Scientists assess storage value in blue carbon ecosystems

When Hurricane Dorian roared up the East Coast during the first week of September, the places where people live and work in several states were under threat. The first line of protection against storm damage was made up of coastal vegetated ecosystems, including nearly 300,000 acres of salt marshes in Georgia.

The salt marsh, seagrass, and mangrove ecosystems that bore the brunt of pounding waves are not, however, immune from damage. Increasingly frequent and intense storms, coupled with rising sea levels, break apart and erode these ecosystems, threatening their ability to protect coastal communities and act as a globally important soil carbon reservoir.

Coastal salt marsh, seagrass and mangrove ecosystems – known as blue carbon ecosystems – account for a small fraction of the world’s land surface but store more carbon per unit area than forests. A new University of Georgia-led research study stresses the importance of understanding the value of carbon buried along the coasts worldwide – how much there is and how to best protect it.

The article, published in Nature Geoscience, explains the significance of blue carbon ecosystems and the need to better understand the processes that promote soil carbon storage and how disturbances, such as hurricanes, impact long-term preservation. This information is critical for predicting how well blue carbon ecosystems will protect coastal communities in the future and provide other ecosystem services, such as habitat for recreationally and commercially valuable fish and shellfish species.

“Blue carbon ecosystems are unique because they sit at the land-sea interface,” said Amanda Spivak, associate professor in the UGA Franklin College of Arts and Sciences department of marine sciences and lead author on the article. “We can look to marine and terrestrial systems for guidance as to the important mechanisms affecting soil carbon preservation so that we can better understand how blue carbon ecosystems work and respond to disturbances.”

Blue carbon ecosystems literally build up land by turning atmospheric carbon dioxide into plant biomass and trapping sediment particles washed in by tides. The organic carbon of this material may remain buried in this way temporarily or for thousands of years, depending on oxygen levels and water chemistry that in turn effect how bacteria access the carbon. A soil core sample from a marsh in Georgia, and a marsh in New England, and a marsh in Micronesia, would each reveal a great variation in carbon storage value, or the carbon stock in the soils of marshes. One priority for the researchers is the need to investigate the factors driving that variability.

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