Korea to restore East Sea beaches with underwater seagrass 'breakwaters'

South Korea is set to develop technology to protect the East Sea coastline from sand erosion using underwater seagrass rather than concrete breakwaters. The plan calls for creating "living natural breakwaters" from native eelgrass species that dampen wave energy and anchor sand in place, addressing coastal erosion and declining fisheries at the same time.

The Korea Institute of Ocean Science and Technology (KIOST) announced Tuesday that its East Sea Coastal Autonomous Blue Infrastructure Development Project has been selected as one of the Ministry of Science and ICT's Top 10 Public-Benefit R&D Projects for 2027.

The East Sea coastline is simultaneously losing sand, suffering degraded ecosystem functions and seeing fishery stocks decline. Sixty sites along the coast are currently classified as either "serious" or "concerning" for coastal erosion. While artificial structures such as breakwaters have traditionally been the response, the new project takes a different approach — harnessing natural ecosystems to allow the coast to recover on its own.

A research team led by Do Jong-dae at KIOST's East Sea Research Institute will invest a total of 24.71 billion won ($18.2 million) over five years from 2027 to 2031 to develop autonomous blue infrastructure technology using East Sea-native eelgrass species.

The focus is on two species — Zostera asiatica and Zostera caespitosa — that grow at depths of 6 to 25 meters in the East Sea. Their dense leaves weaken wave energy while their roots grip the sand and prevent it from washing away. Seagrass beds also serve as breeding and nursery grounds for fish and shellfish.

Leveraging these properties, the research team plans to establish seagrass habitats that can grow and reproduce on their own after initial planting, without ongoing human intervention. The approach supplements the coastal protection role traditionally filled by breakwaters and artificial reefs with a natural ecosystem alternative.

In the first phase, running through 2029, the team will install monitoring equipment at existing seagrass habitats to measure their effectiveness in reducing wave energy and curbing sand movement. Data collected via satellite, drones and underwater sensors will be analyzed using AI to produce a distribution map of East Sea seagrass beds. The team will also survey fish and shellfish populations in seagrass areas to assess the impact on fishery resources.

The second phase, from 2030 to 2031, will involve establishing seagrass habitats along the East Sea coast to demonstrate the technology under real conditions. Long-term monitoring will quantitatively verify reductions in coastal erosion and gains in biodiversity and fishery resources, and management guidelines will be drawn up for individual sea zones.

By 2031, the team aims to reduce the proportion of coastline rated "concerning" or "serious" for erosion in the demonstration area by 30 percent from current levels, and to increase marine biodiversity by 30 percent. The project also expects to expand blue carbon benefits through the carbon absorbed and stored by the seagrass.

"East Sea-native eelgrass is a living coastal blue infrastructure that protects sand by reducing wave energy while also nurturing fishery resources," Do said. "Because it can grow and sustain itself after establishment, it will help address coastal erosion while reducing the burden of ongoing management costs."