Shandong Binzhou is located on the coast of the Bohai Sea. On its 126.4-kilometer coastline, there is a shell embankment with a total length of 76 kilometers. The shell embankment in Binzhou, the shell embankment in Suriname in South America, and the shell embankment in St. Louisiana in the United States are known as the three largest ancient shell embankments in the world. Even among the three ancient shell embankments, the Binzhou shell embankment is the one with the largest proportion of conchoid, and its conchoid proportion is almost 100%, while the other two are only about 30%. It is estimated that Binzhou Shell Embankment has stored a total of 360 million tons of shells, of which 95% is calcium carbonate. After conversion, Binzhou Shell Embankment has stored 40 million tons of net carbon. Carbon sinks of this scale are rare in the world.
In fact, in addition to terrestrial vegetation carbon sinks, the ocean is also an important carbon sink. The terrestrial carbon sink is called terrestrial green carbon, and correspondingly, the ocean carbon sink is named ocean blue carbon. In addition to rare carbon sinks such as shell dikes, mangroves, seagrass beds and salt marshes are also representative of ocean blue carbon. Although these three cover less than 0.5% of the ocean, their carbon storage accounts for 50% to 71% of the total ocean carbon accumulation. A survey in 2013 showed that the net absorption of blue carbon in the ocean was 88% of that of green carbon that year.
There are three carbon sequestration methods for ocean blue carbon:
1. Naturally dissolve carbon dioxide in the atmosphere and dissolve into seawater. The lower the seawater temperature, the more carbon dioxide dissolved per unit volume;
2. Biological carbon pumps marine phytoplankton, mangroves and other plants through Photosynthesis absorbs and converts carbon dioxide, which is deposited to the seabed along with plant residues;
3. Carbonate pump Shellfish, coral reefs and other marine organisms convert carbon into calcium carbonate and deposit it.
Mangroves, seagrass beds and salt marshes have strong photosynthesis capacity and low decomposition efficiency, and their super carbon sequestration capacity makes them major contributors to ocean blue carbon.
The main ingredient is calcium carbonate
Several ways the ocean absorbs carbon
mangrove forest
The roots of mangroves are deeply rooted in the swamps and tidal flats near the coastal zone. Half of them are submerged in seawater and half of them are above the water surface. Their high salt tolerance makes them one of the few woody plants that can survive in seawater. There are 83 species of mangrove plants in the world.
Mangroves are an efficient carbon sink because: a large part of the dead mangroves will be buried in the mudflat sediments below the mangroves, and the hypoxic environment of the sediments makes it difficult for microorganisms to decompose the mangrove residues. However, after the plant residues on land fall on the soil, they are quickly decomposed by microorganisms, causing the carbon fixed by plants to enter the atmosphere again.
mangrove forest
salt marsh
As the name suggests, salt marshes are swamps with high salt content, and only halophytes or halophytes can survive in salt marshes. The presence of both types of plants is also the secret to carbon sequestration in salt marshes. The secret of halophyte tolerance to high salinity is that their intracellular osmotic pressure is extremely high: the concentration of sodium chloride in ordinary plants generally does not exceed 0.5%, and the concentration of sodium chloride in salt marsh plant cells can even exceed 6%. higher than the sodium chloride concentration in nearby seawater. Under osmotic pressure, water moves to more salty areas, and the high concentration of salt in halophytes allows them to draw water from seawater. Salt-secreting plants, also known as salt-extracting plants, can secrete excess salt in seawater from the salt glands, just like people sweat.
According to preliminary official estimates, the salt marsh ecosystem at the mouth of the Yellow River alone stores more than 4 million tons of carbon, and can store an additional 34,000 tons of carbon every year.
seagrass bed
Tourists who come to Laizhou, Yantai for the first time will first be attracted by the seaweed on the roof here. Seagrass houses are a characteristic architectural form in Jiaodong Peninsula, even though they are grass roofs, but they are not only resistant to insects and mildew, but also non-flammable. After the seagrass roof is built, it does not need to be overhauled again within 40 to 50 years. The use of sun-dried seagrass as an insulating material not only keeps the house warm in winter and cool in summer, but also reflects the wisdom of local people to make the best use of them. Today, however, it is difficult for people to build another seagrass house because the area of seagrass beds near Bohai Bay is shrinking rapidly.
The total area of seagrass beds near the coast of my country is less than 150 square kilometers, and they are mainly distributed in the South China Sea and the Bohai Bay. Seagrasses are not seaweeds, they are herbaceous plants that grow in coastal zones and have structures such as roots, stems and leaves. The long eelgrass and the round-leafed salvia are the two most common seagrasses. Seagrass beds are three times more productive per unit area (using photosynthesis to convert carbon dioxide into sugars) than coral reefs, and marine animals such as fish, turtles, mollusks, and dugongs consider seagrass beds one of the important feeding grounds and shelters . Seagrass beds are also important ocean carbon sinks.
