Seagrass meadows play an important role in the global carbon cycle by storing large amounts of carbon in their sediments. Recent scientific efforts have focused on valuing seagrass ecosystems. However, the robustness of these valuations can be questioned since there are still major knowledge gaps in explaining the influence of species variation and the inherent seagrass environment upon carbon accumulation in seagrass meadows. Based on this outsight, Rozaimi’s PhD thesis aims to:
1. Provide new perspectives into the variability in carbon accumulation among seagrass meadows, with particular reference to Posidonia australis and Halophila ovalis meadows; and
2. Understand the roles of sediment characteristics in controlling carbon preservation in seagrass ecosystems.
To achieve these objectives, several sediment cores in estuarine and oceanic seagrass meadows around Australia will be sampled. Detailed analyses of the cores will mainly revolve around the determination of sedimentary organic carbon content. Other physical aspects of the sediment will be analysed to account for variations in carbon content among seagrass meadows, which include organic matter content, inorganic carbon content, stable carbon isotope composition of the organic matter, sediment dry bulk density and sediment grain-size composition. Selected cores will be analysed to determine their age, biochemical characteristics and microbial metabolism to gain a further understanding of the processes involved in the accumulation of large amounts of organic matter in seagrass sediments. To that effect, this PhD project serves to bridge the differing fields of seagrass ecology and marine biogeochemistry.
How the stocks of carbon preserved in seagrass sediments is affected by the seagrass species and by the habitat in which it occurs will be investigated, thus exploring the role of species and habitat in the preservation and accumulation of organic carbon. In addition the forms of carbon that are preserved in seagrass sediments using NMR analysis will be determined. Finally, an experimental investigation which will test whether the exposure of deep sediments to oxic conditions (as occurs following disturbance) can cause the ‘preserved’ carbon to be re-mineralised. The objective is to obtain a holistic picture of the carbon burial phenomenon in seagrass meadows to contribute to new insights in understanding the processes leading to carbon preservation in seagrass ecosystems.
Australian Institute of Nuclear Science and Engineering
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