation of the SRO growth. The full-length cDNA and gDNA sequences of the S. glomerata IGFBP-5 and IGFBP-7 genes (designated sgIGFBP-5 and sgIGFBP-7, respectively) were cloned and characterised for the first time. For sgIGFBP-5, the ORF consists of 357 bp, encoding a polypeptide of 118 amino acid residues. The deduced amino acid sequence of sgIGFBP-5 contained conserved N- and C-terminal regions, multiple cysteine residues and two conserved motifs (GCGCCXXC and CWCV). There are multiple putative regulatory DNA elements in the promoter region of sgIGBFP-5 which might interact with specific transcription factors to drive gene transcription, including an ERE half site, a SP1 site, an AP-1 site and a HRE. The genomic DNA of sgIGBFP-5 consists of 3 exons and 2 introns. For sgIGFBP-7, its ORF comprises of 780 bp, encoding a polypeptide of 259 amino acid residues. The sgIGFBP-7 protein consists of three conserved domains, including the IGFBP N-terminal domain, the Kazal-type serine protease inhibitor domain and the immunoglobin (Ig) domain, as well as one conserved motif “xCGCCxxC”. The promoter region of sgIGFBP-7 comprises of multiple putative regulatory DNA elements, including an ERE half site, an EGR1 binding site, a NF-κB cells binding site and a HRE core sequence. Phylogenetic analysis showed that the deduced proteins of sgIGFBP-5 and sgIGFBP-7 are clustered with their corresponding homologues from other molluscan species, supporting the proper nomenclature of the SRO genes. All of the observations above suggest that sgIGBFP-5 and sgIGBFP-7 is authentic IGFBP homologues and their genomic and deduced protein structures are conserved evolutionarily. Expression of sgIGFBP-5 and sgIGFBP-7 mRNA was detected in all the tested tissues in both juvenile and adult oysters. Notably, contrasting differential expression profiles of sgIGFBP-5 and sgIGFBP-7 mRNAs between the adult slow-growing and fast-growing oysters were observed in certain tissue types, implying that IGFBPs may play potential roles in regulating the growth of SRO. DNA sequencing of 100 oysters from each of the slow and fast-growing lines revealed the presence of 183 and 76 SNPs in the genomic regions of sgIGFBP-5 and sgIGFBP-7, respectively. Among these, 7 SNPs in sgIGFBP-5 and 16 SNPs in sgIGFBP-7 are significantly different in genotype/allele frequencies between the two oyster lines. The association of the SNPs identified in sgIGFBP-5 and sgIGFBP-7 with growth traits was examined among the oyster individuals grouped according to their genotypes constituted by each SNP. For sgIGFBP-5, significant differences were found in shell length among the genotypes constituted by six SNPs and in shell height among the genotypes constituted by all seven SNPs. For sgIGBFP-7, significant differences in shell length, shell height and whole oyster weight were found among the genotypes constituted by the majority of the identified SNPs. The association of sgIGFBP-5 and sgIGFBP-7 haplotypes with growth traits was also investigated. Statistically significant differences among the haplotypes were observed with respect to shell length and shell height for sgIGFBP-5 while no significant difference among haplotypes with respect to any of the tested growth traits for sgIGFBP-7 was found. These results suggest that the SNPs/haplotypes in sgIGFBP-5 and sgIGFBP-7 may have a significant association with the growth traits in S. glomerata and hence they may provide the basis for developing marker-assisted selection strategies to improve the oyster’s growth performance in the future. An in silico protein-protein interaction analysis was performed to identify the strengths of the potential binding between the deduced protein of each nonsynonymous haplotype groups and their potential ligands. The results revealed that the orders of binding strength of the tested ligands with each of the sgIGFBP-5 and sgIGFBP-7 haplotype groups were different. This finding suggests that sgIGFBP-5 and sgIGFBP-7 may have their own binding preferences for different cellular ligands, implying that the non-synonymous SNPs presented in the haplotype groups may give rise to critical changes in the 3D structure of the encoded IGFBP proteins, which in turn alter IGFBP-ligand interaction. A short-term starvation experiment and investigation of the regulatory effect of hypoxia on mRNA expression of sgIGFBP-5 and sgIGFBP-7 were conducted. For the fasting experiment, the sgIGFBP-5 and sgIGFBP-7 expression levels in both digestive gland and mantle tissue in fasting oysters increased compared to controls at the time points of Days 3, 5 and 7. This lead to the postulation that catabolic activity was increased and IGFBPs in the starved oysters are released into the