Technical, technological measures facilitate restoration of seagrass beds

BEIJING -- The approach of summer coincides with the maturing of seagrass seeds, and it is at this time when Chinese researchers collect seeds underwater, process their reproductive branches and then put them back in the sea along the Jiaodong Peninsula, East China's Shandong province.

The researchers then wait until August, when they take the seeds to shore again for germination in low temperatures. Once autumn arrives, the seagrass seeds are returned to the ocean.

This whole process has run for 17 years, during which time the researchers managed to achieve a 13-fold increase in the retention rate of the seagrass seeds, while also doubling the germination rate of the seeds.

Seagrass is the only angiosperm on Earth that can completely germinate, flower and seed in seawater. It is an important habitat and breeding place for a variety of marine organisms, and has extremely important ecological functions.

Fish, shrimp and crabs can spawn, breed, forage for food and live in seagrass beds.

Seagrass is widely distributed in coastal waters all over the world except Antarctica. In China, seagrass is mainly distributed in tropical-subtropical sea areas including the coastal areas from Hainan to Fujian and temperate sea areas including the coastal areas of Shandong, Hebei, Tianjin and Liaoning.

When the seagrass forms a complete ecosystem, it plays an important role in maintaining the marine environment, regulating the global climate and improving water quality, said Zhang Peidong, professor with the Fisheries College of the Ocean University of China.

Seagrass beds are 90 times more efficient at storing carbon than forests. Both seagrass and biological communities attached to it can realize carbon sequestration through photosynthesis.

Although the global distribution of seagrass beds accounts for less than 0.2 percent of the ocean area, their annual carbon storage capacity can reach up to 15 percent of the total global marine carbon storage, said Zhou Yi, a researcher with the Institute of Oceanology of the Chinese Academy of Sciences. Meanwhile, the seagrass beds also have ecological functions such as alleviating acidification of seawater and reducing disasters by protecting dams.

In spite of this, with the increasing intensity of ocean exploitation and utilization, global seagrass beds have experienced rapid decline at a rate of seven percent per year, due to both human activities and extreme weather events. About 29 percent of seagrass beds have disappeared all over the world, according to a report from Science and Technology Daily.

China has nearly 26,500 hectares of seagrass beds. A technical guide on the ecological restoration of seagrass beds is scheduled to take effect by the end of this year.

As seagrass beds degrade, they absorb less carbon dioxide and release more carbon trapped in sediments, said Zhou. The process becomes a new source of carbon fueling climate change and it increases ocean acidification.

Since 2006, Zhang has led his teammates in developing and implementing the key technologies of the ecological restoration of seagrass beds, such as seed cultivation and planting and transplantation.

At the bottom of Swan Lake in Rongcheng city of Shandong, nearly 80 percent of the seagrass beds have been restored. The restoration technology developed by Zhang and his teammates was introduced to areas of the Bohai Sea and the Yellow Sea, and succeeded in restoring and conserving seagrass beds of 20,000 mu (about 1,333 hectares), equivalent to neutralizing the annual tail gas emissions of more than 400,000 vehicles.

Seagrass beds can be restored either by seed reproduction or plant transplantation. The Chinese Academy of Fishery Sciences has developed a new method of transplanting seagrass plants to seabeds after they have grown enough.

Such emerging technologies are contributing to seagrass bed ecosystem restoration efforts in China.