The end of summer was scorching on Aug. 30 near the ferry dock of Sogyeongdo Island in Yeosu, South Jeolla Province. The sun blazed down, shimmering against the surface of the sea throughout the afternoon. Even with the sea breeze, sweat soon trickled down. After about 10 minutes by boat heading south, the small island shaped like a whale, Daegyeongdo, came into view.
“My team enters the water together three times a day for 40 minutes each. Last October and November, excluding weekends, we planted 2,000 seagrass (Zostera) shoots daily,” said Park Jin-woong, a 52-year-old team leader and diver from the Institute of Coastal Management and Technology, participating in LG Chem’s seagrass habitat restoration and research project that began last year. With 25 years of diving experience, he has become a “sea farmer,” planting seagrass in the waters off Yeosu.
Seagrass is a perennial marine plant known for its excellent carbon absorption capabilities. It is considered one of the key “blue carbon” sources that absorb and store carbon in marine ecosystems. For a long time, the ocean has absorbed vast amounts of carbon dioxide emitted into the atmosphere, acting as a buffer against global warming. However, rising sea surface temperatures and coastal eutrophication have increasingly degraded marine environments. The phenomenon of seagrass die-off, leading to barren seabeds resembling deserts, is becoming more pronounced. Every year, an area of ocean equivalent to about four times the size of Yeouido—1,200 hectares—turns white like lime.
“The sea temperature has risen significantly over the past 15 years. Diving feels like entering a sauna,” said Park. “Fishermen joke that ‘the squid comes out fully cooked.’” According to the Korea Meteorological Administration, this summer, the sea surface temperature in Korean waters reached 23.9°C, which is 1.1°C higher than the average over the past decade (2015–2024).
Kim Kyung-ryul, a supervisor from the Korea Fisheries Resources Agency (FIRA), who was monitoring the seagrass habitat that day, explained, “As sea surface temperatures rise, the ability to absorb carbon dioxide decreases, impairing the ocean’s functions. This is why seagrass meadows play such a crucial role in marine ecosystems.” Seagrass absorbs carbon equivalent to 1.4 times that of forests, earning it the nickname “underwater carbon cleaner.” About 60% of South Korea’s seagrass distribution is found along the southern coast, with Yeosu accounting for about 12%.
The seagrass planting occurs in shallow waters, around 2 meters deep. Although the depth is shallow, thorough preparation is essential for the task. Divers securely fasten their oxygen tanks and enter the water in teams of three to ensure mutual assistance in emergencies. The planted seagrass grows fully submerged, anchoring itself in the sand and mud of the seabed, providing a habitat for fish.
Established in 1976, the LG Chem Yeosu plant stands as a cornerstone of South Korea’s petrochemical industry. Reflecting its commitment to environmental stewardship, LG Chem has been actively working to restore the marine ecosystem in Yeosu, aiming to give back to nature as much as it has benefited from marine resources. Last year, the company secured funding and launched an ambitious project to create a seagrass forest spanning the equivalent of ten soccer fields by 2026. In the first phase, 50,000 seagrass seedlings were transplanted, with plans to add another 20,000 this year.
According to the FIRA, the seagrass transplanted in Yeosu waters last year has exhibited growth comparable to that in natural habitats, with no signs of detachment or die-off. The seagrass transplanted in the eastern waters of Daegyeongdo Island, initially 30 cm long, has grown to 60–70 cm within just one year.
During a visit to the site, the seagrass forest appeared to be a thriving ecosystem in its own right. As the seagrass took root and grew, it provided a safe haven for fish to spawn. Notably, species such as sea cucumbers, blue crabs, and bristle worms have visibly returned to the waters off Yeosu. Interim monitoring results from the seagrass habitat restoration and research project reveal that the number of species found in the area increased from 17, including starfish and bristle worms, at the end of last year to 56 by June this year. The presence of various marine organisms, which serve as indicators of ecosystem restoration, is encouraging. These include benthic organisms like bristle worms and amphipods, swimming species like blue crabs and cuttlefish, and phytoplankton, which play a crucial role as primary producers. The seagrass bed area off the coast of Daegyeongdo expanded from 42.7 hectares last year to 45.5 hectares within one year. This additional 2.8 hectares, roughly the size of four soccer fields, has the capacity to absorb 1,400 tons of carbon annually—the equivalent emissions of 780 cars. Given that the seagrass beds off Daegyeongdo had been in decline, this is a promising development.
The seagrass habitat restoration project is a joint initiative involving LG Chem, Thanks Carbon, and FIRA. For over four years, LG Chem has spearheaded the effort, with FIRA focusing on the restoration and research of the seagrass ecosystem, while the climate tech startup Thanks Carbon oversees the program’s detailed operations.
Local fishermen recall that seagrass and similar marine plants were abundant along Yeosu’s southern coast just a decade ago, highlighting the fact that restoring ecosystems can take considerable time. However, with divers expecting the transplanted seagrass to reach a height of 1 meter by next year, this quiet transformation is already in progress. Could the sight of marine life flourishing once again in Yeosu’s thriving seagrass forests become a familiar one?
☞Blue Carbon: This is the carbon dioxide (CO2) stored in coastal and marine ecosystems, including halophytes like reeds and saltwort, as well as mudflats and seagrasses. It’s called “Blue” Carbon because it is closely associated with the ocean, with most of it stored in soil and silt up to six meters beneath the seabed. This form of carbon storage captures carbon 50 times faster and holds over five times more than green carbon sources, such as coniferous forests on land.
☞Barren Seabed: This is the phenomenon where rising sea temperatures, caused by marine pollution and global warming, lead to the accumulation of calcium carbonate (lime powder) in white patches on marine organisms, sea floors, and rocks. Since the 1960s, this phenomenon has been observed on a large scale in areas like northwest Norway, the California Peninsula, eastern and western Canada, the southern Pacific coast of Australia, and Japan. In South Korea, this whitening effect has also been occurring in parts of the southern coast since the 1980s.
