Four blue carbon sinks from left: Seagrass, marsh, mangroves and cyanobacteria mats.

Blue Carbon

Blue carbon ecosystems—tidal marshes, mangroves and seagrasses—are hotspots of carbon sequestration in oceans. Carbon cycling in tidal wetlands is a major focus of the Biogeochemistry Lab, and we are actively advancing research and policy on this important emerging topic.

Tidal wetlands have been important model ecosystems for studying carbon cycling for decades. Yet, viewing our knowledge on this topic through a blue carbon lens shows that there are large gaps which demand new research. A short list includes:

  • Processes that control methane and nitrous oxide emissions, two greenhouse gases less abundant—but more powerful—than carbon dioxide. These insights will allow us to develop improved proxies for greenhouse gases emissions based on characteristics such as vegetation, water table and salinity that are easily mapped.
     
  • The fraction of carbon sequestration in tidal wetland soils that is both allocthonous (entered the wetland from a different location) and unreactive. Some fraction of the organic carbon deposited with sediments would have been stable over a century or more in any deposition environment. These data are needed in order to calculate the amount of atmospheric CO2 removed by a wetland.
     
  • The stability of tidal wetlands over the next century, particularly with respect to sea level rise. Improvements in forecast models are needed in order to establish that carbon sequestered by created, restored or protected tidal wetlands will remain in place for a specified length of time, often a century.

Conservation

Tidal wetlands and seagrass beds store carbon at rates that exceed even tropical forests, yet the role of blue carbon ecosystems in climate change policy lags far behind that of forests. We are advancing the idea that climate goals can be achieved through conservation and wise management of tidal wetlands and seagrass meadows. As a member of the Blue Carbon International Scientific Working Group since 2010, Pat Megonigal is meeting with scientists and policymakers worldwide to communicate this message.

Blue Carbon in the Middle East

In winter of 2013, Pat Megonigal and the Biogeochemistry Lab joined an international team researching blue carbon in Abu Dhabi (part of the United Arab Emirates). The country's coastal ecosystems—especially mangroves—have the potential to bury vast amounts of carbon. Its coasts also contain large microbial mats of cyanobacteria, more commonly known as "blue-green algae." These mats comprise a fourth blue carbon sink that can soak up carbon dioxide from the atmosphere. Megonigal's team worked with other U.K. and U.S. scientists, and a contingent of local volunteers, to get a better sense of how much carbon the country's marine ecosystems can store.

Read More: Dancing on bacteria

Carbon Crediting

Momentum has been growing to recognize the unique carbon cycling characteristics of blue carbon ecosystems in order to secure financing for wetland activities such as restoration and creation. Methodologies (i.e. rules) for granting carbon credits to activities in tidal wetland ecosystems have been approved under the American Carbon Registry and the Verified Carbon Standard, and the Intergovernmental Panel on Climate Change issued guidance on producing national inventories for tidal marshes and mangroves.