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Turnaround in the port’s eelgrass cultivation

11:04 - 06 Nov 2020 / Press

After a series of unproductive tests, the Gothenburg Port Authority has succeeded in getting eelgrass to grow and thrive. Based on the excellent results that have emerged and new findings in this relatively unexplored area, the project is set to move to the next level.

Each eelgrass plant is handeled individually by the divers. Photo: Marine Monitoring.

Eelgrass meadows provide shelter and a habitat for a number of fish species. At the same time, they improve water quality and protect against shoreline erosion. On the other hand, eutrophication, overfishing, and the development of coastal areas have led to the disappearance of many eelgrass meadows.

“Replanting eelgrass is not an exact science, and we have had to adopt a trial and error approach over a number of years. This explains why we are extremely pleased to be at the point where we are now, and that we are armed with a concept that will allow us to move forward. It is particularly encouraging that we have built up a body of knowledge in an area where it was previously limited,” said Edvard Molitor, Senior Manager Environment at the Gothenburg Port Authority.

Test beds were created back in the summer of 2018 in the northern and southern archipelagos by moving eelgrass from a donor meadow to new locations that it was felt offered the right conditions. However, these beds proved unsuccessful and a decision was made to create new test beds in the summer of 2019.

Major breakthrough
An inventory has been made of the new beds and Edvard Molitor and the Gothenburg Port Authority are extremely pleased with the outcome.

Image: Gothenburg Port Authority.

“The grass has taken exceptionally well in several of our test beds, and the growth rate in some sections has been tenfold. This is a major breakthrough. Not just for us but also for eelgrass research generally where empirical data is lacking,” said Edvard Molitor.

Why have the test beds been successful this time but not previously? According to Edvard Molitor, a number of elements in the planting method were changed during the course of the project and this has produced results.

“We have experimented with different planting depths, densities, and bed size. What has been of greatest significance is the size of the beds. Eelgrass protects itself and the larger the beds the less risk there is of them being destroyed by external forces such as storms, macroalgae, and pleasure boats,” said Edvard Molitor.

Upscaling
To date, 4,300 square metres of eelgrass have been planted and the project will now be scaled up. This is a challenge in itself, not only with regard to finding suitable locations for larger beds, but also in terms of the logistics behind the actual planting process.

“Each individual eelgrass plant is planted by hand by divers, making it incredibly time-consuming. The more we scale up the project, the more divers will be needed. We are working with our experts from Marine Monitoring to find solutions, but it will be tricky nevertheless,” said Edvard Molitor.

Compensation project
The planting of eelgrass is taking place alongside the construction of a new port terminal. The construction permit includes an obligation on the part of the Gothenburg Port Authority to plant 1.7 hectares of eelgrass to compensate for the eelgrass that will disappear during construction. A compensation plan has been drawn up by the Port Authority in consultation with the County Administrative Board and the Swedish Agency for Marine and Water Management.

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