Blue carbon
[2]: 2220 Most commonly, it refers to the role that tidal marshes, mangroves and seagrass meadows can play in carbon sequestration.
[13][8] At the time, the term was coined to highlight that coastal vegetated ecosystems have a disproportionately large contribution to global carbon sequestration.
[15] Although vegetated coastal ecosystems cover less area and have less aboveground biomass than terrestrial plants they have the potential to impact long term C sequestration, particularly in sediment sinks.
[16] As habitats that sequester carbon are altered and decreased, that stored amount of C is being released into the atmosphere, continuing the current accelerated rate of climate change.
Quantifying rates of decrease are difficult to calculate, however measurements have been estimated by researchers indicating that if blue carbon ecosystems continue to decline, for any number of reasons, 30-40% of tidal marshes and seagrasses and approximately 100% of mangroves could be gone in the next century.
[19] Reasons for the decline of mangroves, seagrass, and marshes include land use changes, climate and drought related effects, dams built in the watershed, convergence to aquaculture and agriculture, land development and sea-level rise due to climate change.
Data on the rates at which CO2 is being released into the atmosphere is not robust currently; however, research is being conducted to gather better information to analyze trends.
Loss of underground biomass (roots and rhizomes) will allow for CO2 to be emitted changing these habitats into sources rather than carbon sinks.
[20] Increases in carbon capture and sequestration have been observed in both mangrove and seagrass ecosystems which have been subjected to high nutrient loads, either intentionally or due to waste from human activities.
[26] Marshes sequester C in underground biomass due to high rates of organic sedimentation and anaerobic-dominated decomposition.
[24] Salt marshes may not be expansive worldwide in relation to forests, but they have a C burial rate that is over 50 times faster than tropical rainforests.
[33] Mangroves are naturally disturbed by floods, tsunamis, coastal storms like cyclones and hurricanes, lightning, disease and pests, and changes in water quality or temperature.
[32] Although they are resilient to many of these natural disturbances, they are highly susceptible to human impacts including urban development, aquaculture, mining, and overexploitation of shellfish, crustaceans, fish and timber.
[37] Currently global seagrass meadows are estimated to store as much as 19.9 Pg (gigaton, or billion tons) of organic carbon.
[37] There has been considerable attention to how large-scale seaweed cultivation in the open ocean can act as a form of carbon sequestration.
[46] The decline in seagrasses is due to a number of factors including drought, water quality issues, agricultural practices, invasive species, pathogens, fishing and climate change.
[48] The deeper layers of the ocean are greatly unsaturated in CO2 and its dissolved forms, carbonic and bicarbonic acid, and their salts.
[50] At depths greater than 3 km, CO2 becomes liquefied and sinks to the seafloor due to it being higher density than the surrounding seawater.
Mathematical models have shown that CO2 stored in deep sea sediments beyond 3 km could provide permanent geological storage[51] even with large geomechanical perturbations.
