Conserving our marine environments to combat climate change

OUR ENVIRONMENT Conserving our marine environments to combat climate change

Revealing the role of blue carbon

Cutting-edge Australian research is helping explain the dominant role marine and coastal ecosystems play in storing carbon to offset greenhouse gas emissions; a major cause of climate variability as well as in promoting the conservation and restoration of coastal / marine vegetation.

‘Blue carbon’ is a concept name for the capture and storage of atmospheric carbon in the marine environment.

The concept is that coastal vegetation stores carbon far more effectively and permanently than terrestrial forests and freshwater wetlands, where organic carbon is often re-mineralised and lost to the atmosphere.

Mangrove and saltmarsh are considered the most efficient wetlands for sequestering carbon because the saline conditions inhibit the capacity of methanogenic bacteria which are responsible for methane (greenhouse gas) emissions. Until now though, there has been limited measurable studies to understand this carbon flux process, as estimates of carbon store and carbon accumulation rates at a particular site are beset by issues of scale and provenance and thus do not scale to regional estimates. This is now changing as researchers find ways to identify the possibilities for blue carbon.

The value of their efforts not only helps to explain the potential of these natural phenomena, but it also plays a vital role in promoting the importance of restoration and conservation of coastal vegetation.

Ten south-east Australian estuaries extending across 2000 km of coastline were selected and a range of methods including isotope tracer techniques were used to determine the source of carbon accumulating in mangroves and saltmarsh.

Some of the work involved measurements using a continuous flow isotope ratio mass spectrometer (CF-IRMS) interfaced with an elemental analyser, which is a precise method for analysing stable isotopes and is a capability that’s helping ANSTO contribute to national and international research on climate change.

The results indicate that carbon accumulating on the wetland’s surface is driven primarily by tidal transport of terrestrial carbon and litter fall from forests. However, much of this carbon degrades, and the dominant source of long-term carbon stored in the soil comes from mangrove and saltmarsh root material. Wetlands play an important role in the cycling of carbon, water and nutrients and habitat for many kinds of animals and plants through photosynthesis and accumulation of organic matter in soils, sediments and plant biomass.

In general wetland plants grow at a faster rate than they decompose, contributing to a net annual carbon sink.

It’s hoped the work of these researchers will reinforce the message to decision makers of the importance of protecting marine environments.

Over the past few decades there have been substantial changes to the estuarine ecosystems throughout much of the New South Wales coast.

Changes in vegetation, coastal development for accommodating population growth in the coastal cities, coupled with predicted sea-level rise have impacted mangrove and saltmarsh wetlands and associated biodiversity and ecosystem services of wetlands.

Contact

debashish.mazumder@ansto.gov.au

COLLABORATORS

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ANSTO

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University of Wollongong

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Macquarie University

RESEARCH FACILITY / TECHNIQUE

Continuous flow isotope ratio mass spectrometer (CF-IRMS) RESEARCHER TEAM

Dr Debashish MAZUMDER

Dr Kerrylee ROGERS Prof Neil SAINTILAN

Prof Cloin WOODROFFE

PUBLICATIONS

Estuarine, Coastal and Shelf Science 2013

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