Blue Carbon

Blue carbon refers to carbon captured in coastal and ocean ecosystems. In addition to providing habitat for many different plant and animal species, protecting coastal communities and infrastructure from storms and waves, and providing recreational opportunities, coastal ecosystems like marshes, mangrove forests, and seagrass beds also store large amounts of carbon in their soils. 

Carbon enters the coastal ecosystems through upland runoff, through coastal plant photosynthesis, and by oceanic tides and wave action. While some carbon leaves the system as methane (CH4) or carbon dioxide (CO2), much is deposited belowground by the plants’ roots and accumulation of dead plant material that does not decompose quickly due to the low oxygen conditions. Carbon is also buried in the muddy sea floors farther offshore by the falling detritus of sea life higher in the water column. Artist/Credit: Ben Slyngstad ORISE fellow

Alt text: Comic-style illustration. Panel one shows three types of ecosystems that store large amounts of carbon: marshes, a with long-legged stork looking for fish in partially submerged grass; mangroves, with tangled mangrove roots serving as both a hide away for fish underwater and as a perch for a pelican above water; and seagrass, with a manatee grazing along patches of short grass lining the seabed. Panel two shows carbon flowing through coastal ecosystems. On left side of diagram, arrows indicating carbon flows point from inland mountains to a coastal marsh. Within the marsh (*representative of all three ecosystems), a large arrow points down from the atmosphere to the marsh grass, indicating CO2 being pulled in by photosynthesis, and small arrows show carbon moving from the plants back into the atmosphere (CO2 and CH4 lost via respiration). Moving to the right, getting progressively deeper underwater as you go, marsh, mangroves, and sea grass also move carbon into the soil through their roots and from the accumulation of dead leaves that do not decompose quickly in wet conditions. On the left side of the diagram, in the deepest water, arrows point both towards and away from the coastal ecosystems, representing estuarine carbon that is deposited into coastal habitats by tides and waves. CO2 also flows both into (large arrow) and out of (small arrow) ocean waters. Finally, an arrow points down through the ocean waters, demonstrating how muddy sea floors form reservoirs of carbon made from detritus falling from the waters above.