- Title
- Assessment of estrogenic endocrine disrupting chemicals (EDCs) and their adverse effects on the development and function of Sydney rock oysters, Saccostrea glomerata
- Creator
- Islam, Rafiquel
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Estrogenic compounds include the natural estrogen, 17β-estradiol (E2), and its analogues estrone (E1) and estriol (E3); synthetic estrogen, 17α-ethinylestradiol (EE2); and the industrial chemicals bisphenol A (BPA), 4-nonylphenol (4-NP), and 4-t-octylphenol (4-t-OP). Despite evidence of estrogens in aquatic environments and associated reproductive effects in adult gonads, little is known about estrogen loads in wastewater treatment works (WWTWs) and their efficacy in removing the load, or about the current contamination status of watercourses globally or in Australia, particularly in estuarine and marine environments. Even less knowledge exists of how ongoing estrogenic contamination in Australia and globally has impacted early larval developmental stages in offspring, or about sublethal effects of estrogenic exposure on adult oysters and their metabolome, which may have consequences for oyster reproduction, growth, and development. First, the following topics were addressed: efficiency of removal of estrogenic endocrine-disrupting chemicals (EDCs) throughout the various stages of tertiary WWTW processes; the remaining estrogenic EDCs load that can enter discharge locations; and the localisation of discharge, such as estuarine or marine environments. This study also measured the associated hazard risk for aquatic taxa living in these environments. The seven commonly found estrogenic compounds listed above were measured in wastewaters collected at different stages of the treatment regime and in waters from receiving environments (marine and estuarine), using chromatographic-mass spectrometry after solid-phase extraction. The concentration of EDCs in wastewater ranged from < LOQ (limit of quantification) to 158 ng/L for Tanilba Bay WWTW, and from < LOQ to 162 ng/L for Belmont WWTW. The secondary stages of the treatment process significantly reduced the EDC load, which ranged from 39.21% to 99.98% at both WWTWs. The reductions of natural estrogens (E1, E2, and E3) and 4-t-OP were significantly greater than those of EE2, BPA, and 4-NP at both WWTWs. The potential ecological risks of individual EDCs were calculated as risk quotients (RQs); no ecological risk was shown by targeted compounds in predicted diluted effluents (RQ ≤ 1.65 × 10−2) and shore samples (RQ < 1). Finally, the combined ecological risk or hazard index (HI) suggested zero or low risk for predicted diluted effluents (HI = 0.0097–0.0218) as well as shoreline samples (HI = 0.393–0.522). The effects of estrogenic EDCs on molluscan embryonic and larval development and of parental F0 exposure on F1 offspring are very little known. To address this area, the research assessed the effects on the native Australian Sydney rock oyster (Saccostrea glomerata) and their carry-over embryotoxic impacts on offspring. Males and females were subjected to globally environmentally relevant concentrations (50 ng/L) of EE2, the most potent synthetic estrogen and a major ingredient of contraceptive pills. The parental exposure did not reveal any notable effects on fertilisation success, early F1 larval morphs or unfertilised eggs. However, offspring showed developmental delays, reduction in D-veliger percentages after 45 μm mesh screening and declined swimming capabilities or fitness of larvae at 2 dpf (days post-fertilisation). Although parental exposure did not alter the survival of F1 larvae at 9 dpf, the length was reduced. Subsequent larval exposure (2–9 dpf; 5 and 50 ng/L EE2) revealed further declines in survival and shell length. Overall, parental exposure to EE2 imparts carry-over effects to offspring and exacerbates retardation of larval development. Subsequent larval exposure further reduces physiological development and survival. To understand how estrogens may affect the functioning of adult oysters, a study was undertaken using environmentally relevant mixtures of estrogens in receiving waters to assess alterations of the metabolome of S. glomerata. After seven days of exposure to estrogenic mixtures relevant to Australian and global receiving waters (referred to below as “low” and “high”, respectively), the polar metabolome was assessed in the digestive gland, gill, and gonad tissue using 1H NMR (proton nuclear magnetic resonance) spectroscopy. The soft body mass was significantly lowered in both sexes after exposure to low and high mixtures, and alteration of the metabolome was also observed, with particularly pronounced effects observed in the digestive gland. However, the metabolome of gills and ovaries expressed lower sensitivity, except at high exposure. The male gonad was nonresponsive to both exposure levels. The major metabolites, such as amino acids, carbohydrates, intermediates of the tricarboxylic acid cycle, and adenosine triphosphate (ATP), were all down-regulated in the responsive tissues and exhibited tissue-specific responses; the digestive gland was particularly sensitive. Thus, estrogen mixtures have great impacts on the metabolome and associated energy production in various organs, particularly the digestive gland. The reduced energy metabolism may be translated into lower pools of available ATP energy for cellular homeostasis, normal somatic maintenance and growth, and reproductive fitness. It was also found that seven days of acute exposure to estrogen mixtures relevant to Australian and global receiving waters can also alter the nonpolar metabolites or lipidome of S.glomerata. However, a strong effect of carrier solvent (ethanol, 0.0002% v/v) in causing a lower abundance of the quantified lipids was revealed, particularly in the digestive gland and gill tissue. Again, the male gonad did not exhibit any significant alterations in lipidomes in response to estrogen. But, in the female gonad, the major metabolomes, such as phospholipid and phosphatidylcholine, expressed a significant reduction after high estrogenic mixture exposure. Overall, it was demonstrated that ongoing estrogenic contamination in watercourses globally could affect adult oysters, with carry-over effects on early larval development in offspring. Furthermore, subsequent larval exposure either at Australian or globally relevant concentrations has pronounced effects on larval growth, development, and survival. In addition, the sublethal effects of estrogen exposure on adult oysters, including alterations of the metabolome (polar and non-polar), may have linked consequences for reproduction, growth, development, and ultimately fitness.
- Subject
- endocrine disrupting chemicals (EDCs); adverse effects; growth and development; functioning; Sydney rock oysters; Saccostrea glomerata
- Identifier
- http://hdl.handle.net/1959.13/1509174
- Identifier
- uon:56220
- Rights
- Copyright 2022 Rafiquel Islam
- Language
- eng
- Full Text
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