Baseline:
Lingshui County, officially known as Lingshui Li Autonomous County, is predominantly inhabited by the Li and Miao ethnic groups. Historically, it was the only national-level impoverished county located on the eastern coast of Hainan and the sole coastal national-level impoverished county among over 2,000 impoverished counties in China (up to 2012). After 2012, benefiting from rapid economic development, Lingshui County is no longer classified as a national-level impoverished county. According to the 2021 statistical data, the county had a total land area of 110,695.86 hectares, registered 19.552 billion yuan in GDP, and was ranked third in economic growth rate in Hainan Province. The county is characterized by a complex network of rivers, with a total of 127 rivers, including the Lingshui River, Duzong River, Jincong River, and Gangpo River. The Lingshui River, the largest river in the area, has an average annual flow of 1 billion cubic meters and empties into the South China Sea at Shuikou Port in Lingcheng Town. The county's coastline spans 118.57 kilometers, accounting for 6.09% of the province's total coastline. The natural parts of the county's coastline total approximately 83.48 kilometers, featuring numerous natural harbors such as Xincun Port, Li?an Port, Qingshui Bay, Xiangshui Bay, and Tufu Bay. Of these natural harbors, Xincun Bay and Li?an Bay are the largest ones, and receive the most attention as near-closed natural estuarine harbors completely controlled by tides.
Seagrass beds refer to ecosystems characterized by the extensive and continuous distribution of seagrass. The primary producers within seagrass beds are one or multiple species of seagrass. Seagrass beds, along with coral reefs and mangroves, collectively referred to as the three major blue carbon ecosystems on Earth, are prioritized in the conservation of global marine ecology and biodiversity. It is estimated that the annual ecological service value of seagrass beds is up to $1.9 trillion. Previous studies have demonstrated that seagrass beds can prevent coastal erosion and mitigate the impacts of floods and storm surges. They also provide spawning, incubation and nursery grounds crucial for marine organisms, maintain biodiversity by serving as habitats for protected species such as seahorses, alleviate ocean acidification, and oxygenate the ocean. Furthermore, seagrass beds stabilize sediment, thereby improving water transparency. Most importantly, with an annual carbon storage capacity of 4.2 to 8.4 Pg (1 Pg = 109 ton), seagrass beds help mitigate carbon dioxide emissions and represent a potential solution to the threat of global warming. In some regions of China, e.g., the Jiaodong area in Shandong province, seagrass is also used as a building material that contributes to shaping unique architectural styles and improving the living conditions of local residents.

Problems:
Seagrass beds are important marine ecosystems and carbon sinks, providing habitats, breeding grounds, and food sources for numerous marine organisms [1-2]. However, in recent years, seagrass beds in China have been rapidly degrading, with over 80% of nearshore seagrass beds having disappeared [3]. The Xincun Port and Li'an Port Seagrass Special Protection Area, located in Lingshui County, Hainan Province, is the only seagrass protection area in China. The main seagrass species found in this area is E. acoroides, the world?s largest seagrass species. It is worth mentioning that E. acoroides is an important dominant species in tropical seagrass beds and a unique species in the Indo-Pacific region, having high ecological value [2-8]. However, the distribution area of this species within the Xincun Port and Li'an Port Seagrass Special Protection Area is smaller than 20 km2 and still on the decrease. In view of that, it is urgent to seek methods for the restoration of this resource.

Activities:
Activity 1.
Establishing an indoor rapid propagation system for E. acoroides seedlings to restore seagrass beds.

Activity 2.
2.1 Conducting popular science lectures or technical promotion activities in local communities and authorities, and organizing "scenario-based" seagrass knowledge promotion and "experiential" seagrass restoration activities in schools, along with the distribution of promotional brochures.
2.2 Through questionnaire surveys, comparing the differences in seagrass protection awareness and public satisfaction among local residents before project kickoff, one year after project kickoff, and at the end of the project.

Outcomes:
(i) An indoor rapid propagation system for E. acoroides seedlings will be developed. Specifically, the system comprises the "low oxygen + high oxygen" induction cultivation technique for sexual seedlings of E. acoroides, a transplantation method alleviating the stress caused by high light or low oxygen levels to E. acoroides seedlings, techniques for the rapid cultivation of sexual seedlings of E. acoroides in the nursery, as well as on-site seagrass bed restoration techniques based on the suitable planting depth and timing for the outdoor transplantation of E. acoroides seedlings.
(ii) Within a 2-year period, 1-3 km2 of seagrass beds will be restored, including 1 km2 of bare flats, and 1-2 km2 of damaged seagrass beds to be restored through planting. The restoration will be supported by evidence such as photographs, videos, and biodiversity indicators. Following the restoration, the species diversity of the seagrass beds is expected to reach the level of a healthy seagrass bed in the project area. It is noted that there are currently no methods available to distinguish between bare flats and damaged seagrass beds. In certain areas, there may be small patches of bare flats. That is to say, bare flats and damaged seagrass beds are distributed in a patchy manner. Therefore, the overall target of the project is set at 1-3 km2.