text | Zhou Yi (researcher at the Institute of Oceanography, Chinese Academy of Sciences)
At the beginning of this year, the conclusion meeting of the National Basic Science and Technology Work Special Project "Investigation on Important Seaweeds in my country's Offshore" was held in Beijing.
This indicates that my country has mastered the "family information" of coastal seaweed resources across the country and has taken a solid step towards the protection and restoration of seaweed beds.
humans dig clams to destroy Huludao seaweed bed. Photo provided by the Ocean Institute
Seaweed is not seaweed
Seaweed originated from land angiosperms and is the only higher angiosperm on the earth that can completely live in seawater. Compared with the higher hit on the land , its species are extremely rare. A total of 6 families, 13 genera and 74 species were found in 6 families, 9 genera and 16 species were found in China.
Except for Antarctica, seaweeds are distributed in coastal waters all over the world, usually growing in shallow seas and estuary waters, from the intertidal belt to the subtidal belt, with a maximum water depth of 90 meters.
There are 6 major seaweed distribution areas in the world, including the tropical Indo-Pacific region, the tropical Atlantic region, the temperate North Pacific region, the temperate North Atlantic region, the Mediterranean region and the temperate southern ocean region.
my country's seaweed distribution area is divided into two major regions: temperate sea area distribution area and tropical-subtropical seaweed distribution area. The temperate sea area distribution area includes the coastal areas of Shandong, Hebei, Tianjin and Liaoning, and the tropical-subtropical seaweed distribution area includes the coastal areas of Hainan, Guangxi, Guangdong, Hong Kong, Taiwan and Fujian.
Seaweed and seaweed are one word different but the difference is very big. As a higher plant, seaweed has differentiation of roots, stems and leaves, and the root system is complex. It can fix seaweed in sediments and extract nutrients and minerals from it.
and seaweed can be reproduced sexually through flowering, pollination and seed formation, or asexually through rhizomes .
. Seaweed belongs to the lower plant of and does not have differentiation of roots, stems, and leaves. Some seaweeds (such as kelp) have pseudo-root-like fixators that can be simply fixed on hard substrates, such as rocks or shells, and seaweed can only reproduce through spores.
In addition, seaweeds perform photosynthesis through leaf cells, while all cells of seaweed can perform photosynthesis; seaweeds can transport minerals and nutrients through aeration tissues and cavity (veins), while seaweeds absorb minerals and nutrients from water through diffusion.
In the past, seaweed was often named after the word "algae", which easily made people mistake seaweed for seaweed and caused chaos. Therefore, when the "Eleventh International Seaweed Biology Symposium" was held in China in November 2014, domestic seaweed research experts uniformly named 16 species of seaweed named "algae" after discussion in China, which brought convenience to the research and popularization of Chinese seaweed and promoted the protection and management of Chinese seaweed beds.
Seagrass bed is an important marine fishing ground and carbon library
Seagrass bed refers to a seagrass ecosystem dominated by a single or multiple seagrass plants. It is known as the three typical offshore marine ecosystems on the earth, along with mangroves and coral reefs. It has extremely high ecological service functions and is known as the "pulmonary of the ocean", "undersea grassland" and "undersea forest".
Seagrass bed is an important marine fishing ground, which can provide habitat, childbirth and shelter for various marine organisms. It is an important food source for dugong , green sea turtle and waterfowl. For example, in the Rongcheng Big Swan National Nature Reserve, the lush seagrass raises a large number of fish, crustacean and other marine organisms. It also provides overwintering habitat and food sources for tens of thousands of big swans. More than 60% of the food consumed by the big swan comes from seagrass leaves.
At the same time, seagrass bed is one of the most effective carbon capture and storage systems on the earth. Its carbon storage efficiency is 90 times higher than that of forests and is an important carbon reservoir in the world. Although seagrass beds cover only 0.2% of the global ocean area, their annual carbon storage volume can reach 10% to 15% of the global marine carbon storage volume, and the carbon storage time can reach thousands of years, so it plays an important role in mitigating and adapting to climate change.
Seagrass bed's high efficiency carbon sequestration ability is due to its extremely high productivity, strong suspension capture ability and high stability of organic carbon in seagrass bed sediments. First, 15% to 28% of the annual production of seagrass beds is buried in the seabed for a long time, contributing about 50% to the organic carbon reservoir of seagrass bed sediments; second, seagrass canopy can efficiently capture a large amount of organic suspended particles in the water body, thereby achieving carbon sediments; finally, the organic carbon fixed in the sediments of oxygen-deficient seagrass bed has a relatively low decomposition rate and high stability.
