Author Identifier

Sian Edwards's ORCID record ORCID Logo

Date of Award

2026

Keywords

blue carbon, tidal marshes, Western Australia, BlueCAM, carbon sequestration, isotope analysis

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Master of Science by Research

School

School of Science

First Supervisor

David Blake

Second Supervisor

Paul Lavery

Third Supervisor

Anna Lafratta

Abstract

Tidal marshes are highly productive coastal vegetated ecosystems (CVE), capable of sequestering organic carbon (Corg) and retaining it for millennia when left undisturbed. Corg stocks and carbon accumulation rates (CARs) vary across climatic zones and environmental gradients, resulting in regional differences in coastal environments. Additionally, disturbances can impact the capacity of tidal marshes to sequester Corg. Restoring degraded marshes presents a practical solution to enhance Corg sequestration. In Australia, the 2022 Tidal Restoration of Blue Carbon Ecosystems Methodology Determination has been established as a voluntary carbon scheme; Blue Carbon Projects (BCPs) hold significant potential for carbon reduction through tidal reintroduction. The potential abatement for a BCP can be estimated using Australia’s BlueCAM model. Currently, data on the variability of Corg stocks and CARs along the coast of Western Australia, as well as the potential for a BCP through the restoration of tidal marsh wetlands, remain limited. Consequently, quantifying Corg stocks and CAR is essential to understanding the factors influencing Corg sequestration in Western Australian tidal marshes, as well as the carbon dynamics and the development of effective blue carbon strategies.

Four tidal marsh wetlands, spanning a north-south gradient, along Western Australia’s coastline were studied. At each wetland, three replicate soil cores were used to calculate the accumulated Corg stocks at 30 cm, 50 cm and 100 cm depths, along with measurements of explanatory variables including dry bulk density (DBD), %Corg and δ13C. One core per site was analysed for 210Pb concentrations to determine the Sediment Accumulation Rate (SAR mm y-1) and Mass Accumulation Rate (MAR g cm-2 y-1) which facilitated the development of an age-depth model and the estimation of Corg stocks for periods of eighty and one hundred years. The study also examined the effects of tidal restriction and explored the potential for a BCP in a southwest coast tidal marsh wetland, along with demonstrating additionality to estimate carbon abatement using BlueCAM.

The variations in Corg stocks and CAR observed along the north-south gradient in Western Australia are likely influenced by climate and geomorphological factors. Notably, the highest Corg stocks accumulated over 80 years were 77% greater in the southernmost temperate tidal marsh compared to the northern most semi-arid tidal marsh. Moreover, CAR were higher in the southern sites relative to the northern ones. An analysis of Corg stocks of a 100-year period and CAR for both undisturbed and disturbed sites demonstrated additionality and that tidal restriction impacts the site’s capacity to sequester Corg. Site-specific data from this study, along with default values employed in BlueCAM for estimating potential carbon abatement, revealed instances of overestimation or underestimation at particular sites. Given the absence of a formal national database for Corg stocks and carbon accumulation rates in Australia, this research underscores the significance of establishing such a framework, especially to incorporate datasets, thereby enhancing the representation of Western Australia’s coastal variability. The site-specific data provided from a wetland with tidal restrictions can be utilised in BlueCAM to improve the accuracy of carbon abatement estimates and to support future BCPs restoration initiatives and climate change mitigation strategies.

Access Note

Access to this thesis is embargoed until 17th July 2028 

Download

Available for download on Monday, July 17, 2028

Share

 
COinS
 

Link to publisher version (DOI)

10.25958/erep-h548