Seaweed could help counter effects of climate change: Deakin research

A study led by Deakin University and University of Technology Sydney scientists into the carbon capturing capacity of coastal plants and seaweeds provides new insight into the potential of these plants to help counter the effects of climate change on the environment.

The research is the first investigation of how a diverse range of coastal plants and seaweed can contribute to blue carbon stocks - the carbon that is sequestered by the ocean and coastal habitats.

The finding, published in the prestigious Ecology journal, that some seaweed species have the capacity to make a significant contribution to coastal carbon capture may better inform projects designed to mitigate against greenhouse gas emissions.

According to co-first author Stacey Trevathan-Tackett, a PhD candidate in the UTS Plant Functional Biology and Climate Change Cluster (C3), these blue carbon systems are recognised as being more efficient than land-based systems for long-term carbon storage.

But Ms Trevathan-Tackett said a better understanding of how the diverse range of coastal plants contribute to blue carbon "pools" was needed for both carbon accounting and coastal management purposes.

"We wanted to know how the fundamental biology, that is, the cell wall structure and cell wall composition of seaweeds and coastal vascular plants like seagrasses, affected their long term carbon storage potential in blue carbon habitats," Ms Trevathan-Tackett said.

"Seaweeds in particular are of interest because they generally produce a lot of biomass and are "often dislodged, making them potentially important contributors to blue carbon stocks.

"However we don't know if this carbon is as chemically stable as that of coastal plant species or whether seaweed carbon can be stored long term in coastal habitats."

The research team used thermal analysis (Thermogravimetric Analysis) to quantify the decomposition of plant material under increasing temperature.

The results showed that cell wall structure and composition of seaweed in particular are central to their long-term carbon storage potential. In addition the discovery that some species of seaweed

contained compounds that only degraded at very high temperatures means there is potential for a contribution to long term carbon storage.

"This has implications for planning because the role of seaweed as a donor to blue carbon stocks should be considered in coastal carbon sequestration and remediation projects," said fellow C3 PhD candidate and co-first author Jeffrey Kelleway.

The project leader, Dr Alecia Bellgrove, from Deakin University's Centre for Integrative Ecology within the School of Life and Environmental Sciences, said the results of the study were exciting.

"It has been recognized that seaweeds are important for short-term carbon capture because of their huge biomass.  But until now, seaweeds have been thought to break down rapidly and therefore not be significant contributors to long-term carbon sequestration," Dr Bellgrove said.

"However, what we have shown is that not all seaweeds are equal and some show great potential for long-term sequestration.

"There is enormous seaweed biomass in our oceans and understanding where that all ends up and how much of it is locked away is the next big area of research to pursue."

The study forms part of a large coastal carbon accounting project being undertaken by researchers in eight Australian institutions under the CSIRO Marine Geochemistry Coastal Carbon Cluster initiative. The project was co-funded by Deakin University Centre for Integrative Ecology within the School of Life and Environmental Sciences.

Publication details:

Comparison of marine macrophytes for their contributions to blue carbon sequestration.

Stacey M Trevathan-Tackett, Jeffrey Kelleway, Peter Macreadie, John Beardall, Peter Ralph, Alecia Bellgrove Ecology (2015) http://www.esajournals.org/doi/abs/10.1890/15-0149.1