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Fish and crabs on the BlueReef

02 Jul 2009  


Edible crab. Photo © Karsten Dahl
Edible crab. Photo: Karsten Dahl

The restoration project on Læsø Trindel is yielding results. This is the edifying message from The Danish Agency for Spatial and Environmental Planning, the responsible institution. “Observations made by an underwater camera in may this year show shoals of fish, crabs and algae”, says Mrs. Else Marie Stamphøj from the agency, and adds “this is certainly a successful outcome.” DHI has carried out the preliminary hydrodynamic studies of the reef.

All the boulders have been placed in the sea by now and form a reef of different shapes. The position of some of the boulders still needs to be adjusted. This is due to complications in connection with an initial scanning made to decide the right placing of the boulders. It was delayed by the wind- and tidal conditions. Now the contractors are working to improve the situation.

Læsø Trindel just 12 km north-east of the Danish island of Læsø used to be a large cavernous boulder reef formed during the ice-age. Over the years the reef has gradually vanished as the easy to get at boulders have been excavated for constructional purposes, leaving a much depleted reef. This has severely impaired the habitat. Shallow water boulder reefs have a high biodiversity and are important habitats for a wide range of species.

The original boulders were transported by the ice 10.000 years ago from Norway and Sweden. Most of them are now to be found in various breakwaters protecting Danish ports and harbours. Today boulders have arrived again from Norway but this time transported by tugs and huge barges. Almost 95.000 tons of boulders have been blasted out at quarries and carefully dumped where the reef used to be. The hope is that the reef again will provide the biodiversity and habitat it used to do.

On a national level it is estimated that most of the natural reefs have been excavated with only few remaining. BlueReef is the first large marine nature restoration project in Denmark and is expected to provide a wealth of knowledge on how marine habitats can be improved. Information about the project will be given on a conference at Kalmar University in Sweden this year, and on an international conference in Denmark in 2011, where the observations are communicated.

Læsø Trindel is designated as a Natura 2000 Site according to the EU Habitats Directive. The project cost is Euro 4.8 million of which the EU commission has funded 50%.




The Bluereef in May 2009. The pictures originate from a trip with ’Seadog’ arranged by The Danish Forest and Nature Agency.

Want to know more ?

Sanne Lina Niemann

sln@dhigroup.com