Quantifying ‘blue carbon’ stocks in seagrass Posidonia australis and the impact of historical anthropogenic disturbance in Western Australia.

Moulton, Emma (2018) Quantifying ‘blue carbon’ stocks in seagrass Posidonia australis and the impact of historical anthropogenic disturbance in Western Australia. Honours thesis, Murdoch University.

Abstract

Recent research into coastal ecosystems have highlighted the importance of seagrass meadows in their ability to efficiently capture and store carbon into the sediment, however meadows are in decline. This study aims to identify local organic carbon stocks in the aboveground and belowground biomass of the species Posidonia australis whilst comparing effects of human disturbance. Mangles Bay in Cockburn Sound was chosen as a degraded bay indicated by high human use, such as boating and industrial effluent, while Shoalwater Bay was chosen due to its location in a marine sanctuary. A total of 32 samples across 2 bays were sampled in-meadow for meadow characteristics and core samples containing the whole plant and sediment. Three locations were collected for bare sediment outside the meadows of each bay. Samples were dried at 70°C and burnt at 400°C using loss on ignition method to determine carbon content. Organic carbon per hectare was found to be higher overall in Mangles Bay, with a substantial contribution from the carbon stored in the sediment (34.81 ±4.45 Mg Corg per ha). Aboveground biomass in both bays had higher overall percentage carbon than all other categories sampled. True detrital matter in Shoalwater Bay had significantly higher percent carbon and carbon per hectare (5.71 ±4.83 Mg Corg per ha) values. Percent carbon was also highest in the sediment at 2.5 m depth in both bays. Low flushing in Mangles Bay is thought be the primary cause of higher carbon content in the sediment, though it is not significantly higher (P = 0.337). Overall anthropogenic disturbance in each bay had little impact on current Posidonia australis meadow carbon stocks in the aboveground and belowground.

Item Type:	Thesis (Honours)
Murdoch Affiliation(s):	School of Veterinary and Life Sciences
Supervisor(s):	Verduin, Jennifer and Fontaine, Joe
URI:	http://researchrepository.murdoch.edu.au/id/eprint/41932

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