Very little is currently known regarding the effects of estrogenic endocrine disrupting chemicals on embryonic and larval development in molluscs, nor the potential effects of parental (F₀) exposure on resultant F₁ offspring. In this study, we assessed the embryotoxic impacts of exposure to environmentally relevant concentrations of the synthetic estrogen, 17α-ethinylestradiol (EE2), to male and female parents (50 ng/L) and their offspring (5 and 50 ng/L) in the native Australian Sydney rock oyster, Saccostrea glomerata. There were no detectable effects of parental exposure on fertilisation success, proportions of early larval (F₁) morphs and unfertilised eggs. Offspring impacts were evidenced in terms of developmental delays, with decreased percentages of D-veligers retained by 45 μm mesh, along with a reduction of swimming capabilities of larvae at 2 days post-fertilisation (dpf) when both parents had been exposed to 50 ng/L EE2. Although no significant parental effects were found on the survival of F₁ larvae at 9 dpf, retardation of shell growth was observed on F₁ larvae in treatments where both parents had been exposed to 50 ng/L EE2. Subsequent larval exposure from 2 to 9 dpf caused declines in survival and reduction of shell length in F₁ larvae at both 5 and 50 ng/L EE2 across all parental exposure treatments. Collectively, parental EE2 imparts effects on offspring in terms of retardation of larval development, and subsequent offspring exposure to EE2 further exacerbates impacts to development. Future research should aim to understand the potential mechanisms of EE2 induced toxicity and its transmission resulting in altered phenotypes of the F₁ generation.

Metal concentrations are reported for a seagrass ecosystem receiving industrial inputs. δ13C and δ15N isotope ratios were used to establish trophic links. Copper concentrations (dry mass) ranged from <0.01 μg/g in fish species to 570 μg/g (μ = 49 ± SD = 90 μg/g) in the oyster Saccostrea glomerata. Zinc concentrations ranged from 0.6 μg/g in the seagrass Zostera capricorni to 10,800 μg/g in the mud oyster Ostrea angasi (μ = 434 ± 1390 μg/g). Cadmium concentrations ranged from <0.01 μg/g in fish species to 268 μg/g in Ostrea angasi (μ = 6 ± 25 μg/g). Lead concentrations ranged from <0.01 μg/g for most fish species to 20 μg/g in polychaetes (μ = 2 ± 3 μg/g). Biomagnification of metals did not occur. Organisms that fed on particulate organic matter and benthic microalgae had higher metal concentrations than those that fed on detritus. Species physiology also played an important role in the bioaccumulation of metals.

Vitellogenin (Vtg) is a well-established biomarker of estrogenic exposure in aquatic animals. In vertebrates, Vtg gene transcription is controlled by the estrogen receptors (ERs). Although an ER ortholog is present in molluscs, its role as a transcriptional regulator remains elusive. Here, we tested the hypothesis that in the Sydney rock oyster, Saccostrea glomerata, the ER ortholog activates Vtg gene transcription through specific interaction with its promoter. Luciferase reporter assays indicated that sgER activated both a minimal promoter containing the consensus estrogen-responsive elements (EREs) and the sgVtg promoter in an estrogen-independent manner. The sgVtg promoter-luciferase activation was significantly reduced when any of three putative ERE half sites (½EREs) in the promoter were mutated. Electrophoretic mobility shift assay (EMSA) confirmed that sgER binds specifically to a 68-bp promoter sequence where these ½EREs reside. Overall, the results suggest that sgER is a constitutively active transcription factor that binds and activates the sgVtg promoter.

The current study aimed to examine the relationship between metals in sediments and metal bioaccumulation in oyster tissue in a highly-modified estuary (Sydney estuary, Australia). While extensive metal contamination was observed in surficial sediments, suspended particulate matter and oyster tissue, a significant relationship between these media could not be established. No relationship was determined between sediment quality guidelines and oyster size or weight, nor with human consumption levels for metals in oyster tissue. Moreover, oyster tissue metal concentrations varied greatly at a single locality over temporal scales of years. Oyster tissue at all 19 study sites exceeded consumptions levels for Cu. Bioaccumulation of metals in oyster tissue is a useful dynamic indicator of anthropogenic influence within estuaries, however oysters cannot be used in Sydney estuary as a valid biomonitor due to overriding internal regulation (homoestasis) by the animal, or by external natural (sediment resuspension) and anthropogenic (sewer/stormwater discharges) pressures, or both.

Perfluorinated alkyl compounds (PFCs) including perfluorooctane sulphonate (PFOS) and perfluorooctanoate (PFOA) were measured in environmental samples collected from around Homebush Bay, an urban/industrial area in the upper reaches of Sydney Harbour and Parramatta River estuary. Water, surface sediment, Sea Mullet (Mugil cephalus), Sydney Rock Oyster (Saccostrea commercialis) and eggs of two bird species; White Ibis (Threskiornis molucca), and Silver Gull (Larus novaehollandiae) were analysed. In most samples PFOS was the dominant PFC. Geometric mean PFOS concentrations were 33ng/gww (wet weight) in gull eggs, 34ng/gww in ibis eggs, and 1.8ng/gww and 66ng/gww in Sea Mullet muscle and liver, respectively. In sediment the PFOS geometric mean was 1.5ng/g, in water average PFOS and PFOA concentrations ranged from 7.5 to 21ng/L and 4.2 to 6.4ng/L, respectively. In oysters perfluorododecanoic acid was most abundant, with a geometric mean of 2.5ng/gww.

Solutions are being sought to ameliorate the impacts of anthropogenic climate change. Seagrass may be a solution to provide refugia from climate change for marine organisms. This study aimed to determine if the seagrass Zostera muelleri sub spp. capricorni benefits the Sydney rock oyster Saccostrea glomerata, and if these benefits can modify any anticipated negative impacts of ocean acidification. Future and ambient ocean acidification conditions were simulated in 52 L mesocosms at control (381 μatm) and elevated (848 μatm) CO₂ with and without Z. muelleri. Oyster growth, physiology and microbiomes of oysters and seagrass were measured. Seagrass was beneficial to oyster growth at ambient pCO₂, but did not positively modify the impacts of ocean acidification on oysters at elevated pCO₂. Oyster microbiomes were altered by the presence of seagrass but not by elevated pCO₂. Our results indicate seagrasses may not be a panacea for the impacts of climate change.

This study investigated relationships between Sydney Rock Oyster (SRO) health and element concentrations in sediments and oysters from the Richmond River estuary. Six sites were sampled between November 2019 and May 2020. Multivariate permutational analysis of variance was used to compare oyster health parameters and element concentrations between sites, wet and dry conditions, and in oyster and sediment samples. Statistical analysis revealed significant spatial differences in oyster mortality, condition index, and size. Metal concentrations in oyster flesh significantly differed from metals in sediments. Most metals in sediments were below guideline values, except for Ni at some sites. Mortality, condition index, and weight correlated negatively with individual elements in oyster flesh (P, Zn, Mg, Al, Ni). BEST statistical models included various combinations of metals in sediment and flesh. This study highlights that spatial differences in SRO health tend to be related to site-specific metal compositions in sediment and oysters.

Oysters and clams are abundant and popularly consumed seafood in Viet Nam. These bivalves were proved to be suitable bioindicators to assess the heavy metal accumulation in the aquatic environment. The study is to investigate heavy metals such as As, Cd, Hg and Pb in the cultured oysters Saccostrea glomerata and clams Meretrix lyrata collected in VanDon - Quang Ninh, and CatBa - Hai Phong. The results showed that the metal heavy concentrations in the oysters Saccostrea glomerata and clams Meretrix lyrata presented in the order of As > Cd > Pb > Hg. The most polluted concentration with As among four heavy metals studied in six sampling sites was 2.81 ± 1.07 and 1.6 ± 0.62 mg/kg wet weight for clams and oysters, respectively. Investigated heavy metals in cultured oysters and clams indicated potential risks for human health in future by assessment of the heavy metals.

Heatwaves are an increasing threat to organisms across the globe. Marine and atmospheric heatwaves are predicted to impact sessile intertidal marine organisms, especially when exposed at low tide and unable to seek refuge. The study aimed to determine whether a simulated atmospheric heatwave will alter the survival of selectively bred families of Sydney rock oysters (Saccostrea glomerata), and whether survival is dependent on morphological and physiological traits. The survival of S. glomerata families to a simulated atmospheric heatwave varied from 25 to 60% and was not correlated with morphology or physiology. Survival may depend on the presence of genotypes that translate into molecular defenses such as heat-shock proteins and inhibitor of apoptosis proteins that provide oysters with resilience. Understanding the responses among families of oysters to heatwaves is critical if we are to restore the ecological services of oyster reefs and sustain oyster aquaculture.