In addition, seaweed can regulate suspended substances, dissolved oxygen, heavy metals and nutrient salts in the water, playing a role in purifying water quality. It can also reduce the energy of waves and water flow through the blocking effect of elongated leaves, while the dense roots of seaweed can solidify the base, thereby preventing or slowing down loss and erosion of beaches and coasts.
According to rough statistics, taking the Tangshan Seagrass Bed (3217 hectares), the largest seagrass bed in my country, as an example, it can support 240 million fish and 300 billion invertebrates, and can fix 12,000 to 21,000 tons of carbon dioxide each year, absorb nutrient salt (3.6 tons) of domestic sewage of 600,000 people every year, and release 300 million liters of oxygen each year, and its assessed value is US$120 million per year.
More than 80% of seagrass beds in my country have disappeared
As the intensity of marine development and utilization increases, the marine ecological environment and biological resources are facing serious threats, and my country's seagrass beds have undergone serious degradation.
The direct causes of seagrass bed degradation in my country include habitat loss and damage, mechanical damage to seagrass, decreased transparency of water bodies, and water temperature exceeding seagrass tolerance limits.
At present, the main threats facing my country's seaweed include coastal engineering construction and sea reclamation activities, land source pollution, fishery activities, large-scale algae outbreaks, mud-flowered rice grass invasion, climate warming, and typhoon and other extreme climate events occur frequently.
According to the latest census results (2015-2020), the seagrass bed area in my country is about 26,495.69 hectares, and 16 species of 4 families, 9 genera.
Comparing historical distribution and species records, it was found that six types of seaweed, including wide-leaf eelgrass, stem-leaf eelgrass, black-fiber shrimp-shaped grass, all-weed grass, hairy salt-loving grass and big fruit river vinegrass, have disappeared, and more than 80% of seagrass beds in my country's nearshore waters have disappeared.
For example, in 1982, there were more than 1,300 hectares of eelgrass community near Furong Island in Laizhou Bay, but now there is no trace; from 2015 to 2021, more than 1,000 hectares of Japanese eelgrass beds at the mouth of the Yellow River disappeared due to the invasion of Typhoon Liqima (2019) and the invasion of the mutual flower rice grass; in the past eight years, the seagrass distribution area has been filled along the coast of Guangxi and converted into port terminal land, real estate land, etc., which has caused a permanent loss of a total of 354 hectares of seagrass habitat.
Protection and repair
In recent years, the international community has gradually realized the importance of seagrass beds, and the protection and recovery of seagrass beds have gradually become one of the hot topics in the international research.
In terms of seagrass bed protection, first of all, a seagrass protection management system should be established as soon as possible, and regulations on seagrass bed protection management should be formulated to make seagrass protection work regularized and legalized, and direct damage to seagrass beds by human activities such as seagrass reclamation should be prohibited.
Secondly, it is recommended to set up 6-8 national seagrass bed nature reserves. Up to now, my country has only built two provincial seagrass bed protection areas - the Lingshui Xincun Port and Li'an Port Seagrass Special Reserve in Hainan Province and the Tangshan Seagrass Bed Nature Reserve in Hebei Province.
Again, establish a seagrass bed habitat monitoring system to scientifically manage and protect seagrass beds. It is recommended to establish 1-2 national-level seagrass bed field ecological monitoring research stations.
In addition, it is necessary to control pollutant emissions and improve seagrass bed habitat quality; scientifically manage and develop seagrass bed fishery resources, encourage and guide the development of marine pastures and aquaculture industries based on seagrass bed habitat construction, strengthen the planning and construction of seagrass bed ecological tourism areas; strengthen scientific research on seagrass beds, improve seagrass resource protection capabilities; popularize the ecological value of seagrass beds, strengthen publicity of seagrass bed knowledge through multiple channels, and improve seagrass protection awareness.
In terms of seagrass bed restoration, the ecological restoration and reconstruction of seagrass beds should be strengthened, the ecological restoration project of seagrass beds should be implemented, and the submarine forest should be restored.
Strengthen scientific research on seagrass beds and improve the protection capacity of seagrass resources. In particular, we must concentrate our efforts on the research and development of key technologies for efficient seagrass bed ecological restoration based on the degradation status and habitat characteristics of my country's seagrass beds.
With the deepening of research, seagrass bed protection and restoration will gradually become a public welfare action for environmental protection with the participation of the whole people. I believe that in the near future, just like "planting trees and afforestation", everyone can participate in the protection and restoration of seaweeds.
