A recent study has revealed that a marine heatwave in Western Australia in 2010 released a “carbon bomb” that damaged the world’s largest seagrass meadow and released millions of tons of carbon that had collected over thousands of years under the water.
The research, performed by Oscar Serrano and colleagues from Edith Cowan University in Western Australia, examined how carbon released impacted the world’s largest collection of seagrass at Shark Bay between 2010 and 2011.
Shark Bay is home to between 0.6% and 2.4% of the world’s seagrass coverage where it has been growing for 8,000 years.
Seagrass is a flowering grass-like plant that grows in shallow waters. The plant gathers carbon dissolved in the sea and buries it under the surface. The amount of carbon stored is very similar to the amounts of carbon stored in tropical forests sediments.
The big difference between the two, forests will store the carbon for roughly 60 years before releasing most of it, while seagrasses will store the carbon for thousands of years if left undisturbed.
As science explores the importance of seagrass, new research has shown that when the top layer of actively growing seagrass is disturbed by impacts such as boat anchors or heatwaves, the carbon that has collected can be quickly released.
The carbon in Shark Bay was released when heatwaves caused the death of the seagrass, allowing oxygen to penetrate the layers of dead seagrass, changing the bacteria that live in it.
“Despite seagrasses having thrived over millennia’s in Shark Bay, unprecedented widespread losses occurred in the austral summer of 2010/2011,” the authors wrote in their paper published in Nature Climate Change.
The authors discussed how the loss has a double-whammy impact on emissions.
“When you have an event such as the losses at Shark Bay, you not only lose the seagrass as a way of removing CO2, but the sequestered gas is released back into the atmosphere during seagrass matter decomposition.”
Since the beginning of the 20th century, seagrass meadows have declined at an average rate of 0.9% per year, mostly due to coastal development and decreased water quality caused by human
When looking at trying to fix the problem, the researchers suggested manually sowing seeds or transplanting seedlings as options that should be considered, since encouraging faster recovering would limit the amount of carbon lost after the disturbance.