A once polluted lagoon in Portugal is showing remarkable signs of recovery after scientists successfully restored underwater seagrass meadows that had been wiped out by decades of industrial contamination.
The restoration effort, supported by European Union funding, has transformed parts of the Ria de Aveiro lagoon, where mercury and arsenic pollution had poisoned sediments and severely damaged aquatic ecosystems. Researchers say the project demonstrates how nature based solutions can play a major role in repairing environmental damage.
Largo do Laranjo, a section of the lagoon, was once covered with extensive meadows of Zostera noltei seagrass. However, industrial pollution over several decades contaminated the area, destroying much of the underwater vegetation. Although water quality improved after stricter environmental regulations were introduced in the 1990s, toxic substances remained trapped in the sediments and continued to affect wildlife and ecosystem health.
To address the problem, biologist João Pedro Coelho and his team launched the ReMoliço project with support from the European Union. 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 laboratory trials designed to determine whether seagrass could survive in contaminated conditions. After testing several techniques, the team selected a transplantation method using 20 by 30 centimeter sediment blocks that protected the plants roots during relocation to the degraded estuary.
Funding from the European Maritime and Fisheries Fund enabled researchers to build tidal simulation tanks, hire specialized staff and refine restoration methods before large-scale planting began.
The results appeared within months. Scientists observed declining contamination levels, reduced erosion and the gradual return of biodiversity to the area. While some ecosystem functions recovered more quickly than others, the overall environmental improvement was significant.
Researchers noted that chemical stabilization and sediment retention occurred rapidly, while the full recovery of biodiversity is expected to take longer. Nevertheless, the area is already becoming safer for activities such as fishing, birdwatching and recreation.
Building on the project’s success, follow-up initiatives including RemediGrass and LIFE SeagrassRIAwild expanded restoration efforts to 300 square metres in 2025. Community involvement has also increased, with volunteers, students, local authorities and environmental groups participating in seagrass transplantation and conservation activities.
Officials say the project has evolved from a local experiment into a model that could be replicated in contaminated coastal regions across Europe, offering a practical and sustainable approach to ecosystem restoration.