Did you know that coastal ecosystems store carbon dioxide (CO2) from the atmosphere 40 times faster than forests?

The process of storing and accumulating organic matter in depths of the earth crust and in the ocean floor is what causes the formation of oil, coal and gas with time, pressure and heat. These are the energy sources we depend on - called fossil fuels. The petrol and gas accumulated over thousands of years is originated by ancient forests and algae that removed CO2 from the ancient atmosphere and converted it onto plant tissues and organic exudates. The products were then accumulated in the bottom of the ancient forests and ocean floor throughout millennia.

 Blue Carbon Ecosystems

They are coastal ecosystems (mangrove, salt marsh, seagrass, and other tidal wetlands) where carbon dioxide is removed from the water and atmosphere, converted into organic matter and stored for millennia in the bottom sediments and root system - the term "Blue Carbon" Ecosystem was coined in 2009. Forests are known as "Green Carbon" Ecosystems. Yes, coastal ecosystems such as mangrove, salt marshes, seagrass meadows can remove and store carbon from the atmosphere for over thousands of years if undisturbed - functioning as carbon sinks. These coastal ecosystems occupy only a small area of the oceans, which is calculated to be around 2%; however, their role in removing CO2 from the atmosphere and storing it is estimated to be near half of total oceanic carbon storage. It has been estimated that Blue Carbon Ecosystems store 40 times faster more carbon dioxide than forests (= Green Carbon Ecosystems). 

Carbon Storage

With time, the suspended material present in the water column added to that organic matter produced by the local flora and fauna within the system gets deposited and stored with depths. The amount and rate of deposition will oscillate from one environment to another, and will depend on the sedimentation rates and loads of particulate material.  The process in which carbon is stored is very simple; it all happens between the plant roots and sediments where  active microbial interactions occur. The microbes dwelling in such habitats consume the all the oxygen available rapidly through a process called aerobic respiration, also known  as aerobic degradation of organic matter.

These areas become anoxic when dissolved oxygen is depleted. Under anoxia, the degradation of organic matter with the consequence release of carbon dioxide is halted or significantly decreased as anaerobic decomposition takes place (a thermodynamic reaction much less favourable to happen than aerobic respiration). As a result, Blue Carbon ecosystems are hotspots of carbon storage due to its immobilisation in the anoxic sediments and root system.  


These ecosystems store tens of tonnes of carbon that if disturbed by anthropogenic activities such as dredging and urban development, that carbon stored for thousand of years can be lost as carbon dioxide back to the atmosphere in extraordinary proportions, according to recently published studies. Blue Carbon ecosystems are also well known as protecting the coasts against erosion and as nurseries for several economic important species of fish, crustaceans and molluscs.  We all have an important role in preserving and protecting these coastal habitats. The more information we get the more we can act. Keep informed!

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