A polluted lagoon in Portugal is showing remarkable signs of recovery after scientists successfully restored underwater seagrass meadows that had been destroyed by decades of industrial contamination.
The restoration effort took place in Largo do Laranjo, part of the Ria de Aveiro lagoon, where mercury and arsenic pollution had severely damaged the ecosystem. Researchers say the project demonstrates how nature based solutions can help clean contaminated environments and bring degraded habitats back to life.
According to the European Commission, the area was once covered with dense meadows of Zostera noltei seagrass. However, years of industrial pollution poisoned the sediments, leading to the disappearance of the underwater vegetation. Although water quality improved after stricter environmental regulations were introduced in the 1990s, toxic substances remained trapped in the lagoon’s sediments, continuing to affect wildlife and ecosystem health.
To address the problem, biologist João Pedro Coelho and his team launched the EU-funded ReMoliço project. The researchers focused on restoring seagrass, which acts as a natural filter by trapping pollutants, stabilizing sediments and reducing erosion.
The project began in 2019 with extensive laboratory testing to determine whether seagrass could survive in contaminated conditions. After experimenting with different techniques, the team developed a method using sediment blocks measuring 20 by 30 centimeters to protect the plants’ roots during transplantation.
Supported by the European Maritime and Fisheries Fund, the team installed tidal simulation tanks, hired specialized staff and refined the restoration process before planting the seagrass in the degraded estuary.
The results appeared sooner than expected. Within months, contamination levels began to decline, erosion was reduced and biodiversity started returning to the area.
Researchers noted that while some ecological functions recover quickly, others take longer. Chemical stabilization and sediment retention improved rapidly, while the return of diverse wildlife is expected to occur over a longer period.
The restored lagoon is gradually becoming safer for activities such as fishing, birdwatching and recreation. Scientists say the project highlights the important role that seagrass ecosystems can play in environmental recovery and climate resilience.
Building on the success of ReMoliço, follow up initiatives including RemediGrass and LIFE SeagrassRIAwild expanded restoration efforts to 300 square metres in 2025. Community participation has also increased, with volunteers, students, local authorities and environmental groups taking part in restoration activities.
Researchers believe the project could serve as a model for restoring contaminated coastal ecosystems across Europe and beyond, demonstrating that natural solutions can help reverse decades of environmental damage.