What Is Blue Carbon?

The sea grass blue carbon ecosystem has stored over 19.9 billion tons of carbon.
The sea grass blue carbon ecosystem has stored over 19.9 billion tons of carbon.

Blue carbon is the carbon arrested by the coastal ecosystems including intertidal salt marshes, sea grass meadow or mangrove forest, and the oceans across the Globe. The carbon capture by these organisms living in the oceans is stored in the form of sediments and biomass from potential algae, sea grasses, mangroves, and salt marshes. These ecosystems trap vast carbon reservoirs which they capture from the carbon dioxide present in the atmosphere and then deposit the carbon in the sediments.


Carbon dioxide is one of the major contributors to climate change and in a bad way. The ocean and the coasts provide a perfect way of reducing this gas through sequestering the carbon. In fact, historically, the terrestrial forest and ocean ecosystems are the main natural carbon sinks. Although the vegetation on the ocean covers less than 0.5% of the seabed, this ecosystem is responsible for storing more than 70% of the carbon in the atmosphere. This ecosystem captures the carbon dioxide by sequestering the carbon in the underlying sediment, which is present in the dead biomass, and the below ground and underground biomass. The blue carbon can be stored for millions of years in the plant sediments found under water. Organic carbon can be sequestered from the ocean if it reaches the floor of the sea and get covered by the sediment layer. The lowered oxygen levels in the already buried environment means that the bacteria which eat organic matter cannot produce carbon dioxide since they cannot decompose carbon. This means that the carbon is removed from the atmosphere completely.

Blue Carbon Ecosystem Types

Although these ecosystems are way smaller in size than the world’s forest, they sequester carbon way faster and can continue sequestering for many years, where the carbon is captured and stored underwater and away from the atmosphere where it cannot affect the atmosphere. When these ecosystems are damaged a large amount of carbon is released into the atmosphere which can be detrimental to the climate. There are many different ecosystems of blue carbon ecosytems.

Sea grass Blue Carbon Ecosystem

These are a group of over sixty angio-sperm species which have adapted to the aquatic life and can easily grow in the meadows on the shores in all the continents except the Antarctica. The sea grass grows in a depth of up to 165 feet depending on light availability and quality of water. The sea grasses are very productive and can produce a highly effective ecosystem services like biodiversity and habitat, sediment stabilization, and nutrient and carbon sequestration. Although these grasses occupy only 0.1% of the ocean floor, they account for up to 18% of the oceanic blue carbon burial. Currently this ecosystem has stored over 19.9 billion tons of carbon.

Mangrove Blue Carbon Ecosystem

These are forested halophytes which form the intertidal forest while providing various crucial ecosystem services including carbon sequestration and coastal protection, among others. There are 73 identified mangrove species found in 123 countries. These trees are responsible for about 10% of the world carbon burial, just like sea grasses. Mangrove accounts for about 3% of the world’s carbon sinking by all the tropical forests and about 14% of the coastal ocean carbon trapping.

Marsh Blue Carbon Ecosystem

The marshes ecosystem can be found on the coastal lines from the subtropical to the arctic. The marshes have a high productivity and their biomass can create a deposit of over 26 feet depth. Marshes can sequester carbon in their underground biomass due to their anaerobic-dominated decomposition and the high organic sedimentation. Marshes cover over 400,000 square kilometers worldwide.

Algae Blue Carbon Ecosystem

Because both microalgae and macroalgae do not have the complex lignin, the carbon they store tends to be freed quickly into the atmosphere compared to the carbon sequestered on land. On the other hand, algae are short-term storage for carbon and they are used as feedstock for different biogenic fuel production. Microalgae are the potential feed-stock for bio-methane and carbon-neutral biodiesel. While macroalgae lack the high oil content, they have an inadequate potential for being biodiesel feedstock, but they can be used as the feedstock for other types biofuel generation.

Why Is Restoring These Ecosystems Important?

Studies have suggested that the coastal wetlands and mangrove can sequester carbon twice or four times greater than the tropical forests. They can also store up to five times more carbon than the tropical forest. The sequestered carbon is stored underground and not above the ground as it is the case with the tropical forests.

Although these habitats provide a good service by capturing the carbon, their destruction tend to pose a greater risk. When these ecosystems are damaged, their sequestering capability are not only destroyed, but the already stored carbon is released into the atmosphere. This contributes to the increase of greenhouse gas levels in the atmosphere. This will result in the coastal ecosystem changing from carbon sinks to carbon emitters. But this ecosystem is being destroyed at a very high rate.

The carbon blue is actually one of the major coastal ecosystems conservations. When this ecosystem is damaged a large amount of carbon is released into the atmosphere and this contributes to the change in climate. Therefore, protecting the coastal ecosystem is a great way to slow down climate change, with the potential of reversing the damage. When we prevent the emission of the already stored carbon, we protect the coastal environment which is quite beneficial to the population. Some of the benefits of the coastal habitat include storm protection, recreational fishing, and various recreational sports on the shores.

Factors Affecting Carbon Sedimentation

Marshes, seagrasses and mangroves vegetation cover more than 49 million hectares across the world. The mangroves are located in the sub-tropical and tropical ecosystems, while the seagrasses range from tropical to polar. The tidal marshes can be found in the temperate regions. Various factors are affecting these ecosystems including a decrease of the vegetation in the coastal habitat. The declines in these seagrasses are caused by numerous factors including climate changes, overfishing, pathogens, drought, various agricultural practices, and water quality issues. These factors affect the density of the vegetation which in return affects blue carbon sedimentation in the ocean. The vegetation density should be sufficient enough to change the flow of water thus reducing erosion and increasing carbon deposition.


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