Saltmarsh profile survey and soil blue carbon storage sampling on Eyre Peninsula

24 June 2021

The latest saltmarsh profile survey was completed at Acraman Creek – between Streaky Bay and Ceduna – as part of a baseline data comparison of the condition of saltmarsh at 11 sites across the Eyre Peninsula.

Acraman Creek is the fifth profile survey to be completed as part of the Saltmarsh Threat Abatement and Recovery Project supported by Eyre Peninsula Landscape Board through funding from the Australian Government’s National Landcare Program.

Eyre Peninsula Landscape Board staff were joined in the field by scientists from Adelaide University, local surveyors, Far West Coast Rangers and staff from Department for Environment and Water’s Coast and Marine Branch.

They worked together to collect a range of information, including vegetation type, vegetation height and density, land height, evidence of animal presence and any signs of disturbance.

Landscape Officer with the Eyre Peninsula Landscape Board, Alex Fraser said it was great to work and learn from a range of people, some who have a great depth of knowledge about saltmarsh.

“Saltmarshes are a critically important vegetation community we have on Eyre Peninsula. Many are supporting early stages of marine species and provide important feeding areas for many shorebirds,” Mr Fraser said.

“These surveys are really important to help us to manage the more than 3,000km of saltmarsh coastline across the Eyre Peninsula.”

Results from the five surveys undertaken so far are still being analysed, however early indications reveal some sites have changed very little in approximately 25 years since they were previously surveyed while others are showing more significant changes. The results will be provided in a detailed report at the end of the project.

During the field work, Adelaide University Researcher Dr Alice Jones and PhD student Sophie Russell collected soil cores from different types of saltmarsh vegetation communities at different heights along the profile.

Funding provided by the Eyre Peninsula Landscape Board and Coast Protection Board is being used to assess blue carbon stocks in coastal ecosystems at Acraman Creek as well as Davenport Creek.

Blue carbon is the term used to describe organic carbon that is stored in the plants and soils of coastal ecosystems, like saltmarshes, seagrasses and mangroves.

These ecosystems can capture more carbon than forests on land, storing it for up to thousands of years which prevents it being released to the atmosphere as carbon dioxide – and means that coastal ecosystem conservation and restoration are nature-based options for reducing climate change through decreasing the amount of carbon dioxide in the atmosphere.

Carbon analysis is currently being undertaken on the sediment samples and will investigate the influence of tides, sea level, vegetation type and disturbance on carbon storage in saltmarshes.

The results from the western Eyre Peninsula sites will add to the results from the 181 sediment core samples taken at Mount Young, Franklin Harbour and Tumby Bay sites last year. Results from the three eastern Eyre Peninsula sites showed sediment organic carbon stocks (tonnes per hectare) were highest in mangroves, followed by intertidal saltmarsh and then supratidal saltmarsh. In addition there was some variability between sites, with Franklin Harbour having greater organic carbon stocks than the other two sites. A copy of the report is available.

Dr Alice Jones said this study of Eyre Peninsula saltmarsh sites sheds new light on the influence of vegetation types and saltmarsh on carbon stock in South Australia.

“It highlights that different environmental conditions affect soil blue carbon stocks, causing variability within sites and between sites,” Dr Jones said.

A final report for all sediment sample sites will be undertaken once the western Eyre Peninsula sediment analysis has been completed.