circulation to bind to IGFs, thereby restricting IGFs from binding to their cognate receptors and hence slow down the oysters’ growth. The study also pointed out that re-feeding (2 days) of fasting oysters restored the basal expression of the IGFBP mRNA. This may suggest that the downregulation of these genes could in turn release the availability of IGFs for IGF-receptor binding or growth. However, this was the short-term starvation experiment, and the changes in growth traits of S. glomerata were not measured. Thus, it remains premature to conclude the roles of the sgIGFBPs in growth regulation. For the hypoxic experiment, no significant change in HIF-1 and IGFBP mRNA expression were detected in any of the tested oyster tissues after 5 days of air exposure. These observations do not agree with a hypothesis that HIF-1 expression is increased under hypoxic conditions and the increased HIF-1 availability can in turn activate IGFBP gene transcription via binding to the HRE(s) located in the IGFBP gene promoter. Overall, the findings from this research provide information on the structures and potential functions of IGFBPs in relation to growth and stress effects. In the future, from the SNPs and/or haplotypes in sgIGFBP-5 and sgIGFBP-7, identification of growth associated genetic markers will contribute to improving the genetic stock, productivity, sustainability and profitability of the SRO (and potentially other molluscan species).

There has been a continuous decline in both the production and general performance of the SRO in NSW estuaries over the past three decades. The relationship of this decline to both environmental and oyster-density related factors are assessed in this thesis. This question has been examined at different scales: a large scale that compares two different estuaries (Clyde and Shoalhaven Rivers, southern NSW); a regional scale that encompasses variations within an estuary and, at a lease scale that examines processes pertaining to individual or small groups of oysters. ... A set of environmental indices were used to complement the model and to assess the sustainability of the culture system. The combined indices indicated that while the ecological carrying capacity of the Clyde was exceeded the production capacity at an estuarine scale was not. On the lease scale, density experiments showed that while growth was not reduced as a result of current stocking densities, the condition index was significantly affected.

Research Doctorate - Doctor of Philosophy (PhD)
Environmental estrogens are known to interfere with normal development and reproduction in a wide range of marine invertebrates. Previous studies have developed an oyster biomonitor to indicate the presence of estrogenic compounds in marine environments through exploiting the induction of the egg yolk protein precursor vitellogenin (Vtg). Despite this advance, the mechanism through which estrogens exert their action on Vtg gene expression, in particular the functional role of the estrogen receptor (ER), is currently unknown. In an attempt to fill this knowledge gap, the present research aims to isolate the genes encoding Vtg (sgVtg) and ER (sgER) from the Sydney rock oyster Saccostrea glomerata and investigate different potential mechanisms contributing to estrogen mediated induction of sgVtg. Our results indicated that the deduced protein of sgVtg is substantially longer than those of the other oyster Vtgs reported so far and contains all the conserved domains as found in other marine molluscs. The sgVtg promoter contains multiple putative half-EREs which are closely spaced, implying that they may function as an estrogen response unit (ERU) to interact with ER. In line with the potential involvement of ER in sgVtg regulation, the induction of sgVtg mRNA expression in ovarian explants was shown to be abolished by the ER antagonist ICI 182, 780. Considering that the vertebrate-like ER so far reported in molluscs lacks estrogen-binding ability, this finding supports the requirement of a novel estrogen-binding receptor for gene activation. The sgER cDNA is predicted to encode a 477-amino acid protein, which contains a DNA binding domain (DBD) and a ligand binding domain (LBD) conserved among vertebrate and invertebrate ERs. Comparison of the sgER LBD sequence with those of other ligand-dependent ERs indicated that the sgER LBD is degenerate at several conserved residues critical for ligand binding and receptor activation. Its inability to bind estrogens was then confirmed by a ligand binding assay using fluorescent-labelled E2 and purified sgER protein. The 5′-flanking region of sgER contains three putative ½EREs and several other putative elements for ER-interacting transcription factors, suggesting potential autoregulation of sgER expression. sgER mRNA is ubiquitously expressed in various tissues, with the highest expression level observed in the ovary where sgVtg is highly expressed. Functional analyses, including luciferase gene reporter assays, point mutation of ½ EREs and an electrophoretic mobility shift assay (EMSA), confirmed that sgER binds and activates the sgVtg promoter through ½EREs. In addition, sgER mRNA was significantly upregulated following in vitro and in vivo exposure to E2 and the enhancing effect of E2 on sgER expression was abolished by co-treatment with the specific ER antagonist ICI 182, 780 in vitro. These findings support the presence of a novel estrogen-binding receptor in S. glomerata. To elucidate whether estrogens modulate sgVtg and sgER expression at the epigenetic level, we assessed the DNA methylation levels of a 5’ intragenic CpG island in sgVtg and a promoter CpG island in sgER in ovaries after E2 exposure in vivo. Bisulfite sequencing revealed that both of these CpG islands are hypomethylated in both control and E2-treated oysters. Neither significant differential DNA methylation nor correlation between DNA methylation and mRNA levels was observed for either sgVtg or sgER. Overall, the findings from this research provides new molecular insights into how environmental estrogens regulate Vtg expression in marine molluscs and lays the foundation for further research into the mechanism of action of estrogenic compounds on molluscan vitellogenesis.

Throughout the Earth’s history climate change has led to a proliferation and disappearance of species thus playing a major role in shaping the structure of marine ecosystems. Over the next century, rising atmospheric carbon dioxide (CO2) levels will cause a rise in the partial pressure of CO2 (pCO2) in the surface ocean leading to a reduction in surface ocean pH from 8.1 to 7.7 units and a reduction in the concentration of surface ocean carbonate ions (in a process known as ‘ocean acidification’) vital in the construction of calcium carbonate (CaCO3) shells and skeletons. At the same time, this rise in atmospheric CO2 levels will lead to an increase in sea‐surface temperatures (SSTs). Of growing concern are the potentially serious implications that ocean acidification and rising SSTs may have on marine organisms and ecosystems and the potential risk to marine aquaculture internationally. Recent studies, which have mimicked ocean acidification, have reported adverse consequences of elevated pCO2, including reduced calcification and growth, and increased rates of abnormality and mortality in larvae and adults of a range of marine organisms. Yet, we know comparatively little of the synergistic consequences of elevated pCO2 and temperature nor the potential for species to acclimate through genetic adaptation, at the population and ecosystem level. This lack of knowledge limits our ability to create models that accurately predict the consequences of future climate change. Among the organisms most likely to be affected in an acidifying and warming ocean are marine calcifying organisms which construct shells and skeletons of CaCO3. Studies on these organisms, to date, have focused predominately on adults, with comparatively few considering the sensitive early life history stages. This study compared the synergistic effects of elevated pCO2 and temperature on the early life history stages of two ecologically and economically important oysters: the Sydney rock oyster, Saccostrea glomerata and the Pacific oyster, Crassostrea gigas. Gametes, embryos, larvae and spat were exposed to four pCO2 (375, 600, 750, 1000 ppm) and four temperature (18, 22, 26, 30 °C) levels in acute exposure experiments. At elevated pCO2 and suboptimal temperatures there was a reduction in the fertilisation success of gametes, a reduction in the development of embryos and size of larvae and spat and an increase in abnormal morphology of larvae. These effects varied between species with S. glomerata having greater sensitivity than C. gigas. Combined, elevations in pCO2 of 750–1000 ppm and a temperature of 30 °C resulted in 100% mortality of D‐veliger larvae of S. glomerata. In contrast, the same pCO2 and temperature combination resulted in only 26% mortality of D‐veliger larvae of C. gigas. A comparison between two commonly used methods for manipulating the seawater carbonate system (HCl‐acidification and CO2‐acidification) showed that there was no significant difference in the responses of S. glomerata and C. gigas to the two methods. This indicates that both HCl‐acidification and CO2‐acidification are adequate methods for determining the effects of elevated pCO2 for these species.