A Sydney marine ecologist researching the immense potential of seagrasses to store carbon for thousands of years, and therefore highlighting its conservation value.
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Peter Macreadie's love of fishing and snorkelling in seagrass environments makes his work as a marine ecologist a pleasure. But the research he is doing into the carbon-storing potential of seagrasses may soon boost everybody's appreciation of the sometimes neglected marine plantlife.
Seagrass can store carbon for thousands of years with little leakage, according to Peter's research. This compares to the just decades-long capture and storage provided by the current carbon-sink favourites, land-based forests.
The news has the seagrass world abuzz and Peter hopes the rest of the population will feel the same before too long.
"The research that we've got from seagrass systems indicates that they're really good at capturing and storing carbon. Unlike terrestrial systems, which often only capture and store carbon for a decade or so, the seagrass systems can store the carbon for thousands of years. And Australia has more seagrass than anywhere else in the world."
Currently these grasses - together with saltmarshes and mangroves - are thought to be responsible for up to 70 per cent of all submarine carbon capture, despite only covering 1 per cent of the sea floor. Australia has an exceptionally large seagrass habitat, being 25 per cent larger than the size of Tasmania.
This resource not only captures carbon - it is also vital for the survival of fisheries in Australia and around the world with half the world's fisheries relying on sea grass meadows. Unfortunately it is rapidly being depleted by coastal development and warming oceans and nearly a third has been destroyed already.
By extracting 4-metre deep cores from the seabed, Peter and his team are looking thousands of years back in time to see how things have changed. They use radio-dating and carbon labelling to assess the age of the sediments and then look at what sort of carbon signatures are there. Is the carbon residue derived from seagrasses, microalgae, or terrestrial plants? What does the answer suggest about changes in that landscape over time?
"Our research shows that since the time of European settlement in Botany Bay there's been a sudden change in the landscape. We see that we used to have this really important carbon sink for 6,000 years up until European settlement and then suddenly you don't see the signature of this seagrass carbon source and it shifts to a microalgal carbon source."
Peter's research is now directed towards making what he calls the "coalmine canaries of the coastal ecosystems", more resilient. Preserving genetic diversity is already high on this list.
"Australia needs to recognise these are very, very powerful carbon sinks and they are being destroyed."
Peter is a Chancellor's Postdoctoral Research Fellow at the University of Technology, Sydney and entered his research into the Eureka Prize for Outstanding Young Researcher.
How much control do we have over the amount of seagrass? Can we, for example, plant more to increase the level of sequestration, as we can do with trees? And does it sequester atmospheric carbon?
Yes, seagrass can be planted, although it's considered to be much more challenging than planting trees. Research is underway around the world to find ways to improve the success and feasibility of planting seagrass. The other way to control the amount of seagrass is by managing existing meadows to increase the likelihood that they'll expand. Atmospheric carbon readily dissolves in seawater, and then is taken up by seagrasses during photosynthesis.
I am doing a science assignment biography on you- When and where were you born? What did you study? What is your marital status?
I was born in Melbourne in 1981. I spent most of my life growing up in Melbourne's eastern suburbs. After high school (Donvale Christian College), I did a Bachelor of Science (inc. Honours) and PhD at the University of Melbourne. I then took up a postdoctoral fellowship at the University of Technology, Sydney (UTS), which is the position I currently hold. I married my high school sweetheart.
What role do dugongs play in the propagation of sea grass beds? Shouldn't dugongs be protected to maintain healthy sea grass beds and thus enhance carbon capture and storage?
Great question. I'm unaware of any evidence that dugongs contribute towards propagation of seagrass beds, but it is possible that their feeding could facilitate the spread of seeds and whole plants.
Some argue that dugongs are detrimental to seagrasses because they remove and fragment large amounts of seagrass (they can eat up to 50 kg a day!), but I think it's fair to say that our love of dugongs indirectly benefits the seagrasses because you have to protect the seagrasses if you want to protect dugongs.
In Australia, dugongs are protected under the Environmental Protection and Biodiversity Act 1999, but we still have a long way to go towards minimising human threats (e.g. collision with boats, entanglement in fishing nets, degradation of seagrass meadows).
Overall, I think the message should be: ‘Look after the seagrasses (and dugongs!), and they'll look after you'
How much sea grass (roughly) is there in the world? Is it more than the Amazon (in helping w/ carbon dioxide)?
Another great question. Seagrasses occur on every continental margin of our planet (except Antarctica), and recent estimates put the total global seagrass area between 177,000 and 600,000 km2.
Australia has more seagrass area than anywhere else in the world: around 95,000 km2. To put this in perspective, it's an area the size of the state of Victoria!
Although the seagrasses represent a much smaller area than terrestrial forests, their total contribution to long-term global carbon capture and storage is comparable. This is because they are so effective at burying carbon. Seagrasses bury carbon at a rate 30 times greater than tropical rainforests!
If you want the hard core numbers, here they are: global carbon burial of seagrasses has recently been estimated at 48-112 Tg C yr-1, whereas the world's tropical rainforests (which includes the Amazon Rainforest) are estimated to bury to 78.5 Tg C yr-1.