Returning home⑨丨Long-lost Ecological Beauty: Seagrass flourishing again in Bohai Sea
Feb 8,2023 Great Wall New Media


It was a mid-Autumn day. Flocks of seagulls were swarming the beautiful sea-view Xiangyun Bay, Tangshan, Hebei Province. Late in the afternoon, the fishing port burst into a seething fish and seafood market as fishing boats have returned and pulled onto the shore, bringing back their catches.


“I've netted more than 500 kg of octopus today. It is not rare to see sea eel, sea bass, batfish, flounder and hairtail that had been unseen for years,”said captain of Jileyu-03456 Wang Liyou, with a broad smile.“This was unimaginable five or six years ago.”

开渔期,河北唐山祥云湾近百艘渔船满载而归,渔民们享受着丰收的喜悦。长城网·冀云客户端记者 贺宏伟

During the fishing period, nearly 100 fishing boats go out fishing and return to the Xiangyun Bay every day, fully loaded with their catches. Fishermen are enjoying their good harvest. (Photo by He Hongwei/Great Wall New Media)


To know why the sea catches have increased, we have to go back to the story about the "return of seagrass".


According to Zhang Zhenhai, Board Chairman of the Tangshan Aquafarm Industrial Co. Ltd., the sea off the Xiangyun Bay used to belong to the Luohekou Fishing Ground, one of the four major fishing grounds on the Bohai Sea. Before the 1980s, there used to have a complete typical offshore marine ecosystem, with seagrass beds and algal reefs growing everywhere.

But due to offshore breeding, over-catching and industrial pollution, the seagrass beds began to deteriorate, the seabed vegetation began to be decertified and such common fish species as tonguefish, yellow croaker, hairtail were rarely seen, almost extinct.


"If the marine ecosystem is not to be repaired, there will be only sea water left and therefore there will be no fish or other seafood." That was what Zhang Zhenhai heard when he came to the Xiangyun Bay a dozen years ago. If the mountain slope becomes barren, we can plant trees. But how to repair the seabed ecosystem? A man came into his mind, that is, Zhou Yi, a research fellow at the Institute of Oceanology of the Chinese Academy of Sciences.

中国科学院海洋研究所研究员周毅(左一)望着修复后的海域,满是欣慰。长城网·冀云客户端记者 乔娅 摄

Zhou Yi (Left) a research fellow of the Institute of Oceanology, Chinese Academy of Sciences (Left) is full of joy to see the sea area that has been restored. (Photo by Qiao Ya/Great Wall New Media)


"Many people mistake seagrass for seaweeds or algae. In fact, seagrass is the only flowering plant able to live in seawater and pollinate while submerged. Together with mangrove forests and color coral reefs, they form three major typical offshore ecological systems, reputed as a 'submarine meadow' or 'submarine forest', which is an important hallmark of a healthy oceanic environment." said Zhou Yi, who has been studying and practicing how to repair the seagrass bed ecosystem in recent years.

He said that once the seagrass bed is destroyed, it is hard to restore to its original state and artificial means has to be employed.


The ecosystem repair team fix the artificially bred seagrass rhizomes, also called creeping rootstalk, horizontal underground plant stem capable of producing the shoot and root systems of a new plant, onto a stone and sink it to the seabed in a bid to build new seagrass beds. (Photo provided by the Institute of Oceanology, Chinese Academy of Sciences)


Coincidentally, the seabed in the Tangshan section of the Bohai Sea is sand-muddy, the water current is slow, and the subterranean ground is flat, providing the best niche for repairing the seagrass beds. In 2017, the Tangshan Aquafarm Industrial Co. Ltd. started the repair project under the guidance by Zhou Yi's team. The company selected a 60-hectare area for experiment, where they choose two methods of building the new seagrass bed: rhizomes transplanting and seagrass seed sowing.


The rhizomes transplanting made it easy to sink rhizomes to the bottom and the survival rate has reached over 95 percent. The seed sowing method is to plant the seeds wrapped in mud. It has the advantage of increasing the genetic diversity.


Zhou Yi compares a seagrass bed to a huge "community", in which all kinds of fish, turtles, shrimps and crabs and other marine animals live and multiply. A half-football-field seagrass bed is able to accommodate 40,000 fish and 50 million small invertebrates.


The repaired seagrass bed provides all kinds of marine animals with habitats and food. (Photo provided by the Institute of Oceanology, Chinese Academy of Sciences)


"The seagrass bed has a strong capacity of capturing and storing carbon. Although it covers only 0.2 percent of the sea bottom, it has captured and stored 10%-18% of global marine carbon a year, an extremely important blue carbon sink," said Zhou, adding that it can also purify sea water and cushion the attack by sea waves to protect the coastlines.


On the morning of September 24, when the sun just jumped out of the horizon, Zhang Zhenhai and Zhou Yi set off by boat for the seagrass bed repair experimental area. "Look, quick, the tide is ebbing, and the seagrass planted on the tidal flats are showing up," said Zhou, adding that such season is quite suitable for transplanting rhizomes as it is a cool plant.

"We can transplant it by wearing the shorts as it is a low ebb in the morning. On the tidal flats, we can also transplant rhizomes. But during the high tide period, we have to dive in to transplant them." said Zhou.


"Under the sea water, the seagrasses are undulating with the waves. In this area, with the repair and rebuilding of seagrass bed and algal reefs, the marine biomass has increased by more than 40 times. In the next step, we will expand the experimental area to 400 more hectares," said Zhang Zhenhai, unable to hold back his joy over the initial success.


"After five or six years, the seagrass bed has already become proliferating. A vigorous seabed and new oasis on the sea bottom has appeared before us," said Zhou excitedly. "After the marine meadow is rebuilt, such marine organisms as sea bass, sea horse, shellfish will return to their familiar homeland and this part of the Bohai Sea will again become a paradise for various marine creatures to live and multiply."

Editor: Song Lifang