Dahl, K., Stenberg, C., Lundsteen, S., Støttrup, J., Dolmer, P., & Tendal, O.S. 2009: Ecology of Læsø Trindel - A reef impacted by extraction of boulders. National Environmental Research
Institute, Aarhus University. 48 pp. - NERI Technical Report No. 757.
The aim of the ‘Blue Reef’ project is to improve the quality of the reef habitat at Læsø Trindel. The reef is part of the Natura 2000 area Læsø Trindel and Tønneberg Banke. The report describes the results of the baseline investigation carried out in the area to document the present biological components at the reef.
221 different species were found at Læsø Trindel, which was considered as a relatively high biodiversity. The biomasses on benthic macro algal vegetation were on the other hand rather small compared to reef areas dominated by large stable boulders and with the same depth. The biomasses were dominated by small members of perennial species or fast-growing species.
The fauna biomass was small and dominated by bryozoans growing on the algal leaves. Newly settled blue mussels (Mytilus edulis) were numerous but made up a small fraction of the overall biomass in June. Large blue mussels were not observed at all. There was a good positive correlation between the fauna biomass and the algal biomass in the samples.
The fish community was dominated by species from the wrasse family, whereas commercial species like cod (Gadus morhua) were few. Lobsters were not caught within the planned restoration area but in few numbers just outside on the deeper parts of the reef. Juvenile cod tagged with small acoustic transmitters used the reef area during night time in June indicating that the reef area is an important habitat.
Blue mussels and gammaridae were often found in the stomachs of goldsinny wrasse (Ctenolabrus rupestris) in the autumn, indicating that they are important pray items for this fish species. Gammaridae were also numerous in cod stomachs but a range of other pray species were also common indicating a more opportunistic pray preference.
The investigation indicated that the restoration of the reef most likely will result in a more developed seaweed forest with higher biomasses of both algal and fauna species. Such improvements of the biological components will most likely also result in better living conditions for fish and shellfish.
The project is carried out with contribution from the LIFE financial instrument of the European Community.
Full report in pdf (3.91MB)
