- Title
- Adverse effects of metal(loid)s in saltmarsh ecosystems and the potential of Australian saltmarsh halophytes for phytoremediation
- Creator
- Voigt, Rebecca Ann Lily
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2025
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Saltmarshes are valuable ecosystems that provide a range of ecosystem services. Over the last two centuries, saltmarshes have experienced decline globally. Frequently situated in proximity to urban and industrial development, saltmarshes around the globe are susceptible to contamination from metal(loid)s and other anthropogenic pollutants. Metal(loid)s accumulate in saltmarsh sediments and can be taken up by the resident flora and fauna, posing a serious ecotoxicological risk to a community that is already under threat from a multitude of pressures. Metal(loid)s can have significant adverse effects on plants from the molecular to population level and have the capacity to bioaccumulate in the food chain. Internationally some halophytic plant species have demonstrated the ability to tolerate and even remediate high concentrations of metal(loid)s in contaminated sediments and waters through phytoremediation. Whilst the potential of halophytes for phytoremediation has been increasingly recognized in the literature internationally, there is still a dearth of studies on Australian species, generally limited to cosmopolitan species found globally. Given Australia’s geographical isolation and the high degree of endemism at a species level, unique halophytic adaptations may exist in Australian saltmarsh flora that facilitate their use in phytoremediation. However, the ecotoxicological risk of metal(loid)s in Australian saltmarshes is also largely unexplored. Given this context, the overall aim of this thesis is to investigate the uptake and partitioning of metal(loid)s in Australian halophytes, examine their sub-lethal effects and evaluate their potential use for phytoremediation. In Chapter 2, I reviewed the literature to examine the contamination status of Australian saltmarsh and the phytoremediation potential of Australian halophytic saltmarsh species. Of 93 species reviewed, 6 species showed potential to remediate organic pollutants, and 15 for metal(loid)s. Of these, 6 species showed the potential to remediate both inorganic and organic contaminants. This chapter also demonstrated that there is a lack of research available for Australian halophytic species. In Chapter 3 I focused on the uptake and partitioning of metal(loid)s (Cu, Zn, As, Se, Cd, Pb) in two rare saltmarsh species novel to the literature, Tecticornia pergranulata and Wilsonia backhousei. These species generally accumulated the lowest levels observed among Australian taxa, as indicated by their BCFs. The uptake of metals into roots was largely influenced by total sediment metal loads as well as pH, soil organic matter, and salinity. The limited uptake and translocation of metal(loid)s in these species may offer a competitive advantage for their establishment and survival in their last urbanised populations, where legacy metal contamination acts as a selective pressure. In Chapter 4, I examined the sub-lethal effects of chronic single and mixed metal exposure (Pb and Zn) on an Australian saltmarsh species Sarcocornia quinqueflora. Metals were found to have an adverse effect on plant photosynthetic performance and growth and biomass. Lead was more toxic than Zn, and Zn appeared to have an antagonistic effect on the toxicological effects of Pb in S. quinqueflora. Metals were primarily accumulated to roots, suggesting S. quinqueflora may be suitable for phytostabilisation of Pb and Zn, and could effectively reduce the mobility of these metals in saltmarsh ecosystems. The work of Chapter 5 builds on Chapter 4, whereby I further examined the sub-lethal effects of mixed metal(loid) contamination on the photosynthetic performance and biomass of S.quinqueflora, though now under field conditions. The findings were consistent with those ofChapter 4, whereby metal(loid)s were primarily accumulated in roots, with limited translocation to non-photosynthetic stems. Findings suggest that metal(loid)s present in the sediment and plant tissues were correlated to the photosynthetic performance and biomass of S. quinqueflora. The action of metal(loid)s on photosynthetic biochemistry and the subsequent effect on plant biomass appear to be suitable targets for future molecular analysis to further elucidate mechanisms of toxicity working towards the development of adverse outcome pathways. Finally, in Chapter 6, I reviewed the literature on common anthropogenically enhanced metals (Cu, Zn, Cd, and Pb) in saltmarsh ecosystems globally and their effects on halophyte transcriptome, proteome, metabolome, and physiology. The review revealed that targets of metal toxic effect are predominantly biomolecules involved in metal transport and detoxification, antioxidant pathways associated with metal-induced oxidative stress, and photosynthetic biochemistry. These findings suggest these targets would be useful biomarkers in future studies designed to develop adverse outcome pathways in saltmarsh ecosystems. Overall, this thesis concludes that the phytoremediation potential and mechanisms of metal(loid) tolerance varied among Australian species. Whilst most species exhibit properties of phytostabilisation, whereby metal(loid)s are primarily accumulated in root tissues, the novel findings we reported for two rare saltmarsh species in Sydney Olympic Park highlight the need for further examination of novel Australian species and cosmopolitan species within Australian environments, to fully understand their phytoremediation capacity and mechanisms of metal(loid) tolerance. Furthermore, S. quinqueflora, appears to be relatively tolerant to metal(loid) contamination and a promising candidate for phytostabilisation of metal(loid)s in sediments and saline waters. Metal(loid)s exposure was found to be linked to adverse effects in halophytes from the transcriptome to population levels, though further research is still required to establish adverse outcome pathways.
- Subject
- saltmarsh; environmental Science; ecotoxicology; phytoremediation; metals; Australia
- Identifier
- http://hdl.handle.net/1959.13/1519460
- Identifier
- uon:57398
- Rights
- Copyright 2025 Rebecca Ann Lily Voigt
- Language
- eng
- Full Text
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