Aquafarm "Roter Sand"
In early March 2002, a protected research area (Fig. 1) for aquaculture purposes was set up (Fig. 2 & 3) close to the lighthouse "Roter Sand" (Fig. 4) about 17 sm offshore. Due to the strong tidal currents at that location wave heights can reach 3-4 m with a current velocity up to 2 m/s. This study area borders the zone of a proposed wind farm site, where the first windmills will be installed by the end of 2006. Before technical elaborated and costly aquaculture systems will be fixed at near offshore windmills, it is necessary to determine their (a) biological feasibility, e.g. growth rates, settlement densities, etc. (b) biotic and abiotic impacts (positive and negative) such structures impose on the cultured species themselves and (c) compatibility to requirements needed for other offshore installations. For this purpose a longline system for mussel and oyster culture and an offshore floating/submersed ring for seaweed culture were installed, in cooperation with the Research Center Terramare (Wilhelmshaven).
Technique and Candidates
For mussels (Mytilus edulis) and oysters (Crassostrea gigas, Ostrea edulis) several types of cultivation can be used in the North Sea region. Predominately, longline constructions are proposed for the cultivation of bivalves, by which submersible ropes provide the habitat on which the candidates can settle (Fig. 5 & 6). Other techniques, such as ring and cage constructions, which can be placed on the water surface and under water, as well as the construction SOSSEC (Submersible Offshore Shellfish and Seaweed Cage) can be operated, too. For seaweed (Saccharina latissima (Laminaria saccharina), Palmaria palmata) cultivation seedlings will be raised on ropes (Fig. 7) under lab conditions and later fixed to floating or submersed ring constructions (Fig. 8).
The advantage of submersible culture constructions are the avoidance of the impact of harsh weather conditions and strong wave mechanics. Thus, a combination of these techniques with the main pillar (tripod or jacket) of the windmill installation dispenses the need for a sophisticated and expensive mooring of the aquaculture system, which would also impact strongly on the benthic ecosystem. Due to the solid construction of the windmills, such systems would be very stable fixed (Fig. 9).
Saccharina latissima (Laminaria saccharina)