Transplanted Posidonian Ocean: Scientific Advances for the Conservation of Seagrass Pastures

This study has resulted in the implantation of 384m² of Posidonian Marine Seagrass on the scale of an industrial project as part of Monaco’s maritime work. This success challenges the idea that these ecosystems are “non-portable.” This unprecedented experiment, carried out over eight years, opens up new prospects for the preservation of seagrass pastures threatened by coastal urbanization.

As part of a construction project for Monaco’s “Maletella” district, Marines involved the destruction of several hectares of Posidonia Marine Pasture, an underwater plant essential to the Mediterranean ecosystem. To limit this impact, Andromè de Océanologie and Liège University have set up unprecedented large-scale port operations.

The experiment began in 2017, when a 384m² sea grass pasture was relocated from the construction zone to the Lalbot Marine Reserve. A technique known as “clod” transplantation allows roots and associated substrates to be kept intact, improving plant survival. This study examined operational techniques that allow for the implantation of most of the seagrass during a record time, a major step in conserving these vulnerable ecosystems.

“For eight years, strict monitoring was carried out to observe the elasticity of the transplanted pasture,” explains Uriège oceanographer Sylvie Gobert. “Even though major marine works have been made nearby, transplanted pastures show significant resilience, and health indicators are rapidly approaching indicators of adjacent natural pastures.”

Three years after the transplant, both the transplanted seaweed and the natural seaweed were in bloom. Eight years later, the surface area of ​​the implanted sea grass exceeded the area that was first implanted, recording an expansion of 25.8% in 2024. ” These results test the idea that porting is a viable and ecologically relevant alternative as a mitigation measure for coastal development projects.

This experience has revolutionized the way sea grass conservation approaches in coastal development projects. Until now, destruction of sea grass beds has been considered incompatible, and compensation measures have often been limited to the installation of artificial reefs. However, this study proves that porting is a viable alternative that should be fully integrated into environmental protection strategies.

Long-standing expertise

The University of Liège played a central role in this study thanks to the expertise of researchers, particularly Professor Gobert and Arnaud Boulanger. A marine ecology expert, Goatt has provided an essential scientific perspective to assess transplant survival and ensure rigorous monitoring of physiological and structural parameters of pastures. A doctoral student at the Institute of Biological Oceanography, Boulenger helped set up data analysis and monitoring protocols.

The Institute of Biological Oceanography at Liège University has major expertise in the study and preservation of sea grass beds dating back to the 1970s. This long research tradition is based on observations made in particular at Stereso, the Institute of Underwater and Oceanography at the University of Liege on the protected marine region of Corsica.

For over 50 years, the station has studied the evolution of Posidonia Oceanica Meadows under natural conditions, providing unique and valuable data on its growth, resilience and ecological role. Thanks to the work carried out at this exceptional site, Uriegge has developed detailed knowledge of pasture dynamics and best strategies for its conservation and recovery. This expertise has been a key asset in ensuring the success of a transplant project in Monaco by ensuring a rigorous protocol and a detailed scientific assessment of long-term outcomes.

The success of this experiment raises questions of current practices and paves the way for better management of marine ecosystems. “Integrating transplants as a mitigation tool for coastal development projects will allow us to significantly reduce environmental impacts while preserving these precious habitats for Mediterranean biodiversity,” Goat concludes.

The survey results are published in the Environmental Issues Journal.