http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11112 Although mounting evidence suggests exposure to estrogenic contaminants increases vitellogenin production in molluscs, demonstration of dose–response relationships and knowledge of the temporal nature of the vitellogenin response with continual exposure is currently lacking for biomarker utility. To address this knowledge gap, adult Sydney rock oysters, Saccostrea glomerata, were exposed to a range of environmentally relevant concentrations of 17α-ethynylestradiol (EE2) (0, 6.25, 12.5, 25 or 50 ng/l) in seawater under laboratory conditions. Vitellogenin induction and gonadal development was assessed following 4, 21 and 49 days exposure to EE2. Vitellogenin was found to increase in a dose dependent manner with EE2 exposure for females (4 and 49 days) and males (4 and 21 days). Histological examination of gonads revealed a number of individuals exhibited intersex (ovotestis) in 50 ng/l EE2 (after 21 days) and in 6.25 and 12.5 ng/l EE2 (after 49 days). Furthermore, a significant shift towards females was observed following 49 days exposure at 50 ng/l EE2 suggesting estrogenic exposure is capable of facilitating a progression for protandric males from male-intersex-female gametal status. Increases in female vitellogenin (4 days) were predictive of later increases in female developmental stages at 21 days and increases in oocyte area following 49 days. Male vitellogenin (4 days) was predictive of decreased male percentages and lower male developmental stages at 49 days. Vitellogenin in S. glomerata is a predictive biomarker of estrogenic exposure and effect if sampled soon after exposure and at the commencement of a gonadal development cycle. 2012-07-19T23:20:03.795Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1171 The Akoya pearl oyster (Pinctada imbricata) was experimentally exposed to (a) constant levels of lead (Pb) at 180 μg L⁻¹ for nine weeks, or (b) two short term (pulse) exposures of Pb at 180 μg L⁻¹ (three weeks each) with an intervening depuration period (three weeks), to assess its utility as an (i) accumulative monitor of Pb contamination and an (ii) archival monitor for discriminating constant versus pulsed Pb exposure events. P. imbricata showed similar reductions in growth (based on shell morphology and wet weight) and Pb accumulation patterns for whole tissue and shell in response to both Pb exposure regimes. Thus the whole oyster was deemed an inappropriate accumulative monitor for assessing short-term temporal variation of Pb exposure and effect. However, using secondary ion mass spectrometry, Pb was shown to accumulate in the successively deposited nacreous layers of the shell of P. imbricata, documenting the exposure history of constant versus pulsed Pb events. Patterns of Pb deposition not only reflected the frequency of Pb exposure events but also their relative durations. Thus, the shell of P. imbricata may be employed as a suitable biological archive of Pb exposure. 2010-04-27T06:38:13.803Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:2480 Bivalve molluscs are filter feeders, with pearl oysters able to filter water at rates up to 25 l h‾¹ g‾¹ of dry wt. tissue. Since this process leads to rapid bioaccumulation of recalcitrant pollutants such as heavy metals, organochlorine pesticides and hydrocarbons from impacted sites, it has prompted the widespread use of molluscs as biomonitors to quantify levels of marine pollution. This paper proposes pearl oyster deployment as a novel bioremediation technology for impacted sites to remove toxic contaminants, reduce nutrient loads and lower concentrations of microbial pathogens. Estimates extrapolated from the literature suggest that a modest pearl oyster farm of 100 t oyster material per year could remove 300 kg heavy metals plus 24 kg of organic contaminants via deposition into the tissue and shell. Furthermore, it was estimated that up to 19 kg of nitrogen may be removed from the coastal ecosystem per tonne of pearl oyster harvested. Pearl oysters are also likely to filter substantial amounts of sewage associated microbial pathogens from the water column. Method of cultivation and site selection are the key to minimising negative environmental impacts of bivalve cultivation. Deployment of oysters at sites with high nutrient and contaminant loadings would be advantageous, as these compounds would be removed from the ecosystem whilst generating a value-added product. Future potential may exist for harvesting bio-concentrated elements for commercial production. 2010-04-27T06:23:34.666Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:263 The use of pearl oysters has recently been proposed as an environmental remediation tool in coastal ecosystems. This study quantified the nitrogen, phosphorus and heavy metal content of the tissue and shell of pearl oysters harvested from a small pearl oyster farm at Port Stephens, Australia. Each tonne of pearl oyster material harvested resulted in approximately 703 g metals, 7452 g nitrogen, and 545 g phosphorus being removed from the waters of Port Stephens. Increasing current farm production of 9.8 t yr(-1) to 499 t yr(-1) would balance current nitrogen loads entering Port Stephens from a small Sewage Treatment Plant (STP) located on its southern shores. Furthermore, manipulation of harvest dates to coincide with oyster condition would likely remove substantially greater quantities of nutrients. This study demonstrates that pearl aquaculture may be used to assist in the removal of pollutants from coastal waters while producing a commercially profitable commodity. © 2004 Elsevier Ltd. All rights reserved. 2010-04-27T05:57:03.297Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:5448 Adult Saccostrea glomerata were exposed to environmentally relevant concentrations of 4-nonylphenol (1 μg/L and 100 μg/L) and 17α-ethynylestradiol (5 ng/L and 50 ng/L) in seawater over 8 weeks. Exposures were performed to assess effects on vitellogenin induction and gonadal development during reproductive conditioning. Chronic direct estrogenicity within gonadal tissue was assessed via an estrogen receptor-mediated, chemical-activated luciferase reporter gene-expression assay (ER-CALUX®). Estradiol equivalents (EEQ) were greatest in the 100 μg/L 4-nonylphenol exposure (28.7 ± 2.3 ng/g tissue EEQ) while 17α-ethynylestradiol at concentrations of 50 ng/L were 2.2 ± 1.5 ng/g tissue EEQ. Results suggest 4-nonylphenol may be accumulated in tissue and is partly resistant to biotransformation; maintaining its potential for chronic estrogenic action, while 17α-ethynylestradiol, although exhibiting greater estrogenic potency on biological endpoints possibly exerts its estrogenic action before being rapidly metabolised and/or excreted. A novel methodology was developed to assess vitellogenin using high-performance liquid chromatography (HPLC). Exposure to both 17α-ethynylestradiol (50 ng/L) and 4-nonylphenol (100 μg/L) produced increases in vitellogenin for females, whereas males exhibited increases in vitellogenin when exposed to 50 ng/L 17α-ethynylestradiol only. Females exhibited greater vitellogenin responses than males at 50 ng/L 17α-ethynylestradiol only. Histological examination of gonads revealed a number of individuals exhibiting intersex (ovotestis) in 50 ng/L 17α-ethynylestradiol exposures. Male individuals in 1 μg/L and 100 μg/L 4-nonylphenol exposures and 5 ng/L 17α-ethynylestradiol were at earlier stages of spermatogenic development than corresponding controls. 2010-04-27T04:48:52.766Z ]